Mario E Gomez - Academia.edu (original) (raw)

Papers by Mario E Gomez

Research paper thumbnail of Muon g-2, Neutralino Dark Matter and Stau NLSP

We explore the implications of resolving the muon g-2 anomaly in a SU(4)_c x SU(2)_L x SU(2)_R mo... more We explore the implications of resolving the muon g-2 anomaly in a SU(4)_c x SU(2)_L x SU(2)_R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 sigma resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass

Research paper thumbnail of Yukawa couplings and proton decay in SUSY models

Proceedings of European Network on Physics beyond the Standard Model — PoS(trieste99), 1999

We discuss proton decay induced by dimension-5 operators in supersymmetric models containing extr... more We discuss proton decay induced by dimension-5 operators in supersymmetric models containing extra hypercharge-1/3 colour-triplets. We derive a general formula relating dimension-5 operator to the colour-triplet mass matrix. We show that certain zeros in the triplet mass-matrix together with some triplet coupling selection rules can lead to elimination of dimension-5 operators. We apply this mechanism to SU (5) and flipped SU (5) theories with extended Higgs sectors.

Research paper thumbnail of Neutrino mass textures and lepton flavor violation with a determined $\theta_{13}

Proceedings of VIII International Workshop on the Dark Side of the Universe — PoS(DSU 2012), 2013

Research paper thumbnail of SUSY Cold Dark Matter Detection at large tan\beta

We study the direct detection rate for SUSY cold dark m atter (CDM) predicted by the minimal supe... more We study the direct detection rate for SUSY cold dark m atter (CDM) predicted by the minimal supersymmetric standard model with universal boundary conditions and large values for tan\beta. The relic abundance of the lightest supersymmetric particle (LSP), assumed to be approximately a bino, is obtained by including its coannihilations with the next-to-lightest supersymmetric particle (NLSP), which is the lightest s-tau. We find detectable rates in the currently planned experiments for a sector of the parameter space consistent with the cosmological constraint on the LSP relic abundance and the ones imposed by b->s gamma and the Higgs searches.

Research paper thumbnail of SUSY Dark Matter Detection, The Directional Rate and the Modulation effect

The detection of the theoretically expected dark matter is central to particle physics and cosmol... more The detection of the theoretically expected dark matter is central to particle physics and cosmology. Current fashionable supersymmetric models provide a natural dark matter candidate which is the lightest supersymmetric particle (LSP). Such models combined with fairly well understood physics like the quark substructure of the nucleon and the nuclear structure (form factor and/or spin response function), permit the evaluation of the event rate for LSP-nucleus elastic scattering. The thus obtained event rates are, however, very low or even undetectable. So it is imperative to exploit the modulation effect, i.e. the dependence of the event rate on the earth's annual motion. Also it is useful to consider the directional rate, i.e its dependence on the direction of the recoiling nucleus. In this paper we study such a modulation effect both in non directional and directional experiments. We calculate both the differential and the total rates using both isothermal, symmetric as well a...

Research paper thumbnail of Lepton-Flavour Violation in SUSY with and without R-parity

We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged secto... more We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged sector can lead to measurable rates for BR(mu->e gamma) and BR(tau->mu gamma). We consider three different scenarios, the fist one corresponds to the Minimal Supersymmetric Standard Model with non-universal soft terms. In the other two cases the violation of flavor in the leptonic charged sector is associated to the neutrino problem in models with a see-saw mechanism and with R-parity violation respectively.

Research paper thumbnail of Cold dark matter detection in SUSY models at large tanβ

Physics Letters B, 2001

We study the direct detection rate for SUSY cold dark matter (CDM) predicted by the minimal super... more We study the direct detection rate for SUSY cold dark matter (CDM) predicted by the minimal supersymmetric standard model with universal boundary conditions and large values for tanβ. The relic abundance of the lightest supersymmetric particle (LSP), assumed to be approximately a bino, is obtained by including its coannihilations with the next-to-lightest supersymmetric particle (NLSP), which is the lightest s-tau. The cosmological constraint on this quantity severely limits the allowed SUSY parameter space, especially in the case the CP-even Higgs has mass of around 114 GeV. We find that for large tanβ it is possible to find a subsection of the allowed parameter space, which yields detectable rates in the currently planned experiments.

