4,679 research outputs found
Non-minimally coupled dark matter: effective pressure and structure formation
We propose a phenomenological model in which a non-minimal coupling between
gravity and dark matter is present in order to address some of the apparent
small scales issues of \lcdm model. When described in a frame in which gravity
dynamics is given by the standard Einstein-Hilbert action, the non-minimal
coupling translates into an effective pressure for the dark matter component.
We consider some phenomenological examples and describe both background and
linear perturbations. We show that the presence of an effective pressure may
lead these scenarios to differ from \lcdm at the scales where the non-minimal
coupling (and therefore the pressure) is active. In particular two effects are
present: a pressure term for the dark matter component that is able to reduce
the growth of structures at galactic scales, possibly reconciling simulations
and observations; an effective interaction term between dark matter and baryons
that could explain observed correlations between the two components of the
cosmic fluid within Tully-Fisher analysis.Comment: 18 pages, 6 figures, references added. Published in JCA
TOpic: rare and special cases, the real "Strange cases"
Introduction: The bladder hernia represents approximately 1-3% of
all inguinal hernias, where patients aged more than 50 years have a
higher incidence (10%). Many factors contribute to the development of a bladder hernia,
including the presence of a urinary outlet obstruction causing chronic
bladder distention, the loss of bladder tone, pericystitis, the perivesical
bladder fat protrusion and the obesity
Constraints on supersymmetry with light third family from LHC data
We present a re-interpretation of the recent ATLAS limits on supersymmetry in
channels with jets (with and without b-tags) and missing energy, in the context
of light third family squarks, while the first two squark families are
inaccessible at the 7 TeV run of the Large Hadron Collider (LHC). In contrast
to interpretations in terms of the high-scale based constrained minimal
supersymmetric standard model (CMSSM), we primarily use the low-scale
parametrisation of the phenomenological MSSM (pMSSM), and translate the limits
in terms of physical masses of the third family squarks. Side by side, we also
investigate the limits in terms of high-scale scalar non-universality, both
with and without low-mass sleptons. Our conclusion is that the limits based on
0-lepton channels are not altered by the mass-scale of sleptons, and can be
considered more or less model-independent.Comment: 20 pages, 8 figures, 2 tables. Version published in JHE
New Physics at the LHC. A Les Houches Report: Physics at TeV Colliders 2009 - New Physics Working Group
We present a collection of signatures for physics beyond the standard model
that need to be explored at the LHC. First, are presented various tools
developed to measure new particle masses in scenarios where all decays include
an unobservable particle. Second, various aspects of supersymmetric models are
discussed. Third, some signatures of models of strong electroweak symmetry are
discussed. In the fourth part, a special attention is devoted to high mass
resonances, as the ones appearing in models with warped extra dimensions.
Finally, prospects for models with a hidden sector/valley are presented. Our
report, which includes brief experimental and theoretical reviews as well as
original results, summarizes the activities of the "New Physics" working group
for the "Physics at TeV Colliders" workshop (Les Houches, France, 8-26 June,
2009).Comment: 189 page
Tuning supersymmetric models at the LHC: A comparative analysis at two-loop level
We provide a comparative study of the fine tuning amount (Delta) at the
two-loop leading log level in supersymmetric models commonly used in SUSY
searches at the LHC. These are the constrained MSSM (CMSSM), non-universal
Higgs masses models (NUHM1, NUHM2), non-universal gaugino masses model (NUGM)
and GUT related gaugino masses models (NUGMd). Two definitions of the fine
tuning are used, the first (Delta_{max}) measures maximal fine-tuning wrt
individual parameters while the second (Delta_q) adds their contribution in
"quadrature". As a direct result of two theoretical constraints (the EW minimum
conditions), fine tuning (Delta_q) emerges as a suppressing factor (effective
prior) of the averaged likelihood (under the priors), under the integral of the
global probability of measuring the data (Bayesian evidence p(D)). For each
model, there is little difference between Delta_q, Delta_{max} in the region
allowed by the data, with similar behaviour as functions of the Higgs, gluino,
stop mass or SUSY scale (m_{susy}=(m_{\tilde t_1} m_{\tilde t_2})^{1/2}) or
dark matter and g-2 constraints. The analysis has the advantage that by
replacing any of these mass scales or constraints by their latest bounds one
easily infers for each model the value of Delta_q, Delta_{max} or vice versa.
For all models, minimal fine tuning is achieved for M_{higgs} near 115 GeV with
a Delta_q\approx Delta_{max}\approx 10 to 100 depending on the model, and in
the CMSSM this is actually a global minimum. Due to a strong (
exponential) dependence of Delta on M_{higgs}, for a Higgs mass near 125 GeV,
the above values of Delta_q\approx Delta_{max} increase to between 500 and
1000. Possible corrections to these values are briefly discussed.Comment: 23 pages, 46 figures; references added; some clarifications (section
2
Les Houches 2015: Physics at TeV colliders - new physics working group report
We present the activities of the 'New Physics' working group for the 'Physics
at TeV Colliders' workshop (Les Houches, France, 1-19 June, 2015). Our report
includes new physics studies connected with the Higgs boson and its properties,
direct search strategies, reinterpretation of the LHC results in the building
of viable models and new computational tool developments. Important signatures
for searches for natural new physics at the LHC and new assessments of the
interplay between direct dark matter searches and the LHC are also considered.Comment: Proceedings of the New Physics Working Group of the 2015 Les Houches
Workshop, Physics at TeV Colliders, Les Houches 1-19 June 2015. 197 page
Les Houches 2011: Physics at TeV Colliders New Physics Working Group Report
We present the activities of the "New Physics" working group for the "Physics
at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our
report includes new agreements on formats for interfaces between computational
tools, new tool developments, important signatures for searches at the LHC,
recommendations for presentation of LHC search results, as well as additional
phenomenological studies.Comment: 243 pages, report of the Les Houches 2011 New Physics Group; fix
three figure
MFV Reductions of MSSM Parameter Space
The 100+ free parameters of the minimal supersymmetric standard model (MSSM)
make it computationally difficult to compare systematically with data,
motivating the study of specific parameter reductions such as the cMSSM and
pMSSM. Here we instead study the reductions of parameter space implied by using
minimal flavour violation (MFV) to organise the R-parity conserving MSSM, with
a view towards systematically building in constraints on flavour-violating
physics. Within this framework the space of parameters is reduced by expanding
soft supersymmetry-breaking terms in powers of the Cabibbo angle, leading to a
24-, 30- or 42-parameter framework (which we call MSSM-24, MSSM-30, and MSSM-42
respectively), depending on the order kept in the expansion. We provide a
Bayesian global fit to data of the MSSM-30 parameter set to show that this is
manageable with current tools. We compare the MFV reductions to the
19-parameter pMSSM choice and show that the pMSSM is not contained as a subset.
The MSSM-30 analysis favours a relatively lighter TeV-scale pseudoscalar Higgs
boson and with multi-TeV sparticles.Comment: 2nd version, minor comments and references added, accepted for
publication in JHE
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