arXiv subjects

M. E. Gomez

Publications and source records attributed to M. E. Gomez.

At least 19 recordsLinked to original sources

arXiv2024

Interplay between $M_W$, $Ω_{\rm CDM} h^2$, and $(g-2)_μ$ in Flavor Symmetry-Based Supersymmetric Models

We study the phenomenological implications of the minimal supersymmetric standard model (MSSM) augmented by a non-abelian flavor symmetry labeled as sMSSM. Incorporating this flavor symmetry allows for a significant reduction in the original plethora of free parameters present in the MSSM, ultimately reducing them down to just seven in sMSSM. This reduction of free parameters is not achieved through ad hoc assumptions like in the constrained MSSM (CMSSM); rather, it is grounded in theoretical considerations. Our work focuses on exploring the interplay between the $W$ boson mass ($M_W$) predictions, the cold dark matter (CDM) relic abundance ($Ω_{\rm CDM} h^2$), and the $(g-2)_μ$ anomaly. We identified correlations among the theoretical parameters arising from this interplay, which can be complemented by experimental constraints such as the Higgs boson mass, B-physics observables, and charge and color breaking minima. Additionally, our investigations show that the $(g-2)_μ$ discrepancy and the Planck bounds on $Ω_{\rm CDM} h^2$ can be addressed within the sMSSM, but only in a very narrow region of the parameter space.

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arXiv2020

Excited lepton triplet contribution to electroweak observables at one loop level

In this paper, we present the one-loop radiative corrections to the electroweak precision observable $Δρ$ coming from the $I_W=1$ multiplet excited leptons. We have calculated the couplings of the exotic lepton triplet to the vector bosons and ordinary leptons using effective Lagrangian approach. These couplings are then used to estimate the excited lepton triplet contribution to the $Δρ$ parameter. The mass degenerate excited lepton contribution to $Δρ$ is small and can be neglected. However, if the excited leptons are non-degenerate, their contribution can be large which can result in more stringent constraints on the excited fermion parameter space compared to the constraints from present experimental searches and perturbative unitarity condition.

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arXiv2020

Confronting Grand Unification with Lepton Flavour Violation, Dark Matter and LHC Data

We explore possible signatures for charged lepton flavour violation (LFV), sparticle discovery at the LHC and dark matter (DM) searches in grand unified theories (GUTs) based on SU(5), flipped SU(5) (FSU(5)) and SU(4)$_c \times $SU(2)$_L \times $SU(2)$_R$ (4-2-2). We assume that soft supersymmetry-breaking terms preserve the group symmetry at some high input scale, and focus on the non-universal effects on different matter representations generated by gauge interactions at lower scales, as well as the charged LFV induced in Type-1 see-saw models of neutrino masses. We identify the different mechanisms that control the relic DM density in the various GUT models, and contrast their LFV and LHC signatures. The SU(5) and 4-2-2 models offer good detection prospects both at the LHC and in LFV searches, though with different LSP compositions, and the SU(5) and FSU(5) models offer LFV within the current reach. The 4-2-2 model allows chargino and gluino coannihilations with neutralinos, and the former offer good detection prospects for both the LHC and LFV, while gluino coannihilations lead to lower LFV rates. Our results indicate that LFV is a powerful tool that complements LHC and DM searches, providing significant insights into the sparticle spectra and neutrino mass parameters in different models.

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arXiv2018

Confronting SUSY GUT with Dark Matter, Sparticle Spectroscopy and Muon $(g-2)$

We explore the implications of LHC and cold dark matter searches for supersymmetric particle mass spectra in two different grand unified models with left-right symmetry, $SO(10)$ and $ SU(4)_c \times SU(2)_L \times SU(2)_R$ (4-2-2). We identify characteristic differences between the two scenarios, which imply distinct correlations between experimental measurements and the particular structure of the GUT group. The gauge structure of 4-2-2 enhances significantly the allowed parameter space as compared to $SO(10)$, giving rise to a variety of coannihilation scenarios compatible with the LHC data, LSP dark matter and the ongoing muon g-2 experiment.

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arXiv2018

Dark Matter, Sparticle Spectroscopy and Muon $(g-2)$ in $SU(4)_c \times SU(2)_L \times SU(2)_R$

We explore the sparticle mass spectra including LSP dark matter within the framework of supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R$ (422) models, taking into account the constraints from extensive LHC and cold dark matter searches. The soft supersymmetry-breaking parameters at $M_{GUT}$ can be non-universal, but consistent with the 422 symmetry. We identify a variety of coannihilation scenarios compatible with LSP dark matter, and study the implications for future supersymmetry searches and the ongoing muon g-2 experiment.

