There are 59record(s).

Tuesday, April 11, 2017, 10:30 AM (Beijing time) seminar

The 58th HENPIC Seminar: Jet quenching in heavy-ion collisions

Speaker: Guangyou Qin (秦广友),CCNU

Date:Tuesday, April 11, 2017, 10:30 AM (Beijing time)

Download: (after April 09)


The strongly-interacting quark-gluon plasma (QGP) was one of the most important discoveries in relativistic heavy-ion collisions performed at RHIC and the LHC. Jet quenching, mainly characterized by energy loss and transverse momentum broadening experienced by high energy partons as they traverse and interact with the QGP, provides one of the important tools to study the properties of the hot and dense nuclear matter. In this talk, I will present some recent studies on jet-medium interaction, with focus on the nuclear modifications of jet rates, jet structures, and jet-like correlations.


Tuesday, March 07, 2017, 10:30 AM (Beijing time) seminar

The 57th HENPIC Seminar: Anomalous chiral effects in hydrodynamic media

Speaker: Yuji Hirono,BNL, USA

Date:Tuesday, March 07, 2017, 10:30 AM (Beijing time)

Download: (after March 05)


Abstract: The chiral magnetic effect (CME) is a macroscopic non-dissipative transport phenomenon caused by the chiral anomaly. CME is experimentally observed in Weyl semimetals, and is expected to be occurring in heavy-ion collisions. In this talk, I’ll discuss some consequences of those anomalous effects in hydrodynamic media, especially when electrodynamic fields are treated as dynamical fields. The framework to describe such system is called chiral magnetohydrodynamics. I’ll explain how this theory is constructed as a low-energy effective theory, and the properties of excitations will be discussed.


Thursday, Jan. 5th, 2017, 10:30 AM (Beijing time) seminar

The 56th HENPIC Seminar: Recent $J/\\psi$ measurments from STAR experiment

Speaker: Wangmei Zha,USTC

Date:Thursday, Jan. 5th, 2017, 10:30 AM (Beijing time)



The Relativistic Heavy Ion Collider (RHIC) is built to search for the quark-gluon plasma (QGP) and to study its properties in laboratory through high energy heavy-ion collisions. $J/\\psi$ suppression in heavy-ion collisions due to color screening of quark and antiquark potential in the deconfined medium has been proposed as a signature of QGP formation. Other mechanisms, such as the cold nuclear matter effect and charm quark recombination, are likely to contribute to the observed modification of $J/\\psi$ production in heavy-ion collisions. Interpretation of $J/\\psi$ modification requires good understandings of its production mechanism in elementary collisions. Despite decades of efforts, the quarkonium production mechanism still remains an open question to date. New measurements of $J/\\psi$ in p+p collisions are necessary to constrain different models. On the other hand, measurements of $J/\\psi$ invariant yields in different collision energies, collision system, and centralities can shed new light on understanding the interplay of these mechanisms for $J/\\psi$ production and medium properties.

Recently, an significant excess of $J/\\psi$ yield at very low $p_{T}$ ($<$ 0.3 GeV/c) in peripheral hadronic Pb+Pb collisions at $\\sqrt{s_{NN}}$= 2.76 TeV at forward-rapidity has been observed by ALICE collaboration, which can not be explained within the scenarios mentioned above. The excess observed may originate from the coherent photoproduction of $J/\\psi$, which would be very challenging for the existing coherent photoproduction models. Measurements and calculations of $J/\\psi$ production at very low $p_{T}$ in different collision energies, collision systems, and centralities can shed new light on the origin of the excess .\\\\
In this presentation, we report on the measurements of $J/\\psi$ invariant yields as a function of transverse momentum at midrapidity ($|y| < 1.0$) in p+p collisions at $\\sqrt{s} =$ 500 GeV and Au$+$Au collisions at $\\sqrt{s_{NN}} =$ 39 GeV, 62.4 GeV and 200 GeV from STAR. Measurements of $J/\\psi$ production at very low $p_{T}$ in hadronic Au+Au collisions at $\\sqrt{s_{NN}}$ = 200 GeV and U+U collisions at $\\sqrt{s_{NN}}$ = 193 GeV at mid-rapidity will also be presented. The calculations of $J/\\psi$ coherent photon-production for different scenarios will be discussed and compared to data.


Thursday, Dec 08, 2016, 10:30 AM (Beijing time) seminar

The 55th HENPIC Seminar: New quantum effects in relativistic magnetohydrodynamics: topology, instability and self-similarity

Speaker: Yi Yin (尹伊),MIT

Date:Thursday, Dec 08, 2016, 10:30 AM (Beijing time)

Download: (after Dec 04)


Abstract:Chiral anomaly induces a family of macroscopic quantum behaviors in chiral medium, including the chiral magnetic effect. The application of these effects covers systems of enormous varieties and scales, ranging from the structure of primordial magnetic field in the early universe to charged particle correlation in heavy-ion collisions and negative magnetoresistivity in the newly discovered Weyl semimetal. In this talk, I will present three closely related aspects of new quantum effects present in fluids that contain chiral fermions: topology, instability and self-similarity. I will demonstrate the magnetic reconnections changing chirality of magnetic flux induces in the fluid a quantized electric current, a new kind of the \"chiral magnetic effect\". I further show self-similar inverse cascade driven by the chiral magnetic current. Finally, I report a new type of instability in a magnetohydrodynamics due to anomaly.
[1]Phys. Rev. Lett. 117 (2016) 152002, arXiv:1607.01513
[2]Phys. Rev. Lett. 117 (2016) 172301, arXiv:1606.09611
[3]Phys. Rev. D 92 (2015), 125031, arXiv:1509.07790


Thursday, Nov. 10th, 2016, 10:30 AM (Beijing time) seminar

The 54th HENPIC Seminar: Overpopulated Glasma: Five Years After

Speaker: Jinfeng Liao (廖劲锋),Indiana University

Date:Thursday, Nov. 10th, 2016, 10:30 AM (Beijing time)



The approach toward equilibrium from the initial state in a heavy ion collision, has been a most challenging problem in heavy ion phenomenology, often referred to as the so-called “thermalization puzzle”. The tension lies particularly in that “rapid thermalization” requires strong scatterings while the matter at very early stage (characterized by the semi-hard saturation scale Qs) should be more or less weakly coupled. The key to reconcile such tension, as suggested in a paper (arXiv:1107.5296) five years ago, is that the matter formed shortly after the collision (as often referred to as the glasma) is a very dense, and in fact highly overpopulated system of gluons. The high overpopulation means the gluon occupation number is parametrically much larger than a system in thermal equilibrium with the same energy density. A number of key features of such overpopulated glasma outlined there has since been extensively studied, including: the emergence of a strongly interacting fluid even though with small elementary coupling constant, the approach toward hydrodynamic stage with finite longitudinal/transverse anisotropy, the rapid infrared local thermalization as well as the novel idea of a possible Bose-Einstein condensation . We review those conceptual ideas and highlight subsequent developments in recent years.
[Refs]: arXiv:1107.5296; arXiv:1303.7214; arXiv:1305.2119; arXiv:1503.07260; arXiv:1503.07263; arXiv:1609.02580.


Thursday, Oct. 13rd, 2016, 10:30 AM (Beijing time) seminar

The 53rd HENPIC Seminar: Medium Induced Transverse Momentum Broadening in Hard Processes

Speaker: Bin Wu (吴斌),Ohio State University

Date:Thursday, Oct. 13rd, 2016, 10:30 AM (Beijing time)



In this talk I shall start with the double logarithmic correction to the transverse momentum broadening of high-energy parton in QCD matter. Such a double logarithmic term, averaged over the path length of the partons, can be taken as the radiative correction to the jet quenching parameter $\\hat{q}$ and contributes to radiative energy loss. Then, I shall talk about our recent work on deep inelastic scattering on a large nucleus. We find that one can factorize such a medium-induced double log and the vacuum radiation contribution, Sudakov double logs. Our derivations can be generalized to other hard processes, such as dijet productions, which can be used as a probe to measure the medium p_T-broadening effects in heavy-ion collisions when Sudakov effects are not overwhelming.


