118425985
Spatial anisotropy: a method to study anisotropic flow in heavy ion collisions
We introduce a method to study anisotropic flow parameter vn as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients n of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by vn/n. In this paper, we will discuss in particular the second (n = 2) and the fourth (n = 4) harmonics.
112553011
MULTI-GAP RESISTIVE PLATE CHAMBER- A NEW TYPE OF DETECTOR FOR TIME OF FLIGHT
123771953
A high dynamic range readout unit for a calorimeter
A high dynamic range readout system, consisting of a multi-dynode readout PMT and a VA32 chip, is presented. An LED system is set up to calibrate the relative gains between the dynodes, and the ADC counts per MIPs from dynode 7 are determined under cosmic-ray calibration. A dynamic range from 0.5 MIPs to 1 x 10(5) MIPs is achieved.
14036517
Multiple parton scattering in nuclei: Quark–quark scattering
Abstract Modifications to quark and antiquark fragmentation functions due to quark–quark (antiquark) double scattering in nuclear medium are studied systematically up to order O ( α s 2 ) in deeply inelastic scattering (DIS) off nuclear targets. At the order O ( α s 2 ) , twist-four contributions from quark–quark (antiquark) rescattering also exhibit the Landau–Pomeranchuk–Migdal (LPM) interference feature similar to gluon bremsstrahlung induced by multiple parton scattering. Compared to quark–gluon scattering, the modification, which is dominated by t-channel quark–quark (antiquark) scattering, is only smaller by a factor of C F / C A = 4 / 9 times the ratio of quark and gluon distributions in the medium. Such a modification is not negligible for realistic kinematics and finite medium size. The modifications to quark (antiquark) fragmentation functions from quark–antiquark annihilation processes are shown to be determined by the antiquark (quark) distribution density in the medium. The asymmetry in quark and antiquark distributions in nuclei will lead to different modifications of quark and antiquark fragmentation functions inside a nucleus, which qualitatively explains the experimentally observed flavor dependence of the leading hadron suppression in semi-inclusive DIS off nuclear targets. The quark–antiquark annihilation processes also mix quark and gluon fragmentation functions in the large fractional momentum region, leading to a flavor dependence of jet quenching in heavy-ion collisions.
117009407
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.
16183314
Highlight of the parallel session on QCD
Abstract I will give a critical review of the parallel session on QCD and the related talks in the Quark Matter'97 meeting.
16258194
Energy loss effects on charm and bottom production in high-energy heavy-ion collisions
We study the effect of energy loss on charm and bottom quarks in high-energy heavy-ion collisions including longitudinal expansion and partial thermalization. We find that high-p{sub {perpendicular}} heavy quarks are greatly suppressed, and consequently, high-mass dileptons from heavy quark decays are also suppressed. We consider in detail the detector geometry and single lepton energy cuts of the PHENIX detector at the Relativistic Heavy Ion Collider. Because of the longitudinal expansion, the suppressions of ee, e{mu}, and {mu}{mu} pairs resulting from the heavy quark energy loss are very different due to the different rapidity coverages and energy cuts. The assumed energy loss rate, on the order of 1 GeV/fm, results in a large suppression on dielectrons, and dielectrons from heavy quark decays become comparable or even lower than the Drell-Yan yield. It is thus possible to probe the energy loss rate of the medium using dileptons from heavy quark decays. {copyright} {ital 1998} {ital The American Physical Society}
17897637
Parton Equilibration in Ultrarelativistic Heavy Ion Collisions
Medium effects which include color screening and Landau-Pomeranchuk-Migdal suppression of induced radiation are discussed in connection with the equilibration of dense partonic system in ultrarelativistic heavy ion collisions. Taking into account of these medium effects, the equilibration rate for a gluonic gas are derived and the consequences are discussed.