Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session EC: Ultrarelativistic Heavy-Ions I |
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Chair: Ivan Vitev, Los Alamos National Laboratory Room: Kohala 1 |
Friday, October 16, 2009 9:00AM - 9:15AM |
EC.00001: From RHIC to EIC: structure functions Jamal Jalilian-Marian We consider nuclear structure functions at small x using the Color Glass Condensate formalism. Using the successful parameterization of the dipole cross section from dA data at RHIC, we make predictions for the shadowing of nuclear structure functions F$_2$ and gluon distribution function. [Preview Abstract] |
Friday, October 16, 2009 9:15AM - 9:30AM |
EC.00002: Pair creation of quarks and gluons under color electric fields Naoto Tanji Non-perturbative pair creation of quarks and gluons from a uniform electric field and its back reaction are investigated to explore the mechanism of matter formation in heavy-ion collisions. Time-evolution of a system where a classical color electric field and quantum fields of quark and gluon interact with each other is studied up to leading order of quantum fields. We reveal how an initial electric field decays into particles and compare momentum distributions of quark and gluon. [Preview Abstract] |
Friday, October 16, 2009 9:30AM - 9:45AM |
EC.00003: Kadanoff-Baym approach to nonequilibrium field theories with kinetic entropy Akihiro Nishiyama Recent phenomenological analysis of hadron production in ultrarelativistic nucleus-nucleus collisions at RHIC in terms of hydrodynamic model suggests that local thermalization is achieved very rapidly in dense matter created by the collision, much earlier than the time scale which has been expected from naive parton cascade picture. This poses a difficulty of applying the Boltzmann equation with usual binary collision term to describe the early thermalization process. We apply the relativistic Kadanoff-Baym (KB) theory to describe the time evolution of the gluonic matter produced by ultrarelativistic nucleus-nucleus collision. The merit of this approach is that it can incorporate the off-shell quantum evolution of partons as well as the memory effect in the collision process, both of these effects are usually ignored in the Boltzmann equation approach. As a preparatory step of our research, we study the non-equilibrium quantum evolution of the model systems described by scalar field theories. We present the analytic proof of the H-theorem with the relativistic KB equation and derive an equation to describe the entropy production. Numerical solutions of these equations are discussed. [Preview Abstract] |
Friday, October 16, 2009 9:45AM - 10:00AM |
EC.00004: Instabilities of Initial Gauge Field Configurations in Heavy Ion Collisions H. Fujii, K. Itakura, A. Iwazaki The color-glass-condensate effective theory predicts that strong longitudinal chromo-electric and magnetic fields are generated in the initial stage of high-energy nuclear collisions. We investigate analytically time-evolution of such unique gauge field configurations, and point out that unstable fluctuations are inherent to the longitudinal chromomagnetic background because of the non-abelian field nature, which was first recognized by Nielsen and Olesen (N-O) in a different context some time ago. We argue that characteristic features of the instabilities observed in the preceding simulations can be explained by identifying them as the N-O instability, and discuss possible implications to thermalization mechanism of the colliding system. [Preview Abstract] |
Friday, October 16, 2009 10:00AM - 10:15AM |
EC.00005: Freeze-out dynamics of expanding quantum meson clouds Yoshiaki Onishi, Tetsuo Matsui We construct kinetic equations for self-interacting meson fields in a manifestly covariant form in order to describe the boost invariant expansion in the freeze out stage of the relativistic nucleus-nucleus collision. We employ the two-time Wigner functions in order to ensure manifest covariance. The equations of motion for two times are obtained in terms of the Wigner functions. We eliminate the off-diagonal elements of the Wigner functions from these equations in the long wave approximation and derive a closed form of kinetic equations for the diagonal component of the Wigner functions. The result is a manifestly covariant form of the kinetic equations. We show that this construction is equivalent to perform a local Bogoliubov transformation to the particle creation/annihilation operators taking into account the local change of the mass parameter due to the space-time dependent self-energy. These equations together with the non-linear Klein-Goldon equation for meson condensates form a closed set of equations. We show that these equations lead to essentially the same results to the collective excitation of the system near equilibrium as obtained using one-time Wigner functions. We construct a boost invariant solutions of these kinetic equations in order to describe the expansion of meson cloud. [Preview Abstract] |
Friday, October 16, 2009 10:15AM - 10:30AM |
