23 research outputs found
One-loop calculations for SUSY processes
Strategy and results for complete one-loop computations in the Minimal
Supersymmetric Standard Model are reviewed, with applications to the
calculation of SUSY mass spectra and SUSY-particle processes. Determination of
renormalization constants and counterterms are described in the on-shell
renormalization scheme, and a translation between and on-shell
parameters is given. As an example, cross sections for chargino and neutralino
pair production in annihilation are presented, complete at the
one-loop level.Comment: Talk presented at Loops and Legs in Quantum Field Theory, Zinnowitz,
Germany, April 200
Analysis of the chargino and neutralino mass parameters at one-loop level
In the Minimal Supersymmetric Standard Model (MSSM) the masses of the
neutralinos and charginos depend on the gaugino and higgsino mass parameters M,
M' and . If supersymmetry is realized, the extraction of these parameters
from future high energy experiments will be crucial to test the underlying
theory. We present a consistent method how on-shell parameters can be properly
defined at one-loop level and how they can be determined from precision
measurements. In addition, we show how a GUT relation for the parameters M and
M' can be tested at one-loop level. The numerical analysis is based on a
complete one-loop calculation. The derived analytic formulae are given in the
appendix.Comment: 16 pages, 8 figure
Two-loop SUSY QCD corrections to the chargino masses in the MSSM
We have calculated the two-loop strong interaction corrections to the
chargino pole masses in the DRbar'-scheme in the Minimal Supersymmetric
Standard Model (MSSM) with complex parameters. We have performed a detailed
numerical analysis for a particular point in the parameter space and found
corrections of a few tenths of a percent. We provide a computer program which
calculates chargino and neutralino masses with complex parameters including the
one-loop corrections and all two-loop SQCD effects.Comment: 12 pages, 11 figures, references modified, clarifications adde
Full one-loop corrections to SUSY Higgs boson decays into charginos
We present the decay widths of the heavier Higgs bosons and into
chargino pairs in the minimal supersymmetric standard model, including full
one-loop corrections. All parameters for charginos are renormalized in the
on-shell scheme. The importance of the corrections to the chargino mass matrix
and mixing matrices is pointed out. The full corrections are typically of the
order of 10 %.Comment: 15 pages, 9 figure
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
Radiative corrections to scalar-fermion pair production in high energy e+e- collisions
We study the one-loop radiative corrections to pair production of the
supersymmetric scalar partners of the standard fermions in e+e- annihilation.
Both electroweak and SUSY-QCD corrections are considered. Applications are for
production of scalar fermions of the third generation, e^+e^-\to \wt{f}_i
\wt{f}_j^* (i,j=1,2), , as well as for production of scalar
quarks of the first and second generation. Effects on integrated cross sections
are discussed and also the one-loop induced forward-backward asymmetries are
studied. It is found that at low energy, \sqrt{s}\approx 500 \to 1000 GeV, the
corrections are dominated by the QCD contributions, At high energy,
TeV, the electroweak box diagrams give a substantial
contribution and even dominate in some regions of parameters space. The purely
loop-induced forward-backward asymmetry can reach values of several per cent.Comment: 23 pages, latex, 13 figure
Top Squarks and Bottom Squarks in the MSSM with Complex Parameters
We present a phenomenological study of top squarks (~t_1,2) and bottom
squarks (~b_1,2) in the Minimal Supersymmetric Standard Model (MSSM) with
complex parameters A_t, A_b, \mu and M_1. In particular we focus on the CP
phase dependence of the branching ratios of (~t_1,2) and (~b_1,2) decays. We
give the formulae of the two-body decay widths and present numerical results.
We find that the effect of the phases on the (~t_1,2) and (~b_1,2) decays can
be quite significant in a large region of the MSSM parameter space. This could
have important implications for (~t_1,2) and (~b_1,2) searches and the MSSM
parameter determination in future collider experiments. We have also estimated
the accuracy expected in the determination of the parameters of ~t_i and ~b_i
by a global fit of the measured masses, decay branching ratios and production
cross sections at e^+ e^- linear colliders with polarized beams. Analysing two
scenarios, we find that the fundamental parameters apart from A_t and A_b can
be determined with errors of 1% to 2%, assuming an integrated luminosity of 1
ab^-1 and a sufficiently large c.m.s. energy to produce also the heavier ~t_2
and ~b_2 states. The parameter A_t can be determined with an error of 2 - 3%,
whereas the error on A_b is likely to be of the order of 50%.Comment: 31 pages, 8 figures, comments and references added, conclusions
unchanged; version to appear in Phys. Rev.
Mass Bounds on a Very Light Neutralino
Within the Minimal Supersymmetric Standard Model (MSSM) we systematically
investigate the bounds on the mass of the lightest neutralino. We allow for
non-universal gaugino masses and thus even consider massless neutralinos, while
assuming in general that R-parity is conserved. Our main focus are laboratory
constraints. We consider collider data, precision observables, and also rare
meson decays to very light neutralinos. We then discuss the astrophysical and
cosmological implications. We find that a massless neutralino is allowed by all
existing experimental data and astrophysical and cosmological observations.Comment: 36 pages, 13 figures, minor modification in astro-physical bounds.
EPJC versio
Chargino Decays in the Complex MSSM: A Full One-Loop Analysis
We evaluate two-body decay modes of charginos in the Minimal Supersymmetric
Standard Model with complex parameters (cMSSM). Assuming heavy scalar quarks we
take into account all decay channels involving charginos, neutralinos, (scalar)
leptons, Higgs bosons and Standard Model gauge bosons. The evaluation of the
decay widths is based on a full one-loop calculation including hard and soft
QED radiation. Special attention is paid to decays involving the Lightest
Supersymmetric Particle (LSP), i.e. the lightest neutralino, or a neutral or
charged Higgs boson. The higher-order corrections of the chargino decay widths
involving the LSP can easily reach a level of about \pm 10%, while the
corrections to the decays to Higgs bosons are slightly smaller, translating
into corrections of similar size in the respective branching ratios. These
corrections are important for the correct interpretation of LSP and Higgs
production at the LHC and at a future linear e+e- collider. The results will be
implemented into the Fortran code FeynHiggs.Comment: 75 pages, 43 figures. Minor corrections; version to appear in EPJC.
arXiv admin note: substantial text overlap with arXiv:1111.728