153 research outputs found
See-saw neutrino masses and large mixing angles in the vortex background on a sphere
In the vortex background on a sphere, a single 6-dimensional fermion family
gives rise to 3 zero-modes in the 4-dimensional point of view, which may
explain the replication of families in the Standard Model. Previously, it had
been shown that realistic hierarchical mass and mixing patterns can be
reproduced for the quarks and the charged leptons. Here, we show that the
addition of a single heavy 6-dimensional field that is gauge singlet, unbound
to the vortex, and embedded with a bulk Majorana mass enables to generate 4D
Majorana masses for the light neutrinos through the see-saw mechanism. The
scheme is very predictive. The hierarchical structure of the fermion zero-modes
leads automatically to an inverted pseudo-Dirac mass pattern, and always
predicts one maximal angle in the neutrino see-saw matrix. It is possible to
obtain a second large mixing angle from either the charged lepton or the
neutrino sector, and we demonstrate that this model can fit all observed data
in neutrino oscillations experiments. Also, U_{e3} is found to be of the order
~0.1.Comment: 23 pages, 1 figur
Thermal production of axino Dark Matter
We reconsider thermal production of axinos in the early universe, adding: a)
missed terms in the axino interaction; b) production via gluon decays
kinematically allowed by thermal masses; c) a precise modeling of reheating. We
find an axino abunance a few times larger than previous computations.Comment: 6 pages, 2 figures. Final version, to appear on JHE
TeV scale mirage mediation in NMSSM
We study the next-to-minimal supersymmetric standard model. We consider soft
supersymmetry breaking parameters, which are induced by the mirage mediation
mechanism of supersymmetry breaking. We concentrate on the mirage mediation,
where the so-called mirage scale is the TeV scale. In this scenario, we can
realize the up-type Higgs soft mass of O(200) GeV, while other masses such as
gaugino masses and stop masses are heavy such as 1 TeV or more. Cancellation
between the effective \mu-term and the down-type Higgs soft mass ameliorates
the fine-tuning in the electroweak symmetry breaking even for \mu=O(500) GeV.
The mixing between the doublet and singlet Higgs bosons is suppressed by
(\lambda/\kappa)/tan\beta. Then the lightest doublet Higgs mass naturally
reaches 125 GeV lifted by the new quartic coupling. The higgsino and singlino
are light and their linear combination is the lightest superparticle.Comment: 24 pages, 24 figures, Numerical analysis is replaced with the version
calculated by NMSSMTools. Comments and references are added on the suppressed
doublet-singlet mixing and cases in which the 125 GeV boson is the 2nd
lightest CP-even scalar. The version accepted by JHE
Neutron Electric Dipole Moment Constraint on Scale of Minimal Left-Right Symmetric Model
Using an effective theory approach, we calculate the neutron electric dipole
moment (nEDM) in the minimal left-right symmetric model with both explicit and
spontaneous CP violations. We integrate out heavy particles to obtain
flavor-neutral CP-violating effective Lagrangian. We run the Wilson
coefficients from the electroweak scale to the hadronic scale using one-loop
renormalization group equations. Using the state-of-the-art hadronic matrix
elements, we obtain the nEDM as a function of right-handed W-boson mass and
CP-violating parameters. We use the current limit on nEDM combined with the
kaon-decay parameter to provide the most stringent constraint yet on
the left-right symmetric scale TeV.Comment: 20 pages and 8 figure
Higgs boson enhancement effects on squark-pair production at the LHC
We study the Higgs boson effects on third-generation squark-pair production
in proton-proton collision at the CERN Large Hadron Collider (LHC), including
\Stop \Stop^*, \Stop\Sbot^*, and \Sbot \Sbot^*. We found that substantial
enhancement can be obtained through s-channel exchanges of Higgs bosons at
large , at which the enhancement mainly comes from , , and initial states. We compute the complete set of electroweak
(EW) contributions to all production channels. This completes previous
computations in the literature. We found that the EW contributions can be
significant and can reach up to 25% in more general scenarios and at the
resonance of the heavy Higgs boson. The size of Higgs enhancement is comparable
or even higher than the PDF uncertainties and so must be included in any
reliable analysis. A full analytical computation of all the EW contributions is
presented.Comment: 23 pages, 7 figures, 1 tabl
P-odd and CP-odd Four-Quark Contributions to Neutron EDM
In a class of beyond-standard-model theories, CP-odd observables, such as the
