Moon Shadow by Cosmic Rays under the Influence of Geomagnetic Field and Search for Antiprotons at Multi-TeV Energies

Abstract

We have observed the shadowing of galactic cosmic ray flux in the direction of the moon, the so-called moon shadow, using the Tibet-III air shower array operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic rays are positively charged; for that reason, they are bent by the geomagnetic field, thereby shifting the moon shadow westward. The cosmic rays will also produce an additional shadow in the eastward direction of the moon if cosmic rays contain negatively charged particles, such as antiprotons, with some fraction. We selected 1.5 x10^{10} air shower events with energy beyond about 3 TeV from the dataset observed by the Tibet-III air shower array and detected the moon shadow at $\sim 40\sigma$ level. The center of the moon was detected in the direction away from the apparent center of the moon by 0.23${}^{\circ }$ to the west. Based on these data and a full Monte Carlo simulation, we searched for the existence of the shadow produced by antiprotons at the multi-TeV energy region. No evidence of the existence of antiprotons was found in this energy region. We obtained the 90% confidence level upper limit of the flux ratio of antiprotons to protons as 7% at multi-TeV energies.

arXiv comment13pages,4figures; Accepted for publication in Astroparticle Physics

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Cited by in corpus (9)

• Observation of the Cosmic Ray Moon shadowing effect with ARGO-YBJ
• Multi-Tev Gamma-Ray Observation from the Crab Nebula Using the Tibet-III Air Shower Array Finely Tuned by the Cosmic-Ray Moon's Shadow
• Measurement of the cosmic ray antiproton/proton flux ratio at TeV energies with the ARGO-YBJ detector
• A cosmic-ray database update: CRDB v4.1
• Chemical Composition of Galactic Cosmic Rays with Space Experiments
• Constraining the $\bar{p}/p$ Ratio in TeV Cosmic Rays with Observations of the Moon Shadow by HAWC
• Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope
• Simulation of the Cosmic Ray Moon Shadow in the Geomagnetic field
• Energy calibration of LHAASO-KM2A using the cosmic ray Moon shadow