153 research outputs found
Top-quark Polarization and Asymmetries at the LHC in the Effective Description of Squark Interactions
A detailed study of top-quark polarizations and charge
asymmetries, induced by top-squark-pair production at the LHC and the
subsequent decays , is performed within the
effective description of squark interactions, which includes the effective
Yukawa couplings and another logarithmic term encoding the supersymmetry
breaking. This effective approach is more suitable for its introduction into
Monte-Carlo simulations and we make use of its implementation in {\tt MadGraph}
in order to investigate the possibilities of the charge asymmetry ,
measured at the LHC and consistent with SM expectations, to discriminate among
different SUSY scenarios and analyze the implications of these scenarios in the
top polarizations and related observables.Comment: LaTeX file. 27 pages, 6 figures, 10 tables: v3 matches published
manuscript Eur.Phys.J. C75 (2015) 1, 3
Determining the ratio of the H^+ -> \tau \nu to H^+ -> t b-bar decay rates for large \tan\beta at the Large Hadron Collider
We present results on the determination of the observable ratio R=BR(H^+ ->
\tau \nu)/BR(H^+ -> t b-bar) of charged Higgs boson decay rates as a
discriminant quantity between Supersymmetric and non-Supersymmetric models.
Simulation of measurements of this quantity through the analysis of the charged
Higgs production process gb-> t b H^+ and relative backgrounds in the two above
decay channels has been performed in the context of ATLAS. A ~12-14% accuracy
on R can be achieved for \tan\beta=50, \mHc=300-500 GeV and after an integrated
luminosity of 300 fb^-1. With this precision measurement, the Large Hadron
Collider (LHC) can easily discriminate between models for the two above
scenarios, so long as \tan\beta > 20.Comment: LaTeX, 11 pages, 3 figures, 3 tables, Contribution to the Les Houches
workshop ``Physics at TeV Colliders'', 26 May - 6 June, 200
Discriminating between SUSY and Non-SUSY Higgs Sectors through the Ratio with a 125 GeV Higgs boson
It is still an open question whether the new scalar particle discovered at
the LHC with a mass of 125 GeV is the SM Higgs boson or it belongs to models of
new physics with an extended Higgs sector, as the MSSM or 2HDM. The ratio of
branching fractions = BR()/BR() of
Higgs boson decays is a powerful tool in order to distinguish the MSSM Higgs
sector from the SM or non-supersymmetric 2HDM. This ratio receives large
renormalization-scheme independent radiative corrections in supersymmetric
models at large , which are insensitive to the SUSY mass scale and
absent in the SM or 2HDM. Making use of the current LHC data and the upcoming
new results on Higgs couplings to be reported by ATLAS and CMS collaborations
and in a future linear collider, we develop a detailed and updated study of
this ratio which improves previous analyses and sets the level of accuracy
needed to discriminate between models.Comment: 11 pages, 3 figures, 1 tabl
Higgs Boson Masses in the MSSM with Heavy Majorana Neutrinos
We present a full diagrammatic computation of the one-loop corrections from
the neutrino/sneutrino sector to the renormalized neutral CP-even Higgs boson
self-energies and the lightest Higgs boson mass, Mh, within the context of the
so-called MSSM-seesaw scenario. This consists of the Minimal Supersymmetric
Standard Model with the addition of massive right handed Majorana neutrinos and
their supersymmetric partners, and where the seesaw mechanism is used for the
lightest neutrino mass generation. We explore the dependence on all the
parameters involved, with particular emphasis in the role played by the heavy
Majorana scale. We restrict ourselves to the case of one generation of
neutrinos/sneutrinos. For the numerical part of the study, we consider a very
wide range of values for all the parameters involved. We find sizeable
corrections to Mh, which are negative in the region where the Majorana scale is
large (10^{13}-10^{15} GeV) and the lightest neutrino mass is within a range
inspired by data (0.1-1 eV). For some regions of the MSSM-seesaw parameter
space, the corrections to Mh are substantially larger than the anticipated
Large Hadron Collider precision.Comment: Latex, 50 pages, 15 figures, 6 tables. Discussion improved. Comments
and some new approximate formulae have been added. Published version on JHE
Interplay between Hbs and bsgamma in the MSSM with Non-Minimal Flavour Violation
We investigate the constraints on flavour-changing neutral heavy Higgs-boson
decays H-> b \bar s from b -> s gamma bounds on the flavour-mixing parameters
of the MSSM with non-minimal flavour violation (NMFV). In our analysis we
include the contributions from the SM and new physics due to general flavour
mixing in the squark mass matrices. We study the case of one and two non-zero
flavour-mixing parameters and find that in the latter case the interference can
raise the Higgs flavour-changing branching ratios by one or two orders of
magnitude with respect to previous predictions based on a single non-zero
parameter and in agreement with present constraints from physics. In the
course of our work we developed a new "FeynArts" model file for the NMFV MSSM
and added the necessary code for the evaluation to "FormCalc". Both extensions
are publicly available.Comment: LaTeX2e, 15 pages, 4 figures. Computation improved and figures
replaced accordingly. Some references added. Main conclusions remain
untouche
M_W, sin^2 \theta_{eff} and m_h in the NMFV MSSM
The effects of loop contributions to the electroweak precision observables
and m_h in the MSSM with non-minimal flavour violation (NMFV) are analyzed,
including the mixing between third and second generation squarks. The
mixing-induced shift in M_W can amount to 140 MeV and to 70x10^{-5} in sin^2
\theta_{eff} for extreme values of squarks mixing, allowing to set limits on
the NMFV parameters. The corrections for m_h are usually small and can amount
up to O(5 GeV) for large flavour violation.Comment: 6 pages, latex, 3 figures, to appear in the proceedings of the "2005
International Linear Collider Workshop" (LCWS05), Stanford, 200
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