374 research outputs found
QCD Corrections to Radiative B Decays in the MSSM with Minimal Flavor Violation
We compute the complete supersymmetric QCD corrections to the Wilson
coefficients of the magnetic and chromomagnetic operators, relevant in the
calculation of b -> s gamma decays, in the MSSM with Minimal Flavor Violation.
We investigate the numerical impact of the new results for different choices of
the MSSM parameters and of the scale where the quark and squark mass matrices
are assumed to be aligned. We find that the corrections can be important when
the superpartners are relatively light, and that they depend sizeably on the
scale of alignment. Finally, we discuss how our calculation can be employed
when the scale of alignment is far from the weak scale.Comment: 16 pages, 5 figures; v2: version to appear in Phys. Lett.
On the NLO QCD corrections to Higgs production and decay in the MSSM
We present explicit analytic results for the two-loop top/stop/gluino
contributions to the cross section for the production of CP-even Higgs bosons
via gluon fusion in the MSSM, under the approximation of neglecting the Higgs
boson mass with respect to the masses of the particles circulating in the
loops. The results are obtained employing the low-energy theorem for Higgs
interactions adapted to the case of particle mixing. We discuss the validity of
the approximation used by computing the first-order correction in an expansion
in powers of the Higgs boson mass. We find that, for the lightest CP-even Higgs
boson, the gluino contribution is very well approximated by the result obtained
in the limit of vanishing Higgs mass. As a byproduct of our calculation, we
provide results for the two-loop QCD contributions to the photonic Higgs decay.Comment: 24 pages, 4 figures; v2 to appear in Nucl.Phys.B; v3 minor
corrections, note added in section 3.
QCD Corrections in two-Higgs-doublet extensions of the Standard Model with Minimal Flavor Violation
We present the QCD corrections to R_b and to the Delta B=1 effective
Hamiltonian in models with a second Higgs field that couples to the quarks
respecting the criterion of Minimal Flavor Violation, thus belonging either to
the (1,2)_1/2 or to the (8,2)_1/2 representation of SU(3)xSU(2)xU(1). After the
inclusion of the QCD corrections, the prediction for R_b becomes practically
insensitive to the choice of renormalization scheme for the top mass, which for
the type-I and type-II models translates in a more robust lower bound on
tan(beta). The QCD-corrected determinations of Rb and BR(B->Xs gamma) are used
to discuss the constraints on the couplings of a (colored) charged Higgs boson
to top and bottom quarks.Comment: 19 pages, 7 figures. v2: version published in Phys. Rev. D, with
additional reference and not
Towards precise predictions for Higgs-boson production in the MSSM
We study the production of scalar and pseudoscalar Higgs bosons via gluon
fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD
calculation implemented in the public code SusHi, we provide precise
predictions for the Higgs-production cross section in six benchmark scenarios
compatible with the LHC searches. We also provide a detailed discussion of the
sources of theoretical uncertainty in our calculation. We examine the
dependence of the cross section on the renormalization and factorization
scales, on the precise definition of the Higgs-bottom coupling and on the
choice of PDFs, as well as the uncertainties associated to our incomplete
knowledge of the SUSY contributions through NNLO. In particular, a potentially
large uncertainty originates from uncomputed higher-order QCD corrections to
the bottom-quark contributions to gluon fusion.Comment: 62 pages, 24 pdf figures; v2: minor clarifications, improved plot
quality, matches published versio
Two-loop QCD corrections to the MSSM Higgs masses beyond the effective-potential approximation
We compute the two-loop QCD corrections to the neutral Higgs-boson masses in
the MSSM, including the effect of non-vanishing external momenta in the
self-energies. We obtain corrections of O(alpha_t*alpha_s) and
O(alpha*alpha_s), i.e., all two-loop corrections that involve the strong gauge
coupling when the only non-vanishing Yukawa coupling is the top one. We adopt
either the DRbar renormalization scheme or a mixed OS-DRbar scheme where the
top/stop parameters are renormalized on-shell. We compare our results with
those of earlier calculations, pointing out an inconsistency in a recent result
obtained in the mixed OS-DRbar scheme. The numerical impact of the new
corrections on the prediction for the lightest-scalar mass is moderate, but
already comparable to the accuracy of the Higgs-mass measurement at the LHC.Comment: 22 pages, 5 pdf figures; v2: version to appear in EPJ
Politics of meaning in categorizing innovation : how chefs advanced molecular gastronomy by resisting the label
This study examines innovatorsâ efforts to conceptualize and communicate their novel work through categorization. Specifically, we view category formation as a controversial process of meaning making, which we theorize through the concept of âpolitics of meaningâ and operationalize through a social semiotics approach. By analyzing the labelling controversies underlying a new culinary style publicized as âmolecular gastronomyâ, we find that innovatorsâ efforts at categorization unfold along four consecutive stages: experiment ng with a new style, communicating the new style, contesting the dominant label, and legitimating the category meaning. Our study suggests that a new categoryâs dominant label can substantially deviate from the innovatorsâ intended denotations, yet nonetheless bring that category forward by triggering public negotiations around its meaning , which lead to categorical deepening and legitimation. By putting forward a âpolitics of meaningâ view on categorizing innovation, this work advances our understanding of the connection between labeling and category formation in the context of innovation
Towards high-precision predictions for the MSSM Higgs sector
The status of the evaluation of the MSSM Higgs sector is reviewed. The phenomenological impact of recently obtained corrections is discussed. In particular it is shown that the upper bound on mh within the MSSM is shifted upwards. Consequently, lower limits on tanb obtained by confronting the upper bound as function of tanb with the lower bound on mh from Higgs searches are significantly weakened. Furthermore, th e region in the MA-tanb-plane where the coupling of the lightest Higgs boson to down-type fermions is suppressed is modified. The presently not calculated higher-order corrections to the Higgs-boson mass matrix are estimated to shift the mass of the lightest Higgs boson by up to 3 GeV
Precise determination of the neutral Higgs boson masses in the MSSM
We present the implementation of the radiative corrections of the Higgs
sector in three public computer codes for the evaluation of the particle
spectrum in the Minimal Supersymmetric Standard Model, Softsusy, Spheno and
SuSpect. We incorporate the full one-loop corrections to the Higgs boson masses
and the electroweak symmetry breaking conditions, as well as the two-loop
corrections controlled by the strong gauge coupling and the Yukawa couplings of
the third generation fermions. We include also the corrections controlled by
the tau Yukawa coupling that we derived for completeness. The computation is
consistently performed in the DRbar renormalisation scheme. In a selected
number of MSSM scenarios, we study the effect of these corrections and analyse
the impact of some higher order effects. By considering the renormalisation
scheme and scale dependence, and the effect of the approximation of zero
external momentum in the two-loop corrections, we estimate the theoretical
uncertainty on the lighter Higgs boson mass to be 3 to 5 GeV. The uncertainty
on Mh due to the experimental error in the measurement of the SM input
parameters is approximately of the same size. Finally, we discuss the
phenomenological consequences, using the latest value of the top quark mass. We
find, in particular, that the most conservative upper bound on the lighter
Higgs boson mass in the general MSSM is Mh < 152 GeV and that there is no lower
bound on the parameter tan(beta) from non-observation of the MSSM Higgs bosons
at LEP2
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