Search

The search for the chiral magnetic effect (CME) has been a subject of great interest in the field of high-energy heavy-ion collision physics, and various observables have been proposed to probe the CME. Experimental observables are often contaminated with background contributions arising from collective motions (specifically elliptic flow) of the collision system. We present a method study of event-shape engineering (ESE) that projects the CME-sensitive $\gamma_{112}$ correlator and its variations ($\gamma_{132}$ and $\gamma_{123}$) to a class of events with minimal flow. We discuss the realization of the zero-flow mode, the sensitivity on the CME signal, and the corresponding statistical significance for Au+Au, Ru+Ru, and Zr+Zr collisions at $\sqrt{s_{\rm NN}} = 200$ GeV with a multiphase transport (AMPT) model, as well as a new event generator, Event-By-Event Anomalous-Viscous Fluid Dynamics (EBE-AVFD)., Comment: 12 pages, 15 figures

The azimuthal correlations between local flow planes at different (pseudo)rapidities ($\eta$) may reveal important details of the initial nuclear matter density distributions in heavy-ion collisions. Extensive experimental measurements of a factorization ratio ($r_2$) and its derivative ($F_2$) have shown evidence of the longitudinal flow-plane decorrelation. However, nonflow effects also affect this observable and prevent a quantitative understanding of the phenomenon. In this paper, to distinguish decorrelation and nonflow effects, we propose a new cumulant observable, $T_2$, which largely suppresses nonflow. The technique sensitivity to different initial-state scenarios and nonflow effects are tested with a simple Monte Carlo model, and in the end, the method is applied to events simulated by a multiphase transport model (AMPT) for Au+Au collisions at $\sqrt{s_{\rm NN}} =200$ GeV. We also emphasize that a distinct decorrelation signal requires not only the right sign of an observable, but also its proper dependence on the $\eta$-window of the reference flow plane, to be consistent with the pertinent decorrelation picture., Comment: 12 pages, 15 figures

We develop a theoretical framework to study the feed-down effect of higher-lying strange baryons on the spin polarization of the Λ hyperon. In this framework, we consider two-body decays through strong, electromagnetic, and weak processes and derive general formulas for the angular distribution and spin polarization of the daughter particle by adopting the helicity formalism. Using the realistic experimental data as input, we explore the feed-down contribution to the global and the local Λ polarizations and find that such a contribution suppresses the primordial Λ polarization, which is not strong enough to resolve the discrepancy between the current theoretical and the experimental results on the azimuthal-angle dependence of Λ polarization. Our paper may also be useful for the measurement of spin polarization of baryons heavier than Λ (e.g., Ξ−) in future experiments.

For over a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) has been to study the properties of QCD matter under extreme conditions—high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb, and U+U collisions at energies ranging fromsNN=7.7 GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy-flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nucleus-nucleus collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy-flavor hadrons and to outline the scientific opportunities in this sector due to future detector upgrade. We will mainly discuss the elliptic flow of open charmed meson (D-meson),J/ψ, and leptons from heavy-flavor decay at RHIC and LHC energy.

The workshop on Chirality, Vorticity, and Magnetic Field in Heavy Ion Collisions (Chirality Workshop) was held 8–12 April 2019, hosted by Pengfei Zhuang at Tsinghua University, Beijing, China. The ...

We study experimental background reconstruction methods for the measurement of $D-\overline{D}$ correlation using a PYTHIA simulation. Like-sign and side-band background methods that are widely used in the experimental measurements of single $D$-meson production yields were deployed for the correlation background study. It is found that the like-sign method which well describes the combinatorial background of single $D^{0}$ meson yields fails to reproduce the correlated background in the $D^{0}-\overline{D^{0}}$ correlation measurement, while the side-band background method yields a good description of the background for both the single $D^0$ yields and of the correlated background of the $D^{0}-\overline{D^{0}}$ correlation measurement., 13 pages, 7 figures

The STAR Collaboration will complete the Heavy Flavor Tracker (HFT) and the Muon Telescope Detector (MTD) upgrades by 2014. STAR has also embarked on an upgrade plan to extend the capabilities for measuring jets, electron/photon and leading particles in the forward rapidity region in the coming decade. Planned detector upgrades include tracking detectors for charged particles, electro-magnetic and hadronic calorimeters and particle identification detector in the forward direction. We will present physics motivations, status of detector R&D and design considerations for the forward measurements focusing on p + p/p + A and polarized p + p collisions.

