504 research outputs found
Interaction dipole between rare-gas atoms
Formula for coefficient of electric dipole moment of rare gas atoms in S-state
Roll Resonance for a Gravity-gradient Satellite
Roll and attitude stability for gravity gradient satellite
Unknowns after the SNO Charged-Current Measurement
We perform a model-independent analysis of solar neutrino flux rates
including the recent charged-current measurement at the Sudbury Neutrino
Observatory (SNO). We derive a universal sum rule involving SNO and
SuperKamiokande rates, and show that the SNO neutral-current measurement can
not fix the fraction of solar oscillating to sterile neutrinos. The
large uncertainty in the SSM B flux impedes a determination of the sterile
neutrino fraction.Comment: Version to appear in PRL; includes analysis with anticipated SNO NC
measuremen
Confronting mass-varying neutrinos with MiniBooNE
We study the proposal that mass-varying neutrinos could provide an
explanation for the LSND signal for \bar\nu_mu to \bar\nu_e oscillations. We
first point out that all positive oscillation signals occur in matter and that
three active mass-varying neutrinos are insufficient to describe all existing
neutrino data including LSND. We then examine the possibility that a model with
four mass-varying neutrinos (three active and one sterile) can explain the LSND
effect and remain consistent with all other neutrino data. We find that such
models with a 3+1 mass structure in the neutrino sector may explain the LSND
data and a null MiniBooNE result for 0.10 < \sin^2 2\theta_x < 0.30.
Predictions of the model include a null result at Double-CHOOZ, but positive
signals for underground reactor experiments and for \nu_\mu to \nu_e
oscillations in long-baseline experiments.Comment: 22 pages, 3 figures, 1 table. Comment added about recent MINOS dat
Leptonic CP violation studies at MiniBooNE in the (3+2) sterile neutrino oscillation hypothesis
We investigate the extent to which leptonic CP-violation in (3+2) sterile
neutrino models leads to different oscillation probabilities for
and oscillations at
MiniBooNE. We are using a combined analysis of short-baseline (SBL) oscillation
results, including the LSND and null SBL results, to which we impose additional
constraints from atmospheric oscillation data. We obtain the favored regions in
MiniBooNE oscillation probability space for both (3+2) CP-conserving and (3+2)
CP-violating models. We further investigate the allowed CP-violation phase
values and the MiniBooNE reach for such a CP violation measurement. The
analysis shows that the oscillation probabilities in MiniBooNE neutrino and
antineutrino running modes can differ significantly, with the latter possibly
being as much as three times larger than the first. In addition, we also show
that all possible values of the single CP-violation phase measurable at short
baselines in (3+2) models are allowed within 99% CL by existing data.Comment: Fixed a typo following PRD Erratum. 8 pages, 5 figure
Precise determination of the Wtb couplings at LHC
Top pair production at LHC is the ideal place to search for nonstandard Wtb
couplings in t -> W b -> l nu b decays. The lb forward-backward asymmetry in
the W rest frame is very sensitive to sigma_{mu nu} couplings, and can spot
one-loop QCD corrections to the decay vertex with more than 5 sigma statistical
significance. We discuss the potential of this asymmetry to signal nonstandard
gamma_mu and sigma_{mu nu} couplings and compare with top-antitop spin
correlation asymmetries, which have a lower sensitivity. We also briefly
summarise the results for Tevatron.Comment: LaTeX, 12 pages, 2 PS figures. One reference added. To be published
in PR
Maximal atmospheric neutrino mixing and the small ratio of muon to tau mass
We discuss the problem of the small ratio of muon mass to tau mass in a class
of seesaw models where maximal atmospheric neutrino mixing is enforced through
a -- interchange symmetry. We introduce into those models an
additional symmetry such that in the case of exact
invariance. The symmetry may be softly broken in the Higgs potential, and
one thus achieves in a technically natural way. We speculate
on a wider applicability of this mechanism.Comment: 10 pages, plain LaTeX, no figures, minor changes, final version for
J. Phys.
Unitarity Constraints on Anomalous Top Quark Couplings to Weak Gauge Bosons
If there is new physics associated with the top quark, it could show up as
anomalous couplings of the top quark to weak gauge bosons, such as Z\ttbar
and W\tbbar vector and axial-vector couplings. We use the processes
\ttbar\to Z^0Z^0, \ttbar\to W^+W^-, and \ttbar\to Z^0H to obtain the
unitarity constraints on these anomalous couplings, and combine these
constraints with those from precision electroweak data. The unitarity
constraints can impose additional limits on the anomalous couplings when the
scale of new physics is as low as 2 TeV. A nonzero measurement of such an
anomalous coupling leads to an upper limit on the new physics scale from the
unitarity condition.Comment: 12 pages, Latex, 4 postscipt figures included. Resubmitted with major
revisions, including the newest data on $R_b
Single Top Quark Production via FCNC Couplings at Hadron Colliders
We calculate single top-quark production at hadron colliders via the
chromo-magnetic flavor-changing neutral current couplings and . We find that the strength for the anomalous ()
coupling may be probed to () at the Tevatron with of data and
() at the LHC with of data. The two couplings may be
distinguished by a comparision of the single top signal with the direct top and
top decay signals for these couplings.Comment: 18 pages, 6 figures, 3 table
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