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Sean Gavin

Publications and source records attributed to Sean Gavin.

At least 37 records · Page 2Linked to original sources
arXiv2006

Measuring Shear Viscosity Using Transverse Momentum Correlations in Relativistic Nuclear Collisions

Elliptic flow measurements at RHIC suggest that quark gluon plasma flows with very little viscosity compared to weak coupling expectations, challenging theorists to explain why this fluid is so nearly ``perfect''. It is therefore vital to find quantitative experimental information on the viscosity of the plasma. We propose that measurements of transverse momentum fluctuations can be used to determine the shear viscosity. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty.

nucl-th↗
arXiv2005

Probing Quark Gluon Liquid Using Transverse Momentum Fluctuations

The onset of equilibration in nuclear collisions can lead to related trends in the centrality dependence of the average transverse momentum, pt fluctuations and net charge fluctuations. We extend the transport description of S. Gavin (Phys. Rev. Lett. 92, 162301 (2004)) to include radial flow.

nucl-th↗
arXiv2004

Fluctuations from Thermalization at RHIC

The centrality dependence of dynamic fluctuations of the transverse momentum and the net charge can signal the approach to local thermal equilibrium in nuclear collisions. I explore this signal by comparing transport-theory calculations to STAR and PHENIX data at a range of energies. In particular, I find that this model can describe PHENIX data on the dependence of fluctuations on the transverse momentum range in which they are measured.

nucl-th↗
arXiv2004

Causal Diffusion and the Survival of Charge Fluctuations in Nuclear Collisions

Diffusion may obliterate fluctuation signals of the QCD phase transition in nuclear collisions at SPS and RHIC energies. We propose a hyperbolic diffusion equation to study the dissipation of net charge fluctuations. This equation is needed in a relativistic context, because the classic parabolic diffusion equation violates causality. We find that causality substantially limits the extent to which diffusion can dissipate these fluctuations.

nucl-th↗
arXiv2004

Traces of Thermalization at RHIC

I argue that measurements of Au+Au collisions at 20, 130 and 200 GeV of the centrality dependence of the mean p_t together with p_t and net-charge fluctuations reflect the approach to local thermal equilibrium.

nucl-th↗
arXiv2002

Strange Disoriented Chiral Condensate

Disoriented chiral condensate can produce novel fluctuations of kaons as well as pions. Robust statistical observables can be used to extract the novel fluctuations from background contributions in K-short and K-charged correlation measurements in nuclear collisions. To illustrate how this can be done, I present new event-generator computations of these observables.

nucl-th↗
arXiv2001

Kaon and Pion Fluctuations from Small Disoriented Chiral Condensates

Enhancement of omega and antiomega baryon production in Pb+Pb collisions at a c.m. energy of 17 A GeV can be explained by the formation of many small disoriented chiral condensate regions. This explanation implies that neutral and charged kaons as well as pions must exhibit novel isospin fluctuations. We compute the distribution of the fraction of neutral pions and kaons from such regions. We then propose robust statistical observables that can be used to extract the novel fluctuations from background contributions in pion and kaon measurements at RHIC and LHC.

nucl-th↗
arXiv2001

Baryon Fluctuations and the QCD Phase Transition

The dynamic separation into phases of high and low baryon density in a heavy ion collision can enhance fluctuations of the net rapidity density of baryons compared to model expectations. We demonstrate that event-by-event proton and antiproton measurements can be used to observe this phenomenon. We then perform real-time lattice simulations to show how these fluctuations arise and how they can survive through freeze out.

nucl-th↗
arXiv2001

The QCD Mixed Phase: Shaken, not Stirred

Baryon fluctuations exceeding Poisson expectations can signal a nearly first order phase transition at RHIC. We show how these fluctuations can be measured, and apply a dissipative-hydrodynamic formulation used in condensed matter physics to simulate their evolution.

nucl-th↗
arXiv1999

Covariance of Antiproton Yield and Source Size in Nuclear Collisions

We confront for the first time the widely-held belief that combined event-by-event information from quark gluon plasma signals can reduce the ambiguity of the individual signals. We illustrate specifically how the measured antiproton yield combined with the information from pion-pion HBT correlations can be used to identify novel event classes.

nucl-th↗
arXiv1999

Extraordinary Baryon Fluctuations and the QCD Tricritical Point

The dynamic separation into phases of high and low baryon density in a heavy ion collision can enhance fluctuations of the net rapidity density of baryons compared to model expectations. We show how these fluctuations arise and how they can survive through freezeout.

nucl-th↗
arXiv1999

Baryon Fluctuations in High Energy Nuclear Collisions

We propose that dramatic changes in the variances and covariance of protons and antiprotons can result if baryons approach chemical equilibrium in nuclear collisions at RHIC. To explore how equilibration alters these fluctuations, we formulate both equilibrium and nonequilibrium hadrochemical descriptions of baryon evolution. Contributions to fluctuations from impact parameter averaging and finite acceptance in nuclear collisions are numerically simulated.

nucl-th↗
arXiv1996

Transverse Momentum of Psi and Dimuon Production in Pb+Pb Collisions

CERN collaboration NA50 has measured charmonium and Drell-Yan dimuon production in Pb+Pb collisions. Parton scattering broadens the transverse momentum, p_T, distributions for these processes. We predict that the average p_T^{2} will flatten in Pb+Pb collisions as a function of the neutral transverse energy of hadrons, E_T, in contrast to the almost-linear rise seen in S+U - psi +X. If seen, such a flattening will support hadronic explanations of charmonium suppression. Figures 2 and 5 are improved and numerous typographical errors are corrected.

hep-ph↗
arXiv1996

Charmonium Suppression in Nuclear Collisions

Measurements of $ψ$ and $ψ'$ production from experiment NA50 at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression by Vogt and myself. Data on centrality dependence and total cross sections are in good accord with our predictions. Uncertainties in theoretical quanities such as NA50's $L$ parameter are discussed.

hep-ph↗
arXiv1994

Summary of Heavy Ion Theory

Can we study hot QCD using nuclear collisions? Can we learn about metallic hydrogen from the impact of comet Shoemaker-Levy 9 on Jupiter? The answer to both questions may surprise you! I summarize progress in relativistic heavy ion theory reported at DPF `94 in the parallel sessions.

hep-ph↗
arXiv1994

Dynamics of Chiral Symmetry Breaking in Nuclear Collisions

Measurements of disoriented chiral condensates in heavy ion collisions at RHIC and the LHC can yield fundamental information on the nature of the QCD phase transition. I review theoretical efforts to understand the evolution of the condensate and present new results on experimental signals in the single pion spectrum and in pion interferometry. (Invited talk at the Third International Workshop on Relativistic Aspects of Nuclear Physics, Rio de Janeiro.)

hep-ph↗
arXiv1993

Larger Domains of Disoriented Chiral Condensate Through Annealing

Relativistic heavy ion collisions can generate metastable domains in which the chiral condensate is disoriented. Nucleus-sized domains can yield measurable fluctuations in the number of neutral and charged pions. We propose a scenario in which domains are `annealed' by a dynamically evolving effective potential in the heavy ion system. Domains of sizes exceeding 3~fm are possible in this scenario.

hep-ph↗