D. Restrepo - University de Antioquia

D. Restrepo
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D. Restrepo
University de Antioquia

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High Energy Physics - Phenomenology (44)
High Energy Physics - Experiment (5)
Mathematics - Analysis of PDEs (1)
High Energy Astrophysical Phenomena (1)

Publications Authored By D. Restrepo

We study a left right (LR) extension of the Standard Model (SM) where the Dark Matter (DM) candidate is composed of a set of fermionic Majorana triplets. The DM is stabilized by a remnant $Z_{2}$ symmetry from the breaking of the LR group to the SM. Two simple scenarios where the DM particles plus a certain set of extra fields lead to gauge coupling unification with a low LR scale are explored. Read More

We analyze the present bounds of a scotogenic model, the Radiative Type III Seesaw (RSIII), in which an additional scalar doublet and at least two fermion triplets of $SU(2)_L$ are added to the Standard Model (SM). In the RSIII the new physics (NP) sector is odd under an exact global $Z_2$ symmetry. This symmetry guaranties that the lightest NP neutral particle is stable, providing a natural dark matter (DM) candidate, and leads to naturally suppressed neutrino masses generated by a one-loop realization of an effective Weinberg operator. Read More

The singlet-doublet fermion dark matter model (SDFDM) provides a good DM candidate as well as the possibility of generating neutrino masses radiatively. The search and identification of DM requires the combined effort of both indirect and direct DM detection experiments in addition to the LHC. Remarkably, an excess of GeV gamma rays from the Galactic Center (GCE) has been measured with the \textit{Fermi} Large Area Telescope (LAT) which appears to be robust with respect to changes in the diffuse galactic background modeling. Read More

We study a realization of the topology of the Zee model for the generation of neutrino masses at one-loop with a minimal set of vector-like fermions. After imposing an exact $Z_2$ symmetry to avoid tree-level Higgs-mediated flavor changing neutral currents, one dark matter candidate is obtained from the subjacent inert doublet model, but with the presence of new co-annihilating particles. We show that the model is consistent with the constraints coming from lepton flavor violation processes, oblique parameters, dark matter and neutrino oscillation data. Read More

The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region $1.8-2.2$ TeV. Read More

We construct and analyze nonsupersymmetric SO(10) standard model extensions which explain dark matter (DM) through the fermionic Higgs portal. In these SO(10)-based models the DM particle is naturally stable since a $Z_2$ discrete symmetry, the matter parity, is left at the end of the symmetry breaking chain to the standard model. Potentially realistic models contain the $\bf{10}$ and $\bf{45}$ fermionic representations from which a neutralino-like mass matrix with arbitrary mixings can be obtained. Read More

This work discusses the homogenization analysis for diffusion processes on scale-free metric graphs, using weak variational formulations. The oscillations of the diffusion coefficient along the edges of a metric graph induce internal singularities in the global system which, together with the high complexity of large networks constitute significant difficulties in the direct analysis of the problem. At the same time, these facts also suggest homogenization as a viable approach for modeling the global behavior of the problem. Read More

When the singlet-doublet fermion dark matter model is extended with additional $Z_2$--odd real singlet scalars, neutrino masses and mixings can be generated at one-loop level. In this work, we discuss the salient features arising from the combination of the two resulting simplified dark matter models. When the $Z_2$-lightest odd particle is a scalar singlet, $\operatorname{Br}(\mu\to e \gamma)$ could be measurable provided that the singlet-doublet fermion mixing is small enough. Read More

We provide a list of particle physics models at the TeV-scale that are compatible with neutrino masses and dark matter. In these models, the Standard Model particle content is extended with a small number (\leq 4) of scalar and fermion fields transforming as singlets, doublets or triplets under SU(2), and neutrino masses are generated radiatively via 1-loop diagrams. The dark matter candidates are stabilized by a Z_2 symmetry and are in general mixtures of the neutral components of such new multiplets. Read More

Supersymmetric scenarios with R-parity conservation are becoming very constrained due to the lack of missing energy signals, thus motivating those scenarios with R-parity violation. In view of this, we consider a supersymmetric model with R-parity violation and extended by an anomalous horizontal $U(1)_H$ symmetry, where a self-consistent framework with baryon-number violation is achieved along with a proper supression for lepton number violating dimension-5 operators in order to keep a proton decay safe. With the introduction of right-handed neutrinos both Dirac and Majorana masses can be accommodated within this model. Read More