Thursday, Sept. 08, 2016, 10:30AM (Beijing time) seminar

The 52nd HENPIC Seminar: Experimental study of chiral and matter-antimatter symmetries at RHIC

Speaker: Aihong Tang,BNL, USA

Date:Thursday, Sept. 08, 2016, 10:30AM (Beijing time)



Symmetries and the physics laws that they dictate are fundamental in describing the physical world. In this talk I discuss two fundamental symmetries that are well suited to be studied at RHIC, namely, the chiral symmetry and the matter-antimatter symmetry. Under the hot and dense condition at RHIC, quarks and gluons are set free from protons and neutrons, making it feasible for the chiral symmetry to be restored. A restored chiral symmetry is a necessary requirement for the Chiral Magnetic Wave (CMW), a novel QCD phenomena, to propagate. The CMW has experimental consequences - it leads to the separation of elliptic flow between charged pions, which will be discussed in this talk. On the other hand, the abundantly produced antimatter at RHIC offers a unique opportunity to study the matter-antimatter symmetry. In particular the nuclear force between two antinucleons has not been measured previously, although the corresponding force for nucleons or nuclei has been well studied for decades. In this talk I will discuss the measurement of the nuclear force between two antiprotons and compare to that between protons. As direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, this result provides an elemental ingredient for understanding the structure of more complex antinuclear and their properties.


Thursday, August 11, 2016, 10:30 AM (Beijing time) seminar

The 51st HENPIC Seminar: Quarks, mesons, and the inverse magnetic catalysis in strong magnetic fields

Speaker: Toru Kojo,CCNU

Date:Thursday, August 11, 2016, 10:30 AM (Beijing time)



Recently numerical lattice QCD calculations in strong magnetic fields, |eB| >> Lambda_QCD^2, offer ample results which contradict with naive model calculations, posing theoretical challenges. I will discuss the following theoretical problems: the inverse magnetic catalysis, the B-dependence of chiral condensates, quark mass gap, meson spectra and wavefunctions, and the quark back-reaction on the gluon dynamics. I will discuss how to understand all these issues consistently, and also explain why the lattice results differ from typical model predictions.


Thursday, July 21st, 2016, 10:30 AM (Beijing time) seminar

Experimental Search for Chiral Magnetic/Vortical Effects in Heavy-ion Collisions

Speaker: Gang Wang (王刚),UCLA

Date:Thursday, July 21st, 2016, 10:30 AM (Beijing time)



In ultra-relativistic heavy-ion collisions, the produced quark-gluon plasma facilitates the study of microscopic domains that bear interesting physics mechanisms, such as the chiral magnetic effect and the chiral magnetic wave. These mechanisms are theoretically conditioned on the chiral symmetry restoration and a strong magnetic field (both experimentally feasible), and have been investigated with experimental observables. In this talk, we will review the techniques to study this subject at RHIC and the LHC and discuss the evidence observed so far for the chiral magnetic/vortical effects. An outlook for further isobaric collisions will also be presented.


Thursday, June 23rd, 2016, 10:30 AM (Beijing time) seminar

49th HENPIC Seminar: Critical fluctuations near the QCD critical point

Speaker: Jiang Lijia (姜丽佳),Peking University

Date:Thursday, June 23rd, 2016, 10:30 AM (Beijing time)



Recently, the STAR collaboration has measured the energy dependent moments of net-proton multiplicity distributions in Au+Au collisions. The most exciting result is the large deviation of &#954;&#963;^2 from the unity at collision energy below 39 GeV within 0.4 < pT < 2 GeV/c.

In this report, we first introduce a freeze-out scheme for the dynamical models near the QCD critical point through coupling the decoupled classical particles with the order parameter field. We calculate the correlated fluctuations of net protons on the hydrodynamic freeze-out surface. A comparison with the STAR data shows that our model calculations could roughly reproduce energy dependent cumulant C4 and &#954;&#963;^2 of net protons through tuning the related parameters. But the calculated C2 and C3 are always above the experimental data due to the positive contributions from the static critical fluctuations. In the later part of this talk, We will further discuss the dynamical evolution of sigma field? cumulants based on Langevin dynamics. Our calculation of cumulants show the critical slowing down and memory effects near the critical point, which could solve the issue of static critical fluctuations on the sign problem of C3.


Thursday, May 12th, 2016, 10:30 AM (Beijing time) seminar

The 48th HENPIC Seminar: Exploring the QCD phase diagram for a signature of the critical point

Speaker: Jian Deng( 邓建),Shandong University

Date:Thursday, May 12th, 2016, 10:30 AM (Beijing time)



Heavy ion collision experiments search for a critical point in the phase diagram of nuclear matter by measuring non-Gaussian moments of baryon number. Universality of critical phenomena predicts that non-Gaussian moments are enhanced near a critical point. We show that universality near a critical point implies a characteristic relation between higher order baryon susceptibilities. Including the individual enhancements of these susceptibilities near a critical point, the relation between them may be a consistent set of observations supporting the interpretation of baryon fluctuations data as arising from criticality.


Thursday, Apr. 14th, 2016, 10:30 AM (Beijing time) seminar

The 47th HENPIC Seminar: Nonperturbative Computation of Open Heavy Flavor in Relativistic Heavy Ion Collisions

Speaker: Min He(何敏),Nanjing University of Sci. & Tech.

Date:Thursday, Apr. 14th, 2016, 10:30 AM (Beijing time)



We evaluate open heavy-flavor (HF) transport in relativistic heavy-ion
collisions by combining a strong-coupling treatment in both macro- and
microscopic dynamics of the reaction (hydrodynamics and
non-perturbative HF interactions). The hydrodynamic evolution is
quantitatively constrained by bulk-hadron spectra and elliptic flow.
In the Quark-Gluon Plasma (QGP) phase, heavy-quark diffusion
coefficients are taken from a non-perturbative $T$-matrix calculation
of heavy-light quark and heavy quark-gluon scattering. These
interactions lead to resonance formation close to Tc which is
implemented as a hadronization (recombination) mechanism on a
hydrodynamic hypersurface. In the hadronic phase, the diffusion of HF
mesons is treated with effective hadronic theory. We present a
comprehensive study of open HF observables at RHIC and the LHC. A
fair description of current experimental data on $D$, $D_s$, $B$
mesons and HF electrons emerges from our nonperturbative approach, for
both the nuclear modification factor and elliptic flow. Some
discrepancies remain at high pt, indicative of radiative energy loss
that is to be included in our approach. Preliminary results for
dielectrons from correlated $D$$D\\bar$ decay will also be reported.


Thursday, Mar. 10th, 2016, 10:30 AM (Beijing time) seminar

The 46th HENPIC Seminar: Heavy flavor production in relativistic heavy ion collisions and Properties of sQGP medium

Speaker: Dr. Xin Dong(董昕),LBNL

Date:Thursday, Mar. 10th, 2016, 10:30 AM (Beijing time)



Heavy flavors are expected to offer unique sensitivity to study properties of the sQGP medium. I will review recent experimental achievements in heavy flavor measurements at RHIC and LHC. I will discuss what we have learned from these measurements on the interaction mechanisms between heavy flavor quarks and the sQGP medium as well as the medium transport properties. In the end, I will discuss future plans on heavy flavor programs at both RHIC and LHC.


Thursday, Jan. 14th, 2016, 10:30 AM (Beijing time) seminar

The 45th HENPIC Seminar: Chiral symmetry restoration and chiral rotation in the presence of external electric field

Speaker: Dr. Gaoqing Cao (曹高清),Fudan University

Date:Thursday, Jan. 14th, 2016, 10:30 AM (Beijing time)



We systematically studied the chiral symmetry breaking and restoration in the presence of a pure electric field in the Nambu?ona-Lasinio (NJL) model at finite temperature and baryon chemical potential. In addition, we also studied the effect of the chiral phase transition on the charged pair production due to the Schwinger mechanism. The inverse catalysis effect of the electric field to chiral symmetry breaking is recovered. And the Goldstone mode is find to disperse anisotropically such that the transverse velocity is always smaller than the longitudinal one, especially at nonzero temperature and baryon chemical potential. As expected, the quark-pair production rate is greatly enhanced by the chiral symmetry restoration.
Furthermore, we studied the QCD vacuum structure under the influence of an electromagnetic field with a nonzero second Lorentz invariant I_2=E&#8901;B at zero temperature. We will show that the presence of I_2 can induce neutral pion (&#960;_0) condensation in the QCD vacuum through the electromagnetic triangle anomaly. Within the frameworks of chiral perturbation theory at leading small-momenta expansion as well as the Nambu?Jona-Lasinio model at leading 1/N_c expansion, we quantify the dependence of the &#960;_0 condensate I_2.


