204 research outputs found
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
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
Cosmogenic neutrinos and signals of TeV gravity in air showers and neutrino telescopes
The existence of extra dimensions allows the possibility that the fundamental
scale of gravity is at the TeV. If that is the case, gravity could dominate the
interactions of ultra-high energy cosmic rays. In particular, the production of
microscopic black holes by cosmogenic neutrinos has been estimated in a number
of papers. We consider here gravity-mediated interactions at larger distances,
where they can be calculated in the eikonal approximation. We show that for the
expected flux of cosmogenic neutrinos these elastic processes give a stronger
signal than black hole production in neutrino telescopes. Taking the bounds on
the higher dimensional Planck mass M_D (D=4+n) from current air shower
experiments, for n=2 (6) elastic collisions could produce up to 118 (34) events
per year at IceCube. On the other hand, the absence of any signal would imply a
bound of M_D>~5 TeV.Comment: 10 pages, 1 figure; version to appear in Phys. Rev. Let
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