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HENPIC seminars in 2015.



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/undefinedamp;#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 Dundefinedamp;#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.



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