Extensions in FormCalc 5.3

We present a new tool for editing Feynman diagrams as well as several extensions in version 5.3 of the package FormCalc for the calculation of Feynman diagrams.Comment: 8 pages, contribution to the proceedings of the ACAT workshop, Amsterdam, April 23-27, 200

Probing TeV gravity at neutrino telescopes

Models with extra dimensions and the fundamental scale at the TeV could imply sign als in large neutrino telescopes due to gravitational scattering of cosmogenic neu trinos in the detection volume. Apart from the production of microscopic black hol es, extensively studied in the literature, we present gravity-mediated interactions at larger distances, that can be calculated in the e ikonal approximation. In these elastic processes the neutrino loses a small fracti on of energy to a hadronic shower and keeps going. The event rate of these events is higher than that of black hole formation and the signal is distinct: no charged leptons and possibly multiple-bang events.Comment: 5 pages; to appear in the proceedings of the Workshop on Exotic Physics with Neutrino Telesocpes, Uppsala 20-22 September 200

Origin of the high energy neutrino flux at IceCube

We discuss the spectrum of the different components in the astrophysical neutrino flux reaching the Earth and the possible contribution of each component to the high-energy IceCube data. We show that the diffuse flux from cosmic ray interactions with gas in our galaxy implies just 2 events among the 54 event sample. We argue that the neutrino flux from cosmic ray interactions in the intergalactic (intracluster) space depends critically on the transport parameter $\delta$ describing the energy dependence in the diffusion coefficient of galactic cosmic rays. Our analysis motivates a E^{-2.1} neutrino spectrum with a drop at PeV energies that fits well the data, including the non-observation of the Glashow resonance at 6.3 PeV. We also show that a cosmic ray flux described by an unbroken power law may produce a neutrino flux with interesting spectral features (bumps and breaks) related to changes in the cosmic ray composition.Comment: 19 pages, new section about changes in CR composition, version to appear in Ap

TeV gravity at neutrino telescopes

Cosmogenic neutrinos reach the Earth with energies around 10^9 GeV, and their interactions with matter will be measured in upcoming experiments (Auger, IceCube). Models with extra dimensions and the fundamental scale at the TeV could imply signals in these experiments. In particular, the production of microscopic black holes by cosmogenic neutrinos has been extensively studied in the literature. Here we make a complete analysis of gravity-mediated interactions at larger distances, where they can be calculated in the eikonal approximation. In these processes a neutrino of energy E_\nu interacts elastically with a parton inside a nucleon, loses a small fraction y of its energy, and starts a hadronic shower of energy y E_\nu << E_\nu. We analyze the ultraviolet dependence and the relevance of graviton emission in these processes, and show that they are negligible. We also study the energy distribution of cosmogenic events in AMANDA and IceCube and the possibility of multiple-bang events. For any neutrino flux, the observation of an enhanced rate of neutral current events above 100 TeV in neutrino telescopes could be explained by TeV-gravity interactions. The values of the fundamental scale of gravity that IceCube could reach are comparable to those to be explored at the LHC.Comment: 10 pages, 7 figures; new section on air showers added, version to be publishe

Weak Electric Dipole Moments of Heavy Fermions in the MSSM

A minimal supersymmetric version of the Standard Model with complex parameters allows contributions to the weak-electric dipole moments of fermions at the one-loop level. Assuming generation-diagonal trilinear soft-susy-breaking terms and the usual GUT constraint, a set of CP-violating physical phases can be introduced. In this paper the general expressions for the one-loop contribution to the WEDM in a generic renormalizable theory are given and the size of the WEDM of the tau lepton and the b quark in such a supersymmetric model is discussed.Comment: 12 pages, 1 ps + 4 eps figures, LaTeX using epsf.sty. Some comments and references added. Accepted in Phys. Lett. B. The complete ps-file is also available via WWW at http://www-itp.physik.uni-karlsruhe.de/prep/prep.htm

Top-Quark Production and Decay in the MSSM

We review the features of top-quark decays and loop-induced effects in the production cross section and CP-violating observables of e+e- -> t t-bar which are specific to the R-parity conserving Minimal Supersymmetric Standard Model (MSSM).Comment: LaTeX, 28 pages, 10 figures included, uses cite.sty. Contribution to the proceedings of the 2nd Joint ECFA/DESY Workshop on Physics and Detectors for a Linear Electron-Positron Collider. References adde

One-loop MSSM Contribution to the Weak Magnetic Dipole Moments of Heavy Fermions

The MSSM predictions at the one-loop level for the weak-magnetic dipole moments of the $\tau$ lepton and the $b$ quark are analysed. The entire supersymmetric parameter space is scannedwith the usual GUT constraint and common squark and slepton mass parameters. The real part of $a^W_\tau$ is dominated by the chargino contribution, being the same order as the SM one or even larger in the high $\tan\beta$ region whereas the imaginary part, due to Higgs boson diagrams, is negligible comparedto the SM value. The real part of$a^W_b$ is controlled mainly by charginos andalso by gluinos, when the mixing in the bottom squark sector is large, to yield, for high $\tan\beta$, a contribution one order of magnitude largerthan the pure electroweak SM value but a factor five smaller than the standard QCD contribution. The imaginary part of $a^W_b$ is the same order as in the SM.Comment: 14 pages, Latex, 4 eps and 1 ps figure, needs epsfig.sty. Minor changes, new references added. To be published in Phys. Lett.