EC.00006: Investigating nuclear collision geometry at the parton level with a modified Monte-Carlo Glauber model Ryan Ward, J.L. Klay The Glauber model of nuclear collisions describes the geometrical distribution of interacting nucleons. Monte Carlo versions of the Glauber model have been very usefully applied to data from the Relativistic Heavy Ion Collider. This talk will review how it is used to model the collisions of nuclei at RHIC and LHC and describe the addition of a new parton-level interaction algorithm to model the geometric distribution of hard-scattered quarks in high energy nuclear collisions. The simulation, written in Java with full visualization and outputs to ROOT, will be demonstrated and results for collisions at RHIC and LHC will be discussed. [Preview Abstract] |
Friday, October 16, 2009 10:30AM - 10:45AM |
EC.00007: Distortion of the HBT images by meson clouds Koichi Hattori, Tetsuo Matsui We study the effects of mesonic final state interactions on the Hanbury Brown and Twiss intensity interferometry in ultra-relativistic heavy ion collisions. Modification of the one-body amplitude of emitted mesons while traversing a cloud of other mesons is estimated adopting the semiclassical approximation. The difference of the phase shifts causes a distortion of the images reflecting the two particle interference. Many body interaction due to the strong interaction among a particle and the rest of the system except for baryons is modeled with a optical potential which incorporates both coherent forward scattering and the absorption due to the incoherent scattering in the clouds. We found distortion of the images in the direction of both outward and sideward due to the real part of optical potential. Repulsive potential elongate the images in the outward direction, and attractive potential stretches in the sideward direction. However, the surface-dominated emission in the existence of the imaginary part of optical potential weakens the effect of the real part. The distortion is effective below around 100 MeV and weakens at high momentum regime. K. Hattori, T. Matsui, nucl-th/0905.3210 [Preview Abstract] |
Friday, October 16, 2009 10:45AM - 11:00AM |
EC.00008: Calculation of the thermal properties of the QGP with 2D viscous hydrodynamics with LQCD equation of state, pre-equilibrium flow, and cascade freeze-out Ron Soltz, Michael Cheng, Jason Newby, Andrew Glenn, Scott Pratt Several recent developments nuclear theory have made it possible to calculate the thermal properties (spectra, flow, and HBT) of the QGP created at the Relativistic Heavy Ion Collider with a reasonable chance of success. We have incorporated these developments into a multi-stage model that incorporates pre-equilibrium flow into the UVH2+1 viscous hydrodynamic model that includes the recent HotQCD equation of state and uses UrQMD cascade for the final state particle distributions. With this model we will investigate the sensitivity to initial conditions and the equation of state. Results from the model will be compared to recent measurements of spectra, flow, and HBT from the Relativistic Heavy Ion Collider. [Preview Abstract] |
Friday, October 16, 2009 11:00AM - 11:15AM |
EC.00009: FOCAL: a FOrward CALorimeter for PHENIX Carla Vale As RHIC enters its second decade of running, upgrades to the PHENIX experiment are in the planning and construction stages. Among them, the FOrward CALorimeter(FOCAL) aims to enhance the PHENIX acceptance on electromagnetic calorimetry, providing full $2\pi$ coverage in the forward region ($1 < |\eta| <3$). The physics motivation centers on measurements of direct-$\gamma$, $\pi^0$ and $\gamma$-jet in p+p, d+A and A+A collisions, in order to address questions such as gluon polarisation, spin orbit correlations of quarks and the gluon density in the nuclear medium. The FOCAL is a highly segmented W-Si tracking calorimeter, consisting of 3 longitudinal sampling EM segments, with 4 layers of high-resolution Si-strip detectors for position measurements within the first segment. A prototype of this design was tested at CERN in June. Results from this test, and an overview of the FOCAL physics capabilities, will be presented. [Preview Abstract] |
Friday, October 16, 2009 11:15AM - 11:30AM |
EC.00010: A simulation study for a Forward Calorimeter upgrade plan in ALICE at LHC Yasuto Hori, Taku Gunji, Hideki Hamagaki, Jan Lak, Richard Seto, Edwrd Kistenev, Mickey Chiu, Carle Vale, Andrey Sukhanov We plan to install a Forward Calorimeter(FoCAL) in $\eta$=1~4 region of the ALICE experiment at LHC. A main subject is the search for signatures of small-x parton saturation effects, which is recently discussed from the point of Color Glass Condensate(CGC). It also enables to study long range hadron correlations like ``Ridge'' found in the AuAu collision at RHIC. The basic measurements are $\pi^{0}$ and direct $\gamma$ spectrums in p+p, p+A, and A+A collisions. Since two $\gamma$ from a high momentum $\pi^{0}$ decays are merged into a same cluster, $\pi^{0}$/$\gamma$ separation at high momentum is a challenging task. The measurement of single electron from heavy quarks and W boson is also possible in p+p,p+A collisions. A SiW Tracking Calorimeter can be the solution to theses requirements. It is a sampling calorimeter which measures a presice lateral and longitudinal shower shape by a set of silicon sensors. A tungsten is a good choice for absorber material because of its short radiation length and excellent ratio of radiation and absorption lengths. A simulation study for possible physics will be presented. And then the conceputual design of FpCal and its performance study by a GEANT simulation and a beamtest of PHENIX Forward Calorimeter protoype will be also presented. [Preview Abstract] |
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