B. de Carlos

The Baryogenesis Window in the MSSM

Electroweak baryogenesis provides an attractive explanation of the origin of the matterantimatter asymmetry that relies on physics at the weak scale and thus it is testable at present and near future high-energy physics experiments. Although this scenario may not be realized within the Standard Model, it can be accommodated within the MSSM provided there are new CP-violating phases and the lightest stop mass is smaller than the top-quark mass. In this work we provide an evaluation of the values of the stop (mt̃) and Higgs (mH) masses consistent with the requirements of electroweak baryogenesis based on an analysis that makes use of the renormalization group improved Higgs and stop potentials, and including the dominant two-loop effects at high temperature. We find an allowed window in the (mt̃, mH)-plane, consistent with all present experimental data, where there is a strongly first-order electroweak phase transition and where the electroweak vacuum is metastable but sufficiently long-lived. In particular we obtain absolute upper bounds on the Higgs and stop masses, mH . 127 GeV and mt̃ . 120 GeV, implying that this scenario will be probed at the LHC.

R-parity violation effects through soft supersymmetry-breaking terms and the renormalization group.

We present full renormalization group equations for the MSSM with {ital R}-parity violation, including all soft supersymmetry-breaking terms. The inclusion of dimensionless {ital R}-parity-violating couplings can generate many possible low energy effects through the generation of off-diagonal soft masses violating lepton and quark flavor, and through the generation of lepton{endash}Higgs-superfield mixing. We discuss the relation between the weak and unification scale {ital R}-parity violation and study the effects on neutrino mass generation and {mu}{r_arrow}{ital e}{gamma}. {copyright} {ital 1996 The American Physical Society.}

Stabilizing the dilaton in superstring cosmology

We address the important issue of stabilizing the dilaton in the context of superstring cosmology. Scalar potentials which arise out of gaugino condensates in string models are generally exponential in nature. In a cosmological setting this allows for the existence of quasiscaling solutions, in which the energy density of the scalar field can, for a period, become a fixed fraction of the background density, due to the friction of the background expansion. Eventually the field can be trapped in the minimum of its potential as it leaves the scaling regime. We investigate this possibility in various gaugino condensation models and show that stable solutions for the dilaton are far more common than one would have naively thought. @S0556-2821~98!01320-4#

R-parity violation and quark flavor violation

We investigate the implications of R-parity violation (RPV) for quark flavor violation both by constraining the sneutrino masses to be positive and by studying the processes b{r_arrow}s{gamma} and K{sup 0}-{bar K}{sup 0} mixing. In the latter there are two major contributions: one from {open_quotes}direct{close_quotes} one loop diagrams involving RPV couplings, and one from the {open_quotes}indirect{close_quotes} contributions generated by the renormalization group. We compare the effects and discuss the implications of our results. {copyright} {ital 1997} {ital The American Physical Society}

Anomalous U(1), gaugino condensation and supergravity

Abstract The interplay between gaugino condensation and an anomalous Fayet-Iliopoulos term in string theories is not trivial and has important consequences concerning the size and type of the soft SUSY breaking terms. In this paper we examine this issue, generalizing previous work to the supergravity context. This allows, in particular, to properly implement the cancellation of the cosmological constant, which is crucial for a correct treatment of the soft breaking terms. We obtain that the D-term contribution to the soft masses is expected to be larger than the F-term one. Moreover gaugino masses must be much smaller than scalar masses. We illustrate these results with explicit examples. All this has relevant phenomenological consequences, amending previous results in the literature.

Cold dark matter candidate in a class of supersymmetric models with an extra U(1)

Abstract In supersymmetric models whose gauge group includes an additional U (1) factor at the TeV scale, broken by the VEV of an standard model singlet S , the parameter space can accommodate a very light neutralino not ruled out experimentally. This higgsino-like fermion, stable if R -parity is conserved, can make a good cold dark matter candidate. We examine the thermal relic density of this particle and discuss the prospects for its direct detection if it forms part of our galactic halo.

