14 research outputs found
Lepton Flavour Violation in Unified Models with U(1)-Family Symmetries
Lepton flavour non-conserving processes are examined in the context of
unified models with U(1)-family symmetries which reproduce successfully the
low-energy hierarchy of the fermion mass spectrum and the Kobayashi - Maskawa
mixing. These models usually imply mixing effects in the supersymmetric scalar
sector. We construct the fermion and scalar mass matrices in two viable models,
and calculate the mixing effects on the , and
rare decays. The relevant constraints on the sparticle
mass spectrum as well as the role of various MSSM parameters are discussed.Comment: 14 pages, 1 figure included in the ps file, uses epsfig.st
Predictive Ansatz for Fermion Masses in SUSY GUTS
We reexamine a succesful fermion mass Ansatz proposed by Giudice for a wide
range of the ratio (where are
the two standard higgs fields), in the context of supersymmetric grand unified
theories. We find that the 7 predictions of the ansatz, and are in good agreement with the experiment when
either {\it i) } or {\it ii)} . A correct
prediction for the bottom mass gives a lower limit on for case
{\it (i)}, in agreement with the previous analysis, while in case {\it (ii)}
.Comment: 8 pages, 3 figures NOT included, available on request, LaTex, IOA
281/92, NTUA 37/92 preprint
Coupling Reduction and the Higgs Mass
Assuming the existence of a functional relation among the Standard Model (SM)
couplings gauge and quartic , we determine the mass of the
Higgs particle. Similar considerations for the top and bottom Yukawa couplings
in the minimal supersymmetric SM lead to the prediction of a narrow window for
, one of the main parameters that determine the light Higgs mass.Comment: 17 pages, 16 figure
Implications of a Heavy Top in Supersymmetric Theories
In the context of the radiative electroweak symmetry breaking scenario, we
investigate the implications of a heavy top quark mass, close to its infrared
fixed point, on the low energy parameters of the minimal supersymmetric
standard model. We use analytic expressions to calculate the Higgs masses as
well as the supersymmetric masses of the third generation. We further assume
bottom-tau unification at the GUT scale and examine the constraints put by this
condition on the parameter space (,), using the
renormalization group procedure at the two-loop level. We find only a small
fraction of the parameter space where the above conditions can be satisfied,
namely , while . We
further analyse the case where all three Yukawa couplings reach the
perturbative limit just after the unification scale. In this latter case, the
situation turns out to be very strict demanding .Comment: 13 pages plus 3 Figures (hard copy) on request, IOA.303/94 and NTUA
44/9
Gauge Coupling Unification and the Top Mass in String Models with Symmetry
We discuss the low energy implications of gauge coupling unification at the
string scale, taking into account string threshold corrections in the model. We express and as functions of the
calculable string threshold differences and discuss simple examples of spectra
which retain the successful predictions of the supersymmetric unification.
Using further the low energy data and reasonable values of the common gauge
coupling at the string scale, we obtain the range of the threshold corrections.
Finally, we study the top Yukawa coupling () evolution whose initial value
is determined in terms of the common gauge coupling at the string scale. We
find that reaches its (quasi) infra-red fixed point at the weak scale and
discuss the implications on the top mass.Comment: 12 pages, Plain Latex file, macros included in the beginning of the
file, 3 figs on request from the authors. some minor typos are corrected,
uu-encoded figures are included in a separate fil
Low Energy Thresholds and the Scalar Mass Spectrum in Minimal Supersymmetry
We discuss low energy threshold effects and calculate the sparticle masses in
the context of the Minimal Supersymmetric Standard Model. We pay particular
attention to the top squark and the Higgs mass parameters, and calculate the
top Yukawa corrections, taking into account the successive decoupling of each
particle at its threshold. We discuss the phenomenological implications in the
context of the radiative symmetry breaking scenario.Comment: (CERN-TH.7411, Latex file, 12p, 1fig. not included
Supersymmetry Breaking Threshold Corrections in the Model
We evaluate the SUSY and top threshold effects in the context of the MSSM and
the string derived model based on SU(4)SU(2)SU(2). In
both cases we run the two loop RGEs and determine the lower bounds of the
supersymmetric particle masses, dictated by the experimentally accepted regions
of the values of the low energy parameters.Comment: 10 pages, 5 Figs not included (can be sent by mail or fax upon
request), NTUA 41/9