Research paper thumbnail of Lepton-flavor violation with non-universal soft terms

Journal of High Energy Physics, 2001

We study the lepton-flavor violation processes τ → µγ and µ → eγ in two different examples of mod... more We study the lepton-flavor violation processes τ → µγ and µ → eγ in two different examples of models with non-universal soft breaking terms derived from strings. We show that the predictions are quite different from those of universal scenarios. Non-universal A-terms provide an interesting framework to enhance the supersymmetric contributions to CP violation effects. We observe that in the case of the lepton-flavor violation we study, the non-universality of the scalar masses enhances the branching ratios more significantly than the non-universality of the A-terms. We find that the current experimental bounds on these processes restrict both the parameter space of the models and the texture of the Yukawa couplings which predicts the lepton masses, providing at the same time an interesting experimental test for physics beyond the Standard Model.

Research paper thumbnail of Cosmological Constraints in SUSY with Yukawa Unification

The cosmological relic density of the lightest supersymmetric particle of the minimal supersymmet... more The cosmological relic density of the lightest supersymmetric particle of the minimal supersymmetric standard model is calculated under the assumption of gauge and Yukawa coupling unification. We employ radiative electroweak breaking with universal boundary conditions from gravity-mediated supersymmetry breaking. Further constraints are imposed by the experimental bounds on the b-quark mass and the BR(b -> s gamma). We find that coannihilation of the lightest supersymmetric particle, which turns out to be an almost pure bino, with the next-to-lightest supersymmetric particle (the lightest stau) is crucial for reducing its relic density to an acceptable level.

Research paper thumbnail of Neutralino-nucleon cross section and charge and colour breaking constraints

Journal of High Energy Physics, 2003

We compute the neutralino-nucleon cross section in several supersymmetric scenarios, taking into ... more We compute the neutralino-nucleon cross section in several supersymmetric scenarios, taking into account all kind of constraints. In particular, the constraints that the absence of dangerous charge and colour breaking minima imposes on the parameter space are studied in detail. In addition, the most recent experimental constraints, such as the lower bound on the Higgs mass, the b → sγ branching ratio, and the muon g − 2 are considered. The astrophysical bounds on the dark matter density are also imposed on the theoretical computation of the relic neutralino density, assuming thermal production. This computation is relevant for the theoretical analysis of the direct detection of dark matter in current experiments. We consider first the supergravity scenario with universal soft terms and GUT scale. In this scenario the charge and colour breaking constraints turn out to be quite important, and tan β < ∼ 20 is forbidden. Larger values of tan β can also be forbidden, depending on the value of the trilinear parameter A. Finally, we study supergravity scenarios with an intermediate scale, and also with non-universal scalar and gaugino masses where the cross section can be very large.

Research paper thumbnail of CP and lepton-number violation in GUT neutrino models with abelian flavour symmetries

Journal of High Energy Physics, 2007

We study the possible magnitudes of CP and lepton-number-violating quantities in specific GUT mod... more We study the possible magnitudes of CP and lepton-number-violating quantities in specific GUT models of massive neutrinos with different Abelian flavour groups, taking into account experimental constraints and requiring successful leptogenesis. We discuss SU(5) and flipped SU(5) models that are consistent with the present data on neutrino mixing and upper limits on the violations of charged-lepton flavours and explore their predictions for the CP-violating oscillation and Majorana phases. In particular, we discuss string-derived flipped SU(5) models with selection rules that modify the GUT structure and provide additional constraints on the operators, which are able to account for the magnitudes of some of the coefficients that are often set as arbitrary parameters in generic Abelian models.

