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 $Z'$ 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 tan⁡β\tan\beta 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 $m_{H_D}^2$ (for the down type of Higgs) that may turn the later negative at the electroweak scale even for a small $\tan\beta$. A hyperbolic branch/focus point like effect is found for $m_A^2$ 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 $\tan\beta$. 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 μ\mu Term

We compute quadratically divergent supergravity one-loop effects on soft supersymmetry-breaking parameters and the $\mu$ 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 $\mu$ 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 $\mu$ 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