Dileptons in high-energy heavy-ion collisions

Rapp, Ralf

doi:10.1007/bf02705167

Cited by 24 publications

(42 citation statements)

References 35 publications

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“…After the refinements in our theoretical approach for SPS dilepton spectra in the context of the NA60 data, we revisit in this section the consequences for the comparison with CERES/NA45 in semicentral and central Pb-Au collisions, which showed good agreement in our earlier works [24,36,68]. In the following, we constrain ourselves to the above default scenario for the fireball evolution with a transverse acceleration of a ⊥ = 0.085 c 2 /fm.…”

Section: E Update Of Comparison To Ceres/na45 Datamentioning

confidence: 69%

Dilepton radiation at the CERN super-proton synchrotron

2008

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A quantitative evaluation of dilepton sources in heavy-ion reactions is performed taking into account both thermal and non-thermal production mechanisms. The hadronic thermal emission rate is based on an electromagnetic current-correlation function with a low-mass region (LMR, M 1 GeV) dominated by vector mesons (ρ, ω, φ) and an intermediate-mass region (IMR, 1 GeV ≤ M ≤ 3 GeV) characterized by (the onset of) a multi-meson continuum. A convolution of the emission rates over a thermal fireball expansion results in good agreement with experiment in the low-mass spectra, confirming the predicted broadening of the ρ meson in hadronic matter in connection with the prevalence of baryon-induced medium effects. The absolute magnitude of the LMR excess is mostly controlled by the fireball lifetime, which in turn leads to a consistent explanation of the dilepton excess in the IMR in terms of thermal radiation. The analysis of experimental transversemomentum (qT ) spectra reveals discrepancies with thermal emission for qT 1 GeV in noncentral In-In collisions, which we address by extending our calculations by: (i) a refined treatment of ρ decays at thermal freezeout, (ii) primordially produced ρ's subject to energy-loss, (iii) Drell-Yan annihilation, and (iv) thermal radiation from t-channel meson exchange processes. We investigate the sensitivity of dilepton spectra to the critical temperature and hadro-chemical freezeout of the fireball. The ρ broadening in the LMR turns out to be robust, while in the IMR Quark-Gluon Plasma radiation is moderate unless the critical temperature is rather low.

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Section: E Update Of Comparison To Ceres/na45 Datamentioning

confidence: 69%

Dilepton radiation at the CERN super-proton synchrotron

2008

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“…8. This sensitivity does not persist into the low-energy region q 0 ≤ 1 GeV, and thus does not affect low-mass dilepton production [30].…”

Section: B Spsmentioning

confidence: 93%

“…The latter may imply the prevalence of different processes in the corresponding observable, but consistency can and should be tested. In particular, we recall that baryonic sources are very important [16,30] for understanding the observed excess in low-mass (M ≤ 1 GeV) dilepton production in (semi-) central P b-Au collisions at both full (160 AGeV) [31] and lower (40 AGeV) [17] SPS energy. It is therefore mandatory to scrutinize the role of baryons in photon production, especially since most investigations thus far not revealed substantial contributions [32,33,34].…”

Section: In-medium Selfenergies With Baryonsmentioning

confidence: 99%

Hadronic production of thermal photons

2004

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We study the thermal emission of photons from hot and dense strongly interacting hadronic matter at temperatures close to the expected phase transition to the Quark-Gluon Plasma (QGP). Earlier calculations of photon radiation from ensembles of interacting mesons are re-examined with additional constraints, including new production channels as well as an assessment of hadronic form factor effects. Whereas strangeness-induced photon yields turn out to be moderate, the hitherto not considered t-channel exchange of ω-mesons is found to contribute appreciably for photon energies above ∼ 1.5 GeV. The role of baryonic effects is assessed using existing many-body calculations of lepton pair production. We argue that our combined results constitute a rather realistic emission rate, appropriate for applications in relativistic heavy-ion collisions. Supplemented with recent evaluations of QGP emission, and an estimate for primordial (hard) production, we compute photon spectra at SPS, RHIC and LHC energies.

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“…Such corrections are expected to be numerically small. which satisfies the low-energy τ-decay data well [29]. It has the added advantage that its medium modifications have been computed and successfully applied to experiment [30,31].…”

Section: Spectral Functions and Numerical Evaluationmentioning

confidence: 88%

Evaluating chiral symmetry restoration through the use of sum rules

Hohler

Rapp

2012

EPJ Web of Conferences

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Abstract.We pursue the idea of assessing chiral restoration via in-medium modifications of hadronic spectral functions of chiral partners. The usefulness of sum rules in this endeavor is illustrated, focusing on the vector/axial-vector channel. We first present an update on obtaining quantitative results for pertinent vacuum spectral functions. These serve as a basis upon which the in-medium spectral functions can be constructed. A novel feature of our analysis of the vacuum spectral functions is the need to include excited resonances, dictated by satisfying the Weinberg-type sum rules. This includes excited states in both the vector and axial-vector channels. We also analyze the QCD sum rule for the finite temperature vector spectral function, based on a ρ spectral function tested in dilepton data which develops a shoulder at low energies. We find that the ρ peak flattens off which may be a sign of chiral restoration, though a study of the finite temperature axial-vector spectral function remains to be carried out.

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Dileptons in high-energy heavy-ion collisions

Cited by 24 publications

References 35 publications

Dilepton radiation at the CERN super-proton synchrotron

Dilepton radiation at the CERN super-proton synchrotron

Hadronic production of thermal photons

Evaluating chiral symmetry restoration through the use of sum rules

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