By extending the Standard Model with three right-handed neutrinos (N_i) and a second Higgs doublet (H_2), odd under a Z_2 symmetry, it is possible to explain non-zero neutrino masses and to account for the dark matter. We consider the case where the dark matter is a scalar and study its coannihilations with the right-handed neutrinos. These coannihilations tend to increase, rather than reduce, the dark matter density and they modify in a significant way the viable parameter space of the model. Read More

In bilinear R-parity violation (BRpV), in which the superpotential includes a bilinear term between the lepton doublet and the up-type Higgs superfields, a sneutrino LSP can decay into pairs of heavy standard model states: W's, Z's, tops or Higgs bosons. These finals states can dominate over the traditionally considered bottom pair final state. This would lead to unique and novel supersymmetric signals with each supersymmetric event possibly producing two pairs of these heavy standard model fields. Read More

Motivated by the upcoming Higgs analyzes we investigate the importance of the complementarity of the Higgs boson chase on the low mass WIMP search in direct detection experiments and the gamma-ray emission from the Galactic Center measured by the Fermi-LAT telescope in the context of the $SU(3)_c\otimes SU(3)_L\otimes U(1)_N$. We obtain the relic abundance, thermal cross section, the WIMP-nucleon cross section in the low mass regime and network them with the branching ratios of the Higgs boson in the model. We conclude that the Higgs boson search has a profound connection to the dark matter problem in our model, in particular for the case that ($M_{WIMP} < 60$ GeV) the BR($H \rightarrow 2$ WIMPs) $\gtrsim 90%$. Read More

Supersymmetric models with bilinear R-parity violation (BRPV) can account for the observed neutrino masses and mixing parameters indicated by neutrino oscillation data. We consider minimal supergravity versions of BRPV where the lightest supersymmetric particle (LSP) is a neutralino. This is unstable, with a large enough decay length to be detected at the CERN Large Hadron Collider (LHC). Read More

The most commonly used parameterizations of the Yukawa couplings in the two Higgs doublet model are revisited. Their similitudes and differences are emphasized and relations between the different notations used in the literature are derived. Using these relations, bounds on the space of parameters of the charged Higgs sector of the two Higgs doublet model are obtained. Read More

Bilinear R-parity violation provides an attractive origin for neutrino masses and mixings. In such schemes the gravitino is a viable decaying dark matter particle whose R-parity violating decays lead to monochromatic photons with rates accessible to astrophysical observations. We determine the parameter region allowed by gamma-ray line searches, dark matter relic abundance and neutrino oscillation data, obtaining a limit on the gravitino mass $m_{\tilde G} \lsim$ 1-10 GeV corresponding to a relatively low reheat temperature $T_R \lsim$ few $\times 10^7-10^8$ GeV. Read More

We present a $SU(5)\times U(1)_F$ supersymmetric model for neutrino masses and mixings that implements the seesaw mechanism by means of the heavy SU(2) singlets and triplets states contained in three adjoints of SU(5). We discuss how Abelian $U(1)_F$ symmetries can naturally yield non-hierarchical light neutrinos even when the heavy states are strongly hierarchical, and how it can also ensure that $R$--parity arises as an exact accidental symmetry. By assigning two flavons that break $U(1)_F$ to the adjoint representation of SU(5) and assuming universality for all the fundamental couplings, the coefficients of the effective Yukawa and Majorana mass operators become calculable in terms of group theoretical quantities. Read More

It was recently pointed out that in supersymmetric scenarios with gravitino dark matter and bilinear R-parity violation, gravitinos with masses below Mw typically decay with a sizable branching ratio into the 3-body final states W^*+lepton and Z^*+neutrino. In this paper we study the indirect detection signatures of gravitino dark matter including such final states. First, we obtain the gamma ray spectrum from gravitino decays, which features a monochromatic contribution from the decay into photon+neutrino and a continuum contribution from the three-body decays. Read More

