arXiv subjects

Fuqiang Wang

Publications and source records attributed to Fuqiang Wang.

107 records · Page 6Linked to original sources

arXiv2007

Forward- and Mid-Rapidity Jet-like correlations

Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations of hadrons at forward rapidity with a mid-rapidity high-$\pt$ hadron, on the other hand, probe asymmetric partonic scatterings involving large-x quarks and small-x gluons. We present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs ($2.7<|η|<3.9$, $\pt<2$ GeV/$c$) with high-$\pt$ charged hadrons at mid-rapidity from the main TPC ($|η|<1$, $\pt>3$ GeV/$c$) in $pp$, d+Au, and Au+Au collisions at $\snn=200$ GeV. The implications of the results for small-x gluon distributions (Color Glass Condensate formation) and the energy loss of quark jets at forward rapidity in nuclear medium are discussed. %Their measurements in d+Au collisions, separately at the d-side and the Au-side, may be sensitive to Color Glass Condensate in the Au-nucleus. Their measurements in Au+Au collisions may probe quark-jet modification in nuclear medium.

nucl-ex↗

arXiv2006

Supersonic Jets in Relativistic Heavy-Ion Collisions

Mach-cone shock waves were proposed to explain the broad and perhaps double-peaked away-side 2-particle jet-correlations at RHIC; however, other mechanisms cannot be ruled out. Three-particle jet-correlation is needed in order to distinguish various physics mechanisms. In this talk the 3-particle jet-correlation measurements are presented and their implications are discussed.

nucl-ex↗

arXiv2006

Jet-Like Correlations between Forward and Mid-Rapidity

Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations at forward rapidity with a mid-rapidity high-pt hadron, on the other hand, are sensitive primarily to quark-gluon hard-scattering and may probe quark-jet modification in nuclear medium. They may be also sensitive to the Color Glass Condensate by separating d-side and Au-side in d+Au collisions. We present the first results on correlations of charged hadrons at forward rapidity in the STAR FTPCs (2.7 < |eta| < 3.9, pt < 2 GeV/c) with high-pt charged hadrons at mid-rapidity from the main TPC (|eta| < 1, pt > 3 GeV/c). Preliminary results from pp, d+Au, and Au+Au collisions at 200 GeV are compared. Implications of the results are discussed.

nucl-ex↗

arXiv2005

Soft Physics from STAR

New results on soft hadron distributions and correlations measured with the STAR experiment are presented. Knowledge about the bulk properties of relativistic heavy-ion collisions offered by these results is discussed.

nucl-ex↗

arXiv2005

Distributions of Charged Hadrons Associated with High pT Particles

Recent results from STAR on angular correlations of charged hadrons associated with high transverse momentum particles are presented. Emphasis is put on the correlations of soft associated hadrons, which provide rich information on the properties of the bulk medium created in RHIC collisions. The results are discussed in the context of three pertinent questions regarding QGP formation: sufficient energy density, parton thermalization, and deconfinement.

nucl-ex↗

arXiv2004

Measurement of Jet Modification at RHIC

Charged hadrons (0.15 < pt < 4 GeV/c) associated with a large pt trigger particle (4 < pt < 6 GeV/c) are statistically reconstructed in the large acceptance STAR TPC for p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. Preliminary results on transverse momentum distributions of these hadrons are presented, separately on the near and away side from the trigger particle. An increase in the multiplicity and total scalar pt of these hadrons from p+p to central Au+Au collisions is observed. The away side distribution is found to be significantly softened in central Au+Au with respect to p+p collisions. The results are consistent with modification of jets in heavy ion collisions at RHIC.

nucl-ex↗

arXiv2002

Mid-rapidity $π^\pm$, $K^\pm$, and $\bar{p}$ spectra and particle ratios from STAR

Results are presented on $π^\pm$, $K^\pm$, and $\bar{p}$ transverse mass spectra and particle multiplicity ratios at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$=130 and 200 GeV and in p+p collisions at $\sqrt{s}$=200 GeV. Comparisons are made to results from lower energies. The bulk properties of the collision inferred from these results are discussed.

nucl-ex↗

arXiv2002

Systematics of mid-rapidity K-/pi ratio in heavy-ion collisions

It is observed that K-/pi in A+A and possibly p+p and pbar+p collisions follows an interesting systematic in omega, the pion transverse energy per unit of rapidity and transverse overlap area. The systematics show a linear increase of K-/pi with omega in the AGS and SPS energy regime and a saturation at RHIC energy. The systematics indicate that omega might be the relevant variable underlying K-/pi. At high energy, the omega variable is related to the gluon saturation scale in high density QCD, and perhaps to the initial energy density in the Bjorken picture.

