76 research outputs found
Higgs boson bounds in non-minimal supersymmetric standard models
In the minimal supersymmetric standard model (MSSM), when radiative
corrections are included, the mass of the lightest Higgs boson is
bounded by for and a scale of supersymmetry
breaking . In non-minimal supersymmetric standard models (NMSSM)
upper bounds on the mass of the corresponding scalar Higgs boson arise if the
theory is required to remain perturbative up to scales . We
have computed those bounds for two illustrative NMSSM: i) A model with an
arbitrary number of gauge singlets; ii) A model with three triplets
with . We have integrated numerically the corresponding
renormalization group equations (RGE), including the top and bottom quark
Yukawa couplings, and added one-loop radiative corrections. For
the absolute bounds are for both models.Comment: 8 pages, (Talk presented at the XXVI INTERNATIONAL CONFERENCE ON HIGH
ENERGY PHYSICS, August 6-12, 1992, Dallas), latex, IEM-FT-60/92, 3 figures
(available by Fax upon request
On the Spontaneous CP Breaking in the Higgs Sector of the Minimal Supersymmetric Standard Model
We revise a recently proposed mechanism for spontaneous CP breaking at finite
temperature in the Higgs sector of the Minimal Supersymmetric Standard Model,
based on the contribution of squarks, charginos and neutralinos to the one-loop
effective potential. We have included plasma effects for all bosons and added
the contribution of neutral scalar and charged Higgses. While the former have
little effect, the latter provides very strong extra constraints on the
parameter space and change drastically the previous results. We find that CP
can be spontaneously broken at the critical temperature of the electroweak
phase transition without any fine-tuning in the parameter space.Comment: 9 pages, LATEX, 3 appended postscript figures, IEM-FT-76/9
The Inverse Amplitude Method and Heavy Baryon Chiral Perturbation Theory applied to pion-nucleon scattering
We report on our present work, where by means of the Inverse Amplitude Method
we unitarize the elastic pion nucleon scattering amplitudes of Heavy Barion
Chiral Perturbation Theory at O(q^3). We reproduce the scattering up to the
inelastic thresholds including the Delta(1232) resonance. The fitted chiral
constants are rather different from those obtained by fitting the extrapolated
threshold parameters for the non-unitarized theory.Comment: Talk given at the 8th International Conference on Hadron
Spectroscopy, HADRON99, August 24-28, 1999, Beijing, China. 4 pages LaTex,
uses espcrc1.sty (included
Background Dependent Lorentz Violation: Natural Solutions to the Theoretical Challenges of the OPERA Experiment
To explain both the OPERA experiment and all the known phenomenological
constraints/observations on Lorentz violation, the Background Dependent Lorentz
Violation (BDLV) has been proposed. We study the BDLV in a model independent
way, and conjecture that there may exist a "Dream Special Relativity Theory",
where all the Standard Model (SM) particles can be subluminal due to the
background effects. Assuming that the Lorentz violation on the Earth is much
larger than those on the interstellar scale, we automatically escape all the
astrophysical constraints on Lorentz violation. For the BDLV from the effective
field theory, we present a simple model and discuss the possible solutions to
the theoretical challenges of the OPERA experiment such as the Bremsstrahlung
effects for muon neutrinos and the pion decays. Also, we address the Lorentz
violation constraints from the LEP and KamLAMD experiments. For the BDLV from
the Type IIB string theory with D3-branes and D7-branes, we point out that the
D3-branes are flavour blind, and all the SM particles are the conventional
particles as in the traditional SM when they do not interact with the
D3-branes. Thus, we not only can naturally avoid all the known phenomenological
constraints on Lorentz violation, but also can naturally explain all the
theoretical challenges. Interestingly, the energy dependent photon velocities
may be tested at the experiments.Comment: RevTex4, 14 pages, minor corrections, references adde
Bound States and Power Counting in Effective Field Theories
The problem of bound states in effective field theories is studied. A
rescaled version of nonrelativistic effective field theory is formulated which
