arXiv subjects

Nu Xu

Publications and source records attributed to Nu Xu.

64 records · Page 4Linked to original sources

arXiv2004

Centrality Dependence of Chemical Freeze-out in Au+Au Collisions at RHIC

We will report centrality dependence of chemical freeze-out temperature ($T_{ch}$), light quark chemical potential ($μ_{q}$), strange quark chemical potential ($μ_{s}$), and strangeness saturation factor ($γ_{s}$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 130 and 200 GeV. A systematic study for combination of ratios for chemical freeze-out fit is studied and we have found small ombination dependences. The results show $γ_{s}$ increasing with centrality but the other parameters have less sensitivity to the centralities.

nucl-th↗

arXiv2004

Phi-Meson Production at RHIC, Strong Color Fields and Intrinsic Transverse Momenta

We investigate the effects of strong color fields and of the associated enhanced intrinsic transverse momenta on the phi-meson production in ultrarelativistic heavy ion collisions at RHIC. The observed consequences include a change of the spectral slopes, varying particle ratios, and also modified mean transverse momenta. In particular, the composition of the production processes of phi mesons, that is, direct production vs. coalescence-like production, depends strongly on the strength of the color fields and intrinsic transverse momenta and thus represents a sensitive probe for their measurement.

nucl-th↗

arXiv2002

Effects of Strong Color Fields on Baryon Dynamics

We calculate the antibaryon-to-baryon ratios, anti-p/p, anti-Lambda/Lambda, anti-Xi/Xi, and anti-Omega/Omega for Au+Au collisions at RHIC (sqrt{s}_{NN}=200 GeV). The effects of strong color fields associated with an enhanced strangeness and diquark production probability and with an effective decrease of formation times are investigated. Antibaryon-to-baryon ratios increase with the color field strength. The ratios also increase with the strangeness content |S|. The netbaryon number at midrapidity considerably increases with the color field strength while the netproton number remains roughly the same. This shows that the enhanced baryon transport involves a conversion into the hyperon sector (hyperonization) which can be observed in the (Lambda - anti-Lambda)/(p - anti-p) ratio.

nucl-th↗

arXiv2002

Transverse Dynamics at RHIC

Studies of , transverse momentum spectra and anisotropy flow from nuclear collisions at RHIC indicate early thermalization and strong collective expansion. We propose a systematic study of the anisotropy parameter $v_2$ and the transverse momentum distributions of $ϕ, Ω, D^0, Λ_C$ and $J / ψ$ in order to extract information on partonic collective flow.

nucl-ex↗

arXiv2002

Phi meson production at RHIC

The production of phi mesons in Au+Au collisions at RHIC and their propagation in a hot and dense nuclear medium is studied within the microscopic quark-gluon string model. The inverse slope parameter of the transverse mass distribution agrees well with that extracted from the STAR data, while the absolute yield of phi is underestimated by a factor 2. It appears that the fusion of strings alone cannot increase the phi yield either. Less than 30% of detectable phi's experience elastic scattering, this rate is insufficient for the full thermalization of phi. The directed flow of phi at |y|<2 demonstrates strong antiflow behavior, whereas its elliptic flow rises up to about 3.5% in the same rapidity interval. As a function of transverse momentum it rises linearly with increasing p_t, in agreement with the STAR data, and saturates at p_t > 2 GeV/c.

hep-ph↗

arXiv2001

Recent results from heavy ion collisions

Systematic trends of baryon transport, chemical freeze-out, and kinetic freeze-out in high energy nuclear collisions are presented. Further measurements of particles with heavy flavors are proposed in order to shed light on collision dynamics at parton level.

hep-ph↗

arXiv2001

Hadron freeze-out conditions in high energy nuclear collisions

Systematic trend of the hadron freeze-out conditions from AGS/SPS to RHIC is discussed. The most interesting results from collisions at RHIC are that the system is indeed approaching net-baryon free and the transverse expansion is much stronger than that from collisions at AGS/SPS energies. In order to understand the trend of the collective velocity, an energy scan between $\sqrt{s_{NN}} = 20 - 200 GeV, is important. In addition, systematic studies on the anisotropy parameter $v_2$ and the transverse momentum distributions of $ϕ, Ω,$ and $J / ψ$ are necessary as they will help in determining whether the collectivity is developed at the partonic stage.

nucl-ex↗

arXiv2001

Enhancement of $ϕ$ mesons in Pb+Pb collisions at 158A GeV/c

Using a hadron-string cascade model LUCIAE, the $ϕ$ meson production in heavy ion collisions (Pb+Pb) and elementary collisions (p+p) were studied systematically. Within the framework of the model, the experimentally measured $ϕ$ enhancement in Pb+Pb over p+p collisions can be mostly explained by the collective effects in the gluon string emission and the reduction of the s-quark suppression.

nucl-th↗

arXiv1999

Transverse Energy Production at RHIC

We study the mechanism of transverse energy (E_T) production in Au+Au collisions at RHIC. The time evolution starting from the initial energy loss to the final E_T production is closely examined in transport models. The relationship between the experimentally measured E_T distribution and the maximum energy density achieved is discussed.

nucl-th↗

arXiv1997

Relative space-time asymmetries in pion and nucleon production in non-central nucleus-nucleus collisions at high energies

We propose to use the ratio of the pion-proton correlation functions evaluated under different conditions to study the relative space-time asymmetries in pion and proton emission (pion and nucleon source relative shifts) in high energy heavy ion collision. We address the question of the non-central collisions, where the sources can be shifted spatially both in the longitudinal and in the transverse directions in the reaction plane. We use the RQMD event generator to illustrate the effect and the technique.

nucl-th↗