Thursday, Dec. 10th, 2015, 10:30 AM (Beijing time) seminar

The 44th HENPIC Seminar: Differential measurements of dielectron productions at STAR

Speaker: Dr. Bingchu Huang (黄柄矗) ,University of Illinois at Chicago

Date:Thursday, Dec. 10th, 2015, 10:30 AM (Beijing time)



In heavy ion collisions, dileptons are considered as ideal penetrating probes as they are produced in whole evolution of the system and have very little interaction with hadronic medium. Therefore, it allows the study of the system throughout its space-time evolution. It can probe the in-medium modifications of vector meson which may be related to the effect of chiral symmetry restoration in the low mass range (LMR) ($M_{ll}<1.1$~GeV/c$2$), and it allows the study of thermal radiation from hot medium in the intermediate mass range ($1.1<M_{ll}<3.0 ~GeV/c^2$).
With the introduction of the Time-of-Flight detector, the STAR detector at the Relativistic Heavy Ion Collider (RHIC) has been able to perform large acceptance, high purity electron identification. We will present invariant mass and transverse momentum dependent measurements of dielectron production from STAR for the first phase of the RHIC beam energy scan ranging from $\\sqrt{s_{NN}}$ = 19.6 to 200 GeV. Through all beam energies, a low mass excess over expected hadronic contributions has been observed, and is consistent with a theoretical multi-body model incorporating a broadening rho meson spectral function. Furthermore, the acceptance corrected excess yield over expected hadronic contributions will be presented for 19.6 and 200 GeV.


Thursday, Nov. 12th, 2015, 10:30 AM (Beijing time) seminar

The 43rd HENPIC Seminar: Covariance Analysis of Transport Model Parameters relevant for symmetry energy

Speaker: Prof. Yingxun Zhang(张英逊),China Institute of Atomic Energy

Date:Thursday, Nov. 12th, 2015, 10:30 AM (Beijing time)



A new version of the improved quantum molecular dynamics model has been developed by including Skyrme type momentum dependent interaction. Four Skyrme parameter sets, SLy4, SkI2, SkM*, Gs, and 12 kinds of MSL ({K_0, S_0, L, m_s^*, m_v^*}) parameter sets are adopted in the transport model code to calculate the isospin diffusion, single and double ratios of transverse emitted nucleons, neutron proton isoscaling ratios.

Using covariance analysis, we quantify the correlations between the parameters of nuclear matter and the experimental observables commonly used to extract information of the Equation of State of Asymmetric Nuclear Matter. Using the simulations of 124Sn+124Sn, 124Sn+112Sn and 112Sn+112Sn reactions at beam energies of 50 and 120 MeV per nucleon, we have identified that the nucleon effective masses splitting are most strongly correlated to the neutrons and protons yield ratios from central collisions especially at high incident energy. The best observable to determine the slope of the symmetry energy, L, at saturation density is the isospin diffusion observable at low incident energy even though the correlation is not very strong ($\\sim$0.7). Similar magnitude of correlation but opposite in sign exists for isospin diffusion and nucleon isoscalar effective masses. At 120 MeV/u, the effective mass splitting and the isoscalar effective mass also have opposite correlation for the double n/p and isoscaling p/p yield ratios. By combining the data and simulations at high and low energy, it should be possible to disentangle the effects the slope of symmetry energy (L), isoscalar effective mass ($m_s^*/m$) and effective mass splitting and place the constraints on $L$, $m_s^*/m$ and effective mass splitting with reasonable uncertainties.


Thursday, October 22, 2015, 10:30 AM (Beijing time seminar

The 42nd HENPIC Seminar: Transport Theory of Open Heavy Flavor in Heavy-Ion Collisions

Speaker: Shanshan Cao,LBNL

Date:Thursday, October 22, 2015, 10:30 AM (Beijing time



Heavy quarks are valuable probes of the dense nuclear matter produced in relativistic heavy-ion collisions. We establish a comprehensive framework that describes their entire temporal evolution in the QGP matter and the subsequent hadron gas. The dynamics of open heavy quarks in the QGP is described using an improved Langevin approach that simultaneously incorporate the quasi-elastic scattering and medium-induced gluon radiation processes. The hadronization of heavy quarks into their mesonic bound states is calculated utilizing our hybrid model of fragmentation plus heavy-light quark coalescence. And the final rescatterings of heavy hadrons inside the hadron gas are described using the UrQMD model.

Within this newly developed framework, we demonstrate that while quasi-elastic scattering dominates heavy quark energy loss in the QGP at low energies, contributions from gluon radiation at high energies are significant; and the coalescence process is found important for heavy meson production at intermediate pT. Our numerical results provide a good description of the RAA and v2 of both D meson and B-decay non-prompt J/&#968; measured at RHIC and LHC. In addition, two-particle correlation functions of heavy flavor are explored. We show that while the nuclear modification of the pT imbalance of D&#8722;Dbar reflects the total energy loss of heavy quarks, their angular correlations are sensitive to the detailed energy loss mechanisms.


Thursday, Sept 24, 2015, 10:30 AM (Beijing time) seminar

The 41th HENPIC seminar:Jet Quenching and Tomography in semi-Quark-Gluon-Monopole-Plasmas Produced in A+A reactions at RHIC and LHC

Speaker: Miklos Gyulassy,Columbia University

Date:Thursday, Sept 24, 2015, 10:30 AM (Beijing time)



Experiments at RHIC/BNL and LHC/CERN on high energy heavy ion reactions in the past decade found that QCD matter at densities about 100 times higher than in cold nuclei exhibits near ??erfect fluid??bulk collectivity as well as ??et quenching??of high energy QCD jets. The simultaneous compatibility of these two phenomena has remained a challenge to both weakly coupled perturbative QCD based tomographic theories and also to strongly coupled AdS gravity dual based holographic theories. While perturbative QCD tomography accounts quantitatively for jet quenching, it fails to account for bulk perfect fluidity. Conversely, while AdS holography automatically explains perfect fluidity, it fails to account quantitatively for the jet quenching systematics. In this talk, I describe our recent proposal [1] to explain both phenomena simultaneously as due to competing effects related to the non-perturbative non-conformal physics of color confinement in QCD as the system cools through the critical temperature range 150-300 MeV. In this temperature range, partial confinement of quark and gluon color electric charge degrees of freedom and emergent color magnetic monopole degrees of freedom are modeled by a non-perturbative non-conformal semi-Quark-Gluon-Monopole-Plasma (sQGMP) with composition and screening properties completely constrained by lattice QCD data. Consistency and robustness of the sQGPM tomographic framework CUJET3.0 predictions compared with all current RHIC and LHC data are demonstrated. Predictions for future heavy quark jet tagged quenching observables are presented.

[1] J.Xu, J. Liao, MG, Chin.Phys.Lett. 32 (2015) 9, 092501; arXiv:1508.00552


Monday, August 17th, 2015, 10:50 AM (Beijing time) seminar

40th HENPIC Seminar: Discussion on the Hypertriton lifetime measurements

Speaker: Jinhui Chen (陈金辉),Shanghai Institue of Applied Physics (SINAP), CAS

Date:Monday, August 17th, 2015, 10:50 AM (Beijing time)



Hypernuclei is composed of nucleon, proton and hyperon, thus becomes the ideal micro-lab to understand the hyperon-nucleon (YN) interaction. The YN interaction, responsible in part for the binding of hyper nuclei, is of fundamental interest in nuclear physics and nuclear astrophysics. In this talk, I will start from a breif review of the early measurements on hyertriton lifetime from independent experiment. I will focus on the recent precise results from the Relativistic Heavy-Ion Collider at BNL. A comparison with the similar measurements from GSI-HypHI fixed target exp. and the LHC-ALICE will also be made. Physics implications on the YN interaction and the consequence on the light hyper nuclei structure will be discussed.