Research paper thumbnail of Charged-lepton-flavour violation in the CMSSM in view of the muon anomalous magnetic moment

Physics Letters B, 2001

We use the BNL E821 measurement of g µ − 2, the anomalous magnetic moment of the muon, to normali... more We use the BNL E821 measurement of g µ − 2, the anomalous magnetic moment of the muon, to normalize, within a supersymmetric GUT framework, constrained MSSM (CMSSM) predictions for processes that violate charged-lepton flavour conservation, including µ → eγ, µ → e conversion and K 0 L → µ ± e ∓. We illustrate our analysis with two examples of lepton mass matrix textures motivated by data on neutrino oscillations. We find that µ → eγ may well occur at a rate within one or two (two or three) orders of magnitude of the present experimental upper limit if g µ − 2 is within the one-(two-)standard deviation range indicated by E821. We also find that µ → e conversion is likely to occur at rate measurable by MECO, and there is a chance that K 0 L → µ ± e ∓ may be observable in an experiment using an intense proton source.

Research paper thumbnail of Tau flavour violation in sparticle decays at the LHC

Physics Letters B, 2005

We consider sparticle decays that violate τ lepton number, motivated by neutrino oscillation data... more We consider sparticle decays that violate τ lepton number, motivated by neutrino oscillation data. We work in the context of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the different sleptons have identical masses at the GUT scale, and neutrino Dirac Yukawa couplings mix them. We find that the branching ratio for decay of the heavier neutralino χ 2 → χ + τ ± µ ∓ is enhanced when the LSP mass m χ ∼ mτ 1 , including the region of CMSSM parameter space where coannihilation keeps the relic χ density within the range preferred by cosmology. Thus χ 2 → χ + τ ± µ ∓ decay may provide a physics opportunity for observing the violation of τ lepton number at the LHC that is complementary to τ → µ + γ decay. Likewise, χ 2 → χ + e ± µ ∓ decay is also enhanced in the coannihilation region, providing a complement to µ → e + γ decay.

Research paper thumbnail of Neutrino textures and charged lepton flavor violation in light of θ_{13}, MEG, and LHC data

Physical Review D, 2013

In light of recent results from the LHC, MEG and neutrino experiments, we revisit the issue of ch... more In light of recent results from the LHC, MEG and neutrino experiments, we revisit the issue of charged lepton flavor violation (LFV) in supersymmetric theories with massive neutrinos, where flavorviolating soft supersymmetry-breaking masses for sleptons are induced naturally by radiative corrections. We link our results to the expectations for light neutrinos with a normal mass hierarchy in SU(5), enhanced by an Abelian flavor symmetry, with particular focus on 13. We focus on the radiative decays ' i ! ' j and on detection prospects at the LHC and a linear collider (LC). We use supersymmetric parameters consistent with cosmological considerations and with LHC searches for supersymmetry and the Higgs mass. We find a class of scenarios where the LHC may be sensitive to LFV sparticle decays and LFV processes could be detectable at a LC with center-of-mass energy above 1 TeV, whereas LFV lepton decays may be suppressed by cancellations in the decay amplitudes.

Research paper thumbnail of Impact of internal bremsstrahlung on the detection of γ rays from neutralinos

Physical Review D, 2010

We present a detailed study of the effect of internal bremsstrahlung photons in the context of th... more We present a detailed study of the effect of internal bremsstrahlung photons in the context of the minimal supersymmetric standard models and their impact on γ-ray dark matter annihilation searches. We find that although this effect has to be included for the correct evaluation of fluxes of high energy photons from neutralino annihilation, its contribution is relevant only in models and at energies where the lines contribution is dominant over the secondary photons. Therefore, we find that the most optimistic supersymmetric scenarios for dark matter detection do not change significantly when including the internal bremsstrahlung. As an example, we review the γ-ray dark matter detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC stereoscopic system and the CTA project. Though the flux of high energy photons is enhanced by an order of magnitude in some regions of the parameter space, the expected fluxes are still much below the sensitivity of the instruments.