neutron electric dipole moment, receive significant contributions from
flavor-neutral P-odd and CP-odd four-quark operators. However, considerable
uncertainties exist in the hadronic matrix elements of these operators strongly
affecting the experimental constraints on CP-violating parameters in the
theories. Here we study their hadronic matrix elements in combined chiral
perturbation theory and nucleon models. We first classify the operators in
chiral representations and present the leading-order QCD evolutions. We then
match the four-quark operators to the corresponding ones in chiral hadronic
theory, finding symmetry relations among the matrix elements. Although this
makes lattice QCD calculations feasible, we choose to estimate the
non-perturbative matching coefficients in simple quark models. We finally
compare the results for the neutron electric dipole moment and P-odd and CP-odd
pion-nucleon couplings with the previous studies using naive factorization and
QCD sum rules. Our study shall provide valuable insights on the present
hadronic physics uncertainties in these observables.Comment: 40 pages, 7 figures. This is the final version. A discussion of the
uncertainty of the calculation is adde
Suboptimal management of severe menopausal symptoms by Nigerian Gynaecologists: a call for mandatory continuing medical education for physicians
<p>Abstract</p> <p>Background</p> <p>Effective management of menopause is an important way to improve the quality of life of the increasing number of older women. The study sought to find out if Nigerian Gynaecologists offer effective treatment for severe menopausal symptoms.</p> <p>Methods</p> <p>126 Nigerian Gynaecologists representing the six health zones of Nigeria were interviewed to determine the menopausal symptoms they had ever encountered in their practices, frequency of the symptoms, treatments ever offered for severe symptoms including their attitude to, and practice of hormone replacement therapy.</p> <p>Results</p> <p>A Nigerian Gynaecologist encountered an average of one patient with menopausal symptoms every three months (range: 0-3 patients per month). The commoner symptoms they encountered were hot flushes (88%), insomnia (75.4%), depression (58.0%), irritability (56.3%), night sweats (55.6%) and muscle pains (54.8%) while urinary symptoms (16.7%) and fracture (1.6%) were less common. Treatments ever offered for severe symptoms were reassurance (90.5%), anxiolytics (68.3%), analgesics (14.3), HRT (7.9%), Vitamins (4%), Beta-blockers (3.2%) and Danazol (2.4%). These treatments were offered as a matter of institutional traditions rather than being based on any evidence of their efficacy.</p> <p>Conclusion</p> <p>The result revealed that most Nigerian Gynaecologists prefer reassurance and anxiolytics for managing severe menopausal symptoms instead of evidence-based effective therapies. A policy of mandatory continuing medical education for Nigerian physicians is recommended to ensure evidence-based management of gynaecological problems, including menopause.</p
Twenty Years of SUGRA
A brief review is given of the developments of mSUGRA and its extensions
since the formulation of these models in 1982. Future directions and prospects
are also discussed.Comment: Invited talk at the International Conference BEYOND-2003, Schloss
Ringberg, Germany, June 10-14, 2003; 21 pages, Late
Beyond the standard seesaw: neutrino masses from Kahler operators and broken supersymmetry
We investigate supersymmetric scenarios in which neutrino masses are
generated by effective d=6 operators in the Kahler potential, rather than by
the standard d=5 superpotential operator. First, we discuss some general
features of such effective operators, also including SUSY-breaking insertions,
and compute the relevant renormalization group equations. Contributions to
neutrino masses arise at low energy both at the tree level and through finite
threshold corrections. In the second part we present simple explicit
realizations in which those Kahler operators arise by integrating out heavy
SU(2)_W triplets, as in the type II seesaw. Distinct scenarios emerge,
depending on the mechanism and the scale of SUSY-breaking mediation. In
particular, we propose an appealing and economical picture in which the heavy
seesaw mediators are also messengers of SUSY breaking. In this case, strong
correlations exist among neutrino parameters, sparticle and Higgs masses, as
well as lepton flavour violating processes. Hence, this scenario can be tested
at high-energy colliders, such as the LHC, and at lower energy experiments that
measure neutrino parameters or search for rare lepton decays.Comment: LaTeX, 34 pages; some corrections in Section
- …