1,179 research outputs found
Top quark decay into charged Higgs boson in a general Two-Higgs-Doublet model: implications for the TEVATRON data
We analyze the unconventional top quark decay mode t -> H^+ b at the quantum
level within the context of general Two-Higgs-Doublet models by including the
full electroweak effects from the Yukawa couplings. The results are presented
in the on-shell renormalization scheme with a physically well motivated
definition of tan(beta). While the QCD corrections have been taken into account
in the current experimental analyses of that decay, the electroweak effects
have always been neglected. However, we find that they can be rather large and
could dramatically alter the interpretation of the present data from the
Tevatron collider. For instance, in large portions of the parameter space the
electroweak effects prevent the Tevatron data from placing any bound at all to
the charged Higgs mass for essentially any value of tan(beta).Comment: 11 pages, LaTeX, 4 figs included using epsfi
Yukawa-coupling corrections to scalar quark decays
Heavy squark decays into top and charginos or neutralinos could be an
unexpected source of top quarks at hadron colliders. A detailed treatment of
these processes is necessary for a reliable calculation of both the top quark
production cross-section and the standard top quark branching ratio in the
MSSM. Along this line we compute the electroweak corrections to the sbottom
decays sbottom_a --> chargino_i top within the Yukawa coupling approximation.
The calculation of these higher order contributions requires renormalization of
both the bottom squark mixing angle and of tan(beta). This type of corrections
gives the leading order electroweak effects at low and high tan(beta).Comment: 16 pages, LaTeX, 5 figures included using epsfig. Comments added,
equation 25 corrected, labels of fig.2 corrected, references update
Quantum SUSY signatures in low and high energy processes
In the search for phenomenological evidence of supersymmetry through the
indirect method of quantum signatures, it is useful to seek correlations of the
non-standard quantum effects in low and high energy proceses, such as those
involving on one hand the properties of the B-mesons and on the other hand the
physics of the top quark and of the Higgs bosons. There are regions of the MSSM
parameter space where the potential quantum SUSY signatures in the two energy
regimes are strongly interwoven and therefore the eventual detection of these
correlated quantum effects would strongly point towards the existence of
underlying supersymmetric dynamics.Comment: 17 pages, LaTeX, 7 figs included with epsfig. Talk at the 5th
International Workshop on High Energy Physics Phenomenology (WHEPP-5). To
appear in the Proceeding
Production and FCNC decay of supersymmetric Higgs bosons into heavy quarks in the LHC
We analyze the production and subsequent decay of the neutral MSSM Higgs
bosons (h = h^0, H^0, A^0) mediated by flavor changing neutral currents (FCNC)
in the LHC collider. We have computed the h-production cross-section times the
FCNC branching ratio, \sigma(pp -> h -> qq') = \sigma(pp -> h) B(h -> qq'), in
the LHC focusing on the strongly-interacting FCNC sector. Here qq' is an
electrically neutral pair of quarks of different flavors, the dominant modes
being those containing a heavy quark: tc or bs. We determine the maximum
production rates for each of these modes and identify the relevant regions of
the MSSM parameter space, after taking into account the severe restrictions
imposed by low energy FCNC processes. The analysis of \sigma(pp -> h -> qq')
singles out regions of the MSSM parameter space different from those obtained
by maximizing only the branching ratio, due to non-trivial correlations between
the parameters that maximize/minimize each isolated factor. The production
rates for the bs channel can be huge for a FCNC process (0.1-1 pb), but its
detection can be problematic. The production rates for the tc channel are more
modest (10^{-3}-10^{-2} pb), but its detection should be easier due to the
clear-cut top quark signature. A few thousand tc events could be collected in
the highest luminosity phase of the LHC, with no counterpart in the SM.Comment: 25 pages, 9 figures, 2 tables, LaTeX 2e. Typos corrected. Version to
appear in JHE
Detecting heavy charged Higgs bosons at the LHC with triple b-tagging
We investigate the charged Higgs boson signal at the LHC using its dominant
production and decay modes with triple b-tagging, i.e. , followed by leptonic decay of one W and hadronic decay of
the other. We consider the continuum background from the associated production
of with a b- or a light quark or gluon jet, which can be mis-tagged
as b-jet. We reconstruct the top quark masses to identify the 3rd b-jet
accompanying the pair, and use its p_T distribution to distinguish
the signal from the background. Combining this with the reconstruction of the
mass gives a viable signature over two interesting regions of the
parameter space - i.e. and .Comment: 10 pages, latex, 4 figure
FCNC top quark decay in the MSSM: a door to SUSY physics in high luminosity colliders?
We study the FCNC top quark decays t -> c h in the framework of the MSSM,
where h= h^0,H^0,A^0 is any of the supersymmetric neutral Higgs bosons. We
include the leading set of SUSY-QCD and SUSY electroweak contributions. While
the FCNC top quark decay into the SM Higgs boson has such a negligible rate
that will not be accessible to any presently conceivable accelerator, we find
that there is a chance that the potential rates in the MSSM can be measured at
the high luminosity colliders round the corner, especially at the LHC and
possibly at a future LC, but we deem it difficult at the upgraded Tevatron. In
view of the large SUSY-QCD effects that we find in the Higgs channels, and due
to some discrepancies in the literature, we have revisited the FCNC top quark
decay into gluon, t -> c g, in our framework. We confirm that the possibility
of sizeable rates does not necessarily require a general pattern of
gluino-mediated FCNC interactions affecting both the LH and the RH sfermion
sectors -- the LH one being sufficient. However, given the present bounds on
sparticle masses, the gluon channel turns out to lie just below the expected
experimental sensibility, so our general conclusion is that the Higgs channels
t -> c h (especially the one for the light CP-even Higgs) have the largest
potential top quark FCNC rates in the MSSM, namely of order 10^-4.Comment: 22 pages, LaTeX2e, 10 figs. included. Title changed. Note and
references adde
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