Research paper thumbnail of An improved analysis ofb→sγin supersymmetry

Physical Review D, 2006

An improved analysis of the b → s + γ decay in the minimal flavor violating case is given taking ... more An improved analysis of the b → s + γ decay in the minimal flavor violating case is given taking into account additional contributions in the supersymmetric sector which enter in the next-to-leading-order (NLO) and are enhanced by tan β factors. Specifically, we compute a set of twenty one-loop diagrams to give the most complete analysis to date of the NLO supersymmetric corrections. These modifications are computed from the effective charged Higgs and neutral Higgs couplings involving twelve loop diagrams for the charged Higgs sector and eight loop diagrams for the neutral Higgs sector. While the computations of these corrections are available in the literature, their full forms including the complex phase dependence has not be considered. Our analysis takes account of the full allowed set of twenty one-loop diagrams and is more general since it also includes the full dependence on CP phases in non universal sugra and MSSM models. A numerical analysis is carried out to estimate the size of the corrections to b → s + γ. We also briefly discuss the implications of these results for the search for supersymmetry.

Research paper thumbnail of WMAP dark matter constraints and Yukawa unification in supergravity models withCPphases

Physical Review D, 2005

The compatibility of producing the observed amount of dark matter, as indicated by the WMAP data,... more The compatibility of producing the observed amount of dark matter, as indicated by the WMAP data, through the relic abundance of neutralinos with Yukawa unification and with the measured rate of b → sγ is analyzed in mSUGRA and extended SUGRA unified models with the inclusion of CP phases. The CP phases affect the analysis in several ways, e.g., through the threshold corrections to the b-quark mass, via their effects on the neutralino relic density and through the SUSY contribution to the BR(b → sγ) which is sensitive to the CP phases. We present some specific models with large SUSY phases, which can accommodate the fermion electric dipole moment constraints and give a neutralino relic density in agreement with observations as well as with the b-τ unification constraint. The possibility of achieving WMAP relic density constraints with full Yukawa unification is also explored.

Research paper thumbnail of Sensitivity of supersymmetric dark matter to the b quark mass

Physical Review D, 2004

An analysis of the sensitivity of supersymmetric dark matter to variations in the b quark mass is... more An analysis of the sensitivity of supersymmetric dark matter to variations in the b quark mass is given. Specifically we study the effects on the neutralino relic abundance from supersymmetric loop corrections to the mass of the b quark. It is known that these loop corrections can become significant for large tan β. The analysis is carried out in the framework of mSUGRA and we focus on the region where the relic density constraints are satisfied by resonant annihilation through the s-channel Higgs poles. We extend the analysis to include CP phases taking into account the mixing of the CP-even and CPodd Higgs boson states which play an important role in determining the relic density. Implications of the analysis for the neutralino relic density consistent with the recent WMAP relic density constraints are discussed.

Research paper thumbnail of Note on R-parity violation and fermion masses

Physical Review D, 1998

We consider a class of supersymmetric SU(3)×SU(2)×U(1) multihiggs models in which R-parity is vio... more We consider a class of supersymmetric SU(3)×SU(2)×U(1) multihiggs models in which R-parity is violated through bilinear Higgs-lepton interactions. The required, due to R-parity violation, higgs-lepton rotations introduce an alternative way to generate the phenomenologically desirable fermion mass matrix structures independently of the equality of Yukawas, possibly imposed by superstring or other unification.

Research paper thumbnail of Charged lepton flavor violation in supersymmetry with bilinearR-parity violation

Physical Review D, 2002

The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R-pari... more The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R-parity violation naturally predicts a hierarchical neutrino mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We study whether the individual violation of the lepton numbers L e,µ,τ in the charged sector can lead to measurable rates for BR(µ → eγ) and BR(τ → µγ). We find that some of the R-parity violating terms that are compatible with the observed atmospheric neutrino oscillations could lead to rates for µ → eγ measurable in projected experiments. However, the ∆m 2 12 obtained for those parameters is too high to be compatible with the solar neutrino data, excluding therefore the possibility of having measurable rates for µ → eγ in the model.

