1,956 research outputs found
Beyond the Standard Model Higgs at LHC
Models of Beyond the Standard Model (BSM) physics, like the Minimal
Supersymmetric Standard Model (MSSM), often involve an extended Higgs sector,
giving rise to extra neutral or charged Higgs bosons. The discovery reach
expected from simulation studies for such additional Higgs particles is
presented for the ATLAS, CMS and FP420 detectors at the LHC. Emphasis is put on
production and decay modes involving heavy flavour b and tau particles, which
are enhanced in large regions of BSM parameter space. The LHC experiments are
indeed particularly well equipped to tackle final states containing heavy
flavour.Comment: Parallel talk at ICHEP08, Philadelphia, USA, July 2008. 4 pages, 4
figure
Supersymmetry Searches with ATLAS and CMS
Highlights are presented of current searches for supersymmetry produced in
proton-proton collisions at the LHC, operating at sqrt(s)=7TeV. Searches with
missing transverse energy are summarized from both the ATLAS and CMS
experiments. A wide range of final states is covered, including recent searches
with photons, leptons, and purely hadronic final states. Future developments
are anticipated with extra focus on exclusive searches in electroweak and
third-generation supersymmetry production.Comment: Contribution to the proceedings of the Rencontres de Moriond EW 201
Search for Dark Matter at CMS
The results are presented from searches with the CMS experiment for
directly-produced dark matter particles. All these searches use the full LHC
Run-I dataset of ~20/fb of proton-proton collisions at 8TeV centre-of-mass
energy. Final states with a monojet, monophoton, and monolepton signature are
considered, as well as processes with dark-matter particles produced in
association with top quarks. Most of these results have been interpreted using
an effective field theory approach, while first results are also reported with
simplified models.Comment: ICHEP2014 Proceeding
Observability of Same-Charge Lepton Topologies in Fully Leptonic Top Quark Pair Events in CMS
At the Large Hadron Collider di-leptonic ttbar+jets events can be selected with a relatively high signal-to-noise ratio and efficiency, with background events produced via Standard Model diagrams. Within the clean sample of these events, both isolated leptons have an opposite electric charge. In several models beyond the Standard Model tt/tbartbar+jets topologies are predicted, kinematically similar to the Standard Model ttbar+jets signature, where both leptons have an equal electric charge. Such a signal of new physics can be diluted by the mis-identification of the leptons or their electric charge in Standard Model ttbar+jets events. The observability of an excess of same-charge di-lepton signals above the mis-reconstruction of the Standard Model background is presented, assuming the same topology. With an integrated luminosity of 30/fb, a same-charge di-lepton signature of pp->tt/tbartbar events with a cross section larger than 1.2pb is visible in the measurement of the ratio between same-charge and opposite-charge lepton pair events
Simplified SIMPs and the LHC
The existence of Dark Matter (DM) in the form of Strongly Interacting Massive
Particles (SIMPs) may be motivated by astrophysical observations that challenge
the classical Cold DM scenario. Other observations greatly constrain, but do
not completely exclude, the SIMP alternative. The signature of SIMPs at the LHC
may consist of neutral, hadron-like, trackless jets produced in pairs. We show
that the absence of charged content can provide a very efficient tool to
suppress dijet backgrounds at the LHC, thus enhancing the sensitivity to a
potential SIMP signal. We illustrate this using a simplified SIMP model and
present a detailed feasibility study based on simulations, including a
dedicated detector response parametrization. We evaluate the expected
sensitivity to various signal scenarios and tentatively consider the exclusion
limits on the SIMP elastic cross section with nucleons.Comment: 18 pages, 7 figure
Singlet-Doublet Dark Matter Freeze-in: LHC displaced signatures versus cosmology
We study the Singlet-Doublet dark matter model in the regime of feeble
couplings, where the dark matter abundance is obtained via the freeze-in
mechanism. As a consequence of the small couplings, the heavier particles in
the model are long-lived with decay length at typical scales of collider
experiments. We analyse the collider signatures of the model, characterised by
displaced and bosons plus missing momentum, employing current LHC
searches for displaced vertices and missing energy to significantly constrain
the parameter space of the model. We also take into account the cosmological
bounds relevant for our light dark matter candidate arising from Lyman-
forest constraints. Our analysis emphasises the interplay between displaced
signatures at the LHC and cosmology for dark matter candidates whose relic
abundance is obtained through the freeze-in mechanism.Comment: 42 pages, 14 figures; v2: minor discussions, clarifications, and
references adde
Recommendations of the LHC Dark Matter Working Group: Comparing LHC searches for heavy mediators of dark matter production in visible and invisible decay channels
Weakly-coupled TeV-scale particles may mediate the interactions between
normal matter and dark matter. If so, the LHC would produce dark matter through
these mediators, leading to the familiar "mono-X" search signatures, but the
mediators would also produce signals without missing momentum via the same
vertices involved in their production. This document from the LHC Dark Matter
Working Group suggests how to compare searches for these two types of signals
in case of vector and axial-vector mediators, based on a workshop that took
place on September 19/20, 2016 and subsequent discussions. These suggestions
include how to extend the spin-1 mediated simplified models already in
widespread use to include lepton couplings. This document also provides
analytic calculations of the relic density in the simplified models and reports
an issue that arose when ATLAS and CMS first began to use preliminary numerical
calculations of the dark matter relic density in these models.Comment: 19 pages, 4 figures; v2: author list and LaTeX problem fixe
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