884 research outputs found
Chargino and Neutralino Decays Revisited
We perform a comprehensive analysis of the decays of charginos and
neutralinos in the Minimal Supersymmetric Standard Model where the neutralino
is assumed to be the lightest supersymmetric particle. We focus, in
particular, on the three-body decays of the next-to-lightest neutralino and the
lightest chargino into the lightest neutralino and fermion-antifermion pairs
and include vector boson, Higgs boson and sfermion exchange diagrams, where in
the latter contribution the full mixing in the third generation is included.
The radiative corrections to the heavy fermion and SUSY particle masses will be
also taken into account. We present complete analytical formulae for the Dalitz
densities and the integrated partial decay widths in the massless fermion case,
as well as the expressions of the differential decay widths including the
masses of the final fermions and the polarization of the decaying charginos and
neutralinos. We then discuss these decay modes, in particular in scenarios
where the parameter is large and in models without universal
gaugino masses at the Grand Unification scale where some new decay channels,
such as decays into gluinos and pairs, open up.Comment: 51 pages with 13 figures, latex; uses axodraw.sty and epsfig.st
SDECAY: a Fortran code for the decays of the supersymmetric particles in the MSSM
We present the Fortran code SDECAY, which calculates the decay widths and
branching ratios of all the supersymmetric particles in the Minimal
Supersymmetric Standard Model, including higher order effects. Besides the
usual two-body decays of fermions and gauginos and the three-body decays of
charginos, neutralinos and gluinos, we have also implemented the three-body
decays of top squarks, and even the four-body decays of the top squark; the
important loop-induced decay modes are also included. The QCD corrections to
the two-body decays involving strongly interacting particles and the dominant
components of the electroweak corrections to all decay modes are implemented.Comment: 42 page
Determining SUSY Parameters in Chargino Pair-Production in Collisions
In most supersymmetric theories, charginos , mixtures
of charged color-neutral gauginos and higgsinos, belong to the class of the
lightest supersymmetric particles. They are easy to observe at
colliders. By measuring the total cross sections and the left-right asymmetries
with polarized electron beams in , the chargino masses and the gaugino-higgsino mixing angles can be
determined. From these observables the fundamental SUSY parameters can be
derived: the SU(2) gaugino mass , the modulus and
of the higgsino mass parameter, and , the ratio of the
vacuum expectation values of the two neutral Higgs doublet fields. The
solutions are unique; the CP-violating phase can be determined
uniquely by analyzing effects due to the normal polarization of the charginos.Comment: 20 pages, 4 figures, uses axodraw.st
Three-Body Decays of SUSY Particles
We analyze the decays of charginos, neutralinos, gluinos and the first/second
generation squarks in the Minimal Supersymmetric extension of the Standard
Model, focusing on the three-body decays in scenarios where the ratio of vacuum expectation values of the two Higgs doublet fields is large.
We show that the three-body decays of the next-to-lightest neutralinos
(lightest charginos) into () final states,
where third generation sfermion and Higgs boson exchange diagrams play an
important role, are dominant. Furthermore, we show that decays of gluinos into
final states and squark decays into lighter sbottoms through gluino
exchange can also have sizeable branching fractions, especially in scenarios
where the soft SUSY breaking gaugino mass parameters are not unified at the GUT
scale.Comment: 10 pages with 5 figures + axodraw.sty, late
Decays of the Lightest Top Squark
We analyze higher order decay modes of the lightest top squark in the Minimal Supersymmetric extension of the Standard Model (MSSM), where the lightest SUSY particle (LSP) is assumed to be the neutralino . For small masses accessible at LEP2 and the Tevatron, we show that the four--body decay mode into the LSP, a bottom quark and two massless fermions, \tilde{t}_1 \ra b \chi_1^0 f\bar{f}', can dominate in a wide range of the MSSM parameter space over the loop--induced decay into a charm quark and the LSP, \tilde{t}_1 \ra c \chi_1^0. This result might affect the experimental searches on this particle, since only the later signal has been considered so far
The Higgs sector of the phenomenological MSSM in the light of the Higgs boson discovery
The long awaited discovery of a new light scalar at the LHC opens up a new
era of studies of the Higgs sector in the SM and its extensions. In this paper
we discuss the consequences of the observation of a light Higgs boson with the
mass and rates reported by the ATLAS and CMS collaborations on the parameter
space of the phenomenological MSSM, including also the so far unsuccessful LHC
searches for the heavier Higgs bosons and supersymmetric particle partners in
missing transverse momentum as well as the constraints from B physics and dark
matter. We explore the various regimes of the MSSM Higgs sector depending on
the parameters MA and tan beta and show that only two of them are still allowed
by all present experimental constraints: the decoupling regime where there is
only one light and standard--like Higgs boson and the supersymmetric regime in
which there are light supersymmetric particle partners affecting the decay
properties of the Higgs boson, in particular its di-photon and invisible
decays.Comment: 21 pages, 9 figures v2 - Discussion of the impact of LHC data
extended, scan statistics increased, a few figures added and typos correcte
Three-Body Decays of Top and Bottom Squarks
We investigate the decays of third generation scalar quarks in the Minimal
Supersymmetric extension of the Standard Model, focusing on the three-body
modes. We calculate the partial widths of the decays of heavier top and bottom
squarks into the lighter ones and a fermion pair [through virtual vector boson,
Higgs boson or gaugino exchanges] and the partial widths of the three-body
decays of both top squarks into bottom quarks and a pair of fermion and scalar
fermion [we consider the case of lighter or states]
and into a bottom quark, the lightest neutralino and a or a charged Higgs
boson . Some of these decay modes are shown to have substantial
branching ratios in some areas of the parameter space.Comment: 24 pages with 4 psfigures, late
Reconstructing the Chargino System at Linear Colliders
In most supersymmetric theories charginos, , belong
to the class of the lightest supersymmetric particles. The chargino system can
be reconstructed completely in collider experiments:
. By measuring the total
cross sections and the asymmetries with polarized beams, the chargino masses
and the gaugino-higgsino mixing angles of these states can be determined
accurately. If only the lightest charginos are
kinematically accessible in a first phase of the machine, transverse beam
polarization or the measurement of chargino polarization in the final state is
needed to determine the mixing angles. From these observables the fundamental
SUSY parameters can be derived: the SU(2) gaugino mass , the modulus and
the cosine of the CP-violating phase of the higgsino mass parameter , and
, the ratio of the vacuum expectation values of the two
neutral Higgs doublet fields. The remaining two-fold ambiguity of the phase can
be resolved by measuring the normal polarization of the charginos. Sum rules of
the cross sections can be exploited to investigate the closure of the
two-chargino system.Comment: 25 pages, 6 figure
Higgs Physics at Future Colliders: recent theoretical developments
I review the physics of the Higgs sector in the Standard Model and its
minimal supersymmetric extension, the MSSM. I will discuss the prospects for
discovering the Higgs particles at the upgraded Tevatron, at the Large Hadron
Collider, and at a future high--energy linear collider with
centre--of--mass energy in the 350--800 GeV range, as well as the possibilities
for studying their fundamental properties. Some emphasis will be put on the
theoretical developments which occurred in the last two years.Comment: 20 pages, latex, 12 figures. Talk given at PASCOS 2003 (Bombay,
India
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