Importance of High pt Physics for simulating UHECR Air Showers

TL;DR

This paper investigates how high transverse momentum physics influences ultra-high-energy cosmic ray air shower simulations, addressing discrepancies between observed and predicted signals by comparing models and exploring nuclear effects.

Contribution

It analyzes the impact of high pt physics and nuclear effects on air shower simulations, highlighting differences between Pythia and QGSJet II models.

Findings

Differences observed between Pythia and QGSJet II for high Pt particles.

Potential impact of high pt physics on surface detector signals.

Exploration of nuclear effects like the Cronin effect on air shower predictions.

Abstract

Observational evidence from Auger and earlier experiments shows a deficit of signal in a surface detector compared to predictions, which increases as a function of zenith angle, when the energy of the event is fixed by fluorescence measurements. We explore three potential explanations for this: the "Cronin effect" (growth of high-transverse momentum cross sections with nuclear size), the need for more particles at high transverse momentum in p- p collisions than currently predicted by high energy hadronic models used for air shower simulations, and the possibility that secondary interactions in the target air nucleus produces additional soft pions not included in simulations. We report here on the differences between Pythia and QGSJet II, especially for high Pt particles. The possible impact of these effects on the predicted surface array signal and attenuation with zenith angle are also reported.