2008/12/16 by NA60 Collaboration, R. Arnaldi, K. Banicz +62 · 4 citations
Physics and Astronomy · #Bremsstrahlung #Electron #High-Energy Particle Collisions Research #Lambda #Large Hadron Collider #Nuclear physics #Optics #Pair production #Particle physics #Particle physics theoretical and experimental studies #Physics #Polarization (electrochemistry) #Quantum Chromodynamics and Particle Interactions #Radiation #Rest frame #Super Proton Synchrotron #Thermal #nucl-ex
paper · pdf · doi:10.1103/physrevlett.102.222301
published as Phys.Rev.Lett.102:222301,2009 · Submitted to Physical Review Letters
arxiv created 2008/12/16 · openalex publication_date 2009/06/05 · arxiv updated 2014/11/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The NA60 experiment at the CERN Super Proton Synchrotron has studied dimuon production in 158A GeV In-In collisions. The strong excess of pairs above the known sources found in the complete mass region 0.2<M<2.6 GeV has previously been interpreted as thermal radiation. We now present first results on the associated angular distributions. Using the Collins-Soper reference frame, the structure function parameters lambda, mu, and nu are measured to be zero, and the projected distributions in polar and azimuth angles are found to be uniform. The absence of any polarization is consistent with the interpretation of the excess dimuons as thermal radiation from a randomized system.