200 research outputs found
Anomaly-Free Gauged R-Symmetry in Local Supersymmetry
We discuss local \R-symmetry as a potentially powerful new model building
tool. We first review and clarify that a \R-symmetry can only be gauged
in local and not in global supersymmetry. We determine the anomaly-cancellation
conditions for the gauged \R-symmetry. For the standard superpotential these
equations have {\it no} solution, independently of how many Standard Model
singlets are added to the model. There is also no solution when we increase the
number of families and the number of pairs of Higgs doublets. When the
Green-Schwarz mechanism is employed to cancel the anomalies, solutions only
exist for a large number of singlets. We find many anomaly-free
family-independent models with an extra octet chiral superfield. We
consider in detail the conditions for an anomaly-free {\it family dependent} and find solutions with one, two, three and four extra singlets. Only
with three and four extra singlets do we naturally obtain sfermion masses of
order the weak-scale. For these solutions we consider the spontaneous breaking
of supersymmetry and the -symmetry in the context of local supersymmetry. In
general the gauge group is broken at or close to the Planck scale. We
consider the effects of the \R-symmetry on baryon- and lepton-number violation
in supersymmetry. There is no logical connection between a conserved
\R-symmetry and conserved \R-parity. For conserved \R-symmetry we have models
for all possibilities of conserved or broken \R-parity. Most models predict
dominant effects which could be observed at HERA.Comment: 29 pages, latex, including 3 tables. Final version accepted for
publication in NPB. Slight revision of supersymmetry breaking and dropped
sub-section on mu problem, which will appear expaned elsewher
Charged Higgs production from SUSY particle cascade decays at the LHC
We analyze the cascade decays of the scalar quarks and gluinos of the Minimal
Supersymmetric extension of the Standard Model, which are abundantly produced
at the Large Hadron Collider, into heavier charginos and neutralinos which then
decay into the lighter ones and charged Higgs particles, and show that they can
have substantial branching fractions. The production rates of these Higgs
bosons can be much larger than those from the direct production mechanisms, in
particular for intermediate values of the parameter , and could
therefore allow for the detection of these particles. We also discuss charged
Higgs boson production from direct two-body top and bottom squark decays as
well as from two- and three-body gluino decays.Comment: 30 pages with 10 figures, latex. Uses axodraw.sty and epsfig.st
Focus Point SUSY at the LHC Revisited
The estimation of the backgrounds for gluino signals in focus point
supersymmetry is extended by including the backgrounds from the production of
four third generation quarks in the analysis. We find that these backgrounds
are negligible if one uses the strong selection criteria proposed in the
literature (including this analysis) for heavy gluino searches. Softer
selection criteria often recommended for lighter gluino searches yield
backgrounds which are small but numerically significant. We have also repeated
the more conventional background calculations and compared our results with the
other groups. We find that the size of the total residual background estimated
by different groups using different event generators and hard kinematical cuts
agree approximately. In view of the theoretical uncertainties in the leading
order signal and background cross sections mainly due to the choice of the QCD
scale, the gluino mass reach at the LHC cannot be pinpointed. However,
requiring a signal with tagged b-jets (instead of the standard
choice of ) it is shown that gluino masses close to 2 TeV can be
probed at the LHC for a range of reasonable choices of the QCD scale for an
integrated luminosity of 300 fb.Comment: 17 pages, 4 figures, minor typos correctio
Detecting Physics At The Post-GUT And String Scales By Linear Colliders
The ability of linear colliders to test physics at the post-GUT scale is
investigated. Using current estimates of measurements available at such
accelerators, it is seen that soft breaking masses can be measured with errors
of about (1-20)%. Three classes of models in the post-GUT region are examined:
models with universal soft breaking masses at the string scale, models with
horizontal symmetry, and string models with Calabi-Yau compactifications. In
