K. Jayananda
University of Pittsburgh
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Featured researches published by K. Jayananda.
Physics Letters B | 1995
J. Barrette; R. Bellwied; P. Braun-Munzinger; W. Cleland; T. M. Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; J. V. Germani; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; D. Kraus; B. S. Kumar; R. Lacasse; D. Lissauer; W. J. Llope; T. Ludlam; S. McCorkle; R. Majka; S. K. Mark; J.T. Mitchell; M. Muthuswamy; E. O'Brien; C. Pruneau
Abstract We present measurements of pion transverse momentum ( p t ) spectra in central Si-nucleus collisions in the rapidity range 2.0 y p t down to and including p t = 0. The data exhibit an enhanced pion yield at low p t compared to what is expected for a purely thermal spectral shape. This enhancement is used to determine the Δ resonance abundance at freeze-out. The results are consistent with a direct measurement of the Δ resonance yield by reconstruction of proton-pion pairs and imply a temperature of the system at freeze-out close to 140 MeV.We present measurements of the pion transverse momentum (p_t) spectra in central Si-nucleus collisions in the rapidity range 2.0<y<5.0 for p_t down to and including p_t=0. The data exhibit an enhanced pion yield at low p_t compared to what is expected for a purely thermal spectral shape. This enhancement is used to determine the Delta-resonance abundance at freeze-out. The results are consistent with a direct measurement of the Delta-resonance yield by reconstruction of proton-pion pairs and imply a temperature of the system at freeze-out close to 140 MeV.
Physics Letters B | 1990
J. Barrette; R. Bellwied; P. Braun-Munzinger; W. Cleland; G. David; E. Duek; M. Fatyga; D. Fox; S. V. Greene; J. R. Hall; R. Heifetz; T.K. Hemmick; N. Herrmann; R.W. Hogue; G. Ingold; K. Jayananda; D. Kraus; A. Legault; D. Lissauer; W. J. Llope; T. Ludlam; R. Majka; D. Makowiecki; S. K. Mark; J.T. Mitchell; M. Muthuswamy; E. O'Brien; L. Olsen; V. Polychronakos; M. Rawool-Sullivan
Abstract We have initiated a search for strange quark matter in the products of 14.6 GeV/ c per nucleon 28 Si collisions with nuclei, utilizing the apparatus of E-814 at Brookhaven National Laboratorys AGS. We report the first results of this search, which is sensitive to particles with charge-to-mass ratios between 0.1 and 0.3 (GeV/ c 2 ) −1 that are produced within approximately ±0.5 units of the center of mass rapidity.
Physics Letters B | 1994
J. Barrette; R. Bellwied; P. Braun-Munzinger; W. Cleland; T. M. Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; J. V. Germani; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; D. Kraus; D. Shiva Kumar; R. Lacasse; D. Lissauer; W. J. Llope; T. Ludlam; S. McCorkle; R. Majka; S. K. Mark; J.T. Mitchell; M. Muthuswamy; E. O'Brien; S. Panitkin
Abstract The two-pion correlation function has been measured for charged pions produced in central 14.6 A GeV/ c Si + Pb collisions at the AGS. Data for like-sign pions show a clear quantum interference effect as expected for identical bosons. The experimental correlation function agrees well with that obtained for events generated by a cascade code (RQMD). The present data are consistent with a time-averaged rms freeze-out radius of 8.3 fm and a mean duration of pion emission of 9 fm/ c . The system has expanded considerably before freeze-out.