Thursday, July 9th, 2015, 10:30 AM (Beijing time) seminar

The 39th HENPIC Seminar: Relativistic hydrodynamics order by order

Speaker: Dr. Jianhua Gao (高建华),Shandong University, Weihai

Date:Thursday, July 9th, 2015, 10:30 AM (Beijing time)



In this talk, we propose a method of solving the viscous hydrodynamics order by order in a derivative expansion. In such method, the zero order is just the ideal hydrodynamics. All the other higher order corrections satisfy the same first-order partial differential equations but with different inhomogeneous terms. We take the Bjorken flow as an example to test the validity of our method and discuss the initial conditions and perturbation evolution in our method


Thursday, June 18th, 2015, 10:30 AM (Beijing time) seminar

38th HENPIC: Properties of photons in supercritical magnetic fields

Speaker: Koichi Hattori,RIKEN-BNL Research Center

Date:Thursday, June 18th, 2015, 10:30 AM (Beijing time)



I discuss effects of supercritical magnetic fields on photon propagations on the basis of a resummation technique by the proper-time method. I show the refractive index and decay rate of a real photon obtained from the vacuum polarization diagram, and also discuss the photon splitting from triangle diagrams in magnetic fields.


Thursday, May 21, 2015, 2:00 PM (Beijing time) seminar

37th HENPIC: ECal for STAR upgrade and HIEPA

Speaker: Yi-fei Zhang (张一飞),USTC

Date:Thursday, May 21, 2015, 2:00 PM (Beijing time)



Electron-ion collision is one of the fundamental frontiers of physics research. Upgrade of electron-ion (ep and eA) collider (EIC) and searching for new physics in the extreme small scale of nucleon structure are of most interest in future 10-20 years. Studying the gluon and quark distributions in a nucleon structure and the small-x physics is the fundamental goal of the electron-ion collider. Precise measuring the scattered electron energy and scattering angle can study the distributions of Bjorken scale x and the energy transfer Q2.

Detecting photon with good energy resolution is also crucial for high intensity electron positron accelerator (HIEPA) in a tau-charm energy region under a high radiative environment.

BSO is a new scintillating crystal with high light yield output and low cost. It has been proposed as one of the options for future forward electromagnetic calorimeter (ECal) for EIC. However, BSO technology is far from mature yet. In the talk we will present the status of the BSO development and the performance of the BSO crystals as well as a small prototype. The conceptual design of the Ecal for EIC and HIEPA will also be introduced.


Wednesday, April. 22, 2015, 2:00 PM (Beijing time) seminar

36th HENPIC: On the interplay of spin and saturation physics

Speaker: Jian Zhou(周剑),NIKHEF, Netherlands

Date:Wednesday, April. 22, 2015, 2:00 PM (Beijing time)



I will review some recent theoretical developments in a newly emerging research direction: spin physics at small x. Three topics are covered: linearly polarized gluon distribution inside a large nucleus, transverse single spin asymmetries at small x, and the color entanglement effect in polarized pA collisions.


Thursday, March 26, 2015, 10:30 AM (Beijing time) seminar

35th HENPIC: Collective flow in large and small systems at the LHC

Speaker: Xiangrong Zhu(朱祥荣),Peking University

Date:Thursday, March 26, 2015, 10:30 AM (Beijing time)



In this talk, we will discuss our recent progress on flow for the large and small systems, covering the flow of strange and multi-strange hadrons, and chemical and thermal freeze-out of various hadrons species in Pb-Pb collisions at $\\sqrt{s_{NN}$ = 2.76 TeV. We will also discuss hadronic ``flow\'\' in p-Pb collisions at $\\sqrt{s_{NN}$ = 5.02 TeV.


Thursday, Jan. 15, 2015, 10:30 AM (Beijing time) seminar

34th HENPIC: Long-range pseudo-rapidity dihadron correlations measurement in d+Au

Speaker: Li Yi (易立),Purdue University

Date:Thursday, Jan. 15, 2015, 10:30 AM (Beijing time)



A long-range (large |\\Delta\\eta|) two-particle azimuthal (\\Delta\\phi) correlation (?idge? was observed in high-multiplicity p+p and p+Pb collisions at the LHC. Subtraction of two-particle correlations in high- and low-multiplicity events reveals a back-to-back double ridge (\\Delta\\phi=0 or \\pi). A similar double ridge was observed in d+Au collisions with the same technique by the PHENIX experiment at RHIC. This talk reports results of the ridge in d+Au collisions with the STAR detector at RHIC. Dihadron correlations are analyzed in 200 GeV d+Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal. The long-range near-side ridge is observed on the Au-going side for high-multiplicity events. With the STAR detector\'s large acceptance, the near-side (\\Delta\\phi=0) ridge correlated yield \\Delta\\eta and multiplicity dependences are studied. In a Fourier decomposition of the dihadron correlations, the second Fourier coefficients are observed to be the same for low- and high-multiplicity, d- and Au-going side, despite the large multiplicity difference and near-side ridge appearance difference. This near-side ridge yield difference is found to be due to the large negative first Fourier coefficients in the low-multiplicity and d-going side. We will discuss the implications of the STAR data on the theoretical explanations for the ridge mechanism in d+Au collisions.


Tuesday, Dec. 23, 2014, 10:30 AM (Beijing time) seminar

33rd HENPIC: Collectivity in small systems from parton scatterings

Speaker: Guo-Liang Ma (马国亮),SINAP, CAS

Date:Tuesday, Dec. 23, 2014, 10:30 AM (Beijing time)



We show that the incoherent elastic scattering of partons, as present in a multi-phase transport model (AMPT), with a modest parton-parton cross-section of $\\sigma$=1.5-3 mb, naturally explains the long-range two-particle azimuthal correlations as observed in p+p and p+Pb collisions for all measured $N_{track}$ and $p_T$ bins at the Large Hadron Collider. We calculate the elliptic, $v_2$, and triangular, $v_3$, Fourier coefficients of the two-particle azimuthal correlation function in p+Pb and peripheral Pb+Pb collisions. Our results for $v_3$ are in a good agreement with the CMS data. The $v_2$ coefficient is very well described in p+Pb collisions and is underestimated for higher $p_T$ in Pb+Pb collisions. The characteristic mass ordering of $v_2$ in p+Pb is reproduced whereas for $v_3$ such ordering is not observed. We further predict the pseudorapidity dependence of the two-particle azimuthal correlation function. Predictions for the higher order Fourier coefficients, $v_4$ and $v_5$, in p+Pb are also presented. Our numerical results indicate an emergence of collectivity in p+p, p+Pb and peripheral Pb+Pb collisions from parton scatterings.


Thursday, Nov. 13, 2014, 10:30AM (Beijing time) seminar

32nd HENPIC: Gluon Condensation and thermalization far from equilibrium

Speaker: Zhe Xu (徐吉吉),Tsinghua University

Date:Thursday, Nov. 13, 2014, 10:30AM (Beijing time)



We study the thermalization of gluons far from thermal equilibrium in relativistic kinetic theory. The initial distribution of gluons is assumed to resemble that in the early stage of ultrarelativistic heavy ion collisions. Only elastic scatterings in a static, non-expanding gluonic matter are considered. At first we show that the occurrence of condensation in the limit of vanishing particle mass requires a general constraint for the scattering matrix element. Then the thermalization of gluons with Bose-Einstein condensation is demonstrated in a transport calculation. We see a continuously increasing over-population of low energy gluons, followed by a decrease to the equilibrium distribution, when the condensation occurs. The times of the completion of the gluon condensation and of the entropy production are calculated. These times scale inversely with the energy density.


Thursday Oct. 23, 2014, 2:30 pm (Beijing time) seminar

31st HENPIC: Second order viscous corrections to the harmonic spectrum

Speaker: Li Yan,CNRS, Saclay

Date:Thursday Oct. 23, 2014, 2:30 pm (Beijing time)



We calculate the second-order viscous correction to the kinetic distribution, &#948;f(2), and use this result in a hydrodynamic simulation of heavy-ion collisions to determine the complete second-order correction to the harmonic spectrum, vn. At leading order in a conformal fluid, the first viscous correction is determined by one scalar function, &#967;0p. One moment of this scalar function is constrained by the shear viscosity. At second order in a conformal fluid, we find that &#948;f(p) can be characterized by two scalar functions of momentum, &#967;1p and &#967;2p. The momentum dependence of these functions is largely determined by the kinematics of the streaming operator. Again, one moment of these functions is constrained by the parameters of second-order hydrodynamics, &#964;&#960; and &#955;1. The effect of &#948;f(2) on the integrated flow is small (up to v4) but is quite important for the higher harmonics at modestly large pT. Generally, &#948;f(2) increases the value of vn at a given pT and is most important in small systems.