Author(s): Nasim, M; Esha, R; Huang, HZ | Abstract: A systematic study of the pseudorapidity dependence of elliptic flow parameter using transport models (e.g., a multiphase transport model, AMPT, and ultrarelativistic quantum molecular dynamics, UrQMD) has been presented. We have observed that while at mid-pseudorapidity the elliptic flow measured using the event-plane method differs significantly from that measured by actual reaction plane method, both the event-plane and reaction-plane methods give the same elliptic flow for far forward and backward pseudorapidity. This indicates that the magnitude of measured v2 around midrapidity strongly depends on the analysis method. Therefore, one should use the same procedure (as used in data analysis) in model calculations while comparing model results and experimental data. We find the shape of v2(η) measured by the PHOBOS experiment is not reproduced by using actual v2 (i.e., measured with respect to the reaction plane) from AMPT and UrQMD models. The shape and magnitude of measured v2(η) can be explained by the AMPT model with string-melting mode only if one uses the same procedure as used in data analysis. Magnitude of elliptic flow can be reproduced for all pseudorapidity range by taking the parton-parton interaction cross section to be 3 mb at sNN=62.4 and 200 GeV. This implies that the partonic interactions are necessary to reproduce data at sNN=62.4 and 200 GeV and the strength of partonic interactions at far forward and backward rapidity is as strong as at midrapidity. Both UrQMD and AMPT with default mode fail to explain the data.

We review experimental results on baryon production at mid-rapidity in nucleus-nucleus collisions at RHIC. Outstanding physics issues include the mechanism for baryon-anti-baryon production from thermally equilibrated partons, the dynamics of baryon number transport and the evolution dynamics of baryons during hadronic expansion before the final freeze-out. We highlight recent measurements on the production of protons, lambdas and their anti-particles in terms of these physics issues. We propose a physical mechanism of topological baryon formation through gluon junction hadronization and future measurements, which can test this hypothesis experimentally.

A study of elliptic flow of open charm mesons, $D^0$ and $D_S ^\pm$ using quark coalescence as a mechanism of hadronization of heavy quarks implemented in conjunction with A Multi Phase Transport (AMPT) model has been presented. We have studied the transverse momentum dependence of the elliptic flow parameter at mid-rapidity ($|y|$ $, Comment: 8 pages, 8 figures, Accepted in Journal of Physics G

We will review recent results on quantitative description of global properties of bulk partonic matter at RHIC. These results include strangeness phase space factor of the partonic matter, azimuthal angular anisotropy $v_2$, and transverse momentum $p_T$ distributions of effective partons at the hadronization of bulk partonic matter. We present empirical constraints on parton energy loss in the high $p_T$ region ($>$ 5 GeV/c). A flat $R_{AA}$ as a function of $p_T$ at mid-rapidity implies a constant fraction of the parton energy loss ($\Delta p_T/p_T$) and the fraction reaches 25% for neutral $\pi$, charged hadrons and non-photonic electrons of heavy quark decays from central Au+Au collisions at $\sqrt{s_{NN}}$ 200 GeV. Collision centrality dependence of $\Delta p_T/p_T$ from Au+Au and Cu+Cu collisions indicates that the fraction is approximately proportional to particle rapidity density $dn/dy$ divided by the initial transverse overlapping area of the colliding nuclei. Implications on dynamics of parton energy loss will be discussed., Comment: To Appear in SQM2008 Conference Proceedings

This report summarizes the student and post-doc support budget for quark matter 2004 conference, held at Oakland in January 2004.

We present results on pentaquark searches from nuclear collisions at RHIC with the STAR detector system. An intriguing peak has been observed in the invariant mass distribution of $pK^{+}+\overline{p}K^{-}$ from 18.6 Million d+Au collision events at $\sqrt{s_{_{NN}}} = 200$~GeV. The peak centers at a mass $1528 \pm 2 \pm 5$~MeV/c$^{2}$ and the FWHM $\sim15$ MeV/c$^{2}$ limited by detector responses. The statistical significance of the peak is $4.2\sigma$. Such a state if confirmed is manifestly exotic and implies a family of isospin one states. A weak signal of less statistical significance ($\sim3\sigma$) has been observed in 5.6M Au+Au collision events at 62.4 GeV. Searches in 10.7M Au+Au collision events at 200 GeV yield no significant signal. The Au+Au results neither confirm nor rule out the d+Au observation as a possible state., Comment: To appear in proceedings of International Conference on QCD and Hadron Physics at Beijing, June 2005