Nuclear Physics | 1994
J. Stachel; J. Barrette; R. Bellwied; S. Bennett; P. Braun-Munzinger; W. Cleland; Thomas Michael Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; J. V. Germani; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; D. Kraus; B. Shiva Kumar; R. Lacasse; Q. Li; W. J. Llope; T. Ludlam; S. McCorkle; R. Majka; S. K. Mark; R. Matheus; J. T. Mitchell
In this article the authors summarize recent results from the E814 forward spectrometer on proton and pion distributions that give insight into the initial baryon (and energy) density achieved in central collisions as well as the temperature of the system at freeze-out. An independent measure for the latter, complementing the slope constants of particle spectra, is the population of nucleon excited states, in particular the {Delta}(1232) resonance. Besides its influence on the pion spectra it has also been identified directly in the experiment and first results are discussed. The first results from E814 on kaon spectra at low transverse momentum p{sub t} are presented; the spectra show an unexpected very steep rise at the lowest p{sub t}. The two pion correlation function has been studied for positive and negative pions and the authors show that it is consistent with a large source size at freeze-out. Finally, they show that the present data give a consistent picture of a system in thermal and chemical equilibrium at freeze-out.
European Physical Journal C | 1993
J. Barrette; R. Bellwied; P. Braun-Munzinger; W. Cleland; Thomas Michael Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; J. V. Germani; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; D. Kraus; B. Shiva Kumar; R. Lacasse; D. Lissauer; W. J. Llope; T. Ludlam; S. McCorkle; R. Majka; S. K. Mark; J.T. Mitchell; M. Muthuswamy; E. O'Brien; C. Pruneau
We have measured distributions in transverse momentum and rapidity of protons from interactions of 14.6 GeV/nucleon28Si projectiles with targets of Al and Pb. The transverse momentum spectra exhibit a thermal shape with a rapidity dependent temperature parameter. For very central or violent collisions the proton rapidity distributions exhibit the large rapidity shifts and (for Si+Al) a peak at midrapidity as required for full stopping.
Nuclear Physics | 1992
J. Barrette; R. Bellwied; P. Braun-Munzinger; W. Cleland; T. M. Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; M. Fatyga; D. Fox; J. V. Germani; M. Ghalambor-Dezfuli; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; G. Ingold; K. Jayananda; D. Kraus; B. Shiva Kumar; R. Lacasse; D. Lissauer; W. J. Llope; T. Ludlam; S. McCorkle; R. Majka; S. K. Mark
Abstract Recent results from the E814 collaboration are presented for reactions of 14.6 GeV/nucleon 28 Si projectiles with targets of Al, Cu, and Pb. This includes transverse energy distributions over the full solid angle and the distribution of charged particle multiplicity in the forward hemisphere. Furthermore we present recent results on transverse momentum spectra and rapidity distributions for protons and discuss them in terms of stopping and/or transparency. A fraction of nucleons emerges at beam rapidity, even for the most central collisions. These ‘punch-through’ distributions are shown to yield information on the in-medium nucleon-nucleon cross section. Finally, we discuss antiproton production at 0° as a function of event centrality to shed some light on possible reabsorption.
Nuclear Physics | 1992
J. Barrette; R. Bellwied; P. Braun-Munzinger; W. Cleland; T. Cormier; G. David; J. Dee; O. Dietzsch; E. Duek; M. Fatyga; D. Fox; S. V. Greene; J. R. Hall; T.K. Hemmick; N. Herrmann; R.W. Hogue; B. Hong; K. Jayananda; D. Kraus; B. Shiva Kumar; R. Lacasse; D. Lissauer; W. J. Llope; T. Ludlam; R. Majka; D. Makowiecki; S. K. Mark; S. McCorkle; J.T. Mitchell; M. Muthuswamy
Abstract We have used the E814 apparatus to make a systematic study of antiproton production in collisions of 28 Si ions at 14.6 GeV/ c per nucleon with targets of Pb, Cu, and Al. We have measured the antiproton yield per interaction as a function of transverse energy and have found the yield to increase by a factor of ≈ 2 in going from the least to the most central collisions on the Pb target. A simple first-collision picture of antiproton production predicts the yield to increase by a factor of ≈ 11. We suggest that the discrepancy may result from the annihilation of antiprotons within the nuclear medium.
