672 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
See-saw fermion masses in an SO(10) GUT
In this work we study an SO(10) GUT model with minimum Higgs representations
belonging only to the 210 and 16 dimensional representations of SO(10). We add
a singlet fermion S in addition to the usual 16 dimensional representation
containing quarks and leptons. There are no Higgs bi-doublets and so charged
fermion masses come from one-loop corrections. Consequently all the fermion
masses, Dirac and Majorana, are of the see-saw type. We minimize the Higgs
potential and show how the left-right symmetry is broken in our model where it
is assumed that a D-parity odd Higgs field gets a vacuum expectation value at
the grand unification scale. From the renormalization group equations we infer
that in our model unification happens at 10^{15} GeV and left-right symmetry
can be extended up to some values just above 10^{11} GeV. The Yukawa sector of
our model is completely different from most of the standard grand unified
theories and we explicitly show how the Yukawa sector will look like in the
different phases and briefly comment on the running of the top quark mass. We
end with a brief analysis of lepton number asymmetry generated from the
interactions in our model.Comment: 30 pages, 10 figure
Reconciling Supersymmetry and Left-Right Symmetry
We construct the minimal supersymmetric left-right theory and show that at
the renormalizable level it requires the existence of an intermediate
breaking scale. The subsequent symmetry breaking down to MSSM automatically
preserves R-symmetry. Furthermore, unlike in the nonsupersymmetric version of
the theory, the see-saw mechanism takes its canonical form. The theory predicts
the existence of a triplet of Higgs scalars much lighter than the
breaking scale.Comment: 4 pages, revtex, no figure
A screening mechanism for extra W and Z gauge bosons
We generalize a previous construction of a fermiophobic model to the case of
more than one extra and gauge bosons. We focus in particular on the
existence of screening configurations and their implication on the gauge boson
mass spectrum. One of these configurations allows for the existence of a set of
relatively light new gauge bosons, without violation of the quite restrictive
bounds coming from the parameter. The links with Bess and
degenerate Bess models are also discussed. Also the signal given here by this
more traditional gauge extension of the SM could help to disentangle it from
the towers of Kaluza-Klein states over and gauge bosons in extra
dimensions.Comment: 23 pages, 1 figure, extended discussion on precision tests. To appear
in International Journal of Modern Physics
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
Supersymmetry and Large Scale Left-Right Symmetry
We show that the low energy limit of the minimal supersymmetric Left-Right
models is the supersymmetric standard model with an exact R-parity. The theory
predicts a number of light Higgs scalars and fermions with masses much below
the and breaking scales. The non-renormalizable version of the
theory has a striking prediction of light doubly charged supermultiplets which
may be accessible to experiment. Whereas in the renormalizable case the scale
of parity breaking is undetermined, in the non-renormalizable one it must be
bigger than about GeV. The precise nature of the see-saw
mechanism differs in the two versions, and has important implications for
neutrino masses.Comment: LaTeX, 30 pages. Minor changes. Some references adde
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
R-parity violation in SU(5)
We show that judiciously chosen R-parity violating terms in the minimal
renormalizable supersymmetric SU(5) are able to correct all the
phenomenologically wrong mass relations between down quarks and charged
leptons. The model can accommodate neutrino masses as well. One of the most
striking consequences is a large mixing between the electron and the Higgsino.
We show that this can still be in accord with data in some regions of the
parameter space and possibly falsified in future experiments.Comment: 30 pages, 1 figure. Revised version. To appear in JHE
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
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
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