Simulation of the radio signal from ultrahigh energy neutrino-initiated showers

PeV neutrinos produce particle showers when they interact with the atomic nuclei in ice. We briefly describe characteristics of these showers and the radio Cherenkov signal produced by the showers. We study pulses from electromagnetic (em), hadronic, and combined em-hadronic showers and propose extrapolations to EeV energies.Comment: Made changes in figure captions and reference 6. 3 pages, to appear in "Lake Louise Winter Institute 2004" conference proceeding

sin⁡2(θ)w\sin^2(\theta)w estimate and bounds on nonstandard interactions at source and detector in the solar neutrino low-energy regime

We explore the implications of the Borexino experiment's real time measurements of the lowest energy part of the neutrino spectrum from the primary pp fusion process up to 0.420 MeV through the 7^Be decay at 0.862 MeV to the pep reaction at 1.44 MeV. We exploit the fact that at such low energies, the large mixing angle solution to the Mikheyev-Smirnov-Wolfenstein matter effects in the sun are small for 7^Be and pep and negligible for pp. Consequently, the neutrinos produced in the sun change their flavor almost entirely through vacuum oscillations during propagation from the sun's surface and through possible nonstandard interactions acting at the solar source and Borexino detector. We combine the different NSI effects at source and detector in a single framework and use the current Borexino data to bound NSI non-universal and flavor- changing parameters at energies below the reach of reactor neutrino experiments. We also study the implication of the current data for the weak- mixing angle at this "low-energy frontier" data from the Borexino experiment, where it is expected to be slightly larger than its value at the Z mass. We find $\sin^2(\theta)w=0.224+-0.016$, the lowest energy-scale estimate to date. Looking to the future, we use projected sensitivities to solar neutrinos in next generation dedicated solar experiments and direct dark matter detection experiments and find a potential factor five improvement in determination of the weak-mixing angle and up to an order of magnitude improvement in probing the NSI parameters space.Comment: 20 pages, 09 figures, lowest-energy value of sin^2(theta)w to date has been reported. Some text added. New sub-section(7.5) added. Published in JHE

A Nonperturbative, Schwinger-Dyson-Equation Analysis of Quark Masses and Mixings in a Model with QCD and Higgs Interactions

The Landau gauge Schwinger-Dyson Equation for the quark self-energy is solved in the quenched ladder approximation for several cases of one- and two-quark-generations. The exchanges of Standard Model gluons and Higgs bosons are taken into account. It is found that Higgs boson exchange dominates the quark self-energy for sufficiently large input quark masses (>75 GeV), causing the running quark propagator mass to increase with energy-scale. The running of the quark mixing angles is also considered. No running of the quark mixing angles is found, to one part in a billion, for input quark masses up to and including 500 GeV.Comment: 18 pages, LaTeX twice, 4 figures available upon reques