Dilepton bremsstrahlung from pion-pion scattering in a relativistic OBE model

Abstract

We have made a detailed and quantitative study of dilepton production via bremsstrahlung of a virtual photon during pion-pion collisions. Most calculations of electromagnetic radiation from strong interaction processes rely on the soft photon approximation (SPA). The conditions underlying this approximation are generally violated when dilepton spectra are calculated in terms of their invariant mass, so that an approach going beyond the SPA becomes necessary. Superseding previous derivations, we derive an exact formula for the bremsstrahlung cross section. The resulting formulation is compared to various forms based on the SPA, the two-particle phase space approximation and Rückl's formula using a relativistic One Boson Exchange (OBE) model. Within the OBE approach, we show that approximations to the bremsstrahlung dilepton cross sections often differ greatly from the exact result; discrepancies become greater both with rising temperature and with invariant mass. Integrated dilepton production rates are overestimated by Rückl-based approximations by factors 1.5--8.0. The largest discrepancies occur for the reaction ${\pi }^{+}{\pi }^{+}\to {\pi }^{+}{\pi }^{+}{\ell }^{+}{\ell }^{-}$, where such approximations overestimate the exact rate by factors ranging from 2 to 30 for invariant masses between 10 and 500 MeV. Our findings, combined with recent estimates of the Landau-Pomeranchuk effect, indicate that bremsstrahlung dileptons rates in ultrarelativistic heavy ion collisions should be even more suppressed than had been thought before.

REVTeX 3.0, 26 pages plus 15 figures in uuencoded PostScript

References in corpus (8)

• Lepton pairs from thermal mesons
• Dilepton Production in Nucleon-Nucleon Interactions
• Rapidity Distributions of Dileptons from a Hadronizing Quark-Gluon Plasma
• NON-EQUILIBRIUM DESCRIPTION OF BREMSSTRAHLUNG IN DENSE MATTER (Landau - Pomeranchuk - Migdal Effect)
• Influence of the Landau-Pomeranchuk Effect on Lepton-Pair Production
• Soft dilepton production in relativistic heavy ion collisions
• Formalism for dilepton production via virtual photon bremsstrahlung in hadronic reactions
• Virtual bremsstrahlung from pions and quarks in thermalized hadronic matter

Cited by in corpus (13)

• Effective QCD and transport description of dilepton and photon production in heavy-ion collisions and elementary processes
• Centrality dependence of the direct photon yield and elliptic flow in heavy-ion collisions at sqrt(s)=200 GeV
• Hadronic and partonic sources of direct photons in relativistic heavy-ion collisions
• Photon elliptic flow in relativistic heavy-ion collisions: hadronic versus partonic sources
• Low-Energy Thermal Photons from Meson-Meson Bremsstrahlung
• $e^{+}{e}^{-}$ pairs from ${\pi }^{-}$A reactions
• High-energy $\pi \pi$ scattering without and with photon radiation
• Discrepancy in low transverse momentum dileptons from relativistic heavy-ion collisions
• Soft Electromagnetic Radiations from Relativistic Heavy Ion Collisions
• On-Shell Approach to Pion-Nucleon Physics
• Soft Electromagnetic Radiations From Equilibrating Quark-Gluon Plasma
• Bremsstrahlung photon from a hadronizing quark-gluon plasma
• Low-energy Bremsstrahlung photon in relativistic nucleon+nucleon collisions