10,649 research outputs found
Supersymmetry Breaking by Type II Seesaw Assisted Anomaly Mediation
Anomaly mediated supersymmetry breaking (AMSB), when implemented in MSSM is
known to suffer from the problem of negative slepton mass squared leading to
breakdown of electric charge conservation. We show however that when MSSM is
extended to explain small neutrino masses by including a pair of superheavy
Higgs triplet superfields (the type II seesaw mechanism), the slepton masses
can be deflected from the pure AMSB trajectory and become positive. In a simple
model we present in this paper, the seesaw scale is about . Gauge coupling unification can be maintained by embedding the triplet to
SU(5) {\bf 15}-multiplet. In this scenario, bino is the LSP and its mass is
nearly degenerate with NLSP slepton when the triplet mass is right around the
seesaw scale.Comment: 18 pages, 4 figures, added references, added footnote
Grand Unification, Axion, and Inflation in Intermediate Scale Supersymmetry
A class of supersymmetric grand unified theories is introduced that has a
single scale below the cutoff, that of the supersymmetry breaking masses
. For a wide range of the dimensionless parameters, agreement with
the observed mass of the Higgs boson determines , yielding Intermediate Scale Supersymmetry. We show that within this
framework it is possible for seesaw neutrino masses, axions, and inflation to
be described by the scale , offering the possibility of a unified
origin of disparate phenomena. Neutrino masses allowing for thermal
leptogenesis can be obtained, and the axion decay constant lies naturally in
the range , consistent with a recent
observational suggestion of high scale inflation. A minimal model is
presented that illustrates these features. In this model, the only states at
the grand unified scale are those of the heavy gauge supermultiplet. The grand
unified partners of the Higgs doublets have a mass of order ,
leading to the dominant proton decay mode , which
may be probed in upcoming experiments. Dark matter may be winos, with mass
environmentally selected to the TeV scale, and/or axions. Gauge coupling
unification is found to be successful, especially if the wino is at the TeV
scale.Comment: 27 pages, 7 figures; minor corrections, references and discussion
adde
New Paradigm for Baryon and Lepton Number Violation
The possible discovery of proton decay, neutron-antineutron oscillation,
neutrinoless beta decay in low energy experiments, and exotic signals related
to the violation of the baryon and lepton numbers at collider experiments will
change our understanding of the conservation of fundamental symmetries in
nature. In this review we discuss the rare processes due to the existence of
baryon and lepton number violating interactions. The simplest grand unified
theories and the neutrino mass generation mechanisms are discussed. The
theories where the baryon and lepton numbers are defined as local gauge
symmetries spontaneously broken at the low scale are discussed in detail. The
simplest supersymmetric gauge theory which predicts the existence of lepton
number violating processes at the low scale is investigated. The main goal of
this review is to discuss the main implications of baryon and lepton number
violation in physics beyond the Standard Model.Comment: 60 pages, to appear in Physics Report
Radiative seesaw: a case for split supersymmetry
We revive Witten's mechanism for the radiative seesaw induced neutrino masses
in SO(10) grand unified theory. We propose its extension to charged fermion
masses as a possible cure for wrong tree level mass relations. We offer two
simple realizations that can produce a realistic fermionic spectrum. The first
one requires two 10 dimensional Higgses in the Yukawa sector and utilizes
radiative effects for charged fermion masses. The second one trades one 10 for
a 120 dimensional Higgs and leads to the SO(10) theory with less parameters in
the Yukawa sector. The mechanism works only if supersymmetry is broken at the
GUT scale while gauginos and higgsinos remain at TeV. This provides a strong
rationale for the so called split supersymmetry.Comment: 12 pages, 2 figures, a few references and short comment on gluinos
adde
Variations on Supersymmetry Breaking and Neutrino Spectra
The problem of generating light neutrinos within supersymmetric models is
discussed. It is shown that the hierarchy of scales induced by supersymmetry
breaking can give rise to suppression factors of the correct order of magnitude
