Prompt atmospheric neutrinos and muons: Dependence on the gluon distribution function - art. no. 056011

We compute the next-to-leading order QCD predictions for the vertical flux of atmospheric muons and neutrinos from decays of charmed particles, for di fferent PDF's (MRS-R1, MRS-R2, CTEQ-4M and MRST) and different extrapolatio ns of these at a small partonic momentum fraction a. We find that the predi cted fluxes vary up to almost two orders of magnitude at the largest energi es studied, depending on the chosen extrapolation of the PDF's. We show tha t the spectral index of the atmospheric leptonic fluxes depends linearly on the slope of the gluon distribution function at very small x. This suggest s the possibility of obtaining some bounds on this slope in "neutrino teles copes," at values of x not reachable at colliders, provided the spectral in dex of atmospheric leptonic fluxes could be determined.