Measurement of Cosmic Ray ˉ p/p flux ratio at TeV energies with ARGO-YBJ

摘要

Cosmic ray antiprotons provide an important probe for the study of cosmic-ray propagation in the interstellarspace and to investigate the existence of Galactic dark matter. The ARGO-YBJ experiment, located at the YangbajingCosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm2), is the only experiment exploiting the full coverageapproach at very high altitude presently at work. The ARGO-YBJ experiment is particularly effective in measuring thecosmic ray antimatter content via the observation of the cosmic rays Moon shadowing effect. Based on all the datarecorded during the period from July 2006 through November 2009 and a full Monte Carlo simulation, we searched forthe existence of the shadow produced by antiprotons at the few-TeV energy region. No evidence of the existence ofantiprotons was found in this energy region. Upper limits to the antip/p flux ratio are set to 5% at a median energy of 2TeV and 6% at 5 TeV with a confidence level of 90%. In the few-TeV energy range this result is the lowest available.