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Title: Systematic Study of High-p T Direct Photon Production with the PHENIX Experiment at RHIC

Abstract

When studying the initial state and evolution of the matter created in relativistic heavy ion collisions, high-p{sub T} direct photons are a powerful probe. They are created in initial hard processes and in parton fragmentation, and possibly in interactions of partons with the hot and dense medium. We present systematic measurements of high-p{sub T} direct photon production in {radical}s{sub NN} = 200 ; GeV p+p and Au+Au collisions. The nuclear modification factor of direct photons is shown for 5 < p{sub T} < 18 GeV/c, and at very high transverse momenta it seems to be below unity in the most central Au+Au collisions.

Authors:
 [1];  [2];  [3];  [2];  [3];  [2];  [2];  [4];  [2];  [2];  [3];  [5]
  1. University of Tokyo, Tokyo, Japan
  2. ORNL
  3. University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)
  4. University of Tennessee, Knoxville (UTK)
  5. The
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931216
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions: Quark Matter 2006, Shanghai, China, 20061114, 20061120
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 74 ATOMIC AND MOLECULAR PHYSICS; FRAGMENTATION; HEAVY IONS; MODIFICATIONS; PHOTONS; PRODUCTION; QUARK MATTER; COLLISIONS; TRANSVERSE MOMENTUM

Citation Formats

Isobe, T., Awes, Terry C, Batsouli, Sotiria, Cianciolo, Vince, Efremenko, Yuri, Read Jr, Kenneth F, Silvermyr, David O, Sorensen, Soren P, Stankus, Paul W, Young, Glenn R, Zhang, Chun, and PHENIX, Collaboration. Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at RHIC. United States: N. p., 2007. Web.
Isobe, T., Awes, Terry C, Batsouli, Sotiria, Cianciolo, Vince, Efremenko, Yuri, Read Jr, Kenneth F, Silvermyr, David O, Sorensen, Soren P, Stankus, Paul W, Young, Glenn R, Zhang, Chun, & PHENIX, Collaboration. Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at RHIC. United States.
Isobe, T., Awes, Terry C, Batsouli, Sotiria, Cianciolo, Vince, Efremenko, Yuri, Read Jr, Kenneth F, Silvermyr, David O, Sorensen, Soren P, Stankus, Paul W, Young, Glenn R, Zhang, Chun, and PHENIX, Collaboration. Mon . "Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at RHIC". United States. doi:.
@article{osti_931216,
title = {Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at RHIC},
author = {Isobe, T. and Awes, Terry C and Batsouli, Sotiria and Cianciolo, Vince and Efremenko, Yuri and Read Jr, Kenneth F and Silvermyr, David O and Sorensen, Soren P and Stankus, Paul W and Young, Glenn R and Zhang, Chun and PHENIX, Collaboration},
abstractNote = {When studying the initial state and evolution of the matter created in relativistic heavy ion collisions, high-p{sub T} direct photons are a powerful probe. They are created in initial hard processes and in parton fragmentation, and possibly in interactions of partons with the hot and dense medium. We present systematic measurements of high-p{sub T} direct photon production in {radical}s{sub NN} = 200 ; GeV p+p and Au+Au collisions. The nuclear modification factor of direct photons is shown for 5 < p{sub T} < 18 GeV/c, and at very high transverse momenta it seems to be below unity in the most central Au+Au collisions.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

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  • Particle-type dependences of hadron yield suppression/enhancement patterns, especially its difference between mesons and baryons, at intermediate p{sub T} (2-5 GeV/c) is one of the findings in heavy ion collisions at RHIC. A systematic study of identified hadron production was performed in Au+Au/Cu+Cu collisions at {radical}s{sub NN} = 62.4/200 GeV, to investigate the possible origins of this difference. In this paper, we show particle ratios, nuclear modification factors and their scaling properties.
  • The PHENIX experiment at RHIC has analyzed a wealth of data for different particle species, collision energies ({radical}(s{sub NN}) = 62.4, 130, 200 GeV) and collision systems (p+p, d+Au, Cu+Cu, Au+Au) allowing a detailed study of particle production at high pT. A selection of new results on single particle spectra is presented.
  • Direct photons are a powerful probe to study the property of quark-gluon plasma (QGP) in high energy heavy-ion collisions. In non-central collisions, the anisotropy of the collision region produces the different pressure gradients and particle density that results in different anisotropy of particle emission, depending on the production processes of photons. Therefore, an azimuthal anisotropy parameter {upsilon}{sub 2} is a powerful tool to explore the source of direct photons. We report on the latest direct photon analysis of the nuclear modification factor in {radical}s{sub NN} = 200 GeV and 62.4 GeV Au + Au collisions, and {upsilon}{sub 2} at highmore » p{sub T} in 200 GeV Au + Au collisions at RHIC-PHENIX (Run4). We also present the analysis status, using a larger statistics and better reaction plane information from a new detector available from RHIC Run7 data.« less
  • High-p{sub T} hadron-hadron correlations have been measured with the PHENIX experiment in Cu and pp collisions at {radical}s{sub NN}=200 GeV. A comparison of the jet widths and yields between the two colliding systems allows us to study the medium effect on jets. We also present a first measurement of direct photon-hadron correlations in Au and pp collisions. We find that the near-side yields are consistent with zero in both systems. By comparing the jet yields on the away side, we observe a suggestion of the expected suppression of hadrons associated with photons in Au collisions.
  • The production of prompt electron-positron pairs in 16 GeV/c ..pi../sup -/p collisions has been measured using the LASS spectrometer at SLAC. An excess of events is observed above the estimated contributions of direct and Dalitz decay of known resonances in the kinematic range defined by 0.1 less than or equal to x less than or equal to 0.45, 0 less than or equal to P/sub T/ less than or equal to 0.8 GeV/c and 0.2 less than or equal to M(e/sup +/e/sup -/) less than or equal to 0.7 GeV/c/sup 2/. The excess signal decreases slowly with increasing M, butmore » exhibits very steep x and P/sub T//sup 2/ dependence. The contribution of this signal to the e/sup +/e/sup -//..pi../sup +/..pi../sup -/ and ..gamma../..pi.. ratios is discussed. Detailed comparisons are made between e/sup +/e/sup -/ distributions and the corresponding low mass ..mu../sup +/..mu../sup -/ distributions, and a simple production mechanism is proposed which describes the 16 GeV/c data well. The implications for direct photon production are presented, and it is shown that the model provides simultaneously a good description of the experimental data on the (e/..pi..) and (..mu../..pi..) ratios for p/sub T/ < 1 GeV/c.« less