Research paper thumbnail of Muon g-2, Neutralino Dark Matter and Stau NLSP

We explore the implications of resolving the muon g-2 anomaly in a SU(4)_c x SU(2)_L x SU(2)_R mo... more We explore the implications of resolving the muon g-2 anomaly in a SU(4)_c x SU(2)_L x SU(2)_R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 sigma resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass

Research paper thumbnail of Yukawa couplings and proton decay in SUSY models

Proceedings of European Network on Physics beyond the Standard Model — PoS(trieste99), 1999

We discuss proton decay induced by dimension-5 operators in supersymmetric models containing extr... more We discuss proton decay induced by dimension-5 operators in supersymmetric models containing extra hypercharge-1/3 colour-triplets. We derive a general formula relating dimension-5 operator to the colour-triplet mass matrix. We show that certain zeros in the triplet mass-matrix together with some triplet coupling selection rules can lead to elimination of dimension-5 operators. We apply this mechanism to SU (5) and flipped SU (5) theories with extended Higgs sectors.

Research paper thumbnail of Neutrino mass textures and lepton flavor violation with a determined $\theta_{13}

Proceedings of VIII International Workshop on the Dark Side of the Universe — PoS(DSU 2012), 2013

Research paper thumbnail of SUSY Cold Dark Matter Detection at large tan\beta

We study the direct detection rate for SUSY cold dark m atter (CDM) predicted by the minimal supe... more We study the direct detection rate for SUSY cold dark m atter (CDM) predicted by the minimal supersymmetric standard model with universal boundary conditions and large values for tan\beta. The relic abundance of the lightest supersymmetric particle (LSP), assumed to be approximately a bino, is obtained by including its coannihilations with the next-to-lightest supersymmetric particle (NLSP), which is the lightest s-tau. We find detectable rates in the currently planned experiments for a sector of the parameter space consistent with the cosmological constraint on the LSP relic abundance and the ones imposed by b->s gamma and the Higgs searches.

Research paper thumbnail of SUSY Dark Matter Detection, The Directional Rate and the Modulation effect

The detection of the theoretically expected dark matter is central to particle physics and cosmol... more The detection of the theoretically expected dark matter is central to particle physics and cosmology. Current fashionable supersymmetric models provide a natural dark matter candidate which is the lightest supersymmetric particle (LSP). Such models combined with fairly well understood physics like the quark substructure of the nucleon and the nuclear structure (form factor and/or spin response function), permit the evaluation of the event rate for LSP-nucleus elastic scattering. The thus obtained event rates are, however, very low or even undetectable. So it is imperative to exploit the modulation effect, i.e. the dependence of the event rate on the earth's annual motion. Also it is useful to consider the directional rate, i.e its dependence on the direction of the recoiling nucleus. In this paper we study such a modulation effect both in non directional and directional experiments. We calculate both the differential and the total rates using both isothermal, symmetric as well a...

Research paper thumbnail of Lepton-Flavour Violation in SUSY with and without R-parity

We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged secto... more We study whether the individual violation of the lepton numbers L_{e,mu,tau} in the charged sector can lead to measurable rates for BR(mu->e gamma) and BR(tau->mu gamma). We consider three different scenarios, the fist one corresponds to the Minimal Supersymmetric Standard Model with non-universal soft terms. In the other two cases the violation of flavor in the leptonic charged sector is associated to the neutrino problem in models with a see-saw mechanism and with R-parity violation respectively.

Research paper thumbnail of Cold dark matter detection in SUSY models at large tanβ

Physics Letters B, 2001

We study the direct detection rate for SUSY cold dark matter (CDM) predicted by the minimal super... more We study the direct detection rate for SUSY cold dark matter (CDM) predicted by the minimal supersymmetric standard model with universal boundary conditions and large values for tanβ. The relic abundance of the lightest supersymmetric particle (LSP), assumed to be approximately a bino, is obtained by including its coannihilations with the next-to-lightest supersymmetric particle (NLSP), which is the lightest s-tau. The cosmological constraint on this quantity severely limits the allowed SUSY parameter space, especially in the case the CP-even Higgs has mass of around 114 GeV. We find that for large tanβ it is possible to find a subsection of the allowed parameter space, which yields detectable rates in the currently planned experiments.

