2,039 research outputs found
Secondary particles spectra in the decay of a polarized top quark with anomalous coupling
Analytic expression for energy and angular dependence of a secondary charged
lepton in the decay of a polarized top quark with anomalous couplings in
the presence of all anomalous couplings are derived. The angular distribution
of the b-quark is derived as well. It is presented that the charged lepton spin
correlation coefficient is not very sensitive to the anomalous couplings.
However, the b-quark spin correlation coefficient is sensitive to anomalous
couplings and could be used as a powerful tool for searching of non-SM
coupling.Comment: 9 pages, 5 figure
Probing the Anomalous Couplings of the Top Quark with Gluon at the LHC and Tevatron
In this paper, we study the sensitivity of the fraction of events
arising from gluon-gluon fusion to the chromoelectric and chromomagnetic dipole
moments (CEDM and CMDM) as well as the total and differential cross
sections at the LHC and Tevatron. The sensitivity of measured charged asymmetry
at the LHC to CEDM and CMDM is also studied. We find that at the Tevatron and
the LHC, non-zero values of CMDM could suppress the production rate.
It is shown that the ratio of at the Tevatron is more
sensitive to CEDM and CMDM than the LHC case. The presence of CEDM always
increases the contribution of gluon-gluon fusion process in top pair rate at
the Tevatron and LHC. Except for a small range of CMDM, the presence of CEDM
and CMDM can increase the fraction of gluon-gluon fusion at the Tevatron and
LHC. The measured ratio of at the Tevatron is used to
derive bounds on the chromoelectric and chromomagnetic dipole moments as well
as the total and differential () cross sections at the
LHC and Tevatron, and the measured charged asymmetry at the LHC. The
combination of and provides
stringent limits on CMDM and CEDM.Comment: 11 pages,6 figures,2 table
Impact of Torsion Space-Time on observables at Hadron Colliders
Starting from the effective torsion space-time model, we study its effects on
the top pair production cross section at hadron colliders. We also study the
effect of this model on top pair asymmetries at the Tevatron and the LHC. We
find that torsion space-time can explain forward-backward asymmetry according
to measured anomaly at Tevatron. We find an allowed region in the parameters
space which can satisfy simultaneously all observables measured at
Tevatron and LHC.Comment: 17 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1207.064
Probing the top quark chromoelectric and chromomagnetic dipole moments in single top -channel at the LHC
We study the effects of chromoelectric and chromomagnetic dipole moments
(CEDM and CMDM) on the production cross section of single top -channel at
the LHC based on the effective Lagrangian approach. We show that the impact of
CEDM and CMDM could be large. Using the experimental measurement of the
-channel cross section, constraints on CEDM and CMDM are extracted. These
constraints are comparable with the ones obtained from the top pair analysis.Comment: 13 pages, 4 figure
Single top quark production as a probe of anomalous and couplings at the FCC-ee
In this paper, a detailed study to probe the top quark Flavour-Changing
Neutral Currents (FCNC) and at the future
collider FCC-ee in three different center-of-mass energies of 240, 350 and 500
GeV is presented. A set of useful variables are proposed and used in a
multivariate technique to separate signal from standard model background
processes. The study includes a fast detector simulation based on the {\sc
delphes} package to consider the detector effects. The discovery
regions and the upper limits on the FCNC branching ratios at 95\% confidence
level (CL) in terms of the integrated luminosity are presented. It is shown
that with 300 fb of integrated luminosity of data, FCC-ee would be able
to exclude the effective coupling strengths above
which is corresponding to branching fraction of \%. We
show that moving to a high-luminosity regime leads to a significant improvement
on the upper bounds on the top quark FCNC couplings to a photon or a boson.Comment: 21 Pages, 6 Figures, 8 Table
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