each case, linear colliders would be able to test directly theoretical
assumptions made at energies beyond the GUT scale to a good accuracy,
distinguish between different models, and measure parameters that are expected
to be predictions of string models.Comment: Latex, 21 pages, no figure
The modulation effect for supersymmetric dark matter detection with asymmetric velocity dispersion
The detection of the theoretically expected dark matter is central to
particle physics cosmology. Current fashionable supersymmetric models provide a
natural dark matter candidate which is the lightest supersymmetric particle
(LSP). Such models combined with fairly well understood physics like the quark
substructure of the nucleon and the nuclear form factor and the spin response
function of the nucleus, permit the evaluation of the event rate for
LSP-nucleus elastic scattering. The thus obtained event rates are, however,
very low or even undetectable. So it is imperative to exploit the modulation
effect, i.e. the dependence of the event rate on the earth's annual motion. In
this review we study such a modulation effect in directional and undirectional
experiments. We calculate both the differential and the total rates using
symmetric as well as asymmetric velocity distributions. We find that in the
symmetric case the modulation amplitude is small, less than 0.07. There exist,
however, regions of the phase space and experimental conditions such that the
effect can become larger. The inclusion of asymmetry, with a realistic enhanced
velocity dispersion in the galactocentric direction, yields the bonus of an
enhanced modulation effect, with an amplitude which for certain parameters can
become as large as 0.46.Comment: 35 LATEX pages, 7 Tables, 8 PostScript Figures include
Gaugino Mass Nonuniversality and Dark Matter in SUGRA, Strings and D Brane Models
The effects of nonuniversality of gaugino masses on dark matter are examined
within supersymmetric grand unification, and in string and D brane models with
R parity invariance. In SU(5) unified models nonuniversality in the gaugino
sector can be generated via the gauge kinetic energy function which may depend
on the 24, 75 and 200 dimensional Higgs representations. We also consider
string models which allow for nonuniversality of gaugino masses and D brane
models where nonuniversality arises from embeddings of the Standard Model gauge
group on five branes and nine branes. It is found that with gaugino mass
nonuniversality the range of the LSP mass can be extended much beyond the range
allowed in the universal SUGRA case, up to about 600 GeV even without
coannihilation effects in some regions of the parameter space. The effects of
coannihilation are not considered and inclusion of these effects may further
increase the allowed neutralino mass range. Similarly with the inclusion of
gaugino mass nonuniversality, the neutralino-proton () cross-section
can increase by as much as a factor of 10 in some of regions of the parameter
space. An analysis of the uncertainties in the quark density content of the
nucleon is given and their effects on cross-section are discussed.
The predictions of our analysis including nonuniversality is compared with the
current limits from dark matter detectors and implications for future dark
matter searches are discussed.Comment: Revised version, 23 pages, Latex, and 7 figure
Constraints on Supersymmetry from LHC data on SUSY searches and Higgs bosons combined with cosmology and direct dark matter searches
The ATLAS and CMS experiments did not find evidence for Supersymmetry using
close to 5/fb of published LHC data at a center-of-mass energy of 7 TeV. We
combine these LHC data with data on B_s -> mu mu (LHCb experiment), the relic
density (WMAP and other cosmological data) and upper limits on the dark matter
scattering cross sections on nuclei (XENON100 data). The excluded regions in
the constrained Minimal Supersymmetric SM (CMSSM) lead to gluinos excluded
below 1270 GeV and dark matter candidates below 220 GeV for values of the
scalar masses (m_0) below 1500 GeV. For large m_0 values the limits of the
gluinos and the dark matter candidate are reduced to 970 GeV and 130 GeV,
respectively. If a Higgs mass of 125 GeV is imposed in the fit, the preferred
SUSY region is above this excluded region, but the size of the preferred region
is strongly dependent on the assumed theoretical error.Comment: 12 pages, 5 figures, Refs. updated, Published version in Eur. Phys.
