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Measurement of the Pseudorapidity and Centrality Dependence of the Transverse Energy Density in Pb-Pb Collisions at sNN=2.76TeV

S. Chatrchyan et al. (CMS Collaboration)
Phys. Rev. Lett. 109, 152303 – Published 8 October 2012
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Abstract

The transverse energy (ET) in Pb-Pb collisions at 2.76 TeV nucleon-nucleon center-of-mass energy (sNN) has been measured over a broad range of pseudorapidity (η) and collision centrality by using the CMS detector at the LHC. The transverse energy density per unit pseudorapidity (dET/dη) increases faster with collision energy than the charged particle multiplicity. This implies that the mean energy per particle is increasing with collision energy. At all pseudorapidities, the transverse energy per participating nucleon increases with the centrality of the collision. The ratio of transverse energy per unit pseudorapidity in peripheral to central collisions varies significantly as the pseudorapidity increases from η=0 to |η|=5.0. For the 5% most central collisions, the energy density per unit volume is estimated to be about 14GeV/fm3 at a time of 1fm/c after the collision. This is about 100 times larger than normal nuclear matter density and a factor of 2.6 times higher than the energy density reported at sNN=200GeV at the Relativistic Heavy Ion Collider.

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  • Received 12 May 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.152303

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

© 2012 CERN, for the CMS Collaboration

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New Measurements of the Most Perfect Liquid

Published 8 October 2012

Producing quark-gluon matter from higher-energy nuclear collisions will give insight into its fluidlike properties.

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Vol. 109, Iss. 15 — 12 October 2012

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