Where the excess photons and dileptons in SPS nuclear collisions come from ?
نویسندگان
چکیده
Recently the first single photon spectra from CERN energy heavy-ion collisions were reported by WA80, while NA34/3 and NA38 have obtained the spectra for dileptons with the mass up to 4-5 GeV. The production rates for photons and dileptons significantly increase when reactions involving the A 1 meson are included. However, with the conventional expansion scenario, the absolute yields are still significantly smaller than the observed ones. It may indicate that expansion in the " mixed state " takes much more time.
منابع مشابه
Dileptons and Direct Photons at SPS
The study of dilepton and direct photon emission was one of the main topics of the experimental program at the SPS devoted to the search of signals for QGP formation. Three generations of experiments, Helios-3, NA38/NA50, CERES and NA60 measured e+e− or μ+μ− production in various colliding systems and at different energies. While lepton pair production in p-A collisions was found to be reasonab...
متن کاملThermal dileptons in high-energy nuclear collisions
Clear signs of excess dileptons above the known sources were found at the SPS since long. However, a real clarification of these observations was only recently achieved by NA60, measuring dimuons with unprecedented precision in 158A GeV In-In collisions. The excess mass spectrum in the region M<1 GeV is consistent with a dominant contribution from ππ → ρ → μμ annihilation. The associated ρ spec...
متن کاملProbing the spacetime evolution of heavy ion collisions with photons and dileptons
Photons and dileptons are emitted throughout the evolution of the deconfined nuclear medium produced in heavy ion collisions. As such they can provide valuable information about the different phases of the medium, and complement hadronic measurements and other observables. In this work, recent developments related to electromagnetic emissions at early time, in the cross-over region, and at late...
متن کاملSearching for Quark Matter with Dileptons and Photons: from SPS to RHIC
The heavy-ion programme at the CERN SPS, which started back in ’86, has produced a wealth of very interesting and intriguing results in the quest for the quark-gluon plasma. The highlights of the programme on dilepton and direct photon measurements are reviewed emphasizing the most recent results obtained in Pb-Pb collisions at 158 A GeV. Prospects from RHIC are discussed.
متن کاملar X iv : h ep - p h / 01 02 19 2 v 1 1 5 Fe b 20 01 1 Dileptons and photons from central heavy - ion collisions at CERN - SPS
A unique parameterization of secondary (thermal) dilepton and photon yields in heavy-ion experiments at CERN-SPS is proposed. Adding those thermal yields to background contributions the spectral shapes of the CERES/NA45, NA38, NA50, HELIOS/3 and WA98 data from experiments with lead and sulfur beams can be well described.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 1994