Thermal Dileptons from Hot and Dense Strongly Interacting Matter

Journal Article · Tue Dec 28 04:00:00 EST 2010 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3541982· OSTI ID:21511366

Specht, Hans J ^[1]

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1. Physikalisches Institut, Universitaet Heidelberg, Heidelberg (Germany)

The NA60 experiment at the CERN SPS has studied muon-pair production in 158A GeV In-In collisions. The unprecedented precision of the data has allowed to isolate a strong excess of pairs above the known sources in the whole invariant mass region 0.2<M<2.6 GeV. The (mostly) Planck-like shape of the mass spectra, exponential m{sub T} spectra, zero polarization and the general agreement with thermal-model results allow for a consistent interpretation of the excess dimuons as thermal radiation from a randomized system. For M<1 GeV, the process {pi}{sup +}{pi}{sup -}{yields}{rho}{yields}{mu}{sup +}{mu}{sup -} dominates. The associated space-time averaged {rho} spectral function shows a nearly diverging width in approaching chiral symmetry restoration, but essentially no shift in mass. Some in-medium effects are also seen for the {omega}, but not for the {phi}. For M>1 GeV, the average temperature associated with the mass spectrum is about 200 MeV, considerably above T{sub c} = 170 MeV, implying a transition to dominantly partonic emission sources in this region. The transition itself is mirrored by a large jump-like drop in the inverse slope of the transverse mass spectra around 1 GeV.

• OSTI ID: 21511366
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1322; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ACCELERATORS
ACCURACY
BARYONS
BOSONS
CERN SPS SYNCHROTRON
CHIRAL SYMMETRY
COLLISIONS
CYCLIC ACCELERATORS
ELECTROMAGNETIC RADIATION
ELECTRON PAIRS
ELEMENTARY PARTICLES
EMISSION
ENERGY RANGE
FERMIONS
FUNCTIONS
GEV RANGE
GEV RANGE 01-10
HADRONS
HYPERONS
INTERACTIONS
LEPTONS
MASS
MASS SPECTRA
MESONS
MEV RANGE
MEV RANGE 100-1000
MUON PAIRS
MUONS
MUONS MINUS
OMEGA BARYONS
PAIR PRODUCTION
PARTICLE PRODUCTION
PIONS
PIONS MINUS
PIONS PLUS
POLARIZATION
PSEUDOSCALAR MESONS
RADIATIONS
SPACE-TIME
SPECTRA
SPECTRAL FUNCTIONS
STRANGE PARTICLES
SYMMETRY
SYNCHROTRONS
THERMAL RADIATION