Mary Hall Reno

Ultrahigh-energy neutrino interactions

Abstract Cross sections for the interactions of ultrahigh-energy neutrinos with nucleons are evaluated in the light of new information about nucleon structure functions. For 10 2 eV neutrinos, the cross section is about 2.4 times previous estimates. We also review the cross sections for neutrino interactions with atomic electrons. Some consequences for interaction rates in the Earth and for event rates from generic astrophysical sources in large-scale detectors are noted

Neutrino interactions at ultrahigh energies

We report new calculations of the cross sections for deeply inelastic neutrino-nucleon scattering at neutrino energies between 10{sup 9}thinspeV and 10{sup 21}thinspeV. 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}}{sub 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 {hacek C}erenkov detectors and large-area ground arrays. {copyright} {ital 1998} {ital The American Physical Society}

A facility to search for hidden particles at the CERN SPS: the SHiP physics case.

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (search for hidden particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, [Formula: see text] and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the standard model and describe interactions between new particles and four different portals-scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the standard model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation.

Prompt neutrino fluxes from atmospheric charm

We calculate the prompt neutrino flux from atmospheric charm production by cosmic rays, using the dipole picture in a perturbative QCD framework, which incorporates the parton saturation effects present at high energies. We compare our results with the next-to-leading order perturbative QCD result and find that saturation effects are large for neutrino energies above 10^6 GeV, leading to a substantial suppression of the prompt neutrino flux. We comment on the range of prompt neutrino fluxes due to theoretical uncertainties.

Propagation of muons and taus at high energies

The photonuclear contribution to charged lepton energy loss has been reevaluated taking into account DESY HERA results on real and virtual photon interactions with nucleons. With large Q{sup 2} processes incorporated, the average muon range in rock for energies of 10{sup 9} GeV is reduced by only 5% compared with the standard treatment. We have calculated the tau energy loss for energies up to 10{sup 9} GeV taking into consideration the decay of tau. A Monte Carlo evaluation of tau survival probability and range shows that at energies below 10{sup 7}--10{sup 8} GeV, depending on the material, only tau decays are important. At higher energies the tau energy losses are significant, reducing the survival probability of the tau. We show that the average range for tau is shorter than its decay length and reduces to 17 km in water for an incident tau energy of 10{sup 9} GeV, as compared with its decay length of 49 km at that energy. In iron, the average tau range is 4.7 km for the same incident energy.

Reconciling neutrino flux from heavy dark matter decay and recent events at IceCube

A bstractThe IceCube detector has recently reported the observation of 28 events at previously unexplored energies. While the statistics of the observed events are still low, these events hint at the existence of a neutrino flux over and above the atmospheric neutrino background. We investigate the possibility that a significant component of the additional neutrino flux originates due to the decay of a very heavy dark matter (VHDM) particle via several possible channels into standard model particles. We show that a combination of a power law astrophysical neutrino spectrum and the neutrino flux from the decay of a DM species of mass in the range 150 − 400 TeV improves the fit to the observed neutrino events than that obtained from a best-fit astrophysical flux alone. Assuming the existence of an astrophysical background described by the IC best-fit, we also show that, for the decay of even heavier DM particles (mDM ~ 1 PeV), the same observations impose significant constraints on the decay lifetimes. Allowing the astrophysical flux normalization to vary leads to modifications of these limits, however, there is still a range of dark matter mass and lifetime that is excluded by the IC results.

Lepton fluxes from atmospheric charm

We reexamine 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 {ital x}. We show that the charm contribution to the atmospheric muon flux becomes dominant over the conventional contribution from {pi} and {ital K} decays at energies of about 10{sup 5} GeV. We compare our fluxes with previous calculations. {copyright} {ital 1999} {ital The American Physical Society}

Perturbative charm production and the prompt atmospheric neutrino flux in light of RHIC and LHC

A bstractWe re-evaluate the prompt atmospheric neutrino flux, using the measured charm cross sections at RHIC and the Large Hadron Collider to constrain perturbative QCD parameters such as the factorization and renormalization scales, as well as modern parton distribution functions and recent estimates of the cosmic-ray spectra. We find that our result for the prompt neutrino flux is lower than previous perturbative QCD estimates and, consequently, alters the signal-to-background statistics of the recent IceCube measurements at high energies.

Next-to-leading order slepton pair production at hadron colliders

We compute total cross sections for various slepton pair production reactions scr(l{tilde )}{sub L}{tilde {nu}}{sub L}, scr(l{tilde )}{sub L}scr(l{bar {tilde )}}{sub L}, scr(l{tilde )}{sub R}scr(l{bar {tilde )}}{sub R} and {tilde {nu}}{sub L}{anti {tilde {nu}}}{sub L} in next-to-leading order QCD. For p{bar p} collisions at {radical} (S) =2 TeV, we find leading order cross sections to be enhanced by typically 35{percent} to 40{percent}. For pp collisions at {radical} (S) =14 TeV, the enhancement ranges from 25{percent} to 35{percent} depending on the mass of the sleptons. We comment upon the phenomenological implications of these results. {copyright} {ital 1998} {ital The American Physical Society}

Parton Structure of the Nucleon and Precision Determination of the Weinberg Angle in Neutrino Scattering

A next-to-leading-order (NLO) calculation of neutrino cross sections, including power-suppressed mass terms, is used to evaluate the Paschos-Wolfenstein ratio, in order to better assess the validity and significance of the NuTeV anomaly. We study the shift of sin2thetaW obtained in calculations with parton distribution function sets that allow s(x) not = s(x), enabled by recent neutrino dimuon data from CCFR and NuTeV. The extracted value of sin2thetaW is closely correlated with the strangeness asymmetry. Taken together with recent developments of possible isospin violation and electroweak effects, our results suggest that the new dimuon data, the Weinberg angle measurement, and other data sets used in global QCD parton structure analysis can all be consistent within the standard model. A full NLO analysis of the actual experimental measurement will help to clarify this issue further.