496 research outputs found
Proton Stability and Dark Matter in a Realistic String MSSM
We demonstrate the existence of an extra nonanomalous U(1) gauge symmetry in
a three-generation Pati-Salam model constructed with intersecting D6-branes in
Type IIA string theory on a T^6/(Z_2 \times Z_2) orientifold. This extra U(1)
forbids all dimension-4, 5, and 6 operators which mediate proton decay in the
MSSM. Moreover, this results in the effective promotion of baryon and lepton
number to local gauge symmetries, which can potentially result in leptophobic
and leptophilic bosons observable at the LHC. Furthermore, it is not
necessary to invoke R-parity to forbid the dimension-4 operators which allow
rapid proton decay. However, R-parity may arise naturally from a spontaneously
broken U(1)_{B-L}. Assuming the presence of R-parity, we then study the direct
detection cross-sections for neutralino dark matter, including the latest
constraints from the XENON100 experiment. We find that these limits are now
within required range necessary to begin testing the model.Comment: Expanded discussion of Z' boson phenomenology. Accepted for
publication to Physical Review D. arXiv admin note: text overlap with
arXiv:1103.603
Nonlinear Realizations of Supersymmetry and Other Symmetries
Simultaneous nonlinear realizations of spontaneously broken supersymmetry in
conjunction with other spontaneous and/or explicitly broken symmetries
including R symmetry, global chiral symmetry, dilatations and the
superconformal symmetries is reviewed.Comment: 15 pages, invited brief review for Mod. Phys. Lett.
Constraints for the existence of flat and stable non-supersymmetric vacua in supergravity
We further develop on the study of the conditions for the existence of
locally stable non-supersymmetric vacua with vanishing cosmological constant in
supergravity models involving only chiral superfields. Starting from the two
necessary conditions for flatness and stability derived in a previous paper
(which involve the Kahler metric and its Riemann tensor contracted with the
supersymmetry breaking auxiliary fields) we show that the implications of these
constraints can be worked out exactly not only for factorizable scalar
manifolds, but also for symmetric coset manifolds. In both cases, the
conditions imply a strong restriction on the Kahler geometry and constrain the
vector of auxiliary fields defining the Goldstino direction to lie in a certain
cone. We then apply these results to the various homogeneous coset manifolds
spanned by the moduli and untwisted matter fields arising in string
compactifications, and discuss their implications. Finally, we also discuss
what can be said for completely arbitrary scalar manifolds, and derive in this
more general case some explicit but weaker restrictions on the Kahler geometry.Comment: 22 pages, Latex, no figure
On non-universal Goldstino couplings to matter
Using the constrained superfields formalism to describe the interactions of a
light goldstino to matter fields in supersymmetric models, we identify
generalised, higher-order holomorphic superfield constraints that project out
the superpartners and capture the non-universal couplings of the goldstino to
matter fields. These arise from microscopic theories in which heavy
superpartners masses are of the order of the supersymmetry breaking scale
(\sqrt f). In the decoupling limit of infinite superpartners masses, these
constraints reduce to the familiar, lower-order universal constraints discussed
recently, that describe the universal goldstino-matter fields couplings,
suppressed by inverse powers of \sqrt f. We initiate the study of the couplings
of the Standard Model (SM) fields to goldstino in the constrained superfields
formalism.Comment: 28 pages; one comment adde
Densities and phase equilibria of hydrogen, propane and vegetable oil mixtures. Experimental data and thermodynamic modeling
Heterogeneous catalytic gas-liquid reactions are intensified when carried out in the homogenous fluid phase by means of a supercritical co-solvent. For instance, supercritical propane is used to enhance yield in the hydrogenation of vegetable oils. Besides phase equilibrium knowledge, volumetric information is also needed to elucidate kinetic mechanisms and design continuous supercritical reactors. In this work, we report new experimental PvT data of the reactive mixture H2+sunflower oil+propane using the isochoric method. In addition, the phase equilibria and PvT data are modeled with the GCA and RK-PR equations of state, respectively. The isochoric method not only provides PvT information under the reaction conditions, but also the reactive system compressibility, key variable to attain enhanced transport properties in the supercritical reactors.Fil: Hegel, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Cotabarren, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brignole, Esteban Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Pereda, Selva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. University of KwaZulu-Natal; Sudáfric
Higgs funnel region of SUSY dark matter for small and renormalization group effects on pseudoscalar Higgs boson with scalar mass non-universality
A non-universal scalar mass supergravity type of model is explored where the
first two generation of scalars and the third generation of sleptons may be
very massive. Lighter or vanishing third generation of squarks as well as Higgs
scalars at the unification scale cause the radiative electroweak symmetry
breaking constraint to be less prohibitive. Thus, both FCNC/CP-violation
problems as well as the naturalness problem are within control. We identify a
large slepton mass effect in the RGE of (for the down type of
Higgs) that may turn the later negative at the electroweak scale even for a
small . A hyperbolic branch/focus point like effect is found for
that may result in very light Higgs spectra. The lightest stable
particle is dominantly a bino that pair annihilates via Higgs exchange, giving
rise to a WMAP satisfied relic density region for all . Detection
prospects of such LSPs in the upcoming dark matter experiments both of direct
and indirect types (photon flux) are interesting. The Higgs bosons and the
third generation of squarks are light in this scenario and these may be easily
probed besides charginos and neutralinos in the early runs of LHC.Comment: 36 pages and 7 Postscript files. Minor changes in the text. Version
accepted for publication in Phys. Rev.
Supergravity Radiative Effects on Soft Terms and the Term
We compute quadratically divergent supergravity one-loop effects on soft
supersymmetry-breaking parameters and the term in generic hidden sector
supergravity models. These effects can significantly modify the matching
condition for soft parameters at the Planck scale and also provide several new
sources of the term which are naturally of order the weak scale. We also
discuss some phenomenological implications of these effects, particularly the
violation of the scalar mass universality which may lead to dangerous FCNC
phenomena, and apply the results to superstring effective supergravity models.Comment: 12 pages, REVTEX. One reference is adde
On non-perturbative corrections to the Kahler potential
We present the results of a detailed investigation into the consequences of
adding specific string motivated non-perturbative corrections to the usual tree
level Kahler potential in dilaton dominated scenarios. The success of the model
is judged through our ability to obtain a realistic VEV for the dilaton < Re S
> ~ 2, corresponding to the true minima of the scalar potential and being
associated with a reasonable value for the SUSY breaking scale via the
gravitino mass. The status of the so-called moduli problem is also reviewed in
each of the ansatze studied. Those include previous proposals made in the
context of both the chiral and the linear multiplet formalisms to describe
gaugino condensation, and a new ansatz which shows explicitly the equivalence
between the two.Comment: 11 pages, LaTex, uses psfig.sty with 4 figure
A Resolution to the Supersymmetric CP Problem with Large Soft Phases via D-branes
We examine the soft supersymmetry breaking parameters that result from
various ways of embedding the Standard Model (SM) on D-branes within the Type I
string picture, allowing the gaugino masses and to have large CP-
violating phases. One embedding naturally provides the relations among soft
parameters to satisfy the electron and neutron electric dipole moment
constraints even with large phases, while with other embeddings large phases
are not allowed. The string models provide some motivation for large phases in
the soft breaking parameters. The results generally suggest how low energy data
might teach us about Planck scale physics.Comment: 11 pages, 2 eps figures; revised references and updated tex
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