279 research outputs found
Infrared Quasi Fixed Points and Mass Predictions in the MSSM II: Large tan(beta) Scenario
We consider the infrared quasi fixed point solutions of the renormalization
group equations for the Yukawa couplings and soft supersymmetry breaking
parameters in the MSSM in the \underline{large } regime. The
existence of IR quasi fixed points together with the values of gauge couplings,
third generation quarks, lepton and Z-boson masses allows one to predict masses
of the Higgs bosons and SUSY particles as functions of the only free parameter,
, or the gluino mass. The lightest Higgs boson mass for TeV is found to be GeV for and
GeV for .Comment: 15 pages, LateX file with 4 eps figures, corrected numbers, new
column in table, last versio
A New Model for Fermion Masses in Supersymmetric Grand Unified Theories
We present a simple model for fermion mass matrices and quark mixing in the
context of supersymmetric grand unified theories and show its agreement with
experiment. Our model realizes the GUT mass relations , , in a new way and is easily consistent with values of
suggested by MSSM fits to LEP data.Comment: Latex, 8 p., ITP-SB-93-37 (revised version contains minor changes in
some wording and citations; no changes in analytic or numerical results.
MSSM and Large from SUSY Trinification
We construct a supersymmetric model based on the semi-simple gauge group
with the relation automatically arising from its structure. The model below a scale
GeV gives naturally rise just to the minimal supersymmetric
standard model and therefore to the presently favored values for and without fields in representations higher than the
fundamental.Comment: 9 pages, LaTeX, UT-STPD-3-9
Predictions for Constrained Minimal Supersymmetry with Bottom-Tau Mass Unification
We examine the Constrained Minimal Supersymmetric Standard Model (CMSSM) with
an additional requirement of strict b - tau unification in the region of small
tan(beta). We find that the parameter space becomes completely limited below
about 1 TeV by physical constraints alone, without a fine-tuning constraint. We
study the resulting phenomenological consequences, and point out several ways
of falsifying the adopted b - tau unification assumption. We also comment on
the effect of a constraint from the non-observation of proton decay.Comment: Michigan preprint UM-TH-94-03, LaTeX, 18 pages with inline figures
(figures included in uuencoded file). Complete PS file also available by
anonymous FTP to williams.physics.lsa.umich.edu in
/pub/preprints/UM-TH-94-03.ps.Z or by e-mailing reques
Comment On ``Grand Unification and Supersymmetric Threshold"
Barbieri and Hall have argued that threshold effects at the scale of
grand-unification wipe out predictions on the SUSY scale, M_S. Using triviality
arguments we give upper bounds on ultraheavy particles, while proton stability
gives lower bounds on the mass of the higgs color-triplet. We find no useful
lower bound on the supermultiplet, but if the strong coupling constant
is as large as recent experiments suggest, unification in the minimal SUSY
SU(5) model requires that the masses be and that the
color octet and weak triplet be split in mass by a factor of 100.Comment: 6 pages (revised
Top-Down Approach to Unified Supergravity Models
We introduce a new approach for studying unified supergravity models. In this
approach all the parameters of the grand unified theory (GUT) are fixed by
imposing the corresponding number of low energy observables. This determines
the remaining particle spectrum whose dependence on the low energy observables
can now be investigated. We also include some SUSY threshold corrections that
have previously been neglected. In particular the SUSY threshold corrections to
the fermion masses can have a significant impact on the Yukawa coupling
unification.Comment: 19 pages, uuencoded compressed ps file, DESY 94-057 (paper format
corrected
A New Technique for Detecting Supersymmetric Dark Matter
We estimate the event rate for excitation of atomic transition by
photino-like dark matter. For excitations of several eV, this event rate can
exceed naive cross-section by many orders of magnitude. Although the event rate
for these atomic excitation is smaller than that of nuclear recoil off of
non-zero spin nuclei, the photons emitted by the deexcitation are easier to
detect than low-energy nuclear recoils. For many elements, there are several
low-lying states with comparable excitation rates, thus, spectral ratios could
be used to distinguish signal from background.Comment: 6 pages plain te
Third Generation Effects on Fermion Mass Predictions in Supersymmetric Grand Unified Theories
Relations among fermion masses and mixing angles at the scale of grand
unification are modified at lower energies by renormalization group running
induced by gauge and Yukawa couplings. In supersymmetric theories, the
quark and lepton Yukawa couplings, as well as the quark coupling,
may cause significant running if , the ratio of Higgs field
expectation values, is large. We present approximate analytic expressions for
the scaling factors for fermion masses and CKM matrix elements induced by all
three third generation Yukawa couplings. We then determine how running caused
by the third generation of fermions affects the predictions arising from three
possible forms for the Yukawa coupling matrices at the GUT scale: the
Georgi-Jarlskog, Giudice, and Fritzsch textures.Comment: phyzzx, 26 pp., 6 figures not included, e-mailable upon request,
JHU-TIPAC-93000
Scale dependence of the quark masses and mixings: leading order
We consider the Renormalization Group Equations (RGE) for the couplings of
the Standard Model and its extensions. Using the hierarchy of the quark masses
and of the Cabibbo-Kobayashi-Maskawa (CKM) matrix our argument is that a
consistent approximation for the RGE should be based on the parameter . We consider the RGE in the approximation where we
neglect all the relative terms of the order and higher.
Within this approximation we find the exact solution of the evolution equations
of the quark Yukawa couplings and of the vacuum expectation value of the Higgs
field. Then we derive the evolution of the observables: quark masses, CKM
matrix, Jarlskog invariant, Wolfenstein parameters of the CKM matrix and the
unitarity triangle. We show that the angles of the unitarity triangle remain
constant. This property may restrict the possibility of new symmetries or
textures at the grand unification scale.Comment: 15 pages, 4 figures, author of one reference adde
Supercollider Signatures of Supergravity Models with Yukawa Unification
We study the predictions of the simplest SU(5) grand unified model within the
framework of minimal supergravity, including constraints from the radiative
breaking of electroweak symmetry. As a consequence of the unification of the
-quark and -lepton Yukawa couplings, the top quark mass is predicted
to be close to its fixed point value. We delineate the regions of the
supergravity parameter space allowed by constraints from the non-observation of
proton decay and from the requirement that the LSP does not overclose the
universe. These constraints lead to a definite pattern of sparticle masses: the
feature unique to Yukawa unified models is that some of the third generation
squarks are much lighter than those of the first two generations. Despite the
fact that all sparticle masses and mixings are determined by just four SUSY
parameters at the GUT scale (in addition to ), we find that the signals
for sparticle production can vary substantially over the allowed parameter
space. We identify six representative scenarios and study the signals from
sparticle production at the LHC. We find that by studying the signal in various
channels, these scenarios may be distinguished from one another, and also from
usually studied ``minimal models'' where squarks and sleptons are taken to be
degenerate. In particular, our studies allow us to infer that some third
generation squarks are lighter than other squarks---a feature that could
provide the first direct evidence of supergravity grand unification.Comment: 28 pages Revtex files with 5 PS figures available from
[email protected], Preprint nos. FSU-HEP-940311, KEK-TH-392,
MAD/PH/825, UH-511-785-9
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