skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Ultrarelativistic cascades and strangeness production

Abstract

A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy Ion-Ion collisions is applied to the production of strangeness at SPS energies. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS.

Authors:
 [1];  [2]
  1. State Univ. of New York, Stony Brook, NY (United States). Physics Dept.
  2. Brookhaven National Lab., Upton, NY (United States). Physics Dept.
Publication Date:
Research Org.:
Brookhaven National Lab., Upton, NY (United States); State Univ. of New York, Physics Dept., Stony Brook, NY (United States)
Sponsoring Org.:
USDOE Office of Energy Research, Washington, DC (United States)
OSTI Identifier:
658364
Report Number(s):
BNL-65248; CONF-9710193-
ON: DE98004470; BR: KB03; TRN: 98:011092
DOE Contract Number:
AC02-76CH00016; FG02-93ER40768
Resource Type:
Conference
Resource Relation:
Conference: 6. international conference on hypernuclear and strange particle physics, Upton, NY (United States), 13-18 Oct 1997; Other Information: PBD: Feb 1998
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; STRANGENESS; DRELL MODEL; PARTICLE PRODUCTION; RELATIVISTIC RANGE; HEAVY ION REACTIONS; CERN SPS SYNCHROTRON; QUARK MATTER; HADRON-HADRON INTERACTIONS; J PSI-3097 MESONS; COMPUTERIZED SIMULATION

Citation Formats

Kahana, D.E., and Kahana, S.H. Ultrarelativistic cascades and strangeness production. United States: N. p., 1998. Web.
Kahana, D.E., & Kahana, S.H. Ultrarelativistic cascades and strangeness production. United States.
Kahana, D.E., and Kahana, S.H. 1998. "Ultrarelativistic cascades and strangeness production". United States. doi:. https://www.osti.gov/servlets/purl/658364.
@article{osti_658364,
title = {Ultrarelativistic cascades and strangeness production},
author = {Kahana, D.E. and Kahana, S.H.},
abstractNote = {A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy Ion-Ion collisions is applied to the production of strangeness at SPS energies. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons by separating the dynamics into two steps, a fast cascade involving only the nucleons in the original colliding relativistic ions followed, after an appropriate delay, by a normal multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1998,
month = 2
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Bjorken's hydrodynamic description of the space-time evolution of the central rapidity region in ultrarelativistic heavy-ion collisions is extended to incorporate the chemical processes which affect the strangeness abundance. Scaling hydrodynamic equations which contain the rate equation for strangeness production and annihilation both in the plasma phase and in the hadron gas phase are integrated numerically assuming an almost adiabatic first-order phase transition from plasma to hadron gas. It is found that if a plasma is initially formed the resultant K/..pi.. ratio will be enhanced by about a factor of 3 from that in pp collisions. However, this ratio is stillmore » smaller than that in an equilibrium hadron gas and hence cannot be considered a direct signal of plasma formation.« less
  • We develop a kinetic theory of chemical reactions in a quark-gluon plasma in order to study the evolution of flavor composition in ultrarelativistic nucleus-nucleus collisions. The rates of production and annihilation of strange-quark pairs are computed in lowest order in perturbation theory assuming local equilibrium with respect to other, more frequent collision processes. Quantum-statistical effects are taken into account. The hydrodynamic equations coupled to the rate equation are derived and solved numerically in a homogeneous plasma, simulating the approach toward complete chemical equilibrium. The corresponding relaxation times are computed.
  • Strangeness production has been proposed as a signal for the formation of a quark-gluon plasma in ultrarelativistic nucleus-nucleus collisions. We address this problem in the framework of Bjorken's model for the longitudinal hydrodynamic expansion of baryon-free matter. Different scenarios are considered for the assumed first-order phase transition from QCD plasma into hadrons, including a slow transition via the Maxwell construction of coexisting phases, and a rapid transition from supercooling followed by reheating. The rate equations for strange-quark and kaon abundances are solved numerically. With the most likely set of parameters, the K/sup -//..pi../sup -/ ratio is about three times largermore » than in p-barp collisions at the same energy. This results primarily from the large rate constant in the hadron phase and from the long time spent in this phase. Thus, the K/sup -//..pi../sup -/ ratio may not be a direct signal for the formation of quark-gluon plasma; however, it may be an indirect signal, since the system would not live nearly as long if the quark-gluon plasma had not been formed initially.« less
  • The authors solve, in an ultrarelativistic limit, the time-dependent Dirac equation describing electron-positron pair production in peripheral relativistic heavy ion collisions using light front variables and a light-fronts representation, obtaining nonperturbative results for the free pair-creation amplitudes in the collider frame. Their result reproduces the result of second-order perturbation theory in the small charge limit while nonperturbative effects arise for realistic charges of the ions.
  • We have measured angular and momentum distributions for electrons and positrons created as pairs in peripheral collisions of 6.4 TeV bare sulfur ions with fixed targets of Al, Pd, and Au. Singly- and doubly-differential cross sections have been determined for 1--17 MeV/c electrons and positrons detected independently and in coincidence as pairs. Integrated yields for pair production are found to vary as the square of the target nuclear charge. Relative angular and momentum differential cross sections are effectively target independent. Probability distributions for the pair total momentum, the positron fraction of the pair momentum, and the pair traverse momentum havemore » been derived from the coincident electron-positron data.« less