J. C with updated references and minor corrections. arXiv admin note:
substantial text overlap with arXiv:1202.336
Updated Reach of the CERN LHC and Constraints from Relic Density, b->s gamma and a(mu) in the mSUGRA Model
{We present an updated assessment of the reach of the CERN LHC pp collider
for supersymmetric matter in the context of the minimal supergravity (mSUGRA)
model. In addition to previously examined channels, we also include signals
with an isolated photon or with a leptonically decaying Z boson. For an
integrated luminosity of 100 fb^{-1}, values of m_{1/2}\sim 1400 GeV can be
probed for small m_0, corresponding to a gluino mass of m_{\tg}\sim 3 TeV. For
large m_0, in the hyperbolic branch/focus point region, m_{1/2}\sim 700 GeV can
be probed, corresponding to m_{\tg}\sim 1800 GeV. We also map out parameter
space regions preferred by the measured values of the dark matter relic
density, the b\to s\gamma decay rate, and the muon anomalous magnetic moment
a_\mu, and discuss how SUSY might reveal itself in these regions. We find the
CERN LHC can probe the entire stau co-annihilation region and also most of the
heavy Higgs annihilation funnel allowed by WMAP data, except for some range of
large m_0 and m_{1/2} if \tan\beta \agt 50.Comment: 22 page latex file including 10 EPS figures; bug fix in relic density
code modifies figures in co-annihilation regio
Supersymmetric effects on Forward Backward asymmetries of
Leptonic and semi-leptonic rare decays of B-mesons are very clean (both
theoretically and experimentally) signatures of any new physics beyond the
Standard Model (SM). More specifically the decay \btokll has been theoretically
observed to be very sensitive to new physics as the Forward Backward (FB)
asymmetry in this decay mode vanishes in the SM. Supersymmetry, however,
predicts a non-vanishing value of this asymmetry. In this work we will study
the polarized lepton pair FB asymmetry, i.e. the FB asymmetry of the lepton
when one (or both) final state lepton(s) are polarized. We will study these
asymmetries both within the SM and for Supersymmetric corrections to the SM.Comment: 18 pages, RevTeX file including 21 eps figures; version accepted for
publication in Phys. Rev. D. Some references adde
The New Look pMSSM with Neutralino and Gravitino LSPs
The pMSSM provides a broad perspective on SUSY phenomenology. In this paper
we generate two new, very large, sets of pMSSM models with sparticle masses
extending up to 4 TeV, where the lightest supersymmetric particle (LSP) is
either a neutralino or gravitino. The existence of a gravitino LSP necessitates
a detailed study of its cosmological effects and we find that Big Bang
Nucleosynthesis places strong constraints on this scenario. Both sets are
subjected to a global set of theoretical, observational and experimental
constraints resulting in a sample of \sim 225k viable models for each LSP type.
The characteristics of these two model sets are briefly compared. We confront
the neutralino LSP model set with searches for SUSY at the 7 TeV LHC using both
the missing (MET) and non-missing ET ATLAS analyses. In the MET case, we employ
Monte Carlo estimates of the ratios of the SM backgrounds at 7 and 8 TeV to
rescale the 7 TeV data-driven ATLAS backgrounds to 8 TeV. This allows us to
determine the pMSSM parameter space coverage for this collision energy. We find
that an integrated luminosity of \sim 5-20 fb^{-1} at 8 TeV would yield a
substantial increase in this coverage compared to that at 7 TeV and can probe
roughly half of the model set. If the pMSSM is not discovered during the 8 TeV
run, then our model set will be essentially void of gluinos and lightest first
and second generation squarks that are \lesssim 700-800 GeV, which is much less
than the analogous mSUGRA bound. Finally, we demonstrate that non-MET SUSY
searches continue to play an important role in exploring the pMSSM parameter
space. These two pMSSM model sets can be used as the basis for investigations
for years to come.Comment: 54 pages, 22 figures; typos fixed, references adde
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