Abstract
The invariant-mass spectrum of pairs produced in collisions at an incident energy of 2 GeV per nucleon has been measured for the first time. The measured pair production probabilities span over 5 orders of magnitude from the -Dalitz to the invariant-mass region. Dalitz decays of and account for all the yield up to , but for only about 50% above this mass. A comparison with model calculations shows that the excess pair yield is likely due to baryon-resonance and vector-meson decays. Transport calculations based on vacuum spectral functions fail, however, to describe the entire mass region.
- Received 10 August 2006
DOI:https://doi.org/10.1103/PhysRevLett.98.052302
©2007 American Physical Society