349 research outputs found
Bounds on R-parity violating supersymmetric couplings from leptonic and semi-leptonic meson decays
We present a comprehensive update of the bounds on R-Parity violating
supersymmetric couplings from lepton-flavour- and lepton-number-violating decay
processes. We consider tau and mu decays as well as leptonic and semi-leptonic
decays of mesons. We present several new bounds resulting from tau, eta and
Kaon decays and correct some results in the literature concerning B-meson
decays.Comment: 30 pages; changed title, updated some bounds from the literature from
different references, added reference
Chiral Extensions of the MSSM
We present a class of extensions of the MSSM characterized by a fully chiral
field content (no mu-terms) and no baryon or lepton number violating term in
the superpotential due to an extra U'(1) gauge symmetry. The minimal model
consist of the usual matter sector with family dependent U'(1) charges, six
Higgs weak doublets, and three singlets required to give masses to the
Higgsinos and cancel anomalies. We discuss its main features such as the tree
level mass spectrum and the constraints on flavor changing processes.Comment: 13 pages. V2: Superpotential and U'(1) charges changed. Analysis of
the spectrum for the new model added. References update
Lepton Masses and Flavor Violation in Randall Sundrum Model
Lepton masses and mixing angles via localization of 5D fields in the bulk are
revisited in the context of Randall-Sundrum models. The Higgs is assumed to be
localized on the IR brane. Three cases for neutrino masses are considered: (a)
The higher dimensional LH.LH operator (b) Dirac masses (c) Type I see-saw with
bulk Majorana mass terms. Neutrino masses and mixing as well as charged lepton
masses are fit in the first two cases using minimisation for the bulk
mass parameters, while varying the Yukawa couplings between
0.1 and 4. Lepton flavour violation is studied for all the three cases. It is
shown that large negative bulk mass parameters are required for the right
handed fields to fit the data in the LH LH case. This case is characterized by
a very large Kaluza-Klein (KK) spectrum and relatively weak flavour violating
constraints at leading order. The zero modes for the charged singlets are
composite in this case and their corresponding effective 4-D Yukawa couplings
to the KK modes could be large. For the Dirac case, good fits can be obtained
for the bulk mass parameters, , lying between 0 and 1. However, most of
the `best fit regions' are ruled out from flavour violating constraints. In the
bulk Majorana terms case, we have solved the profile equations numerically. We
give example points for inverted hierarchy and normal hierarchy of neutrino
masses. Lepton flavor violating rates are large for these points. We then
discuss various minimal flavor violation (MFV) schemes for Dirac and bulk
Majorana cases. In the Dirac case with MFV hypothesis, it is possible to
simultaneously fit leptonic masses and mixing angles and alleviate lepton
flavor violating constraints for Kaluza-Klein modes with masses of around 3
TeV. Similar examples are also provided in the Majorana case.Comment: 43 pages, 20 figures, Revtex; version 2:a few clarified comments,
added references, Published in PRD versio
Extracting the depolarization coefficient D_NN from data measured with a full acceptance detector
The spin transfer from vertically polarized beam protons to Lambda or Sigma
hyperons of the associated strangeness production pp -> pK Lambda (Sigma) is
described with the depolarization coefficient D_NN. As the polarization of the
hyperons is determined by their weak decays, detectors, which have a large
acceptance for the decay particles, are needed. In this paper a formula is
derived, which describes the depolarization coefficient D_NN by count rates of
a 4 pi detector. It is shown, that formulas, which are given in publications
for detectors with restricted acceptance, are specific cases of this formula
for a 4 pi detector.Comment: Accepted for publication by Nuclear Instruments and Methods in
Physics Research Section
Flavour physics of the RS model with KK masses reachable at LHC
The version of the higher-dimensional Randall-Sundrum (RS) model with matter
in the bulk, which addresses the gauge hierarchy problem, has additional
attractive features. In particular, it provides an intrinsic geometrical
mechanism that can explain the origin of the large mass hierarchies among the
Standard Model fermions. Within this context, a good solution for the gauge