nucl-ex↗

arXiv2000

Correlation between the charged kaon ratio and the baryon phase-space density in heavy-ion collisions

It is found that the baryon phase-space density obtained from the ratio of deuteron to proton yields is nearly constant over centrality in Au+Au collisions at the AGS. The finding offers an explanation for the puzzling centrality independence of the ratio of charged kaon total yields. The correlation between the charged kaon ratio and the average baryon phase-space density is studied for central heavy-ion collisions of various systems over a wide range of beam energy. It is found that the charged kaon ratio and the average baryon phase-space density both increase with decreasing beam energy, and are strongly correlated. Such study may provide a new approach to search for medium effect on the kaon mass.

nucl-ex↗

arXiv2000

Strangeness in dense nuclear matter: A review of AGS results

Enhancement in strangeness production and antihyperon to antibaryon ratio are two important signatures of QGP formation. Both signatures have been measured at the AGS. A review of these measurements is given. Implications of the measurements are discussed.

nucl-ex↗

arXiv1999

Baryon phase-space density in heavy-ion collisions

The baryon phase-space density at mid-rapidity from central heavy-ion collisions is estimated from proton spectra with interferometry and deuteron coalescence measurements. It is found that the mid-rapidity phase-space density of baryons is significantly lower at the SPS than the AGS, while those of total particles (pion + baryon) are comparable. Thermal and chemical equilibrium model calculations tend to over-estimate the phase-space densities at both energies.

nucl-th↗

arXiv1999

Implications of the unusual structure in the pp correlation from Pb+Pb collisions at 158 AGeV

The recent NA49 measurement of two-proton correlation function shows an interesting and unexpected structure at large relative momentum. Applying source imaging techniques to the measurement, we find an unusually steep drop-off in the two-proton source function. We show that the steep drop-off is due to the structure in the correlation and the drop-off cannot be explained using conventional correlation analysis. We suggest possible physics reasons for the unusual source function.

nucl-th↗

arXiv1999

Residual correlation in two-proton interferometry from lambda-proton strong interactions

We investigate the residual effect of lambda-proton strong interactions in pp correlations with one proton from lambda decays. It is found that the residual correlation is about 10% of the lambda-proton correlation strength, and has a broad distribution centered around q~40 MeV/c. The residual correlation cannot explain the observed structure on the tail of the recently measured pp correlation function in central Pb+Pb collisions by NA49 at the SPS.

nucl-th↗

arXiv1999

Lambda-proton correlations in relativistic heavy ion collisions

The prospect of using lambda-proton correlations to extract source sizes in relativistic heavy ion collisions is investigated. It is found that the strong interaction induces a large peak in the correlation function that provides more sensitive source size measurements than two-proton correlations under some circumstances. The prospect of using lambda-proton correlations to measure the time lag between lambda and proton emissions is also studied.

nucl-th↗

arXiv1999

Strangeness and Antibaryon Production in Heavy-Ion Collisions

We review the experimental results on strangeness and antibaryon production in heavy-ion collisions at the AGS and SPS. We argue that the observed enhancement in kaon production at the AGS is consistent with hadronic description, while the multistrange baryon and antibaryon results at the SPS may need physics beyond hadronic nature. We call the need for measurements of low energy antilambda-proton annihilation cross-section in the modeling of antilambda to antiproton ratio; large value of this ratio is observed in central heavy-ion collisions at the AGS and SPS. We speculate the importance of an excitation function measurement of the ratio.

nucl-ex↗

arXiv1998

Na49 Results on Single Particle and Correlation Measurements in Central PB+PB Collisions

Single-particle spectra and two-particle correlation functions measured by the NA49 collaboration in central Pb+Pb collisions at 158 GeV/nucleon are presented. These measurements are used to study the kinetic and chemical freeze-out conditions in heavy ion collisions. We conclude that large baryon stopping, high baryon density and strong transverse radial flow are achieved in central Pb+Pb collisions at the SPS.

nucl-ex↗

arXiv1996

Coulomb Effect on phi->K+K- Invariant Mass

We demonstrate that coulomb interaction between a static charge source and K+ and K- from phi-meson decay could introduce systematic shift in the phi invariant mass reconstructed from the K+K- pair.

nucl-th↗