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X. -N. Wang

Publications and source records attributed to X. -N. Wang.

47 records · Page 3Linked to original sources

Extraction of Heavy-Flavor Transport Coefficients in QCD Matter

We report on broadly based systematic investigations of the modeling components for open heavy-flavor diffusion and energy loss in strongly interacting matter in their application to heavy-flavor observables in high-energy heavy-ion collisions, conducted within an EMMI Rapid Reaction Task Force framework. Initial spectra including cold-nuclear-matter effects, a wide variety of space-time evolution models, heavy-flavor transport coefficients, and hadronization mechanisms are scrutinized in an effort to quantify pertinent uncertainties in the calculations of nuclear modification factors and elliptic flow of open heavy-flavor particles in nuclear collisions. We develop procedures for error assessments and criteria for common model components to improve quantitative estimates for the (low-momentum) heavy-flavor diffusion coefficient as a long-wavelength characteristic of QCD matter as a function of temperature, and for energy loss coefficients of high-momentum heavy-flavor particles.

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Predictions for Cold Nuclear Matter Effects in $p+$Pb Collisions at $\sqrt{s_{_{NN}}} = 8.16$ TeV

Predictions for cold nuclear matter effects on charged hadrons, identified light hadrons, quarkonium and heavy flavor hadrons, Drell-Yan dileptons, jets, photons, gauge bosons and top quarks produced in $p+$Pb collisions at $\sqrt{s_{_{NN}}} = 8.16$ TeV are compiled and, where possible, compared to each other. Predictions of the normalized ratios of $p+$Pb to $p+p$ cross sections are also presented for most of the observables, providing new insights into the expected role of cold nuclear matter effects. In particular, the role of nuclear parton distribution functions on particle production can now be probed over a wider range of phase space than ever before.

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Predictions for $p+$Pb Collisions at $\sqrt{s_{NN}} = 5$ TeV: Comparison with Data

Predictions made in Albacete {\it et al} prior to the LHC $p+$Pb run at $\sqrt{s_{NN}} = 5$ TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication are also shown here.

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Predictions for $p+$Pb Collisions at sqrt s_NN = 5 TeV

Predictions for charged hadron, identified light hadron, quarkonium, photon, jet and gauge bosons in p+Pb collisions at sqrt s_NN = 5 TeV are compiled and compared. When test run data are available, they are compared to the model predictions.

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A NLO analysis on fragility of dihadron tomography in high energy $AA$ collisions

The dihadron spectra in high energy $AA$ collisions are studied within the NLO pQCD parton model with jet quenching taken into account. The high $p_T$ dihadron spectra are found to be contributed not only by jet pairs close and tangential to the surface of the dense matter but also by punching-through jets survived at the center while the single hadron high $p_T$ spectra are only dominated by surface emission. Consequently, the suppression factor of such high-$p_T$ hadron pairs is found to be more sensitive to the initial gluon density than the single hadron suppression factor.

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Punch-through jets in $A+A$ collisions at RHIC/LHC

High $p_T$ single and dihadron production is studied within a NLO pQCD parton model with jet quenching in high energy $A+A$ collisions at the RHIC/LHC energy. A simultaneous $χ^2$-fit to both single and dihadron spectra can be achieved within a narrow range of energy loss parameter. Punch-through jets are found to result in the dihadron suppression factor slightly more sensitive to medium than the single hadron suppression factor at RHIC. Such jets at LHC are found to dominate high $p_T$ dihadron production and the resulting dihadron spectra are more sensitive to the initial parton distribution functions than the single hadron spectra.

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Small Shear Viscosity of a Quark-Gluon Plasma Implies Strong Jet Quenching

We derive an expression relating the transport parameter $\hat{q}$ and the shear viscosity $η$ of a weakly coupled quark-gluon plasma. A deviation from this relation can be regarded as a quantitative measure of ``strong coupling'' of the medium. The ratio $T^3/\hat{q}$, where $T$ is the temperature, is a more broadly valid measure of the coupling strength of the medium than $η/s$, where $s$ denotes the entropy density. Different estimates of $\hat{q}$ derived from existing RHIC data are shown to imply radically different structures of the produced matter.

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A Vision for Nuclear Theory: Report to NSAC

This is the report of the NSAC Subcommittee on Nuclear Theory in response to a charge by the funding agencies to review and evaluate current NSF and DOE supported efforts in nuclear theory and identify strategic plans to ensure a strong U.S. nuclear theory program under various funding scenarios.

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Fluctuations of rare particles as a measure of chemical equilibration

We calculate the time evolution of fluctuations for rare particles such as e.g. kaons in 1 AGeV or charmonium in 200 AGeV heavy ion collisions. We find that these fluctuations are a very sensitive probe of the degree of chemical equilibration reached in these collisions. Furthermore, measuring the second factorial moment the size of the initial population can be determined.

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Enhanced Event-by-Event Fluctuations in Pion Multiplicity as a Signal of Disoriented Chiral Condensates at RHIC

The factorial moments of the pion multiplicity distributions are calculated with HIJING and UrQMD and found to be independent of the pT range included, in contrast to recent simulations with the linear sigma model which leads to large enhancements for pions with transverse kinetic energies below 200 MeV. This supports the use of the ratio of the factorial moments of low and high pT pions as a signal of ``new'' physics at low momentum scales, such as the formation of disoriented chiral condensates.

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Wavelet Perspective of a Disoriented Chiral Condensate

The possible chiral phase transition in high energy heavy-ion collisions may lead to the formation of a disoriented chiral condensate (DCC). However, the existence of many uncorrelated small domains in the rather large interaction volume and the huge combinatorial background make the experimental search for the DCC signal a rather difficult task. We present a novel method for studying the formation of a DCC in high energy heavy-ion collisions utilizing a discrete wavelet transformation. We find the wavelet power spectrum for a DCC to exhibit a strong dependence on the scale while an equilibrium system and the standard dynamical models such as HIJING have a flat spectrum.

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