hierarchy problem corresponds to low masses for the Kaluza-Klein (KK)
excitations of the gauge bosons. Some scenarios have been proposed in order to
render these low masses (down to a few TeV) consistent with precision
electroweak measurements. Here, we give specific and complete realizations of
this RS version with small KK masses, down to 1 TeV, which are consistent with
the entire structure of the fermions in flavour space: (1) all the last
experimental data on quark/lepton masses and mixing angles (including massive
neutrinos of Dirac type) are reproduced, (2) flavour changing neutral current
constraints are satisfied and (3) the effective suppression scales of
non-renormalizable interactions (in the physical basis) are within the bounds
set by low energy flavour phenomenology. Our result, on the possibility of
having KK gauge boson modes as light as a few TeV, constitutes one of the first
theoretical motivations for experimental searches of direct signatures at the
LHC collider, of this interesting version of the RS model which accommodates
fermion masses.Comment: 27 pages, Latex file. References and comments adde
Current-induced dynamical tilting of chiral domain walls in curved microwires
We report on the investigation of current-induced domain wall motion of Néel domain walls in perpendicularly magnetized microwires with curved geometries in the flow regime. The investigation was performed by time-resolved scanning transmission x-ray microscopy. In particular, we studied the dynamical tilting of the Néel domain walls, observing that an asymmetric behavior in the domain wall tilt appears upon an inversion of the polarity of the current pulse driving the motion, an effect not predicted by state-of-the-art theories and micromagnetic modeling
Time-resolved visualization of the magnetization canting induced by field-like spin-orbit torques
We report on the use of time-resolved scanning transmission x-ray microscopy imaging for the visualization of the dynamical canting of the magnetization induced by field-like spin–orbit torques in a perpendicularly magnetized microwire. In particular, we show how the contributions to the dynamical canting of the magnetization arising from the field-like spin–orbit torque can be separated from the heating-induced effects on the magnetization of the microwire. This method will allow for the imaging of the dynamical effects of spin–orbit torques in device-like structures and buried layers.
Part of this work was performed at the Surface Interface Microscopy (SIM - X11MA) beamline of the Swiss Light Source, Paul Scherrer Institut, Villigen PSI, Switzerland. The research leading to these results received funding from the European Community's Seventh Framework Programme (No. FP7/2007-2013) under Grant Agreement No. 290605 (PSI-FELLOW/COFUND), the Swiss National Science Foundation under Grant Agreement No. 172517, and the EMPIR Programme (Grant No. 17FUN08TOPS) co-financed by the participating states, and from the European Union's Horizon 2020 Research and Innovation Programme. ML acknowledges funding received from the European Union's Horizon 2020 Research and Innovation Programme under Marie-Sklodowska Curie Grant Agreement No. 701647
First Model-Independent Measurement of the Spin Triplet Scattering Length from Final State Interaction in the Reaction
The reaction has been measured with the
COSY-TOF detector at a beam momentum of . The polarized
proton beam enables the measurement of the beam analyzing power by the
asymmetry of the produced kaon (). This observable allows the
spin triplet scattering length to be extracted for the first time
model independently from the final-state interaction in the reaction. The
obtained value is . This value is
compatible with theoretical predictions and results from model-dependent
analyses.Comment: Revised version as accepted for publication in PR
High precision measurement of the associated strangeness production in proton proton interactions
A new high precision measurement of the reaction pp -> pK+Lambda at a beam
momentum of 2.95 GeV/c with more than 200,000 analyzed events allows a detailed
analysis of differential observables and their inter-dependencies. Correlations
of the angular distributions with momenta are examined. The invariant mass
distributions are compared for different regions in the Dalitz plots. The cusp
structure at the N Sigma threshold is described with the Flatt\'e formalism and
its variation in the Dalitz plot is analyzed.Comment: accepted for publication in Eur. Phys. J.
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