to produce experimentally allowed neutrino spectra.Comment: 18 pages, LaTeX, Contribution to "Neutrino Workshop", Fuji-Yoshida,
Japan, August 200
Models of Dynamical R-Parity Violation
The presence of R-parity violating interactions may relieve the tension
between existing LHC constraints and natural supersymmetry. In this paper we
lay down the theoretical framework and explore models of dynamical R-parity
violation in which the breaking of R-parity is communicated to the visible
sector by heavy messenger fields. We find that R-parity violation is often
dominated by non-holomorphic operators that have so far been largely ignored,
and might require a modification of the existing searches at the LHC. The
dynamical origin implies that the effects of such operators are suppressed by
the ratio of either the light fermion masses or the supersymmetry breaking
scale to the mediation scale, thereby providing a natural explanation for the
smallness of R-parity violation. We consider various scenarios, classified by
whether R-parity violation, flavor breaking and/or supersymmetry breaking are
mediated by the same messenger fields. The most compact case, corresponding to
a deformation of the so called flavor mediation scenario, allows for the
mediation of supersymmetry breaking, R-parity breaking, and flavor symmetry
breaking in a unified manner.Comment: v2: references adde
Supersymmetry
I review phenomenologically interesting aspects of supersymmetry. First I
point out that the discovery of the positron can be regarded as a historic
analogue to the would-be discovery of supersymmetry. Second I review the recent
topics on the unification of the gauge coupling constants, --
relation, proton decay, and baryogenesis. I also briefly discuss the recent
proposals to solve the problem of flavor changing neutral currents. Finally I
argue that the measurements of supersymmetry parameters may probe the physics
at the Planck scale.Comment: LBL-36175, LaTeX, 27 pages. Psfig1.9 required. Invited talk presented
at the 22nd INS International Symposium on Physics with High Energy
Colliders, Tokyo, Japan, March 8--10, 1994, to appear in Proceedings of INS
Symposium. The original version submitted in June, only references and
spellings corrected. Five EPS figures appended in uuencoded forma
Viable Ultraviolet-Insensitive Supersymmetry Breaking
It is known that one can add D-term contributions for U(1)_Y and U(1)_{B-L}
to the anomaly-mediated supersymmetry breaking to make the superparticle
spectrum phenomenologically viable. We point out that this can be done without
spoiling its important virtue, namely the ultraviolet insensitivity. This
framework can be derived from supersymmetry breaking and U(1)_{B-L} breaking on
hidden brane(s).Comment: 19 pages, Latex, small clarifications adde
An Instanton Toolbox for F-Theory Model Building
Several dimensionful parameters needed for model building can be engineered
in a certain class of SU(5) F-theory GUTs by adding extra singlet fields which
are localized along pairwise intersections of D7-branes. The values of these
parameters, however, depend on dynamics external to the GUT which causes the
singlets to acquire suitable masses or expectation values. In this note, we
demonstrate that D3-instantons which wrap the same 4-cycle as one of the
intersecting D7's can provide precisely the needed dynamics to generate several
important scales, including the supersymmetry-breaking scale and the
right-handed neutrino mass. Furthermore, these instantons seem unable to
directly generate the \mu term suggesting that, at least in this class of
models, it should perhaps be tied to one of the other scales in the problem.
More specifically, we study the simple system consisting of a pair of D7-branes
wrapping del Pezzo surfaces which intersect along a curve of genus 0
or 1 and classify all instanton configurations which can potentially contribute
to the superpotential. This allows one to formulate topological conditions
which must be imposed on \Sigma for various model-building applications. Along
the way, we also observe that the construction of arXiv:0808.1286 which
engineers a linear superpotential in fact realizes an O'Raifeartaigh model at
the KK scale whose 1-loop Coleman-Weinberg potential generically leads to a
metastable, long-lived SUSY-breaking vacuum.Comment: 18 pages, 2 figures; v2: updated to reflect corrections in v2 of
0808.128
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