340 research outputs found
Neutrino Spin Flavor Precession and Leptogenesis
We argue that \Delta L=2 neutrino spin flavor precession, induced by the
primordial magnetic fields, could have a significant impact on the leptogenesis
process that accounts for the baryon asymmetry of the universe. Although the
extra galactic magnetic fields is extremely weak at present time (about 10^{-9}
Gauss), the primordial magnetic filed at the electroweak scale could be quite
strong (of order 10^{17} Gauss). Therefore, at this scale, the effects of the
spin flavor precession are not negligible. We show that the lepton asymmetry
may be reduced by 50% due to the spin flavor precession. In addition, the
leptogenesis will have different feature from the standard scenario of
leptogenesis, where the lepton asymmetry continues to oscillate even after the
electroweak phase transition.Comment: 5 pages, one figure. References adde
A sharp incisor tool for predator house mice back to the wild
The house mouse (Mus musculus domesticus), as a successful invasive species worldwide, has to forage a variety of resources. Subantarctic mice display among the most notable diet shift from the usual omnivorous–granivorous diet, relying on a larger proportion of terrestrial animal prey. In agreement, a recent study of their mandible morphology evidenced an evolution of their mandible shape to optimize incisor biting and hence seize preys. Here, the incisors themselves are the focus of a morphometric analysis combined with a 3D study of their internal structure, aiming at a comparison between subantarctic populations (Guillou island, Kerguelen archipelago) with a range of western European continental, commensal mice. The predatory foraging behavior of Guillou mice was indeed associated with a sharper bevel of the lower incisor, which appears as an efficient morphology for piercing prey. The incisor of these mice also displays a reduced pulp cavity, suggesting slower eruption counterbalancing a reduced abrasion on such soft food material. The dynamics of the ever‐growing incisor may thus allow adaptive incisor sculpting and participate to the success of mice in foraging diverse resources
The baryogenesis window in the MSSM
Thermal two-loop QCD corrections associated with light stops have a dramatic
effect on the strength of the MSSM electroweak phase transition, making it more
strongly first order as required for the viability of electroweak baryogenesis.
We perform a perturbative analysis of the transition strength in this model,
including these important contributions, extending previous work to arbitrary
values of the pseudoscalar Higgs boson mass, m_A. We find a strong enough
transition in a region with 2 120 GeV, a light Higgs
boson with nearly standard couplings, and mass below 85 GeV within the reach of
LEP II, and one stop not much heavier than the top quark. In addition, we give
a qualitative discussion of the parameter space dependence of the transition
strength and comment on the possibility that the transition turns to a
crossover for sufficiently large Higgs masses.Comment: 33 pages, latex2e, 5 figures, epsfig.sty. Final version to appear in
Nuclear Physics
A Consistent Scenario for B to PS Decays
We consider B to PS decays where P stands for pseudoscalar and S for a heavy
(~1500 MeV) scalar meson. We achieve agreement with available experimental data
-- which includes a two orders of magnitude hierarchy -- assuming the scalars
mesons are two quark states. The contribution of the dipolar penguin operator
O_{11} is quantified.Comment: 10 pages, no figure
Baryogenesis at Low Reheating Temperatures
We note that the maximum temperature during reheating can be much greater
than the reheating temperature at which the Universe becomes radiation
dominated. We show that the Standard Model anomalous -violating
processes can therefore be in thermal equilibrium for 1 GeV \simlt T_{r}\ll
100 GeV. Electroweak baryogenesis could work and the traditional upper bound
on the Higgs mass coming from the requirement of the preservation of the baryon
asymmetry may be relaxed. Alternatively, the baryon asymmetry may be
reprocessed by sphaleron transitions either from a asymmetry generated
by the Affleck-Dine mechanism or from a chiral asymmetry between and
in a Universe. Our findings are also relevant to the production
of the baryon asymmetry in large extra dimension models.Comment: 4 pages, version to appear in PRL: references added, new titl
Supersymmetric contributions to and decays in SCET
We study the decay modes and using Soft Collinear Effective Theory. Within Standard Model and
including the error due to the SU(3) breaking effect in the SCET parameters we
find that BR and BR
corresponding to
solution 1 and solution 2 of the SCET parameters respectively.For the decay
mode , we find that BR and BR corresponding to solution 1 and
solution 2 of the SCET parameters respectively. We extend our study to include
supersymmetric models with non-universal A-terms where the dominant
contributions arise from diagrams mediated by gluino and chargino exchanges. We
show that gluino contributions can not lead to an enhancement of the branching
ratios of and . In
addition, we show that SUSY contributions mediated by chargino exchange can
enhance the branching ratio of by about 14% with
respect to the SM prediction. For the branching ratio of , we find that SUSY contributions can enhance its value by about 1% with
respect to the SM prediction.Comment: 25 pages,5 figures, version accepted for publicatio
CP-Violating Asymmetries in Charmless Non-Leptonic Decays in the Factorization Approach
We present estimates of the direct (in decay amplitudes) and indirect
(mixing- induced) CP-violating asymmetries in the non-leptonic charmless
two-body decay rates for , and decays and their
charged conjugates, where P(V) is a light pseudoscalar (vector) meson. These
estimates are based on a generalized factorization approach making use of
next-to-leading order perturbative QCD contributions which generate the
required strong phases. No soft final state interactions are included. We study
the dependence of the asymmetries on a number of input parameters and show that
there are at least two (possibly three) classes of decays in which the
asymmetries are parametrically stable in this approach. The decay modes of
particular interest are: \optbar{B^0} \to \pi^+ \pi^-, \optbar{B^0} \to
K_S^0 \pi^0, \optbar{B^0} \to K_S^0 \eta^\prime, \optbar{B^0} \to K_S^0
\eta and \optbar{B^0} \to \rho^+ \rho^-. Likewise, the CP-violating
asymmetry in the decays \optbar{B^0} \to K_S^0 h^0 with is found to be parametrically stable and large. Measurements
of these asymmetries will lead to a determination of the phases
and and we work out the relationships in these modes in the
present theoretical framework. We also show the extent of the so-called
"penguin pollution" in the rate asymmetry and of the
"tree shadow" in the asymmetry which will effect the
determination of and from the respective
measurements. CP-violating asymmetries in ,
, and are potentially interesting and are studied here.Comment: 42 pages (LaTex) including 19 figures, requires epsfig.sty; submitted
to Phys. Rev.
Flavour physics constraints in the BMSSM
We study the implications of the presence of the two leading-order,
non-renormalizable operators in the Higgs sector of the MSSM to flavour physics
observables. We identify the constraints of flavour physics on the parameters
of the BMSSM when we: a) focus on a region of parameters for which electroweak
baryogenesis is feasible, b) use a CMSSM-like parametrization, and c) consider
the case of a generic NUHM-type model. We find significant differences as
compared to the standard MSSM case.Comment: 22 pages, 7 figure
Constraints on the phase and new physics from Decays
Recent results from CLEO on indicate that the phase may
be substantially different from that obtained from other fit to the KM matrix
elements in the Standard Model. We show that extracted using is sensitive to new physics occurring at loop level. It provides
a powerful method to probe new physics in electroweak penguin interactions.
Using effects due to anomalous gauge couplings as an example, we show that
within the allowed ranges for these couplings information about
obtained from can be very different from the Standard
Model prediction.Comment: Revised version with analysis done using new data from CLEO. RevTex,
11 Pages with two figure
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