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arXiv2017

Lepton flavor violating Higgs Boson Decays in Supersymmetric High Scale Seesaw Models

Within the MSSM, we have evaluated the decay rates for the lepton flavour violating Higgs boson decays (LFVHD) $h \rightarrow l_i l_j$ where $l_{i,j}$ are charged leptons and $i\neq j$. This has been done in a model independent (MI) way as well as in supersymmetric high scale seesaw models, in particular Type I see-saw model. Lepton flavour violation (LFV) is generated by non-diagonal entries in the mass matrix of the sleptons. In a first step we use the model independent approach where LFV (off-diagonal entries in the mass matrix) is introduced by hand while respecting the direct search constraints from the charged lepton flavor violating (cLFV) processes. In the second step we use high scale see-saw models where LFV is generated via renormalization group equations (RGE) from the grand unification scale (GUT) down to electroweak scale. cLFV decays are the most restrictive ones and exclude a large part of the parameter space for the MI as well as the high scale see-saw scenarios. Due to very strict constraints from cLFV, it is difficult to find large corrections to LFVHD. This applies in particular to $h \rightarrow τμ$ where hints of an excess have been observed. If this signal is confirmed, it could not be explained with the models under investigation.

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arXiv2015

Effects of Sfermion Mixing induced by RGE Running in the Minimal Flavor Violating CMSSM

Within the Constrained Minimal Supersymmetric Standard Model (CMSSM) with Minimal Flavor Violation (MFV) for scalar quarks we study the effects of intergenerational squark mixing on $B$-physics observables, electroweak precision observables (EWPO) and the Higgs boson mass predictions. Squark mixing is generated through the Renormalization Group Equations (RGE) running from the GUT scale to the electroweak scale due to presence of non diagonal Yukawa matrices in the RGE's, e.g. due to the CKM matrix. We find that the $B$-Physics observables as well as the Higgs mass predictions do not receive sizable corrections. On the other hand, the EWPO such as the $W$ boson mass can receive corrections by far exceeding the current experimental precision. These contributions can place new upper bounds on the CMSSM parameter space. We extend our analysis to the CMSSM extended with a mechanism to explain neutrino masses (CMSSM-seesaw I), which induces flavor violation in the scalar lepton sector. Effects from slepton mixing on the analyzed observables are in general smaller than from squark mixing, but can reach the level of the current experimenal uncertainty for the EWPO.

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arXiv2012

New gamma ray signal from gravitationally boosted neutralinos at the galactic center

We discuss on the possibility that colliding dark matter particles in the form of neutralinos may be gravitationally boosted near the super-massive black hole at the galactic center so that they can have enough collision energy to annihilate into a stau pair. Since in some phenomenologically favored supersymmetric models the mass splitting between the neutralino and the lightest stau, one of the two scalar superpartners of the tau lepton, is a few GeVs, this channel may be allowed. In addition, staus can only decay into a tau lepton and another neutralino. We calculate the gamma-ray spectrum and flux generated by the tau pair discussing the observability of the obtained features.

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arXiv2011

Searches for Lepton Flavour Violation at a Linear Collider

We investigate the prospects for detection of lepton flavour violation in sparticle production and decays at a Linear Collider (LC), in models guided by neutrino oscillation data. We consider both slepton pair production and sleptons arising from the cascade decays of non-leptonic sparticles. We study the expected signals when lepton-flavour-violating (LFV) interactions are induced by renormalization effects in the Constrained Minimal Supersymmetric extension of the Standard Model (CMSSM), focusing on the subset of the supersymmetric parameter space that also leads to cosmologically interesting values of the relic neutralino LSP density. Emphasis is given to the complementarity between the LC, which is sensitive to mixing in both the left and right slepton sectors, and the LHC, which is sensitive primarily to mixing in the right sector. We also emphasize the complementarity between searches for rare LFV processes at the LC and in low-energy experiments.

hep-ph↗

arXiv2011

A scheme for the extraction of WIMP-nucleon scattering cross sections from total event rates

We propose a scheme that allows to analytically determine the three elementary cross sections and connect the solutions to the relative sign between the proton and the neutron spin scattering amplitudes once the measurements of total event rate from three appropriate targets become available. In this way it is thus possible to extract the maximum information on the supersymmetric parameter space obtainable from direct detection experiments, in the case that the dark matter particle is the lightest neutralino. Our scheme is based on suitably normalized form of the isospin momentum dependent structure functions entering in the spin-dependent elastic neutralino-nucleus cross section. We compare these functions with the commonly used ones and discuss their advantages: in particular, these allow in the spin-dependent cross section to factorize the particle physics degrees of freedom from the momentum transfer dependent nuclear structure functions as it happens in the spin-independent cross section with the nuclear form factor.

hep-ph↗

arXiv2010

Impact of internal bremsstrahlung on the detection of gamma-rays from neutralinos

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 gamma-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 gamma-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.

astro-ph.CO↗

arXiv2010

$τ$-Flavour Violation at the LHC

We study the conditions required for $χ_2 \to χ+ τ^\pm μ^\mp$ decays to yield observable tau flavour violation at the LHC, for cosmologically interesting values of the neutralino relic density. These condition can be achieved in the framework of a SU(5) model with a see-saw mechanism that allows a possible coexistence of a LHC signal a low prediction for radiative LFV decays.

