54 research outputs found
Supersymmetric Effects in Parity-Violating Deep Inelastic Electron-Nucleus Scattering
We compute the supersymmetric (SUSY) corrections to the parity-violating,
deep inelastic electron-deuteron asymmetry. Working with the Minimal
Supersymmetric Standard Model (MSSM) we consider two cases: R parity conserving
and R parity-violating. Under these scenarios, we compare the SUSY effects with
those entering other parity-violating observables. For both cases of the MSSM,
we find that the magnitude of the SUSY corrections can be as large as about 1%
and that they are strongly correlated with the effects on other
parity-violating observables. A comparison of various low-energy
parity-violating observables thus provides a potentially interesting probe of
SUSY.Comment: 12 pages, 5 figure
Parity-Violating Electron Scattering as a Probe of Supersymmetry
We compute the one-loop supersymmetric (SUSY) contributions to the weak
charges of the electron () and proton () using the Minimal
Supersymmetric Standard Model (MSSM). These vector couplings of the
-boson to fermions will be determined in two fixed-target,
parity-violating electron scattering experiments. The SUSY loop contributions
to and can be substantial, leading to several percent
corrections to the Standard Model values for these quantities. We show that the
relative signs of the SUSY loop effects on and are correlated
and positive over nearly all of the MSSM parameter space, whereas inclusion of
R-parity nonconserving interactions can lead to opposite sign relative shifts
in the weak charges. Thus, a comparison of and measurements
could help distinguish between different SUSY scenarios.Comment: 4 pages, 2 figure
Probing Supersymmetry with Neutral Current Scattering Experiments
We compute the supersymmetric contributions to the weak charges of the
electron and proton in the framework of Minimal Supersymmetric Standard Model.
We also consider the ratio of neutral current to charged current cross
sections, R_nu and R_nubar at nu (nubar)-nucleus deep inelastic scattering, and
compare the supersymmetric corrections with the deviations of these quantities
from the Standard Model predictions implied by the recent NuTeV measurement.Comment: 4 pages, contribution to the proceedings of CIPANP 2003 (May, 2003),
New York Cit
Radiative corrections in neutrino-deuterium disintegration
The radiative corrections of order alpha for the charged- and neutral-current neutrino-deuterium disintegration for energies relevant to the SNO experiment are evaluated. Particular attention is paid to the issue of the bremsstrahlung detection threshold. It is shown that the radiative corrections to the total cross section for the charged current reaction are independent of that threshold, as they must be for consistency, and amount to a slowly decreasing function of the neutrino energy E-nu, varying from about 4% at low energies to 3% at the end of the B-8 spectrum. The differential cross section corrections, on the other hand, do depend on the bremsstrahlung detection threshold. Various choices of the threshold are discussed. It is shown that for a realistic choice of the threshold and for the actual electron energy threshold of the SNO detector, the deduced B-8 nu(e) flux should be decreased by about 2%. The radiative corrections to the neutral-current reaction are also evaluated
Neutrinoless Double Beta Decay and Lepton Flavor Violation
We point out that extensions of the Standard Model with low scale (~TeV)
lepton number violation (LNV) generally lead to a pattern of lepton flavor
violation (LFV) experimentally distinguishable from the one implied by models
with GUT scale LNV. As a consequence, muon LFV processes provide a powerful
diagnostic tool to determine whether or not the effective neutrino mass can be
deduced from the rate of neutrinoless double beta decay. We discuss the role of
\mu -> e \gamma and \mu -> e conversion in nuclei, which will be studied with
high sensitivity in forthcoming experiments.Comment: 4 pages, 3 figure
Supersymmetric Effects in Deep Inelastic Neutrino-Nucleus Scattering
We compute the supersymmetric (SUSY) contributions to neutrino
(antineutrino)-nucleus deep inelastic scattering in the Minimal Supersymmetric
Standard Model (MSSM). We consider the ratio of neutral current to charged
current cross sections, and , and compare with the
deviations of these quantities from the Standard Model predictions implied by
the recent NuTeV measurement. After performing a model-independent analysis, we
find that SUSY loop corrections generally have the opposite sign from the NuTeV
anomaly. We discuss one scenario in which a right-sign effect arises, and show
that it is ruled out by other precision data. We also study for R
parity-violating (RPV) contributions. Although RPV effects could, in principle,
reproduce the NuTeV anomaly, such a possibility is also ruled out by other
precision electroweak measurements.Comment: 30 pages, 13 figure
A simple model of reactor cores for reactor neutrino flux calculations for the KamLAND experiment
KamLAND is a reactor neutrino oscillation experiment with a very long
baseline. This experiment successfully measured oscillation phenomena of
reactor antineutrinos coming mainly from 53 reactors in Japan. In order to
extract the results, it is necessary to accurately calculate time-dependent
antineutrino spectra from all the reactors. A simple model of reactor cores and
code implementing it were developed for this purpose. This paper describes the
model of the reactor cores used in the KamLAND reactor analysis.Comment: 14 pages, 7 figures, submitted to Nuclear Instruments and Methods in
Physics Research
Radiative corrections to low energy neutrino reactions
We show that the radiative corrections to charged current (CC) nuclear
reactions with an electron(positron) in the final state are described by a
universal function. The consistency of our treatment of the radiative
corrections with the procedure used to extract the value of the axial coupling
constant is discussed. To illustrate we apply our results to
(anti)neutrino deuterium disintegration and to fusion in the sun. The
limit of vanishing electron mass is considered, and a simple formula valid for
E_{obs}\gsim 1 MeV is obtained. The size of the nuclear structure-dependent
effects is also discussed. Finally, we consider CC transitions with an
electron(positron) in the initial state and discuss some applications to
electron capture reactions.Comment: 23 pages, 5 figure
Lepton Flavor Violation without Supersymmetry
We study the lepton flavor violating (LFV) processes mu -> e gamma, mu -> 3e,
and mu -> e conversion in nuclei in the left-right symmetric model without
supersymmetry and perform the first complete computation of the LFV branching
ratios B(mu -> f) to leading non-trivial order in the ratio of left- and
right-handed symmetry breaking scales. To this order, B(mu -> e gamma) and B(mu
-> e) are governed by the same combination of LFV violating couplings, and
their ratio is naturally of order unity. We also find B(mu -> 3 e)/B(mu -> e)
\sim 100 under slightly stronger assumptions. Existing limits on the branching
ratios already substantially constrain mass splittings and/or mixings in the
heavy neutrino sector. When combined with future collider studies and precision
electroweak measurements, improved limits on LFV processes will test the
viability of low-scale, non-supersymmetric LFV scenarios.Comment: 24 pages, 7 figures, 2 table
Charged Current Universality in the MSSM
We compute the complete one-loop contributions to low-energy charged current
weak interaction observables in the Minimal Supersymmetric Standard Model
(MSSM). We obtain the constraints on the MSSM parameter space which arise when
precision low-energy charged current data are analyzed in tandem with
measurements of the muon anomaly. While the data allow the presence of at least
one light neutralino, they also imply a pattern of mass splittings among first
and second generation sleptons and squarks which contradict predictions of
widely used models for supersymmetry breaking mediation.Comment: 4 pages, 2 figure
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