PT Journal
AU HADES Collaboration (Agakishiev, Gea
   Diaz, J
   Gil, A
TI Origin of the low-mass electron pair excess in light nucleus-nucleus collisions
SO Physics Letters B
JI Phys. Lett. B
PY 2010
BP 118
EP 122
VL 690
IS 2
DI 10.1016/j.physletb.2010.05.010
LA English
DE Virtual bremsstrahlung; Dileptons; Nucleon-nucleon collisions
AB We report measurements of electron pair production in elementary p + p and d + p reactions at 1.25 GeV/mu with the HADES spectrometer. For the first time, the electron pairs were reconstructed for n + p reactions by detecting the proton spectator from the deuteron breakup. We find that the yield of electron pairs with invariant mass Me+e- > 0.15 GeV/c(2) is about an order of magnitude larger in n + p reactions as compared to p + p. A comparison to model calculations demonstrates that the production mechanism is not sufficiently described yet. The electron pair spectra measured in C + C reactions are compatible with a superposition of elementary n + p and p + p collisions, leaving little room for additional electron pair sources in such light collision systems.
ER