Research paper thumbnail of Lepton-flavor violation with non-universal soft terms

Journal of High Energy Physics, 2001

We study the lepton-flavor violation processes τ → µγ and µ → eγ in two different examples of mod... more We study the lepton-flavor violation processes τ → µγ and µ → eγ in two different examples of models with non-universal soft breaking terms derived from strings. We show that the predictions are quite different from those of universal scenarios. Non-universal A-terms provide an interesting framework to enhance the supersymmetric contributions to CP violation effects. We observe that in the case of the lepton-flavor violation we study, the non-universality of the scalar masses enhances the branching ratios more significantly than the non-universality of the A-terms. We find that the current experimental bounds on these processes restrict both the parameter space of the models and the texture of the Yukawa couplings which predicts the lepton masses, providing at the same time an interesting experimental test for physics beyond the Standard Model.

Research paper thumbnail of Cosmological Constraints in SUSY with Yukawa Unification

The cosmological relic density of the lightest supersymmetric particle of the minimal supersymmet... more The cosmological relic density of the lightest supersymmetric particle of the minimal supersymmetric standard model is calculated under the assumption of gauge and Yukawa coupling unification. We employ radiative electroweak breaking with universal boundary conditions from gravity-mediated supersymmetry breaking. Further constraints are imposed by the experimental bounds on the b-quark mass and the BR(b -> s gamma). We find that coannihilation of the lightest supersymmetric particle, which turns out to be an almost pure bino, with the next-to-lightest supersymmetric particle (the lightest stau) is crucial for reducing its relic density to an acceptable level.

Research paper thumbnail of Neutralino-nucleon cross section and charge and colour breaking constraints

Journal of High Energy Physics, 2003

We compute the neutralino-nucleon cross section in several supersymmetric scenarios, taking into ... more We compute the neutralino-nucleon cross section in several supersymmetric scenarios, taking into account all kind of constraints. In particular, the constraints that the absence of dangerous charge and colour breaking minima imposes on the parameter space are studied in detail. In addition, the most recent experimental constraints, such as the lower bound on the Higgs mass, the b → sγ branching ratio, and the muon g − 2 are considered. The astrophysical bounds on the dark matter density are also imposed on the theoretical computation of the relic neutralino density, assuming thermal production. This computation is relevant for the theoretical analysis of the direct detection of dark matter in current experiments. We consider first the supergravity scenario with universal soft terms and GUT scale. In this scenario the charge and colour breaking constraints turn out to be quite important, and tan β < ∼ 20 is forbidden. Larger values of tan β can also be forbidden, depending on the value of the trilinear parameter A. Finally, we study supergravity scenarios with an intermediate scale, and also with non-universal scalar and gaugino masses where the cross section can be very large.

Research paper thumbnail of CP and lepton-number violation in GUT neutrino models with abelian flavour symmetries

Journal of High Energy Physics, 2007

We study the possible magnitudes of CP and lepton-number-violating quantities in specific GUT mod... more We study the possible magnitudes of CP and lepton-number-violating quantities in specific GUT models of massive neutrinos with different Abelian flavour groups, taking into account experimental constraints and requiring successful leptogenesis. We discuss SU(5) and flipped SU(5) models that are consistent with the present data on neutrino mixing and upper limits on the violations of charged-lepton flavours and explore their predictions for the CP-violating oscillation and Majorana phases. In particular, we discuss string-derived flipped SU(5) models with selection rules that modify the GUT structure and provide additional constraints on the operators, which are able to account for the magnitudes of some of the coefficients that are often set as arbitrary parameters in generic Abelian models.

