Measurement of the Proton-Air Cross Section with Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode

TL;DR

This paper reports the measurement of the proton-air inelastic cross section at ultra-high energies using Telescope Array data, and infers the proton-proton cross section at a center-of-mass energy of 95 TeV, providing insights inaccessible to accelerators.

Contribution

First measurement of proton-air cross section at energies around 95 TeV using hybrid cosmic ray detection, and inference of proton-proton cross section at these energies.

Findings

Proton-air inelastic cross section measured as 567 ± 70.5 mb.

Proton-proton total cross section inferred as 170 mb.

Results extend knowledge of hadronic interactions at ultra-high energies.

Abstract

In this work we are reporting on the measurement of the proton-air inelastic cross section $\sigma^{\rm inel}_{\rm p-air}$ using the Telescope Array (TA) detector. Based on the measurement of the $\sigma^{\rm inel}_{\rm p-air}$ the proton-proton cross section $\sigma_{\rm p-p}$ value is also determined at $\sqrt{s} = 95_{-8}^{+5}$ TeV. Detecting cosmic ray events at ultra high energies with Telescope Array enables us to study this fundamental parameter that we are otherwise unable to access with particle accelerators. The data used in this report is the hybrid events observed by the Middle Drum fluorescence detector together with the surface array detector collected over five years. The value of the $\sigma^{\rm inel}_{\rm p-air}$ is found to be equal to $567.0 \pm 70.5 [{\rm Stat.}] ^{+29}_{-25} [{\rm Sys.}]$ mb. The total proton-proton cross section is subsequently inferred from Glauber Formalism and Block, Halzen and Stanev QCD inspired fit and is found to be equal to $170_{-44}^{+48} [{\rm Stat.}] _{-17}^{+19} [{\rm Sys.}] $mb.