Thursday Sep.11, 2014, 2:00 pm (Beijing time) seminar

30th HENPIC: On the perturbative calculation of energy-momentum tensor correlators in hot Yang-Mills theory

Speaker: Yan Zhu,Santiago de Compostela University

Date:Thursday Sep.11, 2014, 2:00 pm (Beijing time)



The hydrodynamic description of an expanding quark-gluon plasma, including a small but nonzero shear viscosity, has been seen to be in a good agreement with experimental results from high energy heavy ion collisions. This highlights the need for an accurate first principles determination of various transport coefficients, in particular the bulk and shear viscosities, of hot QCD. Unfortunately, it is very difficult to obtain direct non-perturbative lattice results for these quantities, at least without perturbative input. In this talk, I will present recent next-to-leading order (NLO) perturbative calculations of the bulk and shear correlators of SU(N) Yang-Mills theory, including determinations of the corresponding spectral functions. The results are subsequently compared to lattice and gauge/gravity predictions, as well as used to verify known sum rules. Finally, I will comment on the application of HTL resummation on the spectral functions and on the prospects of using the results to aid an eventual lattice determination of the viscosities.


Thursday August 14, 2014, 2:00 pm (Beijing time) seminar

29th HENPIC: Energy Dependence of the Dielectron Production in Au+Au Collisions at RHIC

Speaker: Jie Zhao,CCNU

Date:Thursday August 14, 2014, 2:00 pm (Beijing time)



The mission of ultra relativistic heavy ion program is to study the QCD matter at the finite temperature and density in laboratory. Probes that have been explored in experiments are mostly hadrons, which have been used to demonstrate the formation of strongly-coupling Quark Gluon Plasma in high energy RHIC and LHC heavy ion collisions. Electromagnetic probes (e.g. dileptons, photons) escape from the system without further strong interaction once they are produced, therefore they can offer clean information on various stages during the whole system evolution.
Dileptons can be produced in all stages in a heavy ion collision, their sources vary with the kinematic phase space under consideration: in the low mass region (LMR: $M_{ll} < 1.1GeV/c^2$), vector mesons and direct photons are the dominating source, while dileptons in the intermediate mass region (IMR: $1.1 < M_{ll} < 3GeV/c^2$) primarily stem from QGP thermal radiation and semileptonic decays of charmed mesons. In the high mass region (HMR: $M_{ll} > 3GeV/c^2$), heavy quark decays and Drell-Yan processes contribute the most to the dilepton spectrum.
In this talk we will present the recent RHIC results on dielectron measurements in Au+Au collisions at various collisions energy. The results will be compared to hadron decay cocktails with theoretical calculations to study the vector meson in-medium modifications in LMR and the possible QGP thermal radiation in IMR. The detector upgrades related to the dielectron measurements at STAR will also be discussed.


Thursday July 17, 2014, 2:00 PM (Beijing time) seminar

28th HENPIC: Jet Physics with ALICE at the LHC

Speaker: Xiaoming Zhang,Lawrence Berkeley National Laboratory

Date:Thursday July 17, 2014, 2:00 PM (Beijing time)



Collisions between lead nuclei at the LHC produce strongly-interacting matter composed of deconfined quarks and gluons. This quark-gluon plasma (QGP) is predicted to modify the fragmentation of hard scattered partons generated during the initial stage of the nuclear collisions (jet quenching). The studies of the jet production in different colliding systems pp (QCD vacuum), p?b (cold nuclear matter) and Pb?b (hot and dense partonic matter) play a central role in extracting the physical properties, such as density and temperature, of the QGP. Moreover, the measurements of identified particles in jets provide an in-depth sensitivity to the flavor dependence of the jet fragmentation and hadronization processes. We will present results on the jet production in pp, p?b and Pb?b collisions and the measurements of hadron compositions ($\\pi^{\\pm}$, ${\\rm K}^{\\pm}$, ${\\rm K}_{\\rm S}^{0}$, p, $\\Lambda$) in charged jets in pp and p?b collisions performed with ALICE detector.


Thursday June 19, 2014, 2:00 PM (Beijing time) seminar

27th HENPIC: QCD thermodynamics at phenomenologically relevant coupling

Speaker: Nan Su (苏南),(Bielefeld University)

Date:Thursday June 19, 2014, 2:00 PM (Beijing time)



Quark-gluon plasma is a quantum statistical system with emergent scales from collective excitations: (chromo)electric scale gT and (chromo)magnetic scale g^2T, where g is the running coupling. The application of thermal QCD to practice has been a crucial challenge in thermal field theory due to obstacles such as the nonconvergence of the weak-coupling expansion, infrared divergences from the magnetic scale. In order to improve the situation, the collective scales have to be appropriately incorporated into the calculation schemes, and in this talk I would like to discuss some recent progresses in the study of QCD thermodynamics at couplings that are relevant for the RHIC, LHC and forthcoming FAIR heavy-ion experiments.


Thursday May 15, 2014, 10:30 AM (Beijing time) seminar

26th HENPIC: The Hitchhiker抯 Guide to the Hydrodynamics

Speaker: Bo-wen Xiao (肖博文),CCNU

Date:Thursday May 15, 2014, 10:30 AM (Beijing time)



As a hitchhiker to the theory of hydrodynamics myself, I would like to present a guide to the exact solutions of second order conformal hydrodynamics. I will first present some cases with and without vorticity, which are both the first known non-trivial exact solutions to the equations of second order conformal hydrodynamics. In addition, I will also discuss some solutions related to Bjorken flow and elliptic flow.


Thursday April 10, 2014, 10:30 AM (Beijing time) seminar

25th HENPIC: Experimental study of J/psi production mechanism at RHIC-STAR

Speaker: TANG Zebo (唐泽波),USTC

Date:Thursday April 10, 2014, 10:30 AM (Beijing time)



J/psi played an import role in QCD since its discovery about 40 years ago, but its production mechanism remains an open question to date. In p+p collisions, its production mechanism is still unclear as the transition from initially produced ccbar pair to the bound state J/psi involves soft processes which makes modeling of J/psi production difficult. The feed-down contribution of higher charmonium states and B-hadrons makes the problem even more complicated. In heavy-ion collisions, the color-screening effect was proposed to be the signature of the formation of quark-gluon plasma, but the regeneration effect and various cold nuclear matter effects also play significant role in the J/psi production in heavy-ion collisions. I will discuss our experimental investigations of J/psi production mechanism in p+p and heavy-ion collisions at RHIC energy with the STAR detector. The perspectives with STAR newly installed Muon Telescope Detector and Heavy Flavor Tracker will also be touched.


Thursday March 13, 2014,10:30 AM (Beijing time) seminar

24th HENPIC: Thermalization in heavy ion collisions from holography

Speaker: Shu Lin,(Brookhaven National Lab)

Date:Thursday March 13, 2014,10:30 AM (Beijing time)



Phenomenological studies indicate matter produced in heavy ion collisions thermalizes shortly after the collisions. While the mechanism remains unclear, it is believed to attribute to strong coupling. Holography allows us to treat dynamics in strongly coupled field theory. In this talk, I will start by introducing a gravity dual picture of heavy ion collisions, which consists of stringy debris falling in AdS background. The falling of stringy debris naturally leads to a gravitational collapse model for thermalization in heavy ion collisions. I will discuss detail of the model and present results on different probes of the thermalization process, which imply a top-down scenario for thermalization at strong coupling.


Thursday Feburary 20, 2014,10:30 AM (Beijing time) seminar

23rd HENPIC: Energy Dependence of Higher Moments of Net-proton Multiplicity Distributions at STAR

Speaker: Xiao-Feng Luo (罗晓峰),CCNU

Date:Thursday Feburary 20, 2014,10:30 AM (Beijing time)



In the phase diagram of Quantum Chromodynamics (QCD?heory of strong interactions), it is conjectured on the basis of theoretical calculations that there will be a critical point (CP) at high temperature and non-zero baryonic chemical potential region. Experimental confirmation of the QCD Critical Point will be an excellent test of QCD theory in the non-perturbative region and the milestone of exploring the QCD phase diagram. This is one of the main goals of the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Due to the high sensitivity to the correlation length of dynamical systems and directly connected to the susceptibility in the Lattice QCD, higher moments of net-proton distributions have been applied to search for the QCD Critical Point in the heavy-ion collision experiment at STAR. The results were recently published in Phys. Rev. Lett. 112, 032302 (2014). In this talk, we report the beam energy (&#8730;s = 7.7 - 200 GeV) and collision centrality dependence of the mean (M), standard deviation (&#963;), skewness (S), and kurtosis (&#954;) of the net-proton multiplicity distributions in Au + Au collisions. The measurements are carried out by the STAR experiment at mid-rapidity (|y|< 0.5) in the first phase of the BES at RHIC. Deviations for both S&#963; and &#954;&#963;2 from HRG and Skellam expectations are observed for &#8730;s < 27 GeV. The conclusions on the existence of CP can be made only after comparison to QCD calculations with CP behavior which include the dynamics associated with heavy-ion collisions.


