The invariant-mass spectrum of e(+) e(-) pairs produced in C-12 + C-12 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 pi(0)-Dalitz to the rho/omega invariant-mass region. Dalitz decays of pi(0) and eta account for all the yield up to 0.15 GeV/c(2), 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.

Dielectron Production in 12C+12C Collisions at 2A GeV with the HADES Spectrometer

BELLIA, Giorgio Concetto
2007

Abstract

The invariant-mass spectrum of e(+) e(-) pairs produced in C-12 + C-12 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 pi(0)-Dalitz to the rho/omega invariant-mass region. Dalitz decays of pi(0) and eta account for all the yield up to 0.15 GeV/c(2), 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.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11769/26061
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 143
  • ???jsp.display-item.citation.isi??? 114
social impact