Measurement of the cosmic ray antiproton/proton flux ratio at TeV energies with the ARGO-YBJ detector

TL;DR

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

Contribution

First to utilize the Moon shadow effect with ARGO-YBJ data to constrain antiproton flux at TeV energies, providing the most stringent upper limits so far.

Findings

No evidence of antiprotons detected in the TeV range.

Upper limit to the antiproton/proton flux ratio is 5% at 1.4 TeV.

Upper limit to the antiproton/proton flux ratio is 6% at 5 TeV.

Abstract

Cosmic ray antiprotons provide an important probe to study the cosmic ray propagation in the interstellar space and to investigate the existence of dark matter. Acting the Earth-Moon system as a magnetic spectrometer, paths of primary antiprotons are deflected in the opposite sense with respect to those of the protons in their way to the Earth. This effect allows, in principle, the search for antiparticles in the direction opposite to the observed deficit of cosmic rays due to the Moon (the so-called `Moon shadow'). 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 particularly effective in measuring the cosmic ray antimatter content via the observation of the cosmic rays shadowing effect due to: (1) good angular resolution, pointing accuracy and long-term stability; (2) low energy threshold; (3) real sensitivity to the geomagnetic field. Based on all the data recorded during the period from July 2006 through November 2009 and on a full Monte Carlo simulation, we searched for the existence of the shadow cast by antiprotons in the TeV energy region. No evidence of the existence of antiprotons is found in this energy region. Upper limits to the $\bar{p}/p$ flux ratio are set to 5 % at a median energy of 1.4 TeV and 6 % at 5 TeV with a confidence level of 90%. In the TeV energy range these limits are the lowest available.