42 research outputs found
XQCAT: eXtra Quark Combined Analysis Tool
XQCAT (eXtra Quark Combined Analysis Tool) is a tool aimed at determining
exclusion confidence levels for scenarios of new physics characterised by the
presence of one or multiple heavy extra quarks which interact through Yukawa
couplings with any of the Standard Model quarks. The code uses a database of
efficiencies for pre-simulated processes of QCD-induced pair production of
extra quarks and their subsequent on-shell decays. In the version 1.2 of XQCAT
the efficiencies have been computed for a set of seven publicly available
search results by the CMS experiment. The input for the code is a text file in
which masses, branching ratios and dominant chirality of the couplings of the
new quarks are provided. The output of the code is the exclusion confidence
levels of the test point for each implemented experimental analysis considered
individually and, when possible, in statistical combination.Comment: 18 pages, 2 figures, version accepted for publication in Comp. Phys.
Comm., fixed formatting problems caused by the arXiv's autotex syste
Refining light stop exclusion limits with cross sections
If light supersymmetric top (stop) quarks are produced at the LHC and decay
via on- or off-shell -bosons they can be expected to contribute to a
precision cross section measurement. Using the latest results of the
CMS experiment, we revisit constraints on the stop quark production and find
that this measurement can exclude portions of the parameter space not probed by
dedicated searches. In particular we can exclude light top squarks up to
230~GeV along the line separating three- and four-body decays, . We also study the exclusion limits in the case
when the branching ratio for these decays is reduced and we show significant
improvement over previously existing limits.Comment: 5 pages, 2 figures; references updated, minor changes; to appear in
Phys. Lett.
A resonance without resonance: scrutinizing the diphoton excess at 750 GeV
Motivated by the recent diphoton excesses reported by both ATLAS and CMS
collaborations, we suggest that a new heavy spinless particle is produced in
gluon fusion at the LHC and decays to a couple of lighter pseudoscalars which
then decay to photons. The new resonances could arise from a new strongly
interacting sector and couple to Standard Model gauge bosons only via the
corresponding Wess-Zumino-Witten anomaly. We present a detailed recast of the
newest 13 TeV data from ATLAS and CMS together with the 8 TeV data to scan the
consistency of the parameter space for those resonances.Comment: 8 pages, 4 figures, extended discussion of underlying models, new
plots with varying mass of the heavy scalar, to appear in PL
CheckMATE 2: From the model to the limit
We present the latest developments to the CheckMATE program that allows
models of new physics to be easily tested against the recent LHC data. To
achieve this goal, the core of CheckMATE now contains over 60 LHC analyses of
which 12 are from the 13 TeV run. The main new feature is that CheckMATE 2 now
integrates the Monte Carlo event generation via Madgraph and Pythia 8. This
allows users to go directly from a SLHA file or UFO model to the result of
whether a model is allowed or not. In addition, the integration of the event
generation leads to a significant increase in the speed of the program. Many
other improvements have also been made, including the possibility to now
combine signal regions to give a total likelihood for a model.Comment: 53 pages, 6 figures; references updated, instructions slightly
change
Complementarity of Resonant Scalar, Vector-Like Quark and Superpartner Searches in Elucidating New Phenomena
The elucidation of the nature of new phenomena requires a multi-pronged
approach to understand the essential physics that underlies it. As an example,
we study the simplified model containing a new scalar singlet accompanied by
vector-like quarks, as motivated by the recent diphoton excess at the LHC. To
be specific, we investigate three models with -doublet, vector-like
quarks with Yukawa couplings to a new scalar singlet and which also couple
off-diagonally to corresponding Standard Model fermions of the first or third
generation through the usual Higgs boson. We demonstrate that three classes of
searches can play important and complementary roles in constraining this model.
In particular, we find that missing energy searches designed for superparticle
production, supply superior sensitivity for vector-like quarks than the
dedicated new quark searches themselves.Comment: References added; small bug found in model and analysis
implementation, numerical results slightly modified, conclusions unchange
Prospects for natural SUSY
As we anticipate the first results of the 2016 run, we assess the discovery
potential of the LHC to `natural supersymmetry'. To begin with, we explore the
region of the model parameter space that can be excluded with various
centre-of-mass energies (13 TeV and 14 TeV) and different luminosities (20
fb, 100 fb, 300 fb and 3000 fb). We find that the
bounds at 95% CL on stops vary from GeV expected
this summer to GeV at the end of the high
luminosity run, while gluino bounds are expected to range from
GeV to GeV over the
same time period. However, more pessimistically we find that if no signal
begins to appear this summer, only a very small region of parameter space can
be discovered with 5- significance. For this conclusion to change, we
find that both theoretical and systematic uncertainties will need to be
significantly reduced.Comment: 19 pages, 13 figures, minor changes, Phys.Rev.D versio
Collider limits on new physics within micrOMEGAs4.3
Results from the LHC put severe constraints on models of new physics. This
includes constraints on the Higgs sector from the precise measurement of the
mass and couplings of the 125GeV Higgs boson, as well as limits from searches
for other new particles. We present the procedure to use these constraints in
micrOMEGAs by interfacing it to the external codes Lilith, HiggsSignals,
HiggsBounds and SModelS. A few dedicated modules are also provided. With these
new features, micrOMEGAs_4.3 provides a generic framework for evaluating dark
matter observables together with collider and non-collider constraints.Comment: 23 page