39,563 research outputs found
U-Spin Tests of the Standard Model and New Physics
Within the standard model, a relation involving branching ratios and direct
CP asymmetries holds for the B-decay pairs that are related by U-spin. The
violation of this relation indicates new physics (NP). In this paper, we assume
that the NP affects only the Delta S = 1 decays, and show that the NP operators
are generally the same as those appearing in B -> pi K decays. The fit to the
latest B -> pi K data shows that only one NP operator is sizeable. As a
consequence, the relation is expected to be violated for only one decay pair:
Bd -> K0 pi0 and Bs -> Kbar0 pi0.Comment: 12 pages, latex, no figures. References changed to follow MPL
guidelines; info added about U-spin breaking and small NP strong phases;
discussion added about final-state pi-K rescattering; analysis and
conclusions unaltere
Systematic study of nuclear matrix elements in neutrinoless double-beta decay with a beyond mean-field covariant density functional theory
We report a systematic study of nuclear matrix elements (NMEs) in
neutrinoless double-beta decays with a state-of-the-art beyond mean-field
covariant density functional theory. The dynamic effects of particle-number and
angular-momentum conservations as well as quadrupole shape fluctuations are
taken into account with projections and generator coordinate method for both
initial and final nuclei. The full relativistic transition operator is adopted
to calculate the NMEs. The present systematic studies show that in most of the
cases there is a much better agreement with the previous non-relativistic
calculation based on the Gogny force than in the case of the nucleus Nd
found in Song et al. [Phys. Rev. C 90, 054309 (2014)]. In particular, we find
that the total NMEs can be well approximated by the pure axial-vector coupling
term with a considerable reduction of the computational effort.Comment: 9 pages with 7 figures and 3 table
Coulomb Drag of Massless Fermions in Graphene
Using a novel structure, consisting of two, independently contacted graphene
single layers separated by an ultra-thin dielectric, we experimentally measure
the Coulomb drag of massless fermions in graphene. At temperatures higher than
50 K, the Coulomb drag follows a temperature and carrier density dependence
consistent with the Fermi liquid regime. As the temperature is reduced, the
Coulomb drag exhibits giant fluctuations with an increasing amplitude, thanks
to the interplay between coherent transport in the graphene layer and
interaction between the two layers.Comment: 5 pages, 5 figure
Radiative penguin Bs decays at Belle
We report searches for the radiative penguin decays Bs to phi gamma and Bs to
gamma gamma based on a 23.6 fb-1 data sample collected with the Belle detector
at the KEKB e+e- energy-asymmetric collider operating at the Upsilon(5S)
resonance.Comment: On behalf of the Belle Collaboration. To appear in the proceedings of
the International Europhysics Conference on High Energy Physics
(EPS-HEP2007), Manchester, England, 19-25 July 2007. 3 pages, 2 figure
Phase equilibrium in two orbital model under magnetic field
The phase equilibrium in manganites under magnetic field is studied using a
two orbital model, based on the equivalent chemical potential principle for the
competitive phases. We focus on the magnetic field induced melting process of
CE phase in half-doped manganites. It is predicted that the homogenous CE phase
begins to decompose into coexisting ferromagnetic phase and CE phase once the
magnetic field exceeds the threshold field. In a more quantitative way, the
volume fractions of the two competitive phases in the phase separation regime
are evaluated.Comment: 4 pages, 4 figure
CP asymmetries at D0
Using two independent measurements of the semileptonic CP asymmetry in the
system, we constrain the CP violating phase of the system to be
. The data sample corresponds to an integrated
luminosity of 1.1 fb accumulated with D0 detector at the Fermilab
Tevatron collider. We also measure the direct CP violating asymmetry in the
decay to be (stat)(syst). The data corresponds to an integrated
luminosity of 1.6 fb.Comment: contributed paper to EPS07, Manchester, UK, manuscript number
EPSHEPP17
Gap Equations and Electroweak Symmetry Breaking
Recently a new dynamical symmetry breaking model of electroweak interactions
was proposed based on interacting fermions. Two fermions of different SU(2)
representations form a symmetry breaking condensate and generate the lepton and
quark masses. The weak gauge bosons get their usual standard model masses from
a gauge invariant Lagrangian of a composite doublet scalar field. The new
fermion fields become massive by condensation. In this note the gap equations
are given in the linearized (mean field) approximation and the conditions for
symmetry breaking and mass generation are presented. Perturbative unitarity
constrains the self-couplings and the masses of the new fermions, a raw
spectrum is given.Comment: 10 pages, 4 figure
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