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Title: A first look at Au+Au collisions at RHIC energies using the PHOBOS detector.

Abstract

The PHOBOS detector has been used to study Au + Au collisions at {radical}sNN = 56,130, and 200 GeV Several global observables have been measured and the results are compared with theoretical models. These observables include the charged-particle multiplicity measured as a function of beam energy, pseudo-rapidity, and centrality of the collision. A unique feature of the PHOBOS detector is its almost complete angular coverage such that these quantities can be studied over a pseudo-rapidity interval of |{eta}|{<=}5.4. This allows for an almost complete integration of the total charged particle yield, which is found to be about N{sub ch}{sup tot} = 4200 {+-}470 at {radical}sNN = 130 GeV and N{sub ch}{sup tot} = 5300 {+-}530 at {radical}sNN = 200 GeV. The ratio of anti-particles to particles emitted in the mid-rapidity region has also been measured using the PHOBOS magnetic spectrometer. Of particular interest is the ratio of anti-protons to protons in the mid-rapidity region, which was found to be (i.e.921-1) at {radical}sNN = 130 GeV. This high value suggests that an almost baryon-free region has been produced in the collisions.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); National Science Foundation (NSF); FOR
OSTI Identifier:
949560
Report Number(s):
ANL/PHY/JA-42003
Journal ID: ISSN 0304-4289; PRAMCI; TRN: US1003577
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: PRAMAMA - J. Phys.; Journal Volume: 60; Journal Issue: 5 ; May 2003; Conference: International Conference on Physics and Astro-Physics of Quark-Gluon Plasma; Nov. 26, 2001 - Nov. 30, 2001; Jaipur, India
Country of Publication:
United States
Language:
ENGLISH
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CHARGED PARTICLES; MAGNETIC SPECTROMETERS; MULTIPLICITY; PHYSICS; PROTONS; QUARK MATTER

Citation Formats

Back, B. B., George, N., Wousmaa, A. H., Baker, M. D., Barton, D. S., PHOBOS Collaboration, and Physics. A first look at Au+Au collisions at RHIC energies using the PHOBOS detector.. United States: N. p., 2003. Web. doi:10.1007/BF02707011.
Back, B. B., George, N., Wousmaa, A. H., Baker, M. D., Barton, D. S., PHOBOS Collaboration, & Physics. A first look at Au+Au collisions at RHIC energies using the PHOBOS detector.. United States. doi:10.1007/BF02707011.
Back, B. B., George, N., Wousmaa, A. H., Baker, M. D., Barton, D. S., PHOBOS Collaboration, and Physics. Thu . "A first look at Au+Au collisions at RHIC energies using the PHOBOS detector.". United States. doi:10.1007/BF02707011.
@article{osti_949560,
title = {A first look at Au+Au collisions at RHIC energies using the PHOBOS detector.},
author = {Back, B. B. and George, N. and Wousmaa, A. H. and Baker, M. D. and Barton, D. S. and PHOBOS Collaboration and Physics},
abstractNote = {The PHOBOS detector has been used to study Au + Au collisions at {radical}sNN = 56,130, and 200 GeV Several global observables have been measured and the results are compared with theoretical models. These observables include the charged-particle multiplicity measured as a function of beam energy, pseudo-rapidity, and centrality of the collision. A unique feature of the PHOBOS detector is its almost complete angular coverage such that these quantities can be studied over a pseudo-rapidity interval of |{eta}|{<=}5.4. This allows for an almost complete integration of the total charged particle yield, which is found to be about N{sub ch}{sup tot} = 4200 {+-}470 at {radical}sNN = 130 GeV and N{sub ch}{sup tot} = 5300 {+-}530 at {radical}sNN = 200 GeV. The ratio of anti-particles to particles emitted in the mid-rapidity region has also been measured using the PHOBOS magnetic spectrometer. Of particular interest is the ratio of anti-protons to protons in the mid-rapidity region, which was found to be (i.e.921-1) at {radical}sNN = 130 GeV. This high value suggests that an almost baryon-free region has been produced in the collisions.},
doi = {10.1007/BF02707011},
journal = {PRAMAMA - J. Phys.},
number = 5 ; May 2003,
volume = 60,
place = {United States},
year = {Thu May 01 00:00:00 EDT 2003},
month = {Thu May 01 00:00:00 EDT 2003}
}
  • Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |{eta}| < 5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dN{sub ch}/d{eta} and the total charged-particle multiplicity N{sub ch} are found to factorize into a productmore » of independent functions of collision energy, {radical}s{sub NN}, and centrality given in terms of the number of nucleons participating in the collision, N{sub part}. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lns{sub NN}){sup 2} over the full range of collision energy of {radical}s{sub NN} = 2.7-200 GeV.« less
  • Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |{eta}|<5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dN{sub ch}/d{eta} and the total charged-particle multiplicity N{sub ch} are found to factorize into a product of independentmore » functions of collision energy, {radical}(s{sub N{sub N}}), and centrality given in terms of the number of nucleons participating in the collision, N{sub part}. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lns{sub N{sub N}}){sup 2} over the full range of collision energy of {radical}(s{sub N{sub N}})=2.7-200 GeV.« less
  • Forward calorimetry in the PHOBOS detector has been used to study charged hadron production in d + Au, p + Au, and n + Au collisions at root s(NN) = 200 GeV. The forward proton calorimeter detectors are described and a procedure for determining collision centrality with these detectors is detailed. The deposition of energy by deuteron spectator nucleons in the forward calorimeters is used to identify p + Au and n + Au collisions in the data. A weighted combination of the yield of p + Au and n + Au is constructed to build a reference for Aumore » + Au collisions that better matches the isospin composition of the gold nucleus. The p(T) and centrality dependence of the yield of this improved reference system is found to match that of d + Au. The shape of the charged-particle transverse momentum distribution is observed to extrapolate smoothly from p + (p) over bar to central d + Au as a function of the charged-particle pseudorapidity density. The asymmetry of positively and negatively charged hadron production in p + Au is compared to that of n + Au. No significant asymmetry is observed at midrapidity. These studies augment recent results from experiments at the CERN Large Hadron Collider and BNL Relativistic Heavy Ion Collider facilities to give a more complete description of particle production in p + A and d + A collisions, essential for the understanding the medium produced in high-energy nucleus-nucleus collisions.« less