The Quark Matter 2006 conference was held on 14–20 November 2006 at the Shanghai Science Hall of the Shanghai Association of Sciences and Technology in Shanghai, China. It was the 19th International Conference on Ultra-Relativistic Nucleus–Nucleus Collisions. The conference was organized jointly by SINAP (Shanghai Institute of Applied Physics, Chinese Academy of Sciences (CAS)) and CCNU (Central China Normal University, Wuhan). Over 600 scientists from 32 countries in five continents attended the conference. This is the first time that China has hosted such a premier conference in the field of relativistic heavy-ion collisions, an important event for the Chinese high energy nuclear physics community. About one half of the conference participants are junior scientists—a clear indication of the vigor and momentum for this field, in search of the fundamental nature of the nuclear matter at extreme conditions. Professor T D Lee, honorary chair of the conference and one of the founders of the quark matter research, delivered an opening address with his profound and philosophical remarks on the recent discovery of the nature of strongly-interacting quark-gluon-plasma (sQGP). Professor Hongjie Xu, director of SINAP, gave a welcome address to all participants on behalf of the two hosting institutions. Dr Peiwen Ji, deputy director of the Mathematics and Physics Division of the Natural Science Foundation of China (NSFC), also addressed the conference participants and congratulated them on the opening of the conference. Professor Mianheng Jiang, vice president of the Chinese Academy of Sciences (CAS), gave a concise introduction about the CAS as the premier research institution in China. He highlighted continued efforts at CAS to foster international collaborations between China and other nations. The Quark Matter 2006 conference is an example of such a successful collaboration between high energy nuclear physicists in China and other nations all over the world. The scientific program of the conference began with an overview of high energy nuclear physics in China by Professor Wenqing Shen, vice president of the National Natural Science Foundation of China. Professor Shen highlighted many contributions made by the Chinese scientists in both theory and experiment. Dr Nick Samios, former director of Brookhaven National Laboratory (BNL), gave a vivid account of the early years of RHIC and recent accomplishments. Highlights of the conference include new results from RHIC at BNL and SPS (Super Proton Synchrotron) at CERN (European Organization for Nuclear Research). Many experimental results reported at the conference support the notion that the quark-gluon matter at RHIC behaves like a perfect liquid with minimum viscosity to entropy ratio. There were 15 plenary sessions which covered 54 plenary talks, 12 parallel sessions and 1 poster session. A total of 320 abstracts were submitted to the conference out of which 124 were selected for oral presentation and the rest were assigned to the poster session. Talks and posters in the conference covered a broad range of experimental and theoretical progress in ultra-relativistic heavy-ion collisions, which includes new evidence of sQGP, jet quenching and heavy quark energy loss, heavy-ion collision phenomenology, quantum field theory at finite temperature and/or density, and relevant areas of astrophysics and plasma physics. The Quark Matter 2006 conference coincided with the 80th birthday of Professor T D Lee. A special reception was held in the banquet hall of the Shanghai Grand Theatre to celebrate Professor Lee's birthday and to honor his great contributions to physics, in particular, to the development of high energy nuclear physics research in China. We would like to thank the members of the International Advisory Committee for providing valuable advice on a variety of matters, from the general structure of the conference to the selection of the plenary speakers and selection of abstracts for oral presentations. Professors T Hemmick, H Satz, D T Son and N Xu gave excellent pedagogical lectures in the pre-conference student symposium and their efforts were greatly appreciated. The Shanghai Association of Science and Technology (SAST) and the staff of the Shanghai science hall provided valuable assistance and services during the conference. The conference would not have run so smoothly without their professional dedication. We also thank Professor Wenqing Shen, Chairman of the SAST, for his many valuable suggestions to the conference organizers and for providing close cooperation with SAST staff. We thank members of the Local Organizing Committee for many useful suggestions and help. We would like to express our special appreciation for the tireless efforts by many local staff who worked very hard to make this conference a success. Dr Xiang-Zhou Cai, Mrs Wei Zhou and Mrs Yang Shen undertook many duties to coordinate and organize the local services. Dr Kun Wang took responsibility of the conference web page. Dr Wei Guo, Dr Wendong Tian, Mr Chunwang Ma and Mrs Wanyan Qian organized student volunteers for the conference. Without their help and dedication this conference could not have been such a success. The Quark Matter 2006 conference has received substantial financial support from many organizations, including the Chinese Academy of Sciences (CAS), the National Natural Science Foundation of China (NSFC), the Ministry of Education of China (MOE), Shanghai Science and Technology Committee (SSTC), Chinese Nuclear Physics Society (CNPS), Shanghai Institute of Applied Physics (SINAP), Central China Normal University (CCNU), China Center of Advanced Science and Technology (CCAST), Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL), European Laboratory for Particle Physics (CERN), and Journal of Physics G: Nuclear and Particle Physics (IOP Publishing).