3,190 research outputs found
Single Higgs boson production at future linear colliders including radiative corrections
The next generation of high energy e+ e- linear colliders is expected to
operate at \sqrt{s} \gtsim 500 GeV. In this energy range the WW fusion channel
dominates the Higgs boson production cross section e+ e- -> \bar\nu \nu
h^0/H^0. We calculate the one-loop corrections to this process due to fermion
and sfermion loops within the MSSM. We perform a detailed numerical analysis of
the total cross section and the distributions of the rapidity, the transverse
momentum and the production angle of the Higgs boson. The fermion-sfermion
correction is substantial being of the order of -10% and is dominated by the
fermion loops. In addition, we explore the possibility of polarized e+ / e-
beams. In the so-called "intense coupling" scenario the production of the heavy
Higgs boson H^0 is also discussed.Comment: 23 pages, 9 figures, to be published in Nucl. Phys.
CP violation in charged Higgs boson decays in the MSSM with complex parameters
Supersymmetric loop contributions can lead to different decay rates of H+\to
t\bar b and H-\to b\bar t. We calculate the decay rate asymmetry \delta^CP =
\frac{\Gamma(H+\to t\bar b)-\Gamma(H-\to b\bar t)}{{\Gamma(H+\to t\bar
b)+\Gamma(H-\to b\bar t)} at next-to-leading order in the MSSM with complex
parameters. We analyse the parameter dependence of \delta^CP with emphasis on
the phases of A_t and A_b. It turns out that the most important contribution
comes from the loop with stop, sbottom, and gluino. If this contribution is
present, \delta^CP can go up to 10-15% for tan(beta)~10, and to ~5% for large
values of tan(beta).Comment: Eqs. (9) and (25) corrected and numerical analysis modified
accordingl
Radiative corrections to single Higgs boson production in annihilation
For energies relevant to future linear colliders, \sqrt{s} \gsim 500 GeV,
the WW fusion channel dominates the Higgs boson production cross section . We have calculated the one-loop corrections to this
process due to fermion and sfermion loops in the context of the MSSM. As a
special case, the contribution of the fermion loops in the SM has also been
studied. In general, the correction is negative and sizeable of the order of 10
percent, the bulk of it being due to fermion loops.Comment: Version to appear in Phys. Lett.
The decay : a complete 1-loop calculation in the MSSM
In the minimal supersymmetric standard model the decay of
the light neutral scalar is kinematically allowed for low values of
when radiative corrections to the neutral Higgs masses are taken
into account. The width of this decay mode is revisited on the basis of a
complete 1-loop diagrammatic calculation. We give the analytical expressions
and numerical results and compare them with the corresponding ones from the
simpler and compact approximations of the effective potential method and the
renormalization group approach.Comment: 25 pages, LaTex, 10 figures included. Complete ps-file also available
via WWW at http://itpaxp1.physik.uni-karlsruhe.de/prep/prep.htm
Electroweak Precision Observables in the MSSM with Non-Minimal Flavor Violation
The leading corrections to electroweak precision observables in the MSSM with
non-minimal flavor violation (NMFV) are calculated and the effects on M_W and
sin^2 theta_eff are analyzed. The corrections are obtained by evaluating the
full one-loop contributions from the third and second generation scalar quarks,
including the mixing in the scalar top and charm, as well as in the scalar
bottom and strange sector. Furthermore the leading corrections to the mass of
the lightest MSSM Higgs boson, m_h, is obtained. The electroweak one-loop
contribution to M_W can amount up to 140 MeV and up to 70x10^{-5} for sin^2
theta_eff, allowing to set limits on the NMFV parameters. The corrections for
m_h are not significant for moderate generation mixing.Comment: LaTeX, 21 pages, 8 figures. Complete one-loop effects from scalar
quark generation mixing (beyond Delta rho) included for M_W and sin^2
theta_ef
LHC Discovery Potential for Non-Standard Higgs Bosons in the 3b Channel
In a variety of well motivated models, such as two Higgs Doublet Models
(2HDMs) and the Minimal Supersymmetric Standard Model (MSSM), there are neutral
Higgs bosons that have significantly enhanced couplings to b-quarks and tau
leptons in comparison to those of the SM Higgs. These so called non-standard
Higgs bosons could be copiously produced at the LHC in association with b
quarks, and subsequently decay into b-quark pairs. However, this production
channel suffers from large irreducible QCD backgrounds. We propose a new search
strategy for non-standard neutral Higgs bosons at the 7 TeV LHC in the 3b's
final state topology. We perform a simulation of the signal and backgrounds,
using state of the art tools and methods for different sets of selection cuts,
and conclude that neutral Higgs bosons with couplings to b-quarks of about 0.3
or larger, and masses up to 400 GeV, could be seen with a luminosity of 30
fb^{-1}. In the case of the MSSM we also discuss the complementarity between
the 3b channel and the inclusive tau pair channel in exploring the
supersymmetric parameter space.Comment: 14 pages, 3 figures, 4 tables, references added, published versio
Improved full one--loop corrections to A^0 -> \sq_1 \sq_2 and \sq_2 -> \sq_1 A^0
We calculate the full electroweak one-loop corrections to the decay of the
CP-odd Higgs boson A^0 into scalar quarks in the minimal supersymmetric
extension of the Standard Model (MSSM). Due to the complex structure of the
electroweak sector a proper renormalization of many parameters in the on-shell
renormalization scheme is necessary. For the decay into sbottom quarks,
especially for large tanb, the corrections can be very large in the on-shell
renormalization scheme, which makes the perturbation series unreliable. We
solve this problem by an appropriate definition of the tree-level coupling in
terms of running quark masses and running trilinear couplings A_q. We also
discuss the decay of heavy scalar quarks into light scalar quarks and A^0. We
find that the corrections are significant and therefore cannot be neglected.Comment: 15 pages, 9 figures, Fig. 8 correcte
Higgs decays in the Two Higgs Doublet Model: Large quantum effects in the decoupling regime
We study the Higgs-boson decays h0 -> b \bar{b}, h0 -> \gamma \gamma and h0
-> \gamma Z within the framework of the Two Higgs Doublet Model (THDM) in the
context of the decoupling regime, together with tree level unitarity
constraints. We show that when the light CP-even Higgs boson of the THDM mimics
the Standard-Model Higgs boson, not only the one-loop effects to h0 -> {\gamma
\gamma ,\gamma Z} but also the one-loop contribution to h0 -> b \bar{b} can be
used to distinguish between THDM and SM. The size of the quantum effects in h0
-> b \bar{b} are of the same order as in h0 -> {\gamma \gamma ,\gamma Z} and
can reach 25% in both cases.Comment: LaTeX, 13 pages, 5 figures. Improved text, added references, appendix
removed. Version to appear in PL
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