552 research outputs found
Supersymmetric Unification at the Millenium
We argue that the discovery of neutrino mass effects at Super-Kamiokande
implies a clear logical chain leading from the Standard Model, through the MSSM
and the recently developed Minimal Left Right Supersymmetric models with a
renormalizable see-saw mechanism for neutrino mass, to Left Right symmetric
SUSY GUTS : in particular, SO(10) and .
The progress in constructing such GUTS explicitly is reviewed and their
testability/falsifiability by lepton flavour violation and proton decay
measurements emphasized. Susy violations of the survival principle and the
interplay between third generation Yukawa coupling unification and the
structurally stable IR attractive features of the RG flow in SUSY GUTS are also
discussed .Comment: Plenary Talk at WHEPP-6, Chennai, India, Jan. 3-15, 2000. ReVTeX. 9
pages. Two pairs of figures as separate postscript fil
On the vacuum of the minimal nonsupersymmetric SO(10) unification
We study a class of nonsupersymmetric SO(10) grand unified scenarios where
the first stage of the symmetry breaking is driven by the vacuum expectation
values of the 45-dimensional adjoint representation. Three decade old results
claim that such a Higgs setting may lead exclusively to the flipped SU(5) x
U(1) intermediate stage. We show that this conclusion is actually an artifact
of the tree level potential. The study of the accidental global symmetries
emerging in various limits of the scalar potential offers a simple
understanding of the tree level result and a rationale for the drastic impact
of quantum corrections. We scrutinize in detail the simplest and paradigmatic
case of the 45_{H} + 16_{H} Higgs sector triggering the breaking of SO(10) to
the standard electroweak model. We show that the minimization of the one-loop
effective potential allows for intermediate SU(4)_C x SU(2)_L x U(1)_R and
SU(3)_c x SU(2)_L x SU(2)_R x U(1)_{B-L} symmetric stages as well. These are
the options favoured by gauge unification. Our results, that apply whenever the
SO(10) breaking is triggered by , open the path for hunting the simplest
realistic scenario of nonsupersymmetric SO(10) grand unification.Comment: 22 pages, 1 figure. Refs added. To appear in Phys. Rev.
Yukawa sector in non-supersymmetric renormalizable SO(10)
We discuss the ordinary, non-supersymmetric SO(10) as a theory of fermion
masses and mixings. We construct two minimal versions of the Yukawa sector
based on and either or . The latter case is of
particular interest since it connects the absolute neutrino mass scale with the
size of the atmospheric mixing angle . It also relates the smallness
of with the largeness of . These results are based on the
analytic study of the second and third generations. Furthermore, we discuss the
structure of the light Higgs and the role of the Peccei-Quinn symmetry for dark
matter and the predictivity of the theory.Comment: 8 pages. Reference added, one formula correcte
Supersymmetric Unification in the Light of Neutrino Mass
We argue that with the discovery of neutrino mass effects at Super-Kamiokande
there is a clear logical chain leading from the Standard Model through the MSSM
and the recently developed Minimal Left Right Supersymmetric models with a
renormalizable see-saw mechanism for neutrino mass to Left Right symmetric SUSY
GUTS : in particular, SO(10) and . The
progress in constructing such GUTS explicitly is reviewed and their
testability/falsifiability by proton decay measurements emphasized.Comment: 16 pages, REVTEX. Invited talk presented at XIII DAE Symposium on
High Energy Physics, Chandigarh, December 199
A renormalizable SO(10) GUT scenario with spontaneous CP violation
We consider fermion masses and mixings in a renormalizable SUSY SO(10) GUT
with Yukawa couplings of scalar fields in the representation 10 + 120 + 126
bar. We investigate a scenario defined by the following assumptions: i) A
single large scale in the theory, the GUT scale. ii) Small neutrino masses
generated by the type I seesaw mechanism with negligible type II contributions.
iii) A suitable form of spontaneous CP breaking which induces hermitian mass
matrices for all fermion mass terms of the Dirac type. Our assumptions define
an 18-parameter scenario for the fermion mass matrices for 18 experimentally
known observables. Performing a numerical analysis, we find excellent fits to
all observables in the case of both the normal and inverted neutrino mass
spectrum.Comment: 16 pages, two eps figure
Like Sign Dilepton Signature for R-Parity Violating SUSY Search at the Tevatron Collider
The like sign dileptons provide the most promising signature for
superparticle search in a large category of -parity violating SUSY models.
