Investigating the effects of the QCD dynamics in the neutrino absorption by the Earth's interior at ultrahigh energies

The opacity of the Earth to incident ultra high energy neutrinos is directly connected with the behaviour of the neutrino - nucleon ($\sigma^{\nu N}$) cross sections in a kinematic range utterly unexplored. In this work we investigate how the uncertainties in $\sigma^{\nu N}$ due the different QCD dynamic models modify the neutrino absorption while they travel across the Earth. In particular, we compare the predictions of two extreme scenarios for the high energy behaviour of the cross section, which are consistent with the current experimental data. The first scenario considered is based on the solution of the linear DGLAP equations at small-$x$ and large-$Q^2$, while the second one take into account the unitarity effects in the neutrino - nucleon cross section by the imposition of the Froissart bound behaviour in the nucleon structure functions at large energies. Our results indicate that probability of absorption and the angular distribution of neutrino events are sensitive to the the QCD dynamics at ultra high energies.Comment: 6 pages, 3 figures. Improved version to be published in Physical Review

Heavy Quark Production in Ultra High Energy Cosmic Ray Interactions

In this paper we present a comprehensive study of the heavy quark production in ultra high energy cosmic ray interactions in the atmosphere considering that the primary cosmic ray can be either a photon, neutrino or a proton. The analysis is performed using a unified framework -- the dipole formalism --- and the saturation effects, associated to the physical process of parton recombination, are taken into account. We demonstrate that the contribution of heavy quarks for cosmic ray interactions is in general non-negligible and can be dominant depending of the process considered. Moreover, our results indicate that new dynamical mechanisms should be included in order to obtain reliable predictions for the heavy quark production in $pp$ collisions at ultra high cosmic ray energies.Comment: 8 pages, 5 figures. Enlarged version to be published in Astroparticle Physic

Estimating nonlinear QCD effects in ultrahigh energy neutrino events at IceCube

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGSThe number of ultrahigh energy events at IceCube is estimated, for the first time, taking into account nonlinear QCD effects in the neutrino-hadron cross section. We assume that the extragalactic neutrino flux is given by Phi(v)(E-v) = Phi E-0(v)-2 and estimate the neutrino-hadron cross section using the dipole approach and a phenomenological model for the dipole-hadron cross section based on nonlinear QCD dynamics. We demonstrate that the nonlinear prediction is able to describe the current IceCube data and that the magnitude of the nonlinear effects is larger than 20% for visible energies of order of 2 PeV and increases with the neutrino energy. Our main conclusion is that the nonlinear QCD effects are non-negligible and should be taken into account in the analysis of the number of ultrahigh energy events.90515CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGSCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGSSem informaçãoSem informaçãoSem informaçã

On the Impact of Tsallis Statistics on Cosmic Ray Showers

We investigate the impact of the Tsallis nonextensive statistics introduced by intrinsic temperature fluctuations in p-Air ultrahigh energy interactions on observables of cosmic ray showers, such as the slant depth of the maximum Xmax and the muon number on the ground Nμ. The results show that these observables are significantly affected by temperature fluctuations and agree qualitatively with the predictions of Heitler model

Measurement of the (π−\pi^-, Ar) total hadronic cross section at the LArIAT experiment

We present the first measurement of the negative pion total hadronic cross section on argon, which we performed at the Liquid Argon In A Testbeam (LArIAT) experiment. All hadronic reaction channels, as well as hadronic elastic interactions with scattering angle greater than 5~degrees are included. The pions have a kinetic energies in the range 100-700~MeV and are produced by a beam of charged particles impinging on a solid target at the Fermilab Test Beam Facility. LArIAT employs a 0.24~ton active mass Liquid Argon Time Projection Chamber (LArTPC) to measure the pion hadronic interactions. For this measurement, LArIAT has developed the ``thin slice method", a new technique to measure cross sections with LArTPCs. While generally higher than the prediction, our measurement of the ($\pi^-$,Ar) total hadronic cross section is in agreement with the prediction of the Geant4 model when considering a model uncertainty of $\sim$5.1\%.Comment: 15 pages, 15 figures, 3 tables, accepted by PR