makes the velocity power counting of operators manifest. Results obtained using
the rescaled theory are compared with known results from NRQCD. The same ideas
are then applied to study Yukawa bound states in 1+1 and 3+1 dimensions, and to
analyze when the Yukawa potential can be replaced by a delta-function
potential. The implications of these results for the study of nucleon-nucleon
scattering in chiral perturbation theory is discussed.Comment: 23 pages, eps figures, uses revte
Hypercharge and baryon minus lepton number in E6
We study assignments of the hypercharge and baryon minus lepton number for
particles in the grand unification model. It is shown that there are
three assignments of hypercharge and three assignments of baryon minus lepton
number which are consistent with the Standard Model. Their explicit expressions
and detailed properties are given. In particular, we show that the
symmetry in cannot be orthogonal to the symmetry. Based on
these investigations, we propose an alternative SU(5) grand unification model.Comment: 16 pages, JHEP3.cls, To appear in JHE
Upper Bounds on the Lightest Higgs Boson Mass in General Supersymmetric Standard Models
In a general supersymmetric standard model there is an upper bound on
the tree level mass of the lightest Higgs boson which depends on the
electroweak scale, and the gauge and Yukawa couplings of the
theory. When radiative corrections are included, the allowed region in the
plane depends on the scale , below which the theory
remains perturbative, and the supersymmetry breaking scale , that we
fix to . In the minimal model with : $m_h<130\
GeVm_t<185\ GeV\Lambda=10^{16}\ GeVm_h<145\ GeVm_t<185\ GeV\Lambda=10^{16}\ GeVm_h<155\ GeVm_t<190\ GeV\Lambda\Lambda_sm_hm_t\Lambda=10\ TeVm_hm_t415\
GeV385\ GeV$, respectively.Comment: 13 pages, latex, IEM-FT-64/92 (5 postscript figures availables upon
request
The Minimal Supersymmetric Fat Higgs Model
We present a calculable supersymmetric theory of a composite ``fat'' Higgs
boson. Electroweak symmetry is broken dynamically through a new gauge
interaction that becomes strong at an intermediate scale. The Higgs mass can
easily be 200-450 GeV along with the superpartner masses, solving the
supersymmetric little hierarchy problem. We explicitly verify that the model is
consistent with precision electroweak data without fine-tuning. Gauge coupling
unification can be maintained despite the inherently strong dynamics involved
in electroweak symmetry breaking. Supersymmetrizing the Standard Model
therefore does not imply a light Higgs mass, contrary to the lore in the
literature. The Higgs sector of the minimal Fat Higgs model has a mass spectrum
that is distinctly different from the Minimal Supersymmetric Standard Model.Comment: 13 pages, 5 figures, REVTe
Spontaneous CP Violation in Non-Minimal Supersymmetric Models
We study the possibilities of spontaneous CP violation in the Next-to-Minimal
Supersymmetric Standard Model with an extra singlet tadpole term in the scalar
potential. We calculate the Higgs boson masses and couplings with radiative
corrections including dominant two loop terms. We show that it is possible to
satisfy the LEP constraints on the Higgs boson spectrum with non-trivial
spontaneous CP violating phases. We also show that these phases could account
for the observed value of epsilonK.Comment: 21 pages, 7 Figures in Encapsulated Postscrip
Bottom-Tau Unification in SUSY SU(5) GUT and Constraints from b to s gamma and Muon g-2
An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY)
SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in
which the parameter space is restricted by some experimental constraints
including Br(b to s gamma) and muon g-2. The bottom-tau unification can be
accommodated to the measured branching ratio Br(b to s gamma) if superparticle
masses are relatively heavy and higgsino mass parameter \mu is negative. On the
other hand, if we take the latest muon g-2 data to require positive SUSY
contributions, then wrong-sign threshold corrections at SUSY scale upset the
Yukawa unification with more than 20 percent discrepancy. It has to be
compensated by superheavy threshold corrections around the GUT scale, which
constrains models of flavor in SUSY GUT. A pattern of the superparticle masses
preferred by the three requirements is also commented.Comment: 21pages, 6figure
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