We estimate the like sign dilepton signals at the Tevatron collider, predicted
by these models, over a wide region of the MSSM parameter space. One expects an
unambiguous signal upto a gluino mass of GeV ( GeV) with
the present (proposed) accumulated luminosity of .Comment: 12 page LaTeX file; 5 figures available upon request from the autho
Minimal SUSY SO(10) model and predictions for neutrino mixings and leptonic CP violation
We discuss a minimal Supersymmetric SO(10) model where B-L symmetry is broken
by a {\bf 126} dimensional Higgs multiplet which also contributes to fermion
masses in conjunction with a {\bf 10} dimensional superfield. This minimal
Higgs choice provides a partial unification of neutrino flavor structure with
that of quarks and has been shown to predict all three neutrino mixing angles
and the solar mass splitting in agreement with observations, provided one uses
the type II seesaw formula for neutrino masses. In this paper we generalize
this analysis to include arbitrary CP phases in couplings and vevs. We find
that (i) the predictions for neutrino mixings are similar with as before and other parameters in a somewhat bigger range and (ii) that
to first order in the quark mixing parameter (the Cabibbo angle), the
leptonic mixing matrix is CP conserving. We also find that in the absence of
any higher dimensional contributions to fermion masses, the CKM phase is
different from that of the standard model implying that there must be new
contributions to quark CP violation from the supersymmetry breaking sector.
Inclusion of higher dimensional terms however allows the standard model CKM
phase to be maintained.Comment: 22 pages, 6 figure
Lepton Number Violating Radiative Decay in Models with R-parity Violation
Models with explicit R-parity violation can induce new rare radiative decay
modes of the boson into single supersymmetric particles which also violate
lepton number. We examine the rate and signature for one such decay,
, and find that such a mode will be very difficult
to observe, due its small branching fraction, even if the lepton number
violating coupling in the superpotential is comparable in strength to
electromagnetism. This parallels a similar result obtained earlier by Hewett in
the case of radiative decays.Comment: 10 pages, 2 figures(available on request), LaTex, ANL-HEP-PR-92-8
Baryogenesis with Scalar Bilinears
We show that if a baryon asymmetry of the universe is generated through the
out-of-equilibrium decays of heavy scalar bilinears coupling to two fermions of
the minimal standard model, it is necessarily an asymmetry conserving
which cannot survive past the electroweak phase transition because of
sphalerons. We then show that a surviving asymmetry may be generated if
the heavy scalars decay into two fermions, \underline {and into two light
scalars} (which may be detectable at hadron colliders). We list all possible
such trilinear scalar interactions, and discuss how our new baryogenesis
scenario may occur naturally in supersymmetric grand unified theories.Comment: LATEX, 14 pages, one figure include
Impact of R-Parity Violation on Supersymmetry Searches at the Tevatron
We evaluate cross sections for \eslt, 1 and various dilepton and
multilepton event topologies that result from the simultaneous production of
all sparticles at the Tevatron collider, both within the minimal model
framework as well as in two different -parity violating scenarios. Our
analysis assumes that these -violating couplings are small, and that their
sole effect is to cause the lightest supersymmetric particle to decay inside
the detector. We reassess future strategies for sparticle searches at the
Tevatron, and quantify by how much the various signals for supersymmetry could
differ from their minimal model expectations, if -parity is not conserved
due to either baryon number or lepton number violating operators. We also
evaluate the Tevatron reach in for the various models, and find that
rate-limited multilepton signals ultimately provide the largest reach for both
-parity conserving and -parity violating cases.Comment: preprint nos. FSU-HEP-941001, UR-1387, ER-40685-836 and
UH-511-807-94, 13 pages (REVTEX) plus 3 uuencoded figures attache
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