Lepton fluxes from atmospheric charm

Abstract

We re-examine the charm contribution to atmospheric lepton fluxes in the context of perturbative QCD. We include next-to-leading order corrections and discuss theoretical uncertainties due to the extrapolations of the gluon distributions at small-x. We show that the charm contribution to the atmospheric muon flux becomes dominant over the conventional contribution from π and K decays at the energies of about 10 5 GeV. We compare our fluxes with previous calculations.

Saturation physics in ultra high energy cosmic rays: heavy quark production

“…The flux of prompt leptons is directly associated to the charmed particle production and its decays, whose estimation is strongly dependent on the model used to calculate the charm production cross section and energy spectra [5,6,7,8]. It is related to the need of extrapolating charm production data obtained at accelerators energies to the order of magnitudes higher energies of the relevant cosmic rays collisions.…”

“…This framework was used in the prompt lepton fluxes calculations presented in Refs. [5,6,7,8]. However, since the lepton fluxes are strongly dependent on the behavior of the gluon distribution at small-x [10] and it is determined by the QCD dynamics, we have that any new dynamical effect will modify the estimates of the lepton fluxes.…”

Rigidity dependent knee and cosmic ray induced high energy neutrino fluxes

“…When necessary, we also take the β k −dependence from fits to the data compiled and plotted in [2]. Moreover, following [5], the charm interaction lengths and regeneration moments are all set equal to the kaon ones.…”

“…The CR particles reaching the top of the atmosphere produce secondary fluxes of hadrons and leptons that are usually described by means of coupled cascade equations [2,3,4,5], which can be solved analytically under appropriate symplifying assumptions. In this work we will compute the fluxes of muon neutrinos and antineutrinos, which are the ones more readily detectable at underground detectors.…”

“…Several groups have studied the charm particle production by CRs [4,5,6], which actually requires to take into account next to leading order (NLO) processes, which increase the charm production by more than a factor of two, and the cross sections are sensitive to the values of the partonic distribution functions at very small values of the scaling variable x, what introduces further uncertainties in the results, due to the need to extrapolate beyond the measured range. Even if the charmed mesons (D ± , D 0 , D s , Λ c , ...) are produced at a rate ∼ 10 −4 with respect to the non-charmed ones, their very short decay time, with L D ≃ 2 km(E D /10 PeV), implies that the prompt neutrino spectral slope just follows the CR slope, and hence the prompt neutrinos eventually dominate the atmospheric neutrino fluxes above a PeV in the vertical direction, and somewhat above that energy at large zenith angles 1 .…”