5,286 research outputs found
Majorana Neutrinos and Same-Sign Dilepton Production at LHC and in Rare Meson Decays
We discuss same-sign dilepton production mediated by Majorana neutrinos in
high-energy proton-proton collisions pp\ra \ell^+ \ell^{\prime +}X for
at the LHC energy TeV, and
in the rare decays of , , , and mesons of the type M^{+}\ra
M^{\prime -}\ell ^{+}\ell ^{\prime+}. For the reaction, assuming one
heavy Majorana neutrino of mass , we present discovery limits in the
plane where are the mixing
parameters. Taking into account the present limits from low energy experiments,
we show that at LHC for the nominal luminosity L=100 fb there is no room
for observable same-sign dilepton signals. However, increasing the integrated
luminosity by a factor 30, one will have sensitivity to heavy Majorana
neutrinos up to a mass TeV only in the dilepton channels
and , but other dilepton states will not be detectable due to the
already existing strong constraints. We work out a large number of rare meson
decays, both for the light and heavy Majorana neutrino scenarios, and argue
that the present experimental bounds on the branching ratios are too weak to
set reasonable limits on the effective Majorana masses.Comment: 18 pages, 4 figures (requires graphicx), a coefficient in Eq. (4)
corrected leading to drastic reduction in the Majorana-induced same-sign
dilepton cross-section at LHC; revised Figs. 2 and 3; references adde
Homogenization of the planar waveguide with frequently alternating boundary conditions
We consider Laplacian in a planar strip with Dirichlet boundary condition on
the upper boundary and with frequent alternation boundary condition on the
lower boundary. The alternation is introduced by the periodic partition of the
boundary into small segments on which Dirichlet and Neumann conditions are
imposed in turns. We show that under the certain condition the homogenized
operator is the Dirichlet Laplacian and prove the uniform resolvent
convergence. The spectrum of the perturbed operator consists of its essential
part only and has a band structure. We construct the leading terms of the
asymptotic expansions for the first band functions. We also construct the
complete asymptotic expansion for the bottom of the spectrum
Nonlinear Realization of the Local Conform-Affine Symmetry Group for Gravity in the Composite Fiber Bundle Formalism
A gauge theory of gravity based on a nonlinear realization (NLR) of the local
Conform-Affine (CA) group of symmetry transformations is presented. The coframe
fields and gauge connections of the theory are obtained. The tetrads and
Lorentz group metric are used to induce a spacetime metric. The inhomogenously
transforming (under the Lorentz group) connection coefficients serve as
gravitational gauge potentials used to define covariant derivatives
accommodating minimal coupling of matter and gauge fields. On the other hand,
the tensor valued connection forms serve as auxillary dynamical fields
associated with the dilation, special conformal and deformational (shear)
degrees of freedom inherent in the bundle manifold. The bundle curvature of the
theory is determined. Boundary topological invariants are constructed. They
serve as a prototype (source free) gravitational Lagrangian. The Bianchi
identities, covariant field equations and gauge currents are obtained.Comment: 24 pages. to appear in IJGMM
New type of stable particle like states in chiral magnets (Chiral bobbers)
We present a new type of a thermodynamically stable magnetic state at
interfaces and surfaces of chiral magnets. The state is a soliton solution of
micromagnetic equations localized in all three dimensions near a boundary and
contains a singularity, but nevertheless has a finite energy. Both features
combine to a quasi-particle state for which we expect unusual transport and
dynamical properties. It exhibits high thermal stability and thereby can be
considered as promising object for fundamental research and practical
applications in spintronic devices. We provide arguments that such a state can
be found in different B20-type alloys e.g. MnFeGe,
MnFeSi, FeCoSi.Comment: accepted in PR
Spinors for Spinning p-Branes
The group of the p-brane world volume preserving diffeomorphism is
considered. The infinite-dimensional spinors of this group are related, by the
nonlinear realization techniques, to the corresponding spinors of its linear
subgroup, that are constructed explicitly. An algebraic construction of the
Virasoro and Neveu-Schwarz-Ramond algebras, based on this infinite-dimensional
spinors and tensors, is demonstrated.Comment: 18 page
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