Research paper thumbnail of Charged-lepton-flavour violation in the CMSSM in view of the muon anomalous magnetic moment

Physics Letters B, 2001

We use the BNL E821 measurement of g µ − 2, the anomalous magnetic moment of the muon, to normali... more We use the BNL E821 measurement of g µ − 2, the anomalous magnetic moment of the muon, to normalize, within a supersymmetric GUT framework, constrained MSSM (CMSSM) predictions for processes that violate charged-lepton flavour conservation, including µ → eγ, µ → e conversion and K 0 L → µ ± e ∓. We illustrate our analysis with two examples of lepton mass matrix textures motivated by data on neutrino oscillations. We find that µ → eγ may well occur at a rate within one or two (two or three) orders of magnitude of the present experimental upper limit if g µ − 2 is within the one-(two-)standard deviation range indicated by E821. We also find that µ → e conversion is likely to occur at rate measurable by MECO, and there is a chance that K 0 L → µ ± e ∓ may be observable in an experiment using an intense proton source.

Research paper thumbnail of Tau flavour violation in sparticle decays at the LHC

Physics Letters B, 2005

We consider sparticle decays that violate τ lepton number, motivated by neutrino oscillation data... more We consider sparticle decays that violate τ lepton number, motivated by neutrino oscillation data. We work in the context of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the different sleptons have identical masses at the GUT scale, and neutrino Dirac Yukawa couplings mix them. We find that the branching ratio for decay of the heavier neutralino χ 2 → χ + τ ± µ ∓ is enhanced when the LSP mass m χ ∼ mτ 1 , including the region of CMSSM parameter space where coannihilation keeps the relic χ density within the range preferred by cosmology. Thus χ 2 → χ + τ ± µ ∓ decay may provide a physics opportunity for observing the violation of τ lepton number at the LHC that is complementary to τ → µ + γ decay. Likewise, χ 2 → χ + e ± µ ∓ decay is also enhanced in the coannihilation region, providing a complement to µ → e + γ decay.

Research paper thumbnail of Neutrino textures and charged lepton flavor violation in light of θ_{13}, MEG, and LHC data

Physical Review D, 2013

In light of recent results from the LHC, MEG and neutrino experiments, we revisit the issue of ch... more In light of recent results from the LHC, MEG and neutrino experiments, we revisit the issue of charged lepton flavor violation (LFV) in supersymmetric theories with massive neutrinos, where flavorviolating soft supersymmetry-breaking masses for sleptons are induced naturally by radiative corrections. We link our results to the expectations for light neutrinos with a normal mass hierarchy in SU(5), enhanced by an Abelian flavor symmetry, with particular focus on 13. We focus on the radiative decays ' i ! ' j and on detection prospects at the LHC and a linear collider (LC). We use supersymmetric parameters consistent with cosmological considerations and with LHC searches for supersymmetry and the Higgs mass. We find a class of scenarios where the LHC may be sensitive to LFV sparticle decays and LFV processes could be detectable at a LC with center-of-mass energy above 1 TeV, whereas LFV lepton decays may be suppressed by cancellations in the decay amplitudes.

Research paper thumbnail of Impact of internal bremsstrahlung on the detection of γ rays from neutralinos

Physical Review D, 2010

We present a detailed study of the effect of internal bremsstrahlung photons in the context of th... more We present a detailed study of the effect of internal bremsstrahlung photons in the context of the minimal supersymmetric standard models and their impact on γ-ray dark matter annihilation searches. We find that although this effect has to be included for the correct evaluation of fluxes of high energy photons from neutralino annihilation, its contribution is relevant only in models and at energies where the lines contribution is dominant over the secondary photons. Therefore, we find that the most optimistic supersymmetric scenarios for dark matter detection do not change significantly when including the internal bremsstrahlung. As an example, we review the γ-ray dark matter detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC stereoscopic system and the CTA project. Though the flux of high energy photons is enhanced by an order of magnitude in some regions of the parameter space, the expected fluxes are still much below the sensitivity of the instruments.

