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Title: Prospects of medium tomography using back-to-back hadron correlations

Abstract

We discuss the prospects of extracting information on bulk QCD matter distribution and evolution on the basis of hard hadronic back-to-back correlations in ultrarelativistic heavy-ion collisions. Using both hydrodynamic and parametrized evolution models for the space-time evolution of produced matter, which have been tested against data from the BNL Relativistic Heavy-Ion Collider, we study six different setups for the space-time dependence of hard-parton energy losses. Assuming that the energy loss of hard partons traversing the medium is radiative and calculable in the Baier-Dokshitzer-Mueller-Peigne-Schiff formalism, we adjust one parameter, the quenching power scale, to the measured nuclear suppression factor R{sub AA} in each of the setups and study the systematic variations of the back-to-back yield as a function of transverse momentum p{sub T}. We show which space-time regions are probed by one- and two-particle observables and study in some detail the role of longitudinal and transverse expansion. We also comment on the importance of considering fluctuations around the average energy loss. We conclude that while current data are too limited in momentum coverage, future data for higher trigger energy might provide the lever arm in away-side hadron momentum necessary to perform medium tomography, provided that sufficient precision can be achieved.

Authors:
;  [1]
  1. Department of Physics, University of Jyvaeskylae, P.O. Box 35, FI-40014, Jyvaeskylae (Finland) and Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FI-00014, Helsinki (Finland)
Publication Date:
OSTI Identifier:
20995314
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.054910; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BNL; BROOKHAVEN RHIC; CORRELATIONS; ENERGY LOSSES; FLUCTUATIONS; HADRONS; HEAVY ION REACTIONS; QUANTUM CHROMODYNAMICS; RELATIVISTIC RANGE; SPACE-TIME; TOMOGRAPHY; TRANSVERSE MOMENTUM

Citation Formats

Renk, Thorsten, and Eskola, Kari J. Prospects of medium tomography using back-to-back hadron correlations. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.054910.
Renk, Thorsten, & Eskola, Kari J. Prospects of medium tomography using back-to-back hadron correlations. United States. doi:10.1103/PHYSREVC.75.054910.
Renk, Thorsten, and Eskola, Kari J. Tue . "Prospects of medium tomography using back-to-back hadron correlations". United States. doi:10.1103/PHYSREVC.75.054910.
@article{osti_20995314,
title = {Prospects of medium tomography using back-to-back hadron correlations},
author = {Renk, Thorsten and Eskola, Kari J.},
abstractNote = {We discuss the prospects of extracting information on bulk QCD matter distribution and evolution on the basis of hard hadronic back-to-back correlations in ultrarelativistic heavy-ion collisions. Using both hydrodynamic and parametrized evolution models for the space-time evolution of produced matter, which have been tested against data from the BNL Relativistic Heavy-Ion Collider, we study six different setups for the space-time dependence of hard-parton energy losses. Assuming that the energy loss of hard partons traversing the medium is radiative and calculable in the Baier-Dokshitzer-Mueller-Peigne-Schiff formalism, we adjust one parameter, the quenching power scale, to the measured nuclear suppression factor R{sub AA} in each of the setups and study the systematic variations of the back-to-back yield as a function of transverse momentum p{sub T}. We show which space-time regions are probed by one- and two-particle observables and study in some detail the role of longitudinal and transverse expansion. We also comment on the importance of considering fluctuations around the average energy loss. We conclude that while current data are too limited in momentum coverage, future data for higher trigger energy might provide the lever arm in away-side hadron momentum necessary to perform medium tomography, provided that sufficient precision can be achieved.},
doi = {10.1103/PHYSREVC.75.054910},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Azimuthal correlations for large transverse momentum charged hadrons have been measured over a wide pseudo-rapidity range and full azimuth in Au+Au and p+p collisions at = {radical}s{sub NN} = 200 GeV. The small-angle correlations observed in p+p collisions and at all centralities of Au+Au collisions are characteristic of hard-scattering processes already observed in elementary collisions. A strong back-to-back correlation exists for p+p and peripheral Au + Au. In contrast, the back-to-back correlations are reduced considerably in the most central Au+Au collisions, indicating substantial interaction as the hard-scattered partons or their fragmentation products traverse the medium.
  • Azimuthal correlations for large transverse momentum charged hadrons have been measured over a wide pseudorapidity range and full azimuth in Au+Au and p+p collisions at {radical}{ovr S{sub NN}}=200 GeV. The small-angle correlations observed in p+p collisions and at all centralities of Au+Au collisions are characteristic of hard-scattering processes previously observed in high-energy collisions. A strong back-to-back correlation exists for p+p and peripheral Au+Au. In contrast, the back-to-back correlations are reduced considerably in the most central Au+Au collisions, indicating substantial interaction as the hard-scattered partons or their fragmentation products traverse the medium.
  • Hard pQCD processes taking place in ultrarelativistic heavy-ion collisions are a well-calibrated probe. It is believed that the interaction with the surrounding medium of outgoing partons from a hard vertex is capable of revealing details of the medium. We demonstrate that correlation measurements of hard photon-hadron back-to-back coincidences are a tool suitable for extracting such tomographic information. Introducing the concept of averaged energy loss probability distributions, we first argue that almost no information about details of the medium evolution is reflected in the nuclear suppression factor R{sub AA}. Thus, a wide variety of jet quenching scenarios and geometries are compatiblemore » with the measured data. This problem can be overcome by a {gamma}-hadron correlation measurement. We show that averaged probability distributions for quarks are accessible experimentally, and we sketch an analysis procedure capable of distinguishing different energy loss scenarios leading to the same nuclear suppression factor.« less