242 research outputs found
Verifiable Origin of Neutrino Mass at TeV Scale
The physics responsible for neutrino mass may reside at or below the TeV
energy scale. The neutrino mass matrix in the
basis may then be deduced from future high-energy accelerator experiments. The
newly observed excess in the muon anomalous magnetic moment may also be
related.Comment: 9 pages, 1 figure, talk at TAUP 200
Semileptonic decays of polarised top quarks: V + A admixture and QCD corrections
The semileptonic decays of polarised top quarks are analysed for a general
chirality-conserving tbW vertex. We calculate double differential distributions
for the charged lepton and the neutrino to order \alpha_s in the QCD coupling.
We present these QCD corrections in terms of compact parameterisations that
should be useful for the future investigation of the structure of the top decay
vertex on the basis of large data samples.Comment: 7 pages, 2 figures, Late
Softly Broken A_4 Symmetry for Nearly Degenerate Neutrino Masses
The leptonic Higgs doublet model of neutrino masses is implemented with an
A_4 discrete symmetry (the even permutation of 4 objects or equivalently the
symmetry of the tetrahedron) which has 4 irreducible representations: 1, 1',
1'', and 3. The resulting spontaneous and soft breaking of A_4 provides a
realistic model of charged-lepton masses as well as a nearly degenerate
neutrino mass matrix. Phenomenological consequences at and below the TeV scale
are discussed.Comment: 11 pages, no figur
Second order QCD corrections to inclusive semileptonic b \to Xc l \bar \nu_l decays with massless and massive lepton
We extend previous computations of the second order QCD corrections to
semileptonic b \to c inclusive transitions, to the case where the charged
lepton in the final state is massive. This allows accurate description of b \to
c \tau \bar \nu_\tau decays. We review techniques used in the computation of
O(\alpha_s^2) corrections to inclusive semileptonic b \to c transitions and
present extensive numerical studies of O(\alpha_s^2) QCD corrections to b \to c
l \bar \nu_l decays, for l =e, \tau.Comment: 30 pages, 4 figures, 5 table
Combining the Muon Anomalous Magnetic Moment with other Constraints on the CMSSM
We combine the constraint suggested by the recent BNL E821 measurement of the
anomalous magnetic moment of the muon on the parameter space of the constrained
MSSM (CMSSM) with those provided previously by LEP, the measured rate of b to s
gamma decay and the cosmological relic density Omega-hsquared. Our treatment of
Omega-hsquared includes carefully the direct-channel Higgs poles in
annihilation of pairs of neutralinos chi and a complete analysis of chi -
slepton coannihilation. We find excellent consistency between all the
constraints for tan beta > 10 and mu > 0, for restricted ranges of the CMSSM
parameters m_0 and m_1/2. All the preferred CMSSM parameter space is within
reach of the LHC, but may not be accessible to the Tevatron collider, or to a
first-generation e^+ e^- linear collider with centre-of-mass energy below 1.2
TeV.Comment: 14 pages, 3 eps figures, for a version with high-resolution figures,
go to http://www.hep.umn.edu/~olive/ENO4.p
Supersymmetric Model of Muon Anomalous Magnetic Moment and Neutrino Masses
We propose the novel lepton-number relationship , which
is uniquely realized by the interaction in supersymmetry and may account for a possibly large
muon anomalous magnetic moment. Neutrino masses (with bimaximal mixing) may be
generated from the spontaneous and soft breaking of this lepton symmetry.Comment: 10 pages, including 2 figure
Anomalous Neutrino Interaction, Muon g-2, and Atomic Parity Nonconservation
We propose a simple unified description of two recent precision measurements
which suggest new physics beyond the Standard Model of particle interactions,
i.e. the deviation of in deep inelastic neutrino-nucleon
scattering and that of the anomalous magnetic moment of the muon. Our proposal
is also consistent with a third precision measurement, i.e. that of parity
nonconservation in atomic Cesium, which agrees with the Standard Model.Comment: 9 pages, including 1 figure, latest muon g-2 information adde
Electroweak two-loop contribution to the mass splitting within a new heavy SU(2) fermion multiplet
New heavy particles in an SU(2)_L multiplet, sometimes introduced in
extensions of the standard model, have highly degenerate tree-level mass M if
their couplings to the Higgs bosons are very small or forbidden. However, loop
corrections may generate the gauge-symmetry-breaking mass splitting within the
multiplet, which does not vanish in the large M limit due to the threshold
singularity. We calculate the electroweak contribution to the mass splitting
for a heavy fermion multiplet, to the two-loop order. Numerically, two-loop
electroweak contributions are typically O(MeV).Comment: 14 pages, style changed, analytic forms of two-loop functions adde
B-> D* zero-recoil formfactor and the heavy quark expansion in QCD: a systematic study
We present a QCD analysis of heavy quark mesons focussing on the B -> D*
formfactor at zero recoil, F_D*(1). An advanced treatment of the perturbative
corrections in the Wilsonian approach is presented. We estimate the
higher-order power corrections to the OPE sum rule and describe a refined
analysis of the nonresonant continuum contribution. In the framework of a
model-independent approach, we show that the inelastic contribution in the
phenomenological part of the OPE is related to the mQ-dependence of the
hyperfine splitting and conclude that the former is large, lowering the
prediction for F_D*(1) down to about 0.86. This likewise implies an enhanced
yield of radial and D-wave charm excitations in semileptonic B decays and
alleviates the problem with the inclusive yield of the wide excited states. We
also apply the approach to the expectation values of dimension 7 and 8 local
operators and to a few other issues in the heavy quark expansion.Comment: 70 pages, 13 figure
Enhancement of Radiatively Induced Magnetic Moment Form-Factors of Muon: an Effective Lagrangian Approach
Using an effective lagrangian approach, we identify a class of models in
which the loop-induced magnetic moment form-factors of muon are enhanced by
possibly large factors
(\Lambda^2_F/\Lambda^2)(m_\tau/m_\mu)\ln(m_\tau^2/\Lambda^2) or
(\Lambda^2_F/\Lambda^2)\ln(m_\mu^2/\Lambda^2), where \Lambda is the scale of
new physics and \Lambda_F is the Fermi scale. These follow from left- and
right-chirality mixing dimension-8 operators which for relatively small
\Lambda, as required to explain the new (g_\mu-2) measurement, dominate over
dimension-6 operators. Thus significant enhancement of new physics
contributions to (g_\mu-2) and, in the presence of intergenerational couplings,
also to the \mu\to e\gamma decay rate is possible. We discuss the compatibility
of the (g_\mu-2) and \mu\to e\gamma experimental data in this case and comment
on the enhancement of the electron anomalous magnetic moment. An explicit model
is presented to illustrate the general results.Comment: Discussion on the enhancement of electron anomalous magnetic moment
included. New references adde
- …