Thursday January 16, 2013,10:30 AM (Beijing time) seminar

22nd HENPIC: Enhancement of jet quenching around phase transition: result from the dynamical holographic model

Speaker: Mei Huang,(Institue of high energy physics, CAS)

Date:Thursday January 16, 2013,10:30 AM (Beijing time)



The phase transition and jet quenching parameter have been investigated in the framework of dynamical holographic QCD model. It is found that both the trace anomaly and the ratio of the jet quenching parameter over cubic temperature
show a peak around the critical temperature. This indicates that the jet quenching parameter can characterize the phase transition. The effect of jet quenching parameter enhancement around phase transition on nuclear modification factor and elliptic flow have also been analyzed, and it is found that the temperature dependent jet quenching parameter from dynamical holographic QCD model can considerably improve the description of jet quenching azimuthal anisotropy as compared with the conformal case.


Thursday December 12, 2013,10:30 AM (Beijing time) seminar

21st HENPIC: A systematic regularised method to magnetised matter

Speaker: Jing-yi Chao,(Institute of high energy physics, CAS)

Date:Thursday December 12, 2013,10:30 AM (Beijing time)



It is observed that the dimension reduction of Fermi field in the strong magnetic fields may not be a strictly valid statement. The associated Lowest Landau Level is not a good enough approximation, as well, which may induce some totally unreasonable expectations. We developed a systematic regularised method to deal with the summation of all the Landau levels. We found the photon vacuum polarisations is splitter to two parts as usual expected. However, the transverse part will not strongly damped as calculated before. Especially, in the chiral limit, both transverse and longitudinal parts are linear dependent on $eB$, whatever the strength of the magnetic fields. It remind us, a recalculation of the gap equation with full consideration of all Landau Levels is necessary in the next future.


Thursday November 21,2013,10:30 AM (Beijing time) seminar

20th HENPIC: Introduction to EIC and eSTAR program

Speaker: Ming Shao,USTC

Date:Thursday November 21,2013,10:30 AM (Beijing time)



An Electron Ion Collider (EIC) is being considered as the next generation QCD facility to understand the fundamental question that how the visible universe is built up. More specifically, the EIC will probe the low x domain where sea quarks and gluons dominate with unprecedented precision, for both nucleon and nuclei. A brief introduction of the science case of EIC, as well as a possible realization of the accelerator facility based on the Relativistic Heavy Ion Collier (RHIC), is presented. The STAR detector, one of the two major experiments at RHIC, has planned to evolve itself to fit the EIC physics program with a suite of optimized upgrades (eSTAR). The major components of these upgrades will be introduced. The detector performance and a broad range of deliverable measurement of eSTAR are demonstrated through simulation.


Thursday October 17, 2013, 1:30 PM (Beijing time) seminar

19th HENPIC: Recent flow results from ATLAS

Speaker: Jiang-yong Jia,Stony Brook University

Date:Thursday October 17, 2013, 1:30 PM (Beijing time)



In recent years, the measurement of harmonic flow coefficients $v_n$ has provided important insight into the hot and dense matter created in heavy ion collisions at RHIC and LHC. These coefficients are now understood to reflect the hydrodynamic response to the collision geometry in the initial state. This talk present recent ATLAS measurements on vn coefficients, correlations between event planes of different orders and event-by-event distributions of $v_n$ in Pb+Pb collisions at $\\sqrt{s_{NN}}=2.76$~TeV. These measurements have provided new constraints on the initial geometry fluctuation, and have revealed strong non-linear effects in the hydrodynamic response of the produced medium to the initial geometry.


Wednesday, Sept 18, 2013, 1:00 PM (Beijing time) seminar

18th HENPIC: Chiral kinetic theory and Berry phase

Speaker: Shi Pu (浦实),National Taiwan University

Date:Wednesday, Sept 18, 2013, 1:00 PM (Beijing time)



We derive a relativistic chiral kinetic equation with manifest Lorentz
covariance from Wigner functions of spin-1/2 massless fermions in a
constant background electromagnetic field. It contains vorticity terms
and a 4-dimensional Euclidean Berry monopole which gives axial
anomaly. By integrating out the zero-th component of the 4-momentum p,
we reproduce the previous 3-dimensional results derived from the
Hamiltonian approach, together with the newly derived vorticity terms.
This provides a unified interpretation of the chiral magnetic and
vortical effects, chiral anomaly, Berry curvature, and the Berry
monopole in the framework of Wigner functions.


Friday, Aug 16, 2013, 12:00 PM (Beijing Time) seminar

17th HENPIC: The exploration of hot and cold nuclear matter

Speaker: Berndt Muller,(Duke University)

Date:Friday, Aug 16, 2013, 12:00 PM (Beijing Time)



When nuclear matter is heated beyond 2 trillion degrees, it becomes a strongly coupled plasma of quarks and gluons. Experiments using highly energetic collisions between heavy nuclei have revealed that this new state of matter is a nearly ideal, highly opaque liquid. A description based on string theory and black holes in five dimensions has made the quark-gluon plasma an archetypical strongly coupled quantum system. In my lecture I will discuss how heavy ion experiments and theory will address open questions about the structure and theory of the quark-gluon plasma. I will also discuss the role of proton-proton, proton- (or deuteron-) nucleus, and electron-nucleus collisions in the quest of elucidating the parton structure of nucleosn and nuclei. seminar

16th HENPIC: Recent Results on Strangeness Production at STAR

Speaker: Xiang-lei Zhu (朱相雷),Tsinghua University


Download:Thursday, July 25, 2013, 1pm (Beijing time)


Strange hadron productions are sensitive probes to the dynamics of the hot and dense matter created in heavy-ion collisions. In this talk, we will present the recent STAR measurements on the production of various strange hadrons (K0s, phi, Lambda, Xi and Omega) in $\\sqrt{S_{NN}}$ = 7.7 - 39 GeV Au+Au collisions in the STAR beam energy scan program. We will investigate the collision energy dependence of the strangeness enhancement, nuclear modification factors, baryon to meson ratios, as well as the phi meson elliptic flow. We will present the extracted chemical and kinetic freeze-out parameters with the thermal and blast wave models as a function of energy and centrality. The physics implications of these measurements on the collision dynamics will be discussed.


Thursday, June 20, 2013, 12:00 PM (Beijing Time) seminar

15th HENPIC: Di-hadron correlations from CMS

Speaker: Shengquan Tuo (拓圣权),Vanderbilt University

Date:Thursday, June 20, 2013, 12:00 PM (Beijing Time)



Di-hadron correlations are very important for the understanding of heavy ion collisions, especially the initial conditions and the properties of the Quark-Gluon-Plasma (QGP). Measurements of charged di-hadron angular correlations are presented in proton-proton (pp), proton-Lead (pPb) and Lead-Lead (PbPb) collisions, over a broad range of pseudorapidity and azimuthal angle, using the CMS detector at the LHC. A Fourier analysis of the long-range correlations are studied and discussed in the context of CMS measurements of higher order flow coefficients in pPb and PbPb. Direct comparisons of these measurements in pp, pPb and PbPb as a function of transverse momentum and charged particle multiplicity will be presented.


Thursday, May 9, 2013, 12:00 PM (Beijing Time) seminar

14th HENPIC: AMPT model studies of heavy-ion collisions at RHIC and LHC

Speaker: Jun Xu (徐骏),SINAP

Date:Thursday, May 9, 2013, 12:00 PM (Beijing Time)



I will discuss our recent studies at RHIC and LHC based on a multiphase transport (AMPT) model, mainly including initial fluctuations and di-hadron correlations, the specific shear viscosity of quark-gluon plasma (QGP), and the elliptic flow (v2) splitting of particles and antiparticles in the beam-energy scan program. We found that the triangular flow and high-order flows, which originate from initial density fluctuations, contribute significantly to the away-side double-peak structure of di- hadron correlations. In addition, both short-range and long-range di-hadron correlations are studied at LHC, and they are qualitatively consistent with experimental results from the CMS Collaboration. Furthermore, with the same parameter set for the Lund string fragmentation function and the parton scattering cross section at both RHIC and LHC, the charged particle multiplicities and the harmonic flows can be reasonably reproduced compared with experimental data. The specific shear viscosities of QGP extracted from AMPT model studies at both RHIC and LHC are compared with results from other approaches. Including the mean-field potentials in the hadronic phase, we are able to explain qualitatively the v2 splitting of particles and antiparticles in the beam-energy scan program, while including both the partonic and hadronic potentials may help to reproduce quantitatively the experimental results in the near future.