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arXiv2009

The case for a directional dark matter detector and the status of current experimental efforts

We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and experimental groups in the field. We describe the need for a dark matter detector with directional sensitivity; each directional dark matter experiment presents their project's status; and we close with a feasibility study for scaling up to a one ton directional detector, which would cost around $150M.

astro-ph.CO↗

arXiv2009

Quintessential Kination and Thermal Production of Gravitinos and Axinos

The impact of a kination-dominated phase generated by a quintessential exponential model on the thermal abundance of gravitinos and axinos is investigated. We find that their abundances become proportional to the transition temperature from the kination to the radiation era; since this temperature is significantly lower than the initial ("reheating") temperature, the abundances decrease with respect to their values in the standard cosmology. For values of the quintessential energy-density parameter close to its upper bound, at the eve of nucleosynthesis, we find the following: (i) for unstable gravitinos, the gravitino constraint is totally evaded; (ii) If the gravitino is stable, its thermal abundance is not sufficient to account for the cold dark matter of the universe; (iii) the thermal abundance of axinos can satisfy the cold dark matter constraint for values of the initial temperature well above those required in the standard cosmology. A novel calculation of the axino production rate by scatterings at low temperature is also presented.

hep-ph↗

arXiv2009

Dark Matter and Lepton Flavour Violation in Yukawa Unification with Massive Neutrinos

The WMAP dark matter constraints on b-$τ$ Yukawa Unification in the presence of massive neutrinos is revisited. The predictions for the bottom quark mass are observed to be modified by the large neutrino mixing suggested by the data. This enables Yukawa unification also for large $\tanβ$, and for positive $μ$ that were previously disfavoured. Consequently, the allowed parameter space for neutralino dark matter differs from the MSSM one. We also find that the parameter space being compatible with dark matter also predicts detectable rates for Lepton Flavour Violation at the LHC.

hep-ph↗

arXiv2009

Dark Matter and Yukawa Unification with Massive Neutrinos

We revisit the WMAP dark matter constraints on Yukawa Unification in the presence of massive neutrinos. The large neutrino mixing indicated by the data modifies the predictions for the bottom quark mass, and enables Yukawa also for large $\tanβ$, and for positive $μ$ that were previously disfavoured. As a result, the allowed parameter space for neutralino dark matter also increases, particularly for areas with resonant enhancement of the neutralino relic density.

hep-ph↗

arXiv2009

WMAP Dark Matter Constraints on Yukawa Unification with Massive Neutrinos

We revisit the WMAP dark matter constraints on Yukawa Unification in the presence of massive neutrinos. The large lepton mixing indicated by the data may modify the predictions for the bottom quark mass, enabling Yukawa unification also for large $\tanβ$, and for positive $μ$ that was previously disfavoured. As a result, the allowed parameter space for neutralino dark matter increases for positive $μ$, particularly for areas with resonant enhancement of the neutralino relic density. On the contrary, a negative $μ$ is not easily compatible with large lepton mixing and Dirac neutrino Yukawa couplings, and the WMAP allowed parameter space is in this case strongly constrained.

hep-ph↗

arXiv2008

Search for Tau Flavour Violation at the LHC

We explore the prospects for searches at the LHC for sparticle decays that violate $τ$ lepton number, in the light of neutrino oscillation data and the seesaw model for neutrino masses and mixing. We analyse the theoretical and phenomenological conditions required for tau flavour violation to be observable in χ_2 \to χ+ τ^\pm μ^\mp decays, for cosmologically interesting values of the relic neutralino LSP density. We study the relevant supersymmetric parameter space in the context of the Constrained Minimal Supersymmetric Extension of the Standard Model (CMSSM) and in SU(5) extensions of the theory. We pay particular attention to the possible signals from hadronic tau decays, that we analyse using PYTHIA event simulation. We find that a signal for τflavour-violating χ_2 decays may be observable if the branching ratio exceeds about 10%. This may be compatible with the existing upper limit on τ\to μγdecays if there is mixing between right-handed sleptons, as could be induced in non-minimal SU(5) GUTs.

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