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HENPIC seminars in 2016.

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:http://pan.baidu.com/s/1geognuz (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 undefinedamp;#954;undefinedamp;#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 undefinedamp;#954;undefinedamp;#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. undefinedamp; 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=Eundefinedamp;#8901;B at zero temperature. We will show that the presence of I_2 can induce neutral pion (undefinedamp;#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 undefinedamp;#960;_0 condensate I_2.

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