Tuesday, April 16, 2013, 12:30 PM (Beijing Time) seminar

13th HENPIC: Basic Light-front Quantization Approach to Quantum Field Theory

Speaker: Xingbo Zhao (赵行波) ,Iowa State University

Date:Tuesday, April 16, 2013, 12:30 PM (Beijing Time)



We introduce a nonperturbative, first principles approach for solving quantum field theory. Based on light-front Hamiltonian formalism, this method provides direct access to the wavefunction of bound states as well as scattering states in a covariant framework. As an initial application we apply it to QED and specifically study the structure of electron. I will present the numerical results for the electron anomalous magnetic moment as well as various generalized parton distribution functions (GPDs) for an electron. As a method in real time, it can bestraightforwardly extended to the time-dependent regime, which provides an ideal solution for time-evolution processes such as scattering, in particular, in the presence of strong background fields. As a first application we apply it to QED in a strong background laser field, and specifically study the process of nonlinear Compton scattering in which an electron is excited by the background and emits a photon. Finally, I will discuss options for future applications to non-perturbative time-dependent processes such as strong interaction hadronization processes.


Thursday, March 21, 2013, 12:00 PM (Beijing Time) seminar

12th HENPIC: Explore the QCD phase structre with elliptic flow in relativistic heavy ion collisions at STAR

Speaker: Shusu Shi (施梳苏),CCNU

Date:Thursday, March 21, 2013, 12:00 PM (Beijing Time)



The exploration of the QCD phase diagram in the region of a possible phase transition between the Quark Gluon Plasma (QGP) and the hadron gas phase is one of the main goals of the RHIC. One of the most important observables from high-energy nuclear collisions to study the early evolution of the expanding system is the elliptic flow $v_{2}$. At the top RHIC energy, \\sqrt{s_{NN}} = 200 GeV, the number-of-constituent quark (NCQ) scaling of v_{2}(p_{T}) is interpreted as a signature of deconfinement and the formation of the QGP phase. A disappearance of the NCQ scaling is expected for a pure hadronic system at low beam energies. Hence it is a necessary signature to identify the phase transition.

We will present the v_2 measurement at midrapidity from Au+Au collisions at \\sqrt{s_{NN}}=7.7-200 GeV for inclusive charged hadrons and identified hadrons (\\pi^{\\pm}, K^{\\pm}, K_{S}^{0}, p, \\bar{p}, \\phi,
\\Lambda, \\bar{\\Lambda}, \\Xi^{-}, \\bar{\\Xi}^{+}, \\Omega^{-}, \\bar{\\Omega}^{+}). The identified hadron v_{2} are used to discuss the NCQ scaling for different beam energies. The beam energy and centrality dependence of charged hadron v_2 are presented with comparison to hydrodynamic simulations.


Thursday, Feb 28, 2013, 12:00 PM (Beijing Time) seminar

11th HENPIC: Cold and Hot Nuclear Matter Effects on Jpsi production at LHC

Speaker: Kai Zhou (周凯),Tsinghua University

Date:Thursday, Feb 28, 2013, 12:00 PM (Beijing Time)



We investigated the cold and hot nuclear matter effects on J/psi productions at LHC in a detailed transport approach. The hot nuclear effect is included in the collisions terms of the J/psi transport equation, and the cold nuclear effect is reflected in the initial condition of the transport. While the cold nuclear effect reduces the J/psi yield significantly, it changes the J/psi transverse momentum distribution slightly. We also proposed a nuclear modification factor for transverse momentum RAA which can be a very good sensitive tool for studying the created hot/dense medium\'s properties.


Thursday, Jan 10, 2013, 12:00 PM (Beijing Time) seminar

10th HENPIC: Di-electron production in heavy-ion collisions

Speaker: Yifei Zhang (张一飞),USTC

Date:Thursday, Jan 10, 2013, 12:00 PM (Beijing Time)



The electromagnetic probes such as photons and dileptons do not participate in the strong interactions during the space-time evolution of the created system in the heavy-ion collisions. Thus they contain the undistorted information of the hot-dense medium and hence are used as signatures for probing the medium properties. Theoretical predictions believe that the dileptons from thermal emission are different from those produced in hadronic freeze-out, thus studying the behavior of dileptons reaction with medium versus different colliding energies is consider as an ideal tool to trace the possible partonic-hadronic transition in the QCD phase diagram. In experiment, it is very difficult to measure such a signal of the thermal dileptons due to dominant sources from hadronic process. Thus it is crucial to understanding how the background sources behave in a colliding beam energy scan (BES).

In this talk I will present recent experimental measurements of di-electron production in heavy-ion collisions in RHIC energies. Model calculations of di-electrons from vector meson decays, heavy quark dynamic correlations and partonic themal emission will be discussed and compared with data. The dielectron mass spectra, effective temperature, and possible medium modifications versus colliding energies will also be discussed.


Thursday, Dec 13, 2012, 12:00 PM (Beijing Time) seminar

9th HENPIC: The electromagnetic field in heavy-ion collisions

Speaker: Xuguang Huang (黄旭光),Indiana University

Date:Thursday, Dec 13, 2012, 12:00 PM (Beijing Time)



Heavy-ion collisions could generate extremely strong electromagnetic fields. Although after averaging over a large number of events only the magnetic field perpendicular to the reaction plane is sizable in Au+Au or Pb+Pb collisions, the event-by-event fluctuations can cause strong magnetic and electric fields both parallel and perpendicular to the reaction plane. Furthermore, we study the azimuthal fluctuation of these fields and their correlations with the also fluctuating matter geometry (characterized by the participant plane harmonics). We then discuss the possible implications on the hadronic observables.


Thursday, Nov 8, 2012, 12:00 PM (Beijing Time) seminar

8th HENPIC: Energy dependence of hypertriton production and its lifetime measurement

Speaker: Yuhui Zhu (朱瑜卉),SINAP

Date:Thursday, Nov 8, 2012, 12:00 PM (Beijing Time)



The hyperon-nucleon(Y-N) interaction is of great physical interest because it introduces a new quantum number strangeness in nuclear matter. It is predicted to be the decisive interaction in some high-density matter systems, such as neutron stars . RHIC, the Relativistic
Heavy Ion Collider, provides an ideal laboratory to study Y-N interaction because hyperons and nucleons are abundantly produced at high energy nucleus-nucleus collisions. The lifetime and decay modes of the hypertriton, the lightest hypernucleus, which consists of a proton, a neutron and the lightest hyperon Lambda, provide valuable insights into the Y-N interaction.

The strangeness population factor S3, defined as $\\frac{{^3_\\Lambda}H/^{3}He}{\\Lambda/p}$, is a good representation of the local correlation between baryon number and strangeness.
It is predicted that S3 has a different behavior in QGP and pure hadron gas thus can be used as a tool to distinguish Quark-Gluon Plasma (QGP) from a pure hadronic phase.

The RHIC beam energy scan program in 2010-2011 allowed STAR to
collecte data from Au+Au collisions over a broad range of energies. This provides an opportunity to study the beam energy dependence of S3. Also due to the increased statistics, an improved result of lifetime measurement of hypertriton can be obtained.

In this talk, the hypertriton analysis results for Au+Au collisions
at $\\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39 and 200 GeV will be presented. The combined $^{3}_{\\Lambda}H$ plus $^{3}_{\\bar{\\Lambda}}\\bar{H}$ raw yield is about 600 and its significance can reach 9.6$\\sigma$. The beam energy dependence of S3 will also be discussed and our lifetime measurement will be presented.


