3,498 research outputs found
SUSY--QCD corrections to scalar quark decays into charginos and neutralinos
We calculate the supersymmetric QCD corrections in order to the
decays \squark_i \to q' \chargino_j (i,j = 1,2) and \squark_i \to q
\neutralino_k (k = 1,...4) within the Minimal Supersymmetric Standard Model.
In particular we consider the decays of squarks of the third generation,
\stop_i and \sbottom_i (i = 1,2), where the left--right mixing must be
taken into account. The corrections turn out to be of about 10\%, except for
higgsino--like charginos or neutralinos, where they can go up to 40\%.Comment: 15 pages (including 5 figures). Tiny corrections in the text are
made. An acknowledgement is added. Figures 2 - 5 are replaced by new ones
(change in one curve in each figure). To be published in Phys. Lett.
A CP asymmetry in e^+e^- \to \chi^0_i\chi^0_j \to \chi^0_j \tau stau_k with tau polarization
We propose a CP-odd asymmetry in the supersymmetric process e^+e^- \to
\chi^0_i \chi^0_j \to \chi^0_j \tau stau_k by means of the transverse \tau
polarization. We calculate the asymmetry and cross sections at a future linear
collider in the 500 GeV c.m.s. energy range with longitudinal polarized beams
and high luminosity. We work in the Minimal Supersymmetric Standard Model with
complex parameters \mu, M_1 and A_\tau. The asymmetry can reach values up to 60
%. We also estimate the sensitivity for measuring the \tau polarization
necessary to probe the CP asymmetry.Comment: 12 pages, 7 figure
Impact of CP phases on stop and sbottom searches
We study the decays of top squarks (stop_{1,2}) and bottom squarks
(sbottom_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with
complex parameters A_t, A_b, mu and M_1. We show that including the
corresponding phases substantially affects the branching ratios of stop_{1,2}
and sbottom_{1,2} decays in a large domain of the MSSM parameter space. We find
that the branching ratios can easily change by a factor of 2 and more when
varying the phases. This could have an important impact on the search for
stop_{1,2} and sbottom_{1,2} and the determination of the MSSM parameters at
future colliders.Comment: 17 pages, 5 figures, LaTeX2
Selectron production at an e-e- linear collider with transversely polarized beams
We study selectron production at an e-e- linear collider. With the help of
transverse beam polarizations, we define CP sensitive observables in the
production process e- e- --> selectron_L selectron_R. This process proceeds via
t-channel and u-channel exchange of neutralinos, and is sensitive to CP
violation in the neutralino sector. We present numerical results and estimate
the significances to which the CP sensitive observables can be measured.Comment: 14 page
Supersymmetric Signals in Collisions
We study the occurrence of final states with only an electron-positron pair
and missing transverse momentum as a signal of \susy\ in photon-photon
collisions. Suitable high energy photon beams may be provided at linear
colliders by back-scattering laser beams on electron beams. The final states
considered represent a typical signature for the production and decay of
selctron and chargino pairs within the \mssm. We show that, away from the
kinematical threshold, selctrons produce this signal far more abundantly than
charginos. The standard model background is dominated by W-pair production. We
propose a series of kinematical cuts which reduce this background to an
acceptable level. With a 1 TeV collider operated in the -mode, we
find that interesting and complementary tests of \susic\ models can be
performed for selctron masses up to 350 GeV.Comment: 12 pages + 6 pages figures (included as uufile, also with anon. ftp
from gluon.hep.physik.uni-muenchen.de (129.187.198.1)), LaTeX (axodraw,epsf),
CERN-TH.6742/92, MPI-Ph/92-73, LMU-92/07. (forgot the bibliography file - my
excuses
Standard Model and Beyond
We first discuss the basic features of electroweak 1-loop corrections in the
Standard Model. We also give a short and elementary review on Higgs boson
searches, grand unification, supersymmetry and extra dimensions.Comment: 20 pages, LaTeX, 7 eps figures, uses ws-procs9x6.cls, lecture given
by A. Bartl at the VII School on Non-Accelerator Astroparticle Physics,
Trieste, Italy, July 26 - August 6, 200
CP asymmetries in scalar bottom quark decays
We propose CP asymmetries based on triple product correlations in the decays
sbottom_m -> top chargino_j with subsequent decays of top and chargino_j. For
the subsequent chargino_j decay into a leptonic final state l^- \nu
neutralino_1 we consider the three possible decay chains chargino_j -> l^-
sneutrino -> l^- \nu neutralino_1, chargino_j -> slepton_n \nu -> l^- \nu
neutralino_1 and chargino_j -> W^- neutralino_1 -> l^- \nu neutralino_1. We
consider two classes of CP asymmetries. In the first class it must be possible
to distinguish between different leptonic chargino_j decay chains, whereas in
the second class this is not necessary. We consider also the 2-body decay
chargino_j -> W^- neutralino_1, and we assume that the momentum of the W boson
can be measured. Our framework is the minimal supersymmetric standard model
with complex parameters. The proposed CP asymmetries are non-vanishing due to
non-zero phases for the parameters \mu and/or A_b. We present numerical results
and estimate the observability of these CP asymmetries.Comment: 27 page
Radiative Corrections to Chargino Production in Electron-Positron Collisions
We discuss the one-loop radiative corrections to the reaction e^+ e^- ->
X^+_a X^-_b, for a,b=1,2 where X^+_{1,2} are the charginos of the minimal
supersymmetric standard model. We calculate the leading one loop radiative
corrections involving loops of top, stop, bottom and sbottom quarks, working in
the MS-bar scheme. At LEP2 we find positive radiative corrections typically of
10% to 15% and with a maximum value of approximately 30% if the squark mass
parameters are of the order of 1 TeV. If \sqrt{s}=500 GeV we find smaller
corrections but they can be also negative, with extreme values of 13% and -4%.
For a center of mass given by \sqrt{s}=2 TeV we find larger corrections, with
typical values between 20% and -20%.Comment: 44 pages including 22 figures, Late
- …