1992/08/06 by K. Haglin, Kevin Haglin, C. Gale +3 · 31 citations
Physics and Astronomy · #Economics #Heavy ion #High-Energy Particle Collisions Research #Ion #Macroeconomics #Nuclear physics #Particle physics theoretical and experimental studies #Physics #Production (economics) #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #hep-ph
paper · pdf · doi:10.1103/physrevd.47.973
published in Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields 47(3), 973-988 (American Physical Society) · 29 pages typed in revtex, 13 figures (not included), hardcopy available by regular mail upon request, McGill/92-33
arxiv created 1992/08/06 · openalex publication_date 1993/02/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The production of electron-positron pairs with invariant masses less than 300 MeV from thermalized hadronic matter in relativistic heavy-ion collisions is calculated using a soft virtual photon approximation. The general theoretical framework is reviewed and extended to include arbitrarily massed and charged reaction partners, which we apply to pions and quarks. This result, exact within the soft photon approximation, is compared with a widely used approximate result which uses an electromagnetic amplitude limited in validity to momentum transfers less than 4m_\mathrm\ensuremathπ(q)2. This momemtum-restricted method works very well for pions, constituent quarks, and medium quarks, whereas it fails when applied to current quarks. A field-theory calculation is performed for the \ensuremathπ\ensuremathπ elastic cross section which gives excellent agreement with data. Quark-antiquark annihilation diagrams in the Born approximation are estimated and compared with \mathrm\ensuremathπ0 and \ensuremathη Dalitz decay contributions to the e+e^\mathrm\ensuremath- invariant-mass spectra. A comparison is made between the rate of production of zero total momentum soft dileptons obtained using resummation techniques in QCD perturbation theory and that which we calculate using this soft photon approximation. Then a Bjorken picture for the evolution is adopted allowing an integration over the history of the colliding nuclei. Using initial conditions likely to be found at the BNL Relativistic Heavy Ion Collider or CERN Large Hadron Collider we conclude even if Dalitz decays can be identified and subtracted from the experimental data it will be difficult to distinguish quark from pion degrees of freedom in the low-mass e+e^\mathrm\ensuremath- spectra.