Influência da física difrativa em chuveiros atmosféricos extensos ultraenergéticos

Abstract

The detection of ultra-high energy cosmic rays (E ≈ 1020 eV) rely on the observation of the particle showers generated due to its interaction in the upper atmosphere. In order to obtain the properties of the primary particle one has to confront the experimental observations with detailed simulations of the particle cascades. Such simulations employ Monte Carlo event generators in order to account for the hadronic interactions that drive the cascading process, dealing with interactions in an energy regime approximatelly 40 times higher than those reached by the LHC. In particular, hadronic diffraction are a class of processes difficult to detect in collider experiments and in addition they can not be treated by means of perturbative QCD, implying the existence of systematic uncertainties in the study of atmospheric showers. In this dissertation we investigate the impact of diffractive interactions on extensive air shower observables. For this purpose we use the CORSIKA simulation package and the Monte Carlo event generators QGSJET-II 04, EPOS LHC and Sibyll versions 2.1 and 2.3. Our results show that the presence of diffractive physics has a significant impact on the longitudinal shower evolution, increasing the depth of maximum by ≈ 20 g/cm2, and on the muonic component, modifying the ground muon density at 1 km from the shower core by up to 20%. Moreover, we study the impact of the modification in the characteristics of hadronic interactions on shower observables. We perform this proposal by employing the CONEX simulation package linked with the aforementioned event generators and an extrapolation model tailored for this purpose. We show that the inelastic production cross section has a leading role on the evolution of particle cascades, determining the longitudinal development (Xmax e Xmax µ ) and the electron number. We demonstrate that the muon content of the showers is almost insensitive to modifications on the cross secion, however changes in the secondary particle species modify the number of muons.