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Open Access Publications from the University of California

Strangeness Production and Strange V0 & Charged Hadron Correlation in Heavy-Ion Collisions

  • Author(s): Zhao, Feng
  • Advisor(s): Huang, Huan Z.
  • et al.
Abstract

In relativistic heavy-ion collisions, experimental evidence indicates that a new form of matter with de-confined quarks and gluons named the Quark-Gluon Plasma(QGP) has been created. The Relativistic Heavy Ion Collider (RHIC) provides a unique opportunity to study the QGP matter.

Strange hadron production is believed to be sensitive to parton dynamics in heavy-ion collisions. In particular, the strange quark production rate and its subsequent evolution in the dense partonic medium depend on the beam energy and the net baryon density. The productions of KS0, &Lambda, &Xi, &Omega at mid-rapidity from Au+Au collisions at the beam energies of 7.7, 11.5, 19.6, 27, and 39GeV from the RHIC Beam Energy Scan Program are measured. We investigate the strangeness enhancement and ratios of anti-baryon to baryon yields as a function of beam energy at RHIC. Nuclear modification factors and ratios of baryon to meson yields are also studied. Implications on collision dynamics due to the increase in the baryon chemical potential at low beam energy and constraints on chemical freeze-out parameters will also be discussed in this thesis.

Parity-odd domains are theorized to form inside the QGP and to cause electric charge separation with respect to the reaction plane in the relativistic heavy-ion collisions via the Chiral Magnetic Effect (CME). Such charge separation has been studied at RHIC and LHC via the difference in two particle correlation between the opposite charge and same charge hadrons. The &Lambda and KS0 particles are charge-neutral, and are supposed to bear no charge separation effects due to CME. We study the correlation between the neutral particle and charged hadron to investigate background for charged hadron correlation. In addition, the large angular momentum in heavy-ion collisions is predicted to lead to the Chiral Vortical Effect (CVE) which induces a baryon number separation, in analogy with the electric

charge separation caused by CME. We carried out a study of &Lambda-p correlations to search for the CVE. We present measurements of correlations for &Lambda-h±,

KS0-h±, KS0-p, and &Lambda-p in Au+Au collisions at 39GeV and 200GeV, to study the electric charge and baryon number separations across the reaction plane.

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