3,174 research outputs found
Inverting the Supersymmetric Standard Model Spectrum: from Physical to Lagrangian Ino Parameters
We examine the possibility of recovering the supersymmetric (and soft
supersymmetry breaking) Lagrangian parameters as direct {\em analytical}
expressions of appropriate physical masses, for the unconstrained (but CP and
R-parity conserving) minimal supersymmetric standard model. We concentrate
mainly on the algebraically non-trivial "inversion" for the ino parameters, and
obtain, for given values of , simple analytical expressions for the
, and parameters in terms of three arbitrary input physical
masses, namely either two chargino and one neutralino masses, or alternatively
one chargino and two neutralino masses. We illustrate and discuss in detail the
possible occurrence of ambiguities in this reconstruction. The dependence of
the resulting ino Lagrangian parameters upon physical masses is illustrated,
and some simple generic behaviour uncovered in this way. We finally briefly
sketch generalizing such an inversion to the full set of MSSM Lagrangian
parameters.Comment: Latex, 28 pages, 6 figures, 1 table, some typos corrected, one
paragraph extended in section 4.2. Version to appear in Phys. Rev.
Light Stop Decay in the MSSM with Minimal Flavour Violation
In supersymmetric scenarios with a light stop particle and a
small mass difference to the lightest supersymmetric particle (LSP) assumed to
be the lightest neutralino, the flavour changing neutral current decay
can be the dominant decay channel and can
exceed the four-body stop decay for certain parameter values. In the framework
of Minimal Flavour Violation (MFV) this decay is CKM-suppressed, thus inducing
long stop lifetimes. Stop decay length measurements at the LHC can then be
exploited to test models with minimal flavour breaking through Standard Model
Yukawa couplings. The decay width has been given some time ago by an
approximate formula, which takes into account the leading logarithms of the MFV
scale. In this paper we calculate the exact one-loop decay width in the
framework of MFV. The comparison with the approximate result exhibits
deviations of the order of 10% for large MFV scales due to the neglected
non-logarithmic terms in the approximate decay formula. The difference in the
branching ratios is negligible. The large logarithms have to be resummed. The
resummation is performed by the solution of the renormalization group
equations. The comparison of the exact one-loop result and the tree level
flavour changing neutral current decay, which incorporates the resummed
logarithms, demonstrates that the resummation effects are important and should
be taken into account.Comment: 29 page
Indirect Search for Neutralino Dark Matter with High Energy Neutrinos
We investigate the prospects of indirect searches for supersymmetric
neutralino dark matter. Relic neutralinos gravitationally accumulate in the Sun
and their annihilations produce high energy neutrinos. Muon neutrinos of this
origin can be seen in large detectors like AMANDA, IceCube and ANTARES. We
evaluate the relic density and the detection rate in several models---the
minimal supersymmetric model, minimal supergravity, and supergravity with
non-universal Higgs boson masses at the grand unification scale. We make
realistic estimates for the indirect detection rates including effects of the
muon detection threshold, quark hadronization, and solar absorption. We find
good prospects for detection of neutralinos with mass above 200 GeV.Comment: 36 pages in REVTEX, 18 figure
Gender specific age-related changes in bone density, muscle strength and functional performance in the elderly: a-10 year prospective population-based study
Background: Age-related losses in bone mineral density (BMD), muscle strength, balance, and gait have been linked to an increased risk of falls, fractures and disability, but few prospective studies have compared the timing, rate and pattern of changes in each of these measures in middle-aged and older men and women. This is important so that targeted strategies can be developed to optimise specific musculoskeletal and functional performance measures in older adults. Thus, the aim of this 10-year prospective study was to: 1) characterize and compare age- and gender-specific changes in BMD, grip strength, balance and gait in adults aged 50 years and over, and 2) compare the relative rates of changes between each of these musculoskeletal and functional parameters with ageing.Methods: Men (n = 152) and women (n = 206) aged 50, 60, 70 and 80 years recruited for a population-based study had forearm BMD, grip strength, balance and gait velocity re-assessed after 10-years.Results: The annual loss in BMD was 0.5-0.7% greater in women compared to men aged 60 years and older (p < 0.05- < 0.001), but there were no gender differences in the rate of loss in grip strength, balance or gait. From the age of 50 years there was a consistent pattern of loss in grip strength, while the greatest deterioration in balance and gait occurred from 60 and 70 years onwards, respectively. Comparison of the changes between the different measures revealed that the annual loss in grip strength in men and women aged <70 years was 1-3% greater than the decline in BMD, balance and gait velocity.Conclusion: There were no gender differences in the timing (age) and rate (magnitude) of decline in grip strength, balance or gait in Swedish adults aged 50 years and older, but forearm BMD decreased at a greater rate in women than in men. Furthermore, there was heterogeneity in the rate of loss between the different musculoskeletal and function parameters, especially prior to the age of 70 years, with grip strength deteriorating at a greater rate than BMD, balance and gait.</div
