1,752 research outputs found
Resonant slepton production at the LHC in models with an ultralight gravitino
We examine resonant slepton production at the LHC with gravitinos in the
final state. The slepton undergoes gauge decay into a neutralino and a lepton,
the neutralino decays into a photon and a gravitino. By measuring the
transverse masses of the gamma- G and the l-gamma- G subsystems it is possible
to accurately reconstruct both the slepton and neutralino masses. In some
regions of parameter space the slepton decays directly into a lepton and
gravitino, giving an identical experimental topology to W production (l missing
E_T). We present the novel matrix element squared for lepton-gravitino
production. A peak in the tail of the lepton-missing momentum transverse mass
distribution of the W provides a signature for the process and an accurate
measurement of the slepton mass. We display the search reach for the LHC and
300 fb^{-1} of integrated luminosity.Comment: 13 pages. Minor changes in v
Impact of CMS Multi-jets and Missing Energy Search on CMSSM Fits
Recent CMS data significantly extend the direct search exclusion for
supersymmetry. We examine the impact of such data on global fits of the
constrained minimal supersymmetric standard model (CMSSM) to indirect and
cosmological data. By simulating supersymmetric signal events at the LHC, we
construct a likelihood map for the recent CMS data, validating it against the
exclusion region calculated by the experiment itself. A previous CMSSM global
fit is then re-weighted by our likelihood map. The CMS results nibble away at
the high fit probability density region, transforming probability distributions
for the scalar and gluino masses. The CMS search has a non-trivial effect on
tan beta due to correlations between the parameters implied by the fits to
indirect data.Comment: 15 pages, 8 figures. v2 has an appendix added with further checks of
A0-tan beta independence, expected sensitivity curves added to Fig 2a and
typos fixed. v3 has extended discussion of re-weighting procedure and
egregious points in the appendix. v4 minor changes due to very strict (but
good) refere
Theoretical Uncertainties in Sparticle Mass Predictions
We contrast the sparticle spectra obtained from three modern publicly
available codes along model lines in minimal supersymmetric standard model
(MSSM) parameter space. From this we gain an idea of the uncertainties involved
with sparticle spectra calculations. The differences in predicted sparticle
masses are typically at the several percent-level. In the focus-point scenario,
there are differences of 30% in the weak gaugino masses. These uncertainties
need to be reduced in order to obtain accurate information about fundamental
models of supersymmetry breaking.Comment: revTex4 style. Softsusy homepage is at
http://allanach.home.cern.ch/allanach/softsusy.html Written for Snowmass
2001. Replaced version has updated reference. 3 pages, 3 figure
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Multidimensional mSUGRA likelihood maps
We calculate the likelihood map in the full 7 dimensional parameter space of
the minimal supersymmetric standard model (MSSM) assuming universal boundary
conditions on the supersymmetry breaking terms. Simultaneous variations of m_0,
A_0, M_{1/2}, tan beta, m_t, m_b and alpha_s(M_Z) are applied using a Markov
chain Monte Carlo algorithm. We use measurements of b -> s gamma, (g-2)_mu and
Omega_{DM} h^2 in order to constrain the model. We present likelihood
distributions for some of the sparticle masses, for the branching ratio of
B_s^0 -> mu^+ mu^- and for m_{stau}-m_{chi_1^0}. An upper limit of 2.10^{-8} on
this branching ratio might be achieved at the Tevatron, and would rule out 29%
of the currently allowed likelihood. If one allows for non thermal-neutralino
components of dark matter, this fraction becomes 35%. The mass ordering allows
the important cascade decay squark_L -> chi_2^0 -> slepton_R -> chi_1^0 with a
likelihood of 24+/-4%. The stop coannihilation region is highly disfavoured,
whereas the light Higgs region is marginally disfavoured
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Sampling using a 'bank' of clues
An easy-to-implement form of the Metropolis Algorithm is described which,
unlike most standard techniques, is well suited to sampling from multi-modal
distributions on spaces with moderate numbers of dimensions (order ten) in
environments typical of investigations into current constraints on
Beyond-the-Standard-Model physics. The sampling technique makes use of
pre-existing information (which can safely be of low or uncertain quality)
relating to the distribution from which it is desired to sample. This
information should come in the form of a ``bank'' or ``cache'' of space points
of which at least some may be expected to be near regions of interest in the
desired distribution. In practical circumstances such ``banks of clues'' are
easy to assemble from earlier work, aborted runs, discarded burn-in samples
from failed sampling attempts, or from prior scouting investigations. The
technique equilibrates between disconnected parts of the distribution without
user input. The algorithm is not lead astray by ``bad'' clues, but there is no
free lunch: performance gains will only be seen where clues are helpful
Naturalness Priors and Fits to the Constrained Minimal Supersymmetric Standard Model
We examine the effect of a prior that favours low values of fine-tuning on
Bayesian multi-dimensional fits of the constrained minimal supersymmetric
standard model (CMSSM or mSUGRA) to current data. The dark matter relic
density, the anomalous magnetic moment of the muon and the branching ratio of
b->s gamma are all used to constrain the model via a Markov Chain Monte Carlo
sampler. As a result of the naturalness prior, posterior probability
distributions skew towards lighter higgs and sparticle masses, the effect being
most pronounced in the gaugino sector. Interestingly, slepton masses are an
exception and skew towards heavier masses. The lightest CP-even Higgs h^0-pole
region becomes allowed at the 2 sigma level for the latest combination of
measurements of m_t=172.7+/-2.9 GeV, provided we allow for a theoretical error
in the prediction of its mass m_{h^0}. m_{h^0} is constrained to be less than
120 GeV at the 95% C.L. Probing the branching ratio of B_s->mu^+ mu^- to the
level of 2 x 10^{-8}, as might be achieved by the Tevatron experiments, would
cover 32% of the probability density, irrespective of which of the two priors
is used.Comment: 15 pages, 5 figures. Ref adde
R-parity Violation and General Soft Supersymmetry Breaking
We consider the most general class possible of soft supersymmetry breaking
terms that can be added to the MSSM, with and without R-parity violation,
consistent with the sole requirement that no quadratic divergences are induced.
We renormalise the resulting theory through one loop and give an example of how
a previously ignored term might affect the sparticle spectrum.Comment: 11 pages, 1 figure. Plain TeX, uses Harvmac (Big) and epsf. Added
references and typo corrected (v2
Including R-parity violation in the numerical computation of the spectrum of the minimal supersymmetric standard model: SOFTSUSY
Current publicly available computer programs calculate the spectrum and
couplings of the minimal supersymmetric standard model under the assumption of
R-parity conservation. Here, we describe an extension to the SOFTSUSY program
which includes R-parity violating effects. The user provides a theoretical
boundary condition upon the high-scale supersymmetry breaking R-parity
violating couplings. Successful radiative electroweak symmetry breaking,
electroweak and CKM matrix data are used as weak-scale boundary conditions. The
renormalisation group equations are solved numerically between the weak scale
and a high energy scale using a nested iterative algorithm. This paper serves
as a manual to the R-parity violating mode of the program, detailing the
approximations and conventions used.Comment: Updated to SOFTSUSY3.3.3. Program may be downloaded from
http://projects.hepforge.org/softsusy/ and future manuals will be distributed
with the cod
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