Measurement of the antiproton/proton ratio at few-TeV energies with the ARGO-YBJ experiment

TL;DR

This study uses the ARGO-YBJ experiment to analyze the Moon shadow effect for detecting antiprotons in cosmic rays at few-TeV energies, setting an upper limit on the antiproton/proton flux ratio.

Contribution

It provides the first measurement of the antiproton/proton ratio at TeV energies using the Moon shadow technique with high statistical significance.

Findings

Upper limit of the antiproton/proton flux ratio is a few percent at a few TeV.

The Moon shadow method effectively constrains antiparticle fluxes in cosmic rays.

Data from ARGO-YBJ supports the absence of a significant antiproton excess at these energies.

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. Cosmic rays are hampered by the Moon, therefore a deficit of cosmic rays in its direction is expected (the so-called "Moon shadow"). The Earth-Moon system acts as a magnetic spectrometer. In fact, due to the geomagnetic field the center of the Moon shifts westward by an amount depending on the primary cosmic ray energy. Paths of primary antiprotons are therefore deflected in an opposite sense in their way to the Earth. This effect allows, in principle, the search of antiparticles in the opposite direction of the observed Moon shadow. The ARGO-YBJ experiment, in stable data taking since November 2007 with an energy threshold of a few hundreds of GeV, is observing the Moon shadow with high statistical significance. Using about 1 year data, an upper limit of the antip/p flux ratio in the few-TeV energy region is set to a few percent with a confidence level of 90%.