19,672 research outputs found
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
Top Quark and Higgs Boson Masses in Supersymmetric Models
We study the implications for bounds on the top quark pole mass m_t in models
with low scale supersymmetry following the discovery of the Standard Model-like
Higgs boson. In the minimal supersymmetric standard model, we find that m_t >=
164 GeV, if the light CP even Higgs boson mass m_h = 125 +-2 GeV. We also
explore the top quark and Higgs boson masses in two classes of supersymmetric
SO(10) models with t-b-tau Yukawa coupling unification at M_GUT. In particular,
assuming SO(10) compatible non-universal gaugino masses, setting m_h = 125 GeV
and requiring 5% or better Yukawa unification, we obtain the result 172 GeV <=
m_t <= 175 GeV. Conversely, demanding 5% or better t-b-tau Yukawa unification
and setting m_t=173.2 GeV, the Higgs boson mass is predicted to lie in the
range 122 GeV <= m_h <= 126 GeV.Comment: 16 pages, 7 figure
Infrared Fixed Point Solution for the Top Quark Mass and Unification of Couplings in the MSSM
We analyze the implications of the infrared quasi fixed point solution for
the top quark mass in the Minimal Supersymmetric Standard Model. This solution
could explain in a natural way the relatively large value of the top quark mass
and, if confirmed experimentally, may be suggestive of the onset of
nonperturbative physics at very high energy scales. In the framework of grand
unification, the expected bottom quark - tau lepton Yukawa coupling unification
is very sensitive to the fixed point structure of the top quark mass. For the
presently allowed values of the electroweak parameters and the bottom quark
mass, the Yukawa coupling unification implies that the top quark mass must be
within ten percent of its fixed point values.Comment: 11 pages, 3 figures (not included), MPI-Ph/93-5
Yukawa Coupling Unification in Supersymmetric Models
We present an updated assessment of the viability of t-b-tau Yukawa coupling
unification in supersymmetric models. For the superpotential Higgs mass
parameter mu>0, we find unification to less than 1% is possible, but only for
GUT scale scalar mass parameter m_{16}~8-20 TeV, and small values of gaugino
mass m_{1/2}<400 GeV. Such models require that a GUT scale mass splitting
exists amongst Higgs scalars with m_{H_u}^2<m_{H_d}^2. Viable solutions lead to
a radiatively generated inverted scalar mass hierarchy, with third generation
and Higgs scalars being lighter than other sfermions. These models have very
heavy sfermions, so that unwanted flavor changing and CP violating SUSY
processes are suppressed, but may suffer from some fine-tuning requirements.
While the generated spectra satisfy b->s gamma and (g-2)_mu constraints, there
exists tension with the dark matter relic density unless m_{16}<3 TeV. These
models offer prospects for a SUSY discovery at the Fermilab Tevatron collider
via the search for chargino_1 neutralino_2 -> 3 leptons events, or via gluino
pair production. If mu<0, Yukawa coupling unification to less than 5% can occur
for m_{16} and m_{1/2}>1-2 TeV. Consistency of negative mu Yukawa unified
models with b->s gamma, (g-2)_mu, and relic density all imply very large values
of m_{1/2} typically greater than about 2.5 TeV, in which case direct detection
of sparticles may be a challenge even at the LHC.Comment: 38 pages, 15 figures. Fig.15 changed, some references were added. A
copy of the paper with better resolution figures can be found at
http://www.hep.fsu.edu/~balazs/Physics/Papers/2003
Yukawa Unification and the Superpartner Mass Scale
Naturalness in supersymmetry (SUSY) is under siege by increasingly stringent
LHC constraints, but natural electroweak symmetry breaking still remains the
most powerful motivation for superpartner masses within experimental reach. If
naturalness is the wrong criterion then what determines the mass scale of the
superpartners? We motivate supersymmetry by (1) gauge coupling unification, (2)
dark matter, and (3) precision b-tau Yukawa unification. We show that for an
LSP that is a bino-Higgsino admixture, these three requirements lead to an
upper-bound on the stop and sbottom masses in the several TeV regime because
the threshold correction to the bottom mass at the superpartner scale is
required to have a particular size. For tan beta about 50, which is needed for
t-b-tau unification, the stops must be lighter than 2.8 TeV when A_t has the
opposite sign of the gluino mass, as is favored by renormalization group
scaling. For lower values of tan beta, the top and bottom squarks must be even
lighter. Yukawa unification plus dark matter implies that superpartners are
likely in reach of the LHC, after the upgrade to 14 (or 13) TeV, independent of
any considerations of naturalness. We present a model-independent, bottom-up
analysis of the SUSY parameter space that is simultaneously consistent with
Yukawa unification and the hint for m_h = 125 GeV. We study the flavor and dark
matter phenomenology that accompanies this Yukawa unification. A large portion
of the parameter space predicts that the branching fraction for B_s to mu^+
mu^- will be observed to be significantly lower than the SM value.Comment: 34 pages plus appendices, 20 figure
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