Nuclear Physics | 1997
J. Barrette; R. Bellwied; S. Bennett; P. Braun-Munzinger; W. Cleland; T. M. Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; J. V. Germani; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; D. E. Kraus; B. Shiva Kumar; R. Lacasse; Q. Li; D. Lissauer; W. J. Llope; T. Ludlam; A. Lukaszew; R. Majka; S. K. Mark; R. Matheus; S. McCorkle
Abstract The production of pions, protons and deuterons is studied at a laboratory angle of 144° in 28 Si+Pb collisions at 14.6 GeV/ c per nucleon. The centrality dependence of the pion yields is studied over the full impact parameter range using a zero degree calorimeter. The results are compared with the hadronic cascade model RQMD. These calculations are generally in agreement with the experimental results. According to these calculations, the pion yield in our acceptance is completely dominated by Δ-decay at freeze-out. Our measurements thus support the importance of baryon resonance production as one of the central features of relativistic heavy ion collisions at AGS energies. Although the strength of the pion spectrum is adequately described for kinetic energies above 50 MeV, an additional very soft component is observed in the pion spectra which is not predicted by RQMD. This very soft component accounts for a significant fraction of the total pion yield in this rapidity range but remains unexplained.
Archive | 1996
J. P. Wessels; J. Barrette; R. Bellwied; S. Bennett; R. Bersch; P. Braun-Munzinger; W. C. Chang; W. Cleland; M. Clemen; J. D. Cole; T. M. Cormier; Y. Dai; G. David; J. Dee; O. Dietzsch; M. W. Drigert; K. Filimonov; A. French; S. Gilbert; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; S. C. Johnson; Y. Kwon; R. Lacasse; Q. Li; T. Ludlam; A. Lukaszew
The azimuthal distributions of produced transverse energy from the reaction Au + Au at 10.8 AGeV/c have been studied with the nearly 4π calorimetric coverage of the E877-setup at the AGS. A Fourier analysis of these distributions has been performed in different regions of pseudorapidity as a function of centrality. The extracted sideward flow is found to be maximal in semi-central collisions. This analysis has also been employed to extract the orientation of the reaction plane. Spectra of particles identified in the forward spectrometer are then analyzed with respect to the reaction plane and their triple differential cross sections are determined. The nucleons are found to be the carriers of the sideward flow identified in the calorimeters. While the pions are also preferentially emitted into the reaction plane they show a slight tendency for emission to the opposite side of where the nucleons are found.
Archive | 1994
P. Braun-Munzinger; J. Barrette; R. Bellwied; S. Bennett; W. E. Cleland; T. M. Cormier; G. David; J. Dee; G. E. Diebold; O. Dietzsch; J. V. Germani; S. Gilbert; S. V. Greene; J. R. Hall; T. K. Hemmick; N. Herrmann; B. Hong; K. Jayananda; D. Kraus; B. Shiva Kumar; R. Lacasse; Q. Li; A. Lukaszew; W. J. Llope; T. Ludlam; S. McCorkle; R. Majka; S. K. Mark; R. Matheus; J. T. Mitchell
In the following we will present selected aspects of recent data on central nucleus-nucleus collisions taken by the E814/E877 collaboration at the BNL-AGS. We will first demonstrate that stopping is nearly complete in these collisions, and discuss the initial energy and baryon densities inferred from model comparisons with the data. Next we will discuss the amount of expansion the system undergoes from the initial phase until freeze-out by presenting recent results on pion-pion correlations. The (baryonic) resonance composition of the system at freeze-out is obtained by analyzing pion spectra at low transverse momentum P t and by inspection of direct measurements of the ∆(1232) resonance. Based on analysis of these measurements we will then discuss a “local” freeze-out scenario, where the freeze-out volume is connected with the temperature averaged pion-nucleon cross section. A summary of the current results and of future plans for Au-Au collisions with the E877 apparatus concludes the paper.