Research paper thumbnail of An improved analysis ofb→sγin supersymmetry

Physical Review D, 2006

An improved analysis of the b → s + γ decay in the minimal flavor violating case is given taking ... more An improved analysis of the b → s + γ decay in the minimal flavor violating case is given taking into account additional contributions in the supersymmetric sector which enter in the next-to-leading-order (NLO) and are enhanced by tan β factors. Specifically, we compute a set of twenty one-loop diagrams to give the most complete analysis to date of the NLO supersymmetric corrections. These modifications are computed from the effective charged Higgs and neutral Higgs couplings involving twelve loop diagrams for the charged Higgs sector and eight loop diagrams for the neutral Higgs sector. While the computations of these corrections are available in the literature, their full forms including the complex phase dependence has not be considered. Our analysis takes account of the full allowed set of twenty one-loop diagrams and is more general since it also includes the full dependence on CP phases in non universal sugra and MSSM models. A numerical analysis is carried out to estimate the size of the corrections to b → s + γ. We also briefly discuss the implications of these results for the search for supersymmetry.

Research paper thumbnail of WMAP dark matter constraints and Yukawa unification in supergravity models withCPphases

Physical Review D, 2005

The compatibility of producing the observed amount of dark matter, as indicated by the WMAP data,... more The compatibility of producing the observed amount of dark matter, as indicated by the WMAP data, through the relic abundance of neutralinos with Yukawa unification and with the measured rate of b → sγ is analyzed in mSUGRA and extended SUGRA unified models with the inclusion of CP phases. The CP phases affect the analysis in several ways, e.g., through the threshold corrections to the b-quark mass, via their effects on the neutralino relic density and through the SUSY contribution to the BR(b → sγ) which is sensitive to the CP phases. We present some specific models with large SUSY phases, which can accommodate the fermion electric dipole moment constraints and give a neutralino relic density in agreement with observations as well as with the b-τ unification constraint. The possibility of achieving WMAP relic density constraints with full Yukawa unification is also explored.

Research paper thumbnail of Sensitivity of supersymmetric dark matter to the b quark mass

Physical Review D, 2004

An analysis of the sensitivity of supersymmetric dark matter to variations in the b quark mass is... more An analysis of the sensitivity of supersymmetric dark matter to variations in the b quark mass is given. Specifically we study the effects on the neutralino relic abundance from supersymmetric loop corrections to the mass of the b quark. It is known that these loop corrections can become significant for large tan β. The analysis is carried out in the framework of mSUGRA and we focus on the region where the relic density constraints are satisfied by resonant annihilation through the s-channel Higgs poles. We extend the analysis to include CP phases taking into account the mixing of the CP-even and CPodd Higgs boson states which play an important role in determining the relic density. Implications of the analysis for the neutralino relic density consistent with the recent WMAP relic density constraints are discussed.

Research paper thumbnail of Note on R-parity violation and fermion masses

Physical Review D, 1998

We consider a class of supersymmetric SU(3)×SU(2)×U(1) multihiggs models in which R-parity is vio... more We consider a class of supersymmetric SU(3)×SU(2)×U(1) multihiggs models in which R-parity is violated through bilinear Higgs-lepton interactions. The required, due to R-parity violation, higgs-lepton rotations introduce an alternative way to generate the phenomenologically desirable fermion mass matrix structures independently of the equality of Yukawas, possibly imposed by superstring or other unification.

Research paper thumbnail of Charged lepton flavor violation in supersymmetry with bilinearR-parity violation

Physical Review D, 2002

The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R-pari... more The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R-parity violation naturally predicts a hierarchical neutrino mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We study whether the individual violation of the lepton numbers L e,µ,τ in the charged sector can lead to measurable rates for BR(µ → eγ) and BR(τ → µγ). We find that some of the R-parity violating terms that are compatible with the observed atmospheric neutrino oscillations could lead to rates for µ → eγ measurable in projected experiments. However, the ∆m 2 12 obtained for those parameters is too high to be compatible with the solar neutrino data, excluding therefore the possibility of having measurable rates for µ → eγ in the model.