4 research outputs found
Sparticle Spectrum Constraints
The supersymmetric standard model with supergravity-inspired soft breaking
terms predicts a rich pectrum of sparticles to be discovered at the SSC, LHC
and NLC. Because there are more supersymmetric particles than unknown
parameters, one can write down sum rules relating their masses. We discuss the
pectrum of sparticles from this point of view. Some of the sum rules do not
depend on the input parameters and can be used to test the consistency of the
model, while others are useful in determining the input parameters of the
theory. If supersymmetry is discovered but the sum rules turn out to be
violated, it will be evidence of new physics beyond the minimal supersymmetric
standard model with universal soft supersymmetry-breaking terms.Comment: 25 pages. NUB-3067-93TH, UFIFT-HEP-93-16, SSCL-Preprint-439, June
199
Experimental aspects of SU(5)xU(1) supergravity
We study various aspects of supergravity as they relate to
the experimental verification or falsification of this model. We consider two
string-inspired, universal, one-parameter, no-scale soft-supersymmetry-breaking
scenarios, driven by the -terms of the moduli and dilaton fields. The model
is described in terms of the supersymmetry mass scale (\ie, the chargino mass
), , and the top-quark mass. We first determine the
combined effect on the parameter space of all presently available direct and
indirect experimental constraints, including the LEP lower bounds on sparticle
and Higgs-boson masses, the rate, the anomalous magnetic moment
of the muon, the high-precision electroweak parameters
(which imply m_t\lsim180\GeV), and the muon fluxes in underground detectors
(neutrino telescopes). For the still-allowed points in
parameter space, we re-evaluate the experimental
situation at the Tevatron, LEPII, and HERA. In the 1994 run, the Tevatron could
probe chargino masses as high as 100 GeV. At LEPII the parameter space could be
explored with probes of different resolutions: Higgs boson searches, selectron
searches, and chargino searches. Moreover, for m_t\lsim150\GeV, these
Higgs-boson searches could explore all of the allowed parameter space with
\sqrt{s}\lsim210\GeV.Comment: latex, 36 pages, 25 figures (not included). Figures are available via
anonymous ftp from hplaa02.cern.ch (/pub/lopez) as either 33 ps files
(Easpects*.ps, 8.1MB) or one uuencoded file (AllFigures.uu, 3.7MB
Uncertainties in Coupling Constant Unification
The status of coupling constant unification in the standard model and its
supersymmetric extension are discussed. Uncertainties associated with the input
coupling constants, , threshold corrections at the low and high scales,
and possible nonrenormalizable operators are parametrized and estimated. A
simple parametrization of a general supersymmetric new particle spectrum is
given. It is shown that an effective scale can be defined, but for a
realistic spectrum it may differ considerably from the typical new particle
masses. The implications of the lower (higher) values of
suggested by low-energy (-pole) experiments are discussed.Comment: LaTex, 51 pages, 6 figures (available upon request), UPR-0513
Hypercharge and the Cosmological Baryon Asymmetry
Stringent bounds on baryon and lepton number violating interactions have been
derived from the requirement that such interactions, together with electroweak
instantons, do not destroy a cosmological baryon asymmetry produced at an
extremely high temperature in the big bang. While these bounds apply in
specific models, we find that they are generically evaded. In particular, the
only requirement for a theory to avoid these bounds is that it contain charged
particles which, during a certain cosmological epoch, carry a non-zero
hypercharge asymmetry. Hypercharge neutrality of the universe then dictates
that the remaining particles must carry a compensating hypercharge density,
which is necessarily shared amongst them so as to give a baryon asymmetry.
Hence the generation of a hypercharge density in a sector of the theory forces
the universe to have a baryon asymmetry.Comment: 12 pages plus 1 Postscript figure available upon request. LBL 3482