Altered Neurocircuitry in the Dopamine Transporter Knockout Mouse Brain
The plasma membrane transporters for the monoamine neurotransmitters dopamine, serotonin, and norepinephrine modulate the dynamics of these monoamine neurotransmitters. Thus, activity of these transporters has significant consequences for monoamine activity throughout the brain and for a number of neurological and psychiatric disorders. Gene knockout (KO) mice that reduce or eliminate expression of each of these monoamine transporters have provided a wealth of new information about the function of these proteins at molecular, physiological and behavioral levels. In the present work we use the unique properties of magnetic resonance imaging (MRI) to probe the effects of altered dopaminergic dynamics on meso-scale neuronal circuitry and overall brain morphology, since changes at these levels of organization might help to account for some of the extensive pharmacological and behavioral differences observed in dopamine transporter (DAT) KO mice. Despite the smaller size of these animals, voxel-wise statistical comparison of high resolution structural MR images indicated little morphological change as a consequence of DAT KO. Likewise, proton magnetic resonance spectra recorded in the striatum indicated no significant changes in detectable metabolite concentrations between DAT KO and wild-type (WT) mice. In contrast, alterations in the circuitry from the prefrontal cortex to the mesocortical limbic system, an important brain component intimately tied to function of mesolimbic/mesocortical dopamine reward pathways, were revealed by manganese-enhanced MRI (MEMRI). Analysis of co-registered MEMRI images taken over the 26 hours after introduction of Mn^(2+) into the prefrontal cortex indicated that DAT KO mice have a truncated Mn^(2+) distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn^(2+) transport into more posterior midbrain nuclei and contralateral mesolimbic structures at 26 hr post-injection. Thus, DAT KO mice appear, at this level of anatomic resolution, to have preserved cortico-striatal-thalamic connectivity but diminished robustness of reward-modulating circuitry distal to the thalamus. This is in contradistinction to the state of this circuitry in serotonin transporter KO mice where we observed more robust connectivity in more posterior brain regions using methods identical to those employed here
Charged-Higgs phenomenology in the Aligned two-Higgs-doublet model
The alignment in flavour space of the Yukawa matrices of a general
two-Higgs-doublet model results in the absence of tree-level flavour-changing
neutral currents. In addition to the usual fermion masses and mixings, the
aligned Yukawa structure only contains three complex parameters, which are
potential new sources of CP violation. For particular values of these three
parameters all known specific implementations of the model based on discrete
Z_2 symmetries are recovered. One of the most distinctive features of the
two-Higgs-doublet model is the presence of a charged scalar. In this work, we
discuss its main phenomenological consequences in flavour-changing processes at
low energies and derive the corresponding constraints on the parameters of the
aligned two-Higgs-doublet model.Comment: 46 pages, 19 figures. Version accepted for publication in JHEP.
References added. Discussion slightly extended. Conclusions unchange
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the
design of new-physics searches at the LHC and the characterization of their
results. Both ATLAS and CMS have already presented some results in terms of
simplified models, and we encourage them to continue and expand this effort,
which supplements both signature-based results and benchmark model
interpretations. A simplified model is defined by an effective Lagrangian
describing the interactions of a small number of new particles. Simplified
models can equally well be described by a small number of masses and
cross-sections. These parameters are directly related to collider physics
observables, making simplified models a particularly effective framework for
evaluating searches and a useful starting point for characterizing positive
signals of new physics. This document serves as an official summary of the
results from the "Topologies for Early LHC Searches" workshop, held at SLAC in
September of 2010, the purpose of which was to develop a set of representative
models that can be used to cover all relevant phase space in experimental
searches. Particular emphasis is placed on searches relevant for the first
~50-500 pb-1 of data and those motivated by supersymmetric models. This note
largely summarizes material posted at http://lhcnewphysics.org/, which includes
simplified model definitions, Monte Carlo material, and supporting contacts
within the theory community. We also comment on future developments that may be
useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results
from "Topologies for Early LHC Searches" workshop (SLAC, September 2010).
Supplementary material can be found at http://lhcnewphysics.or
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at sqrt(s) up to 209 GeV
A search for the lightest neutral CP-even and neutral CP-odd Higgs bosons of
the Minimal Supersymmetric Standard Model is performed using 216.6 pb-1 of data
collected with the L3 detector at LEP at centre-of-mass energies between 203
and 209 GeV. No indication of a signal is found. Including our results from
lower centre-of-mass energies, lower limits on the Higgs boson masses are set
as a function of tan(beta) for several scenarios. For tan(beta) greater than
0.7 they are mh > 84.5 GeV and mA > 86.3 GeV at 95% confidence level
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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