Propagation in the atmosphere of ultrahigh-energy charmed hadrons

TL;DR

This paper investigates how ultrahigh-energy charmed hadrons propagate in the atmosphere, revealing they can retain significant energy and penetrate deeper than pions or protons due to their unique interaction properties.

Contribution

It provides a detailed analysis of charmed hadron interactions in the atmosphere, highlighting their lower inelasticity and potential to reach greater depths in air showers.

Findings

Charmed hadrons deposit about 55% of pion energy per interaction.

Interactions involving valence c quarks can deposit most of the D meson energy.

Charmed hadrons can retain significant energy after multiple interactions.

Abstract

Charmed mesons may be produced when a primary cosmic ray or the leading hadron in an air shower collide with an atmospheric nucleon. At energies \ge 10^8 GeV their decay length becomes larger than 10 km, which implies that they tend to interact in the air instead of decaying. We study the collisions of long-lived charmed hadrons in the atmosphere. We show that (\Lambda_c,D)-proton diffractive processes and partonic collisions of any q^2 where the charm quark is an spectator have lower inelasticity than (p,\pi)-proton collisions. In particular, we find that a D meson deposits in each interaction just around 55% of the energy deposited by a pion. On the other hand, collisions involving the valence c quark (its annihilation with a sea cbar quark in the target or c-quark exchange in the t channel) may deposit most of D meson energy, but their frequency is low (below 0.1% of inelastic interactions). As a consequence, very energetic charmed hadrons may keep a significant fraction of their initial energy after several hadronic interactions, reaching much deeper in the atmosphere than pions or protons of similar energy.