Domain walls in supersymmetric QCD

Abstract In this talk we construct BPS-saturated domain walls in supersymmetric QCD, for any values of the masses of the chiral matter superfields. We compare our results to those already obtained in the literature and we also discuss their range of applicability, as well as future directions that would be desirable to explore in order to achieve a complete understanding of supersymmetric gluodynamics as a step in improving our knowledge of how QCD works.

WEAK MAGNETIC DIPOLE MOMENTS IN THE MSSM

Abstract We calculate the weak magnetic dipole moment of different fermions in the MSSM. In particular, we consider in detail the predictions for the WMDM of the τ lepton and bottom quark. We compare the purely SUSY contributions with two Higgs doublet models and SM predictions. For the τ lepton, we show that chargino diagrams give the main SUSY contribution, which for tan β = 50 can be one order of magnitude larger than the SM prediction. For the b quark, gluino diagrams provide the main SUSY contribution to its weak anomalous dipole moment, which is still dominated by gluon contributions. We also study how the universality assumption in the slepton sector induces correlations between the SUSY contributions to the τ WMDM and to ( g − 2) of the muon.

Constraints on supersymmetric theories from {mu}{r_arrow}{ital e},{gamma}

In the absence of any additional assumption it is natural to conjecture that sizable flavor-mixing mass entries, {Delta}{ital m}{sup 2}, may appear in the mass matrices of the scalars of the MSSM, i.e., {Delta}{ital m}{sup 2}={ital O}({ital m}{sup 2}). This flavor violation can still be reconciled with experiment if the gaugino mass {ital M}{sub 1/2} is large enough, leading to a {ital gaugino} {ital dominance} framework (i.e., {ital M}{sub 1/2}{sup 2}{gt}{ital m}{sup 2}), which permits a remarkably model-independent analysis. We study this possibility focusing our attention on the {mu}{r_arrow}{ital e},{gamma} decay. In this way we obtain very strong and general constraints, in particular, {ital M}{sub 1/2}{sup 2}/{Delta}{ital m}{approx_gt}34 TeV. On the other hand, we show that our analysis and results remain valid for values of {ital m}{sup 2} much larger than {Delta}{ital m}{sup 2}, namely, for {Delta}{ital m}{sup 2}/{ital m}{sup 2}{approx_gt}{ital m}{sup 2}/10 TeV{sup 2}, thus extending enormously their scope of application. Finally, we discuss the implications for superstring scenarios. {copyright} {ital 1996 The American Physical Society.}

Constraints on supersymmetric theories from mu ---> e gamma

In the absence of any additional assumption it is natural to conjecture that sizable flavor-mixing mass entries, {Delta}{ital m}{sup 2}, may appear in the mass matrices of the scalars of the MSSM, i.e., {Delta}{ital m}{sup 2}={ital O}({ital m}{sup 2}). This flavor violation can still be reconciled with experiment if the gaugino mass {ital M}{sub 1/2} is large enough, leading to a {ital gaugino} {ital dominance} framework (i.e., {ital M}{sub 1/2}{sup 2}{gt}{ital m}{sup 2}), which permits a remarkably model-independent analysis. We study this possibility focusing our attention on the {mu}{r_arrow}{ital e},{gamma} decay. In this way we obtain very strong and general constraints, in particular, {ital M}{sub 1/2}{sup 2}/{Delta}{ital m}{approx_gt}34 TeV. On the other hand, we show that our analysis and results remain valid for values of {ital m}{sup 2} much larger than {Delta}{ital m}{sup 2}, namely, for {Delta}{ital m}{sup 2}/{ital m}{sup 2}{approx_gt}{ital m}{sup 2}/10 TeV{sup 2}, thus extending enormously their scope of application. Finally, we discuss the implications for superstring scenarios. {copyright} {ital 1996 The American Physical Society.}