Ina Sarcevic

We calculate contained and upward muon flux and contained shower event rates from neutrino interactions, when neutrinos are produced from annihilation of the dark matter in the Galactic center. We consider model-independent direct neutrino production and secondary neutrino production from the decay of taus, W bosons, and bottom quarks produced in the annihilation of dark matter. We illustrate how muon flux from dark matter annihilation has a very different shape than the muon flux from atmospheric neutrinos. We also discuss the dependence of the muon fluxes on the dark matter density profile and on the dark matter mass and of the total muon rates on the detector threshold. We consider both the upward muon flux, when muons are created in the rock below the detector, and the contained flux when muons are created in the (ice) detector. We also calculate the event rates for showers from neutrino interactions in the detector and show that the signal dominates over the background for $150\mathrm{GeV}<m_{\chi }<1\mathrm{TeV}$ for $E_{\mathrm{sh}}^{\mathrm{th}}=100\mathrm{GeV}$. DOI: http://dx.doi.org/10.1103/PhysRevD.81.096007 © 2010 The American Physical Society

We study the nuclear shadowing effect in the context of Glauber-Gribov multiple-scattering model and perturbative QCD. We find that at small x, the $Q^2$ evolution of the shadowing is much slower than the DGLAP evolution, due to the multiple scatterings at small x. We show that the gluon shadowing at small x and for $Q^2 > 3GeV^2$ is perturbative in nature and does not depend on the initial, non-perturbative condition. We evaluate the impact parameter dependence of the gluon distribution and show that it is a non-linear effect in the nuclear thickness function.

We propose a novel approach for studying ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillations with extragalactic neutrinos. Active galactic nuclei and gamma ray bursts are believed to be sources of ultrahigh energy muon neutrinos. With distances of 100 Mpc or more, they provide an unusually long baseline for possible detection of ${\nu }_{\mu }\to {\nu }_{\tau }$ with mixing parameters $\Delta m^2$ down to ${10}^{-17}$ ${\mathrm{eV}}^2,$ many orders of magnitude below the current accelerator experiments. By solving the coupled transport equations, we show that high-energy ${\nu }_{\tau }\mathrm{’}\mathrm{s},$ as they propagate through the Earth, cascade down in energy, producing the enhancement of the incoming ${\nu }_{\tau }$ flux in the low energy region, in contrast with the high-energy ${\nu }_{\mu }’\mathrm{s},$ which get absorbed. For an AGN quasar model we find the ${\nu }_{\tau }$ flux to be a factor of 2 to 2.5 larger than the incoming flux in the energy range between ${10}^2$ GeV and ${10}^4$ GeV, while for a GRB fireball model, the enhancement is 10–27 % in the same energy range and for zero nadir angle. This enhancement decreases with larger nadir angle, thus providing a novel way to search for ${\nu }_{\tau }$ appearance by measuring the angular dependence of the muons. To illustrate how the cascade effect and the ${\nu }_{\tau }$ final flux depend on the steepness of the incoming ${\nu }_{\tau },$ we show the energy and angular distributions for several generic cases of the incoming tau neutrino flux, $F_{\nu }^0\sim E^{-n}$ for $n=1,$ 2 and $\mathrm{3.6.}$ We show that for the incoming flux that is not too steep, the signal for the appearance of high-energy ${\nu }_{\tau }$ is the enhanced production of lower energy $\mu$ and their distinctive angular dependence, due to the contribution from the $\tau$ decay into $\mu$ just below the detector.

We report new calculations of the cross sections for deeply inelastic neutrino-nucleon scattering at neutrino energies between ${10}^9\mathrm{eV}$ and ${10}^{21}\mathrm{eV}.$ We compare with results in the literature and assess the reliability of our predictions. For completeness, we briefly review the cross sections for neutrino interactions with atomic electrons, emphasizing the role of the $W$-boson resonance in ${\overline{\nu }}_{e}e$ interactions for neutrino energies in the neighborhood of 6.3 PeV. Adopting model predictions for extraterrestrial neutrino fluxes from active galactic nuclei, gamma-ray bursters, and the collapse of topological defects, we estimate event rates in large-volume water Čerenkov detectors and large-area ground arrays.

We report new calculations of the cross sections for deeply inelastic neutrino-nucleon scattering at neutrino energies between $10^{9}\ev$ and $10^{21}\ev$. We compare with results in the literature and assess the reliability of our predictions. For completeness, we briefly review the cross sections for neutrino interactions with atomic electrons, emphasizing the role of the $W$-boson resonance in $\bar{\nu}_{e}e$ interactions for neutrino energies in the neighborhood of $6.3\pev$. Adopting model predictions for extraterrestrial neutrino fluxes from active galactic nuclei, gamma-ray bursters, and the collapse of topological defects, we estimate event rates in large-volume water \v{C}erenkov detectors and large-area ground arrays.