Constraints on atmospheric charmed-meson production from IceCube
  At very-high energies (100 TeV - 1 PeV), the small value of Bjorken-x ($\le10^{-3}-10^{-7}$) at which the parton distribution functions are evaluated makes the calculation of charm quark production very difficult. The charm quark has mass ($\sim$1.5$\pm$0.2 GeV) significantly above the $\Lambda$$_{QCD}$ scale ($\sim$200 MeV), and therefore its production is perturbatively calculable. However, the uncertainty in the data and the calculations cannot exclude some smaller non-perturbative contribution. To evaluate the prompt neutrino flux, one needs to know the charm production cross-section in pN -> c$\bar{c}$ X, and hadronization of charm particles. This contribution briefly discusses computation of prompt neutrino flux and presents the strongest limit on prompt neutrino flux from IceCube. 
Tomasz Palczewski (1,2,3) (for the IceCube Collaboration) ((1)   University of California, Berkeley, USA, (2) Lawrence Berke...
astro-ph.HE hep-ph