Measurement of the gluon parton distribution function at small x with neutrino telescopes - art. no. 036006

We analyze the possibility that neutrino telescopes may provide an experime ntal determination of the slope lambda of the gluon distribution in the pro ton at momentum fractions x smaller than the accelerator reach. The method is based on a linear relation between lambda and the spectral index (slope) of the down-going atmospheric muon fur above 100 TeV, for which there is n o background. Considering the uncertainties in the charm production cross s ection and in the cosmic ray composition, we estimate the error on the meas urement of lambda through this method, excluding the experimental error of the telescopes, to be +/- 0.2.