Wednesday, Oct 10, 2012, 11:00 PM (Beijing Time) seminar

7th HENPIC: Exploring the QCD phase diagram with fluctuations of conserved charges

Speaker: Frithjof Karsch,Brookhaven National Laboratory-RBRC and Bielefeld University

Date:Wednesday, Oct 10, 2012, 11:00 PM (Beijing Time)



One of the central goals in current theoretical and experimental
studies of the thermodynamics of strongly interacting matter is to map
out the structure of the QCD phase diagram and collect evidence for or
against the existence of a critical point, i.e. a second order phase
transition point, in the QCD phase diagram. The study of fluctuations
of conserved charges, e.g. net baryon number, strangeness and electric
charge, play a central role in these studies. In particular higher
order cumulants of net charge fluctuations are expected to provide
sensitive information on critical behavior in QCD that may allow to
locate a critical point at non-zero temperature and baryon chemical
potential. We will discuss basic properties of cumulants on net charge
fluctuations, describe their sensitivity to critical behavior in the
chiral limit of QCD as well as in the vicinity of the elusive critical
point. We discuss how higher order cumulants can be used to determine
the location of a critical point. Furthermore, we compare results on
cumulants of net baryon number and electric charge fluctuations
obtained in lattice QCD calculations with recent experimental results
obtained in the beam energy scan at the Relativistic Heavy Ion


Thursday, Sept 27, 2012, 12:00 PM (Beijing Time) seminar

6th HENPIC: Collision Energy Dependence of Viscous Hydrodynamic Flow

Speaker: Chun SHEN (沈纯),Ohio State University

Date:Thursday, Sept 27, 2012, 12:00 PM (Beijing Time)



We present a systematic study on the evolution of hadron spectra and
their azimuthal anisotropy from the lowest collision energy studied at
the Relativistic Heavy Ion Collider (RHIC), &#8730;s = 7.7A GeV, to the
highest energy reachable at the Large Hadron Collider (LHC), &#8730;s =
5500A GeV [1]. As the collision energy increases, the resulting
increases of the initial temperature, and fireball lifetime, as well
as the evolution of the centrality dependence of final charged
particle multiplicity are quantitatively studied and compared between
the two most popular initial state models, the Monte Carlo Glauber and
Monte-Carlo Kharzeev-Levin-Nardi (MC-KLN) models. For Glauber model
initial conditions with a small specific shear viscosity eta/s = 0.08,
the differential charged hadron elliptic flow v_2^{ch}(pT, &#8730;s) is
found to exhibit a very broad maximum as a function of &#8730;s around top
RHIC energy, rendering it almost independent of collision energy for
39 < &#8730;s < 2760A GeV. Compared to ideal fluid dynamical simulations
[2], this \"saturation\" of elliptic flow is shifted to higher collision
energies by shear viscous effects. For color-glass motivated MC-KLN
initial conditions, which require a larger shear viscosity eta/s = 0.2
to reproduce the measured elliptic flow, a similar \"saturation\" is not
observed up to LHC energies, except for very low pT. We emphasize that
this \"saturation\" of the elliptic flow is not associated with the QCD
phase transition, but arises from the interplay between radial and
elliptic flow which shifts with &#8730;s depending on the fluid\'s viscosity
and leads to a subtle cancellation between increasing contributions
from light and decreasing contributions from heavy particles to v_2 in
the &#8730;s range where v_2^{ch}(pT, &#8730;s) at fixed pT is maximal. By
generalizing the definition of spatial eccentricity ecc_x to
isothermal hyper-surfaces, we calculate ecc_x on the kinetic
freeze-out surface at different collision energies. Up to top RHIC
energy, &#8730;s=200A GeV, the fireball is still out-of-plane deformed at
freeze out, while at LHC energy the final spatial eccentricity is
predicted to approach zero.


Thursday, September 13, 2012, 12:00 PM (Beijing Ti seminar

5th HENPIC:Chiral symmetry breaking and linear confinement in a dynamical holography QCD model

Speaker: Danning Li(李丹凝),IHEP (Beijing)

Date:Thursday, September 13, 2012, 12:00 PM (Beijing Ti



A brief introduction will be given first on holography method, which
is believed to be valid for the study of a gauge theory when the gauge
coupling becomes large and the quasiparticle picture becomes
inappropriate for the physics. A bottom up holographic QCD model will
be discussed, which can incoorperate the linear behavior of light
mesons\' spectra and the linear potential of quark-antiquark
interaction, and incoorperate the chiral condensate and dimension-2
gluon condensate dynamically. The prediction of the model fits the
experimental data quite well and the negative dilaton profile can be
excluded safely.


Thursday, August 9, 2012, 12:00 PM (Beijing Time) seminar

4th HENPIC:Charge azimuthal correlations at RHIC and LHC

Speaker: Guo-Liang Ma (马国亮) ,SINAP

Date:Thursday, August 9, 2012, 12:00 PM (Beijing Time)



With a multi-phase transport model including initial charge separation
and string melting, the charge azimuthal correlations for Au+Au
collisions at center of mass energies 200, 39, 11.5, 7.7 GeV and Pb+Pb
collisions at 2.76 TeV are investigated. Initial charge separations of
about 10 % for 200 GeV, 5 % for 39 GeV, 0 % for 11.5 GeV appear to be
necessary. This is consistent with decreasing Chiral Magnetic Effect
as the incident energy decreases at RHIC. A reduced partonic
interaction cross section is also needed for 11.5 GeV, indicating
possible significant contributions from the hadronic stage. For Pb+Pb
collisions at 2.76 TeV, 10% initial charge separation can produce
similar behaviors as those at the top RHIC energy. We will also
discuss how the same-charge correlation of <cos(1-2)> changes sign
from negative at RHIC to positive at the LHC.


Thursday, July 12, 2012, 12:00 PM (Beijing Time) seminar

3rd HENPIC:Relativistic anomalous fluid dynamics in even and odd dimensions

Speaker: Shi Pu,(浦实) (USTC)

Date:Thursday, July 12, 2012, 12:00 PM (Beijing Time)



Relativistic anomalous fluid dynamics are investigated via the
classical and quantum kinetic theories. In the even dimension (3+1)
with an external field, two new terms correspondent to the quantum
triangle anomaly are induced. These new terms are related to the
Chiral Magnetic Effect (CME) and Chiral Vortical Effect (CVE) in the
heavy ion collisions. In odd dimension (2+1) with an external field,
the parity violated charge current is found. This parity violated
effect is related to the Hall effect in condense matter which is found
in the 2+1 dimensional material, i.e. graphene.


Thursday, June 21, 2012, 12:00 PM (Beijing Time) seminar

2nd HENPIC:Forward di-hadron correlation studies at STAR

Speaker: Xuan Li,(Shandong University)

Date:Thursday, June 21, 2012, 12:00 PM (Beijing Time)



Quarks and Gluons, known generically as partons, are the current known
fundamental constituents of the proton. The gluon density increases as
the longitudinal momentum faction (x) of the gluon decreases, but it
cannot increase without bound and saturation is expected at a certain
low x value. The dynamics of quarks and gluons at low x is an open
question to physicists. Studies of correlations between pairs of
particles emitted in the forward direction at RHIC aim to probe the
gluons in protons and in denser nuclear targets like gold. By studying
the rapidity dependence of the correlations, we aim to address the
question of how sharp the transition is in going from a dilute parton
gas to the dense parton state. Results of di-hadron correlations in
p+p collisions and d+Au collision investigating the parton
distributions will be introduced in this talk.


Thursday, June 7, 2012, 12:00 PM (Beijing Time) seminar

1st HENPIC:Effect of longitudinal fluctuation in (3+1)D hydrodynamics

Speaker: Longgang Pang(庞龙刚),LBNL & USTC

Date:Thursday, June 7, 2012, 12:00 PM (Beijing Time)



Hadron spectra and elliptic flow in high-energy heavy-ion collisions
are studied within a (3+1)D ideal hydrodynamic model with fluctuating
initial conditions given by the AMPT Monte Carlo model. Results from
event-by-event simulations are compared with experimental data at both
RHIC and LHC energies. Fluctuations in the initial energy density come
from not only the number of coherent soft interactions of overlapping
nucleons but also incoherent semi-hard parton scatterings in each
binary nucleon collision. Mini-jets from semi-hard parton scatterings
are assumed to be locally thermalized through a Gaussian smearing and
give rise to non-vanishing initial local flow velocities. Fluctuations
in the initial flow velocities lead to harder transverse momentum
spectra of final hadrons due to non-vanishing initial radial flow
velocities. Initial fluctuations in rapidity distributions lead to
expanding hot spots in the longitudinal direction and are shown to
cause a sizable reduction of elliptic flow.



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