3,995 research outputs found
New HiggsBounds from LEP and the Tevatron
We review the program HiggsBounds that tests theoretical predictions of
models with arbitrary Higgs sectors against the exclusion bounds obtained from
the Higgs searches at LEP and the Tevatron. We explicitly list the bounds that
have been added after the first release of HiggsBounds.Comment: 4 pages, talk given at SUSY09, Boston, June 200
Relic density of neutralino dark matter in the MSSM with CP violation
We calculate the relic density of dark matter in the MSSM with CP violation.
We analyse various scenarios of neutralino annihilation: the cases of a bino,
bino-wino and bino-Higgsino LSP, annihilation through Higgs, as well as
sfermion coannihilation scenarios. Large phase effects are found, on the one
hand due to shifts in the masses, on the other hand due to modifications of the
couplings. Taking special care to disentangle the effects in masses and
couplings, we demonstrate that the presence of CP phases can have a significant
influence on the neutralino relic abundance. Typical variations in \Omega h^2
solely from modifications in the couplings are O(10%-100%), but can reach an
order of magnitude in some cases.Comment: 36 pages, 21 figures (low resolution). A version with high-resolution
figures can be downloaded from http://cern.ch/kraml/papers/omc
Model-Independent Bounds on a Light Higgs
We present up-to-date constraints on a generic Higgs parameter space. An
accurate assessment of these exclusions must take into account statistical, and
potentially signal, fluctuations in the data currently taken at the LHC. For
this, we have constructed a straightforward statistical method for making full
use of the data that is publicly available. We show that, using the expected
and observed exclusions which are quoted for each search channel, we can fully
reconstruct likelihood profiles under very reasonable and simple assumptions.
Even working with this somewhat limited information, we show that our method is
sufficiently accurate to warrant its study and advocate its use over more naive
prescriptions. Using this method, we can begin to narrow in on the remaining
viable parameter space for a Higgs-like scalar state, and to ascertain the
nature of any hints of new physics---Higgs or otherwise---appearing in the
data.Comment: 32 pages, 10 figures; v3: correction made to basis of four-derivative
operators in the effective Lagrangian, references adde
SUSY parameter determination at the LHC using cross sections and kinematic edges
We study the determination of supersymmetric parameters at the LHC from a
global fit including cross sections and edges of kinematic distributions. For
illustration, we focus on a minimal supergravity scenario and discuss how well
it can be constrained at the LHC operating at 7 and 14 TeV collision energy,
respectively. We find that the inclusion of cross sections greatly improves the
accuracy of the SUSY parameter determination, and allows to reliably extract
model parameters even in the initial phase of LHC data taking with 7 TeV
collision energy and 1/fb integrated luminosity. Moreover, cross section
information may be essential to study more general scenarios, such as those
with non-universal gaugino masses, and distinguish them from minimal,
universal, models.Comment: 22 pages, 8 figure
Determining R-parity violating parameters from neutrino and LHC data
In supersymmetric models neutrino data can be explained by R-parity violating
operators which violate lepton number by one unit. The so called bilinear model
can account for the observed neutrino data and predicts at the same time
several decay properties of the lightest supersymmetric particle. In this paper
we discuss the expected precision to determine these parameters by combining
neutrino and LHC data and discuss the most important observables. We show that
one can expect a rather accurate determination of the underlying R-parity
parameters assuming mSUGRA relations between the R-parity conserving ones and
discuss briefly also the general MSSM as well as the expected accuracies in
case of a prospective e+ e- linear collider. An important observation is that
several parameters can only be determined up to relative signs or more
generally relative phases.Comment: 13 pages, 13 figure
Light neutralino dark matter in the MSSM and its implication for LHC searches for staus
It was shown in a previous study that a lightest neutralino with mass below
30 GeV was severely constrained in the minimal supersymmetric standard model
(MSSM), unless it annihilates via a light stau and thus yields the observed
dark matter abundance. In such a scenario, while the stau is the
next-to-lightest supersymmetric particle (NLSP), the charginos and the other
neutralinos as well as sleptons of the first two families are also likely to be
not too far above the mass bounds laid down by the Large Electron Positron
(LEP) collider. As the branching ratios of decays of the charginos and the
next-to-lightest neutralino into staus are rather large, one expects
significant rates of tau-rich final states in such a case. With this in view,
we investigate the same-sign ditau and tri-tau signals of this scenario at the
Large Hadron Collider (LHC) for two MSSM benchmark points corresponding to
light neutralino dark matter. The associated signal rates for these channels
are computed, for the centre-of-mass energy of 14 TeV. We find that both
channels lead to appreciable rates if the squarks and the gluino are not too
far above a TeV, thus allowing to probe scenarios with light neutralinos in the
14 TeV LHC run with 10-100 fb^{-1}.Comment: 19p, 4 Fig
The generalised NMSSM at one loop: fine tuning and phenomenology
We determine the degree of fine tuning needed in a generalised version of the
NMSSM that follows from an underlying Z4 or Z8 R symmetry. We find that it is
significantly less than is found in the MSSM or NMSSM and extends the range of
Higgs mass that have acceptable fine tuning up to Higgs masses of mh ~ 130 GeV.
For universal boundary conditions analogous to the CMSSM the phenomenology is
rather MSSM like with the singlet states typically rather heavy. For more
general boundary conditions the singlet states can be light, leading to
interesting signatures at the LHC and direct detection experiments.Comment: 20 pages, 9 figures, matches published versio
RECAST: Extending the Impact of Existing Analyses
Searches for new physics by experimental collaborations represent a
significant investment in time and resources. Often these searches are
sensitive to a broader class of models than they were originally designed to
test. We aim to extend the impact of existing searches through a technique we
call 'recasting'. After considering several examples, which illustrate the
issues and subtleties involved, we present RECAST, a framework designed to
facilitate the usage of this technique.Comment: 13 pages, 4 figure
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
Interpreting a 1 fb^-1 ATLAS Search in the Minimal Anomaly Mediated Supersymmetry Breaking Model
Recent LHC data significantly extend the exclusion limits for supersymmetric
particles, particularly in the jets plus missing transverse momentum channels.
The most recent such data have so far been interpreted by the experiment in
only two different supersymmetry breaking models: the constrained minimal
supersymmetric standard model (CMSSM) and a simplified model with only squarks
and gluinos and massless neutralinos. We compare kinematical distributions of
supersymmetric signal events predicted by the CMSSM and anomaly mediated
supersymmetry breaking (mAMSB) before calculating exclusion limits in mAMSB. We
obtain a lower limit of 900 GeV on squark and gluino masses at the 95%
confidence level for the equal mass limit, tan(beta)=10 and mu>0.Comment: 18 pages, 11 figure
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