85 research outputs found
Top-quark physics at the first CLIC stage
The Compact Linear Collider (CLIC) is a mature option for a future
electron-positron collider operating at centre-of-mass energies of up to 3 TeV.
CLIC will be built and operated in a staged approach with three centre-of-mass
energies currently assumed to be 380 GeV, 1.5 TeV and 3 TeV. This contribution
discusses the prospects for precision measurements of top-quark properties at
the first stage of CLIC, based on detailed simulation studies, taking into
account luminosity spectra and beam induced backgrounds, full detector
simulation based on Geant4, final state reconstruction based on particle flow
approach with PandoraPFA, jet clustering with the VLC algorithm as implemented
in the FastJet package, and flavour tagging with LcfiPlus.
Based on a dedicated centre-of-mass energy scan around the top-quark pair
production threshold, the top-quark mass can be determined with a precision of
about 50 MeV in a theoretically well-defined manner. This scan is also
sensitive to the top-quark width and Yukawa coupling. Other approaches to
extract the top-quark mass at the first stage of CLIC make use of ISR photons
or the direct reconstruction of the top quarks. Precise measurements of the
differential top-quark pair production cross sections at 380 GeV, for different
electron beam polarisations, allow the study of top-quark couplings to
electroweak gauge bosons sensitive to new physics mass scales beyond 10 TeV.
The large number of top-quark pairs produced also allows competitive searches
for Flavour Changing Neutral Current (FCNC) top-quark decays with charm quarks
in the final state. Exclusion limits expected for 500 fb collected at
the first stage of CLIC are presented for , and channels, reaching down to for BR().Comment: 4 pages, 3 figures, to be submitted to proceedings of ICHEP'2018,
presented on behalf of the CLICdp Collaboratio
Measurement of the leptoquark Yukawa couplings in e+e- collisions at TESLA
Measurement of the Yukawa couplings of the first-generation leptoquarks has
been studied for e+e- collisions at TESLA, at sqrt(s)=800 GeV. By combining
measurements from different production and decay channels, determination of
Yukawa couplings with precision on the few per-cent level is possible. TESLA
will be sensitive to very small leptoquark Yukawa couplings not accessible at
LHC, down to lambda ~ 0.05 [e]. Distinction between left-handed and
right-handed Yukawa couplings is feasible even for leptoquark masses very close
to the pair-production kinematic limit.Comment: 20 pages, 15 figure
Benchmarking the Inert Doublet Model for e+ e- colliders
We present benchmarks for the Inert Doublet Model, a Two Higgs Doublet Model
with a dark matter candidate. They are consistent with current constraints on
direct detection, including the most recent bounds from the XENON1T experiment
and relic density of dark matter, as well as with known collider and low-energy
limits. We focus on parameter choices that promise detectable signals at lepton
colliders via pair-production of H+H- and HA. For these we choose a large
variety of benchmark points with different kinematic features, leading to
distinctly different final states in order to cover the large variety of
collider signatures that can result from the model.Comment: 21 pages, 1 figure, 5 tables; v2: corresponds to published version.
Comments on future prospects adde
Study of the Higgs-boson decays into WW and ZZ at the Photon Collider
Production of the Standard Model Higgs-boson at the Photon Collider at TESLA
is studied for the Higgs-boson masses above 150 GeV. Simulation of signal and
background processes takes into account realistic luminosity spectra and
detector effects. In the considered mass range, large interference effects are
expected in the W+W- decay channel. By reconstructing W+W- and ZZ final states,
not only the h->gamma gamma partial width can be measured, but also the
relative phase of the scattering amplitude. This opens a new window for the
precise determination of the Higgs-boson couplings. Models with heavy,
fourth-generation fermions and with enlarged Higgs sector (2HDM (II)) are
considered.Comment: 19 pages, 18 figures; updated version with improved precision of
estimate
IDM benchmarks for the LHC and future colliders
We present cross-section expectations for various processes and collider
options, for benchmark scenarios of the Inert Doublet Model, a Two Higgs
Doublet Model with a dark matter candidate. The proposed scenarios are
consistent with current dark matter constraints, including the most recent
bounds from the XENON1T experiment and relic density, as well as with known
collider and low-energy limits. These benchmarks, chosen in earlier work for
studies at colliders, exhibit a variety of kinematic features that
should be explored at current and future runs of the LHC. We provide cross
sections for all relevant production processes at 13 TeV, 27 TeV and 100 TeV
proton collider, as well as for a possible 10 TeV and 30 TeV muon collider.Comment: 44 pages, 11 figures; v2: corresponds to published journal version
(slight style differences
- …