Measurement of Cosmic Ray antiproton/proton flux ratio at TeV energies with ARGO-YBJ

TL;DR

This study used the ARGO-YBJ experiment to search for antiprotons in cosmic rays at TeV energies via the Moon shadow effect, setting the lowest upper limits to date on the antiproton/proton flux ratio.

Contribution

First measurement of cosmic ray antiproton/proton flux ratio at TeV energies using the Moon shadow method with ARGO-YBJ.

Findings

No evidence of antiprotons at TeV energies was observed.

Upper limits to the antiproton/proton flux ratio are set at 5% (2 TeV) and 6% (5 TeV).

This provides the most stringent constraints in the few-TeV range.

Abstract

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