259 research outputs found
Long-lived bino and wino in supersymmetry with heavy scalars and higgsinos
We point out that there is a parameter region in supersymmetry with heavy
scalars and higgsinos, in which the heavier of bino and wino becomes long-lived
as a consequence of the heavy higgsinos. In this region these electroweak
gaugino sectors are secluded from each other with very small mixings that are
inversely proportional to the higgsino mass. We revisit the bino and bino
decays and provide simple formulae for the partial decay rates and the
lifetimes in the limit of heavy higgsinos. We discuss the collider signatures
of the long-lived binos and winos in this scenario.Comment: 23 pages, 9 figures, text clarified, additional formulas, comparison
with SDecay; to appear in JHE
Higgs boson to di-tau channel in Chargino-Neutralino searches at the LHC
We consider chargino-neutralino production, , which
results in Higgs boson final states that subsequently decay (inclusively) to
leptons (either or ). Such channels are
dominant in large regions of the allowed supersymmetric parameter space for
many concrete supersymmetric models. The existence of leptons allows for good
control over the backgrounds, rendering this channel competitive to the
conventional channel that has been previously used to
impose constraints. We include hadronic decays of the leptons in our
analysis through a -identification algorithm. We consider integrated
luminosities of 100 fb, 300 fb and 3000 fb, for an LHC
running at centre-of-mass energy of 14 TeV and provide the expected
constraints on the - plane.Comment: 28 pages, 14 figures. Additional efficiency files for signal regions
of analysis included in "efficiencies" director
Can R-parity violation hide vanilla supersymmetry at the LHC?
Current experimental constraints on a large parameter space in supersymmetric
models rely on the large missing energy signature. This is usually provided by
the lightest neutralino which stability is ensured by the R-parity. However, if
the R-parity is violated, the lightest neutralino decays into the standard
model particles and the missing energy cut is not efficient anymore. In
particular, the UDD type R-parity violation induces the neutralino decay to
three quarks which potentially leads to the most difficult signal to be
searched at hadron colliders. In this paper, we study the constraints on the
R-parity violating supersymmetric model using a same-sign dilepton and a
multijet signatures. We show that the gluino and squarks lighter than a TeV are
already excluded in constrained minimal supersymmetric standard model with
R-parity violation if their masses are approximately equal. We also analyze
constraints in a simplified model with R-parity violation. We compare how
R-parity violation changes some of the observables typically used to
distinguish a supersymmetric signal from standard model backgrounds.Comment: 14 pages, 4 figure
Limits on Electroweak Instanton-Induced Processes with Multiple Boson Production
Recently, the CMS collaboration has reported their search for electroweak
instanton-like processes with anomalous violation assuming multi-fermion
but zero-boson final states. On the other hand, many theoretical studies
suggest that anomalous processes may have an observably large production
rate only if their final state contains a large number of electroweak gauge
bosons. In this paper, we compare collider signatures of zero- and multi-boson
events of anomalous violation at the LHC and derive an upper limit on the
cross-section for the multi-boson process by recasting the CMS analysis.Comment: 14 pages, 6 figures; JHEP version with typographic errors fixe
A closer look at a hint of SUSY at the 8 TeV LHC
A recent CMS analysis has reported the observation of an excess in the
invariant mass distribution of the opposite-sign same-flavour lepton pair,
which can be interpreted as a kinematic edge due to new physics. Using collider
simulation tools, we recast relevant LHC search results reported by ATLAS and
CMS collaborations in order to determine constraints on supersymmetric models
that could produce the observed features. In particular, we focus on models
involving cascade decays of light-flavour squarks and sbottoms. We find no
favourable supersymmetry scenario within our exploration that could explain the
origin of the excess when other LHC constraints are taken into account.Comment: v2: 20 pages, 10 figures, corrections in one sbottom model, more
models investigated and extended results section, references adde
New model for radiatively generated Dirac neutrino masses and lepton flavor violating decays of the Higgs boson
We propose a new mechanism to explain neutrino masses with lepton number
conservation, in which the Dirac neutrino masses are generated at the two-loop
level involving a dark matter candidate. In this model, branching ratios of
lepton flavor violating decays of the Higgs boson can be much larger than those
of lepton flavor violating decays of charged leptons. If lepton flavor
violating decays of the Higgs boson are observed at future collider experiments
without detecting lepton flavor violating decays of charged leptons, most of
the models previously proposed for tiny neutrino masses are excluded while our
model can still survive. We show that the model can be viable under constraints
from current data for neutrino experiments, searches for lepton flavor
violating decays of charged leptons and dark matter experiments.Comment: 26 pages, 9 eps file
Fastlim: a fast LHC limit calculator
Fastlim is a tool to calculate conservative limits on extensions of the
Standard Model from direct LHC searches without performing any Monte Carlo
event generation. The program reconstructs the visible cross sections from
pre-calculated efficiency tables and cross section tables for simplified event
topologies. As a proof of concept of the approach, we have implemented searches
relevant for supersymmetric models with R-parity conservation. Fastlim takes
the spectrum and coupling information of a given model point and provides, for
each signal region of the implemented analyses, the visible cross sections
normalised to the corresponding upper limit, reported by the experiments, as
well as the exclusion -value. To demonstrate the utility of the program we
study the sensitivity of the recent ATLAS missing energy searches to the
parameter space of natural SUSY models. The program structure allows the
straight-forward inclusion of external efficiency tables and can be generalised
to R-parity violating scenarios and non-SUSY models. This paper serves as a
self-contained user guide, and indicates the conventions and approximations
used.Comment: 39 pages, 43 figure
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