1,094 research outputs found
Search for top partners with charge 5e/3
A feasibility study of searches for top partners with charge 5e/3 at the
upgraded Large Hadron Collider is performed. The discovery potential and
exclusion limits are presented using integrated luminosities of 300 fb
and 3000 fb at center-of-mass energies of 14 and 33 TeV
Top-Quark Physics at the LHC
We report on the precision determination of the top-quark mass to
next-to-next-to-leading order in QCD in well-defined renormalization schemes
using data from the Large Hadron Collider for single-top and top-quark pair
production. We also discuss the calibration of the so-called Monte Carlo
top-quark mass parameter which is determined from a comparison to events with
top-quark decay products. The implications of the measured value of the
top-quark mass for conclusions about the stability of the electroweak vacuum
state of our Universe are illustrated. At future lepton colliders, we provide
for the first time matched exclusive calculations valid both at the top
threshold and in the continuum, also fully differentially. In addition, we
calculate fully off-shell top-pair production (also with an associated Higgs
boson) at next-to-leading order in QCD, which allows to extract the top-Yukawa
coupling with an unprecedented precision.Comment: 15 pages, 8 figures. Part of the final report of the Collaborative
Research Center 676 "Particles, Strings and the Early Universe" 2006 - 201
Top Partner Discovery in the channel at the LHC
In this paper we study the discovery potential of the LHC run II for heavy
vector-like top quarks in the decay channel to a top and a boson. Despite
the usually smaller branching ratio compared to charged-current decays, this
channel is rather clean and allows for a complete mass reconstruction of the
heavy top. The latter is achieved in the leptonic decay channel of the
boson and in the fully hadronic top channel using boosted jet and jet
substructure techniques. To be as model-independent as possible, a simplified
model approach with only two free parameters has been applied. The results are
presented in terms of parameter space regions for evidence or
discovery for such new states in that channel.Comment: 24 pages, 8 figures, version 2 updated to JHEP 01 (2015) 08
Limits on Fourth Generation Fermions
We present recent results on searches for the fourth generation quarks
performed at the CMS and ATLAS experiments at LHC.Comment: Presented at the 2013 Flavor Physics and CP Violation (FPCP-2013),
Buzios, Rio de Janeiro, Brazil, May 19-24 2013, 8 pages, 7 figures, updated
reference
Implications of a High-Mass Diphoton Resonance for Heavy Quark Searches
Heavy vector-like quarks coupled to a scalar will induce a coupling of
this scalar to gluons and possibly (if electrically charged) photons. The decay
of the heavy quark into , with being a Standard Model quark, provides,
if kinematically allowed, new channels for heavy quark searches. Inspired by
naturalness considerations, we consider the case of a vector-like partner of
the top quark. For illustration, we show that a singlet partner can be searched
for at the 13TeV LHC through its decay into a scalar resonance in the
final states, especially if the diphoton branching ratio of
the scalar is further enhanced by the contribution of non coloured
particles. We then show that conventional heavy quark searches are also
sensitive to this new decay mode, when decays hadronically, by slightly
tightening the current selection cuts. Finally, we comment about the
possibility of disentangling, by scrutinising appropriate kinematic
distributions, heavy quark decays to from other standard decay modes.Comment: 8 pages, 3 figures and 1 table; v3: typos fixed. Matches published
versio
Production of extra quarks decaying to Dark Matter beyond the Narrow Width Approximation at the LHC
This paper explores the effects of finite width in processes of pair
production of an extra heavy quark with charge 2/3 (top partner) and its
subsequent decay into a bosonic Dark Matter (DM) candidate -- either scalar or
vector -- and SM up-type quarks at the Large Hadron Collider (LHC). This
dynamics has been ignored so far in standard experimental searches of heavy
quarks decaying to DM and we assess herein the regions of validity of current
approaches, based on the assumption that the extra quarks have a narrow width.
Further, we discuss the configurations of masses, widths and couplings where
the latter breaks down.Comment: 20 pages, 16 figures. Version accepted by PR
Searching for bosons decaying to gluons
The production and decay of a new heavy vector boson, a chromophilic
vector boson, is described. The chromophilic couples only to two gluons,
but its two-body decays are absent, leading to a dominant decay mode of
. The unusual nature of the interaction predicts a
cross-section which grows with for a fixed coupling and an
accompanying gluon with a coupling that rises with its energy. We study the
decay mode, proposing distinct reconstruction techniques for the
observation of an excess and for the measurement of . We estimate the
sensitivity of current experimental datasets.Comment: For submission to PR
Results on top-quark physics from the CMS experiment
The most recent results on top-quark physics reported by the CMS experiment
at the Large Hadron Collider (LHC) are presented in this talk. The results are
based on a data sample of about 36/pb of data collected during 2010 at a pp
center-of-mass energy of 7 TeV.Comment: 8 pages, 3 figures Contributed to the Ninth International Conference
on Flavor Physics and CP Violation (FPCP 2011), Maale Hachamisha, Israel, May
23--27, 201
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