14,172 research outputs found
R-parity violation: Hide & Seek
We point out that, if R-parity is broken spontaneously, the neutralino can
decay to the final state majoron plus neutrino, which from the experimental
point of view is indistinguishable from the standard missing momentum signal of
supersymmetry. We identify the regions of parameter space where this decay mode
is dominant and show that they are independent of R-parity conserving SUSY
parameters. Thus, (a) only very weak limits on R-parity violating couplings can
be derived from the observation of missing momentum events and (b) at future
collider experiments huge statistics might be necessary to establish that
R-parity indeed is broken. Parameter combinations which give calculated relic
neutralino density larger than the measured dark matter density in case of
conserved R-parity are valid points in this scenario and their phenomenology at
the LHC deserves to be studied.Comment: 8 pages, 2 figures; ref. added; matches published version (title
changed in the published version
Collider signals of gravitino dark matter in bilinearly broken R-parity
In models with gauge mediated supersymmetry breaking the gravitino is the
lightest supersymmetric particle. If R-parity is violated the gravitino decays,
but with a half-live far exceeding the age of the universe and thus is, in
principle, a candidate for the dark matter. We consider the decays of the
next-to-lightest supersymmetric particle, assumed to be the neutralino. We show
that in models where the breaking of R-parity is bilinear, the condition that
R-parity violation explains correctly the measured neutrino masses fixes the
branching ratio of the decay in the
range , if the gravitino mass is in the range required to
solve the dark matter problem, i.e. of the order (few) 100 eV. This scenario is
therefore directly testable at the next generation of colliders.Comment: 13 pages, 3 figure
Meissner effect, Spin Meissner effect and charge expulsion in superconductors
The Meissner effect and the Spin Meissner effect are the spontaneous
generation of charge and spin current respectively near the surface of a metal
making a transition to the superconducting state. The Meissner effect is well
known but, I argue, not explained by the conventional theory, the Spin Meissner
effect has yet to be detected. I propose that both effects take place in all
superconductors, the first one in the presence of an applied magnetostatic
field, the second one even in the absence of applied external fields. Both
effects can be understood under the assumption that electrons expand their
orbits and thereby lower their quantum kinetic energy in the transition to
superconductivity. Associated with this process, the metal expels negative
charge from the interior to the surface and an electric field is generated in
the interior. The resulting charge current can be understood as arising from
the magnetic Lorentz force on radially outgoing electrons, and the resulting
spin current can be understood as arising from a spin Hall effect originating
in the Rashba-like coupling of the electron magnetic moment to the internal
electric field. The associated electrodynamics is qualitatively different from
London electrodynamics, yet can be described by a small modification of the
conventional London equations. The stability of the superconducting state and
its macroscopic phase coherence hinge on the fact that the orbital angular
momentum of the carriers of the spin current is found to be exactly ,
indicating a topological origin. The simplicity and universality of our theory
argue for its validity, and the occurrence of superconductivity in many classes
of materials can be understood within our theory.Comment: Submitted to SLAFES XX Proceeding
Modelling tri-bimaximal neutrino mixing
We model tri-bimaximal lepton mixing from first principles in a way that
avoids the problem of the vacuum alignment characteristic of such models. This
is achieved by using a softly broken A4 symmetry realized with an isotriplet
fermion, also triplet under A4. No scalar A4-triplet is introduced. This
represents one possible realization of general schemes characterized by the
minimal set of either three or five physical parameters. In the three parameter
versions mee vanishes, while in the five parameter schemes the absolute scale
of neutrino mass, although not predicted, is related to the two Majorana
phases. The model realization we discuss is potentially testable at the LHC
through the peculiar leptonic decay patterns of the fermionic and scalar
triplets.Comment: some changing, reference adde
A remark on kinks and time machines
We describe an elementary proof that a manifold with the topology of the
Politzer time machine does not admit a nonsingular, asymptotically flat Lorentz
metric.Comment: 4 page
Testing the Mechanism of R-parity Breaking with Slepton LSP Decays
In supersymmetric models R-parity can be violated through either bilinear or
trilinear terms in the superpotential, or both. If charged scalar leptons are
the lightest supersymmetric particles, their decay properties can be used to
obtain information about the relative importance of these couplings. We show
that in some specific scenarios it is even possible to decide whether bilinear
or trilinear terms give the dominant contribution to the neutrino mass matrix.Comment: Intro rewritten, Fig 1 and Fig 4 slightly changed, conclusions
unchanged, 25 pages, 4 figure
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