The lightest supersymmetric particle may decay with branching ratios that correlate with neutrino oscillation parameters. In this case the CERN Large Hadron Collider (LHC) has the potential to probe the atmospheric neutrino mixing angle with sensitivity competitive to its low-energy determination by underground experiments. Under realistic detection assumptions, we identify the necessary conditions for the experiments at CERN's LHC to probe the simplest scenario for neutrino masses induced by minimal supergravity with bilinear R parity violation. Read More

The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Read More

In supersymmetric models extended with an anomalous $U(1)_H$ different R-parity violating couplings can yield an unstable neutralino. We show that in this context astrophysical and cosmological constraints on neutralino decaying dark matter forbid bilinear R-parity breaking neutralino decays and lead to a class of purely trilinear R-parity violating scenarios in which the neutralino is stable on cosmological scales. We have found that among the resulting models some of them become suitable to explain the observed anomalies in cosmic-ray electron/positron fluxes. Read More

Affiliations: 1Unesp, Guaratingueta, 2U. Sao Paulo, 3FSA, Santo Andre, 4U. de Antioquia, 5U. de Valencia, IFIC

The study of displaced vertices containing two b--jets may provide a double discovery at the Large Hadron Collider (LHC): we show how it may not only reveal evidence for supersymmetry, but also provide a way to uncover the Higgs boson necessary in the formulation of the electroweak theory in a large region of the parameter space. We quantify this explicitly using the simplest minimal supergravity model with bilinear breaking of R-parity, which accounts for the observed pattern of neutrino masses and mixings seen in neutrino oscillation experiments. Read More

Supersymmetric theories with bilinear R-parity violation can give rise to the observed neutrino masses and mixings. One important feature of such models is that the lightest supersymmetric particle might have a sufficiently large lifetime to give rise to detached vertices. Working in the framework of supergravity models we analyze the potential of the LHCb experiment to search for supersymmetric models exhibiting bilinear R-parity violation. Read More

Extending the standard model with three right-handed neutrinos ($N_k$) and a second Higgs doublet ($\eta$), odd under the discrete parity symmetry $Z_2$, Majorana neutrino masses can be generated at 1-loop order. In the resulting model, the lightest stable particle, either a boson or a fermion, might be a dark matter candidate. Here we assume a specific mass spectrum ($M_1\ll M_2 < M_3 < m_\eta$) and derive its consequences for dark matter and collider phenomenology. Read More

In supersymmetric models the lightest Higgs boson may decay with a sizable branching ratio into a pair of light neutralinos. We analyze such decays within the context of the minimal supersymmetric standard model with R-parity violation, where the neutralino itself is unstable and decays into Standard Model fermions. We show that the R-parity violating couplings induce novel Higgs decay signals that might facilitate the discovery of the Higgs boson at colliders. Read More


This review presents flavour related issues in the production and decays of heavy states at LHC, both from the experimental side and from the theoretical side. We review top quark physics and discuss flavour aspects of several extensions of the Standard Model, such as supersymmetry, little Higgs model or models with extra dimensions. This includes discovery aspects as well as measurement of several properties of these heavy states. Read More

We study the collider phenomenology of bilinear R-parity violating supergravity, the simplest effective model for supersymmetric neutrino masses accounting for the current neutrino oscillation data. At the CERN Large Hadron Collider the center-of-mass energy will be high enough to probe directly these models through the search for the superpartners of the Standard Model (SM) particles. We analyze the impact of R-parity violation on the canonical supersymmetry searches - that is, we examine how the decay of the lightest supersymmetric particle (LSP) via bilinear R-parity violating interactions degrades the average expected missing momentum of the reactions and show how this diminishes the reach in the 'usual' channels for supersymmetry searches. Read More

We consider the version of the Zee model where both Higgs doublets couple to leptons. Within this framework we study charged Higgs decays. We focus on a model with minimal number of parameters consistent with experimental neutrino data. Read More

In models with gauge mediated supersymmetry breaking the gravitino is the lightest supersymmetric particle. If R-parity is violated the gravitino decays, but with a half-live far exceeding the age of the universe and thus is, in principle, a candidate for the dark matter. We consider the decays of the next-to-lightest supersymmetric particle, assumed to be the neutralino. Read More

Supersymmetric extensions of the standard model exhibiting bilinear R-parity violation can generate naturally the observed neutrino mass spectrum as well mixings. One interesting feature of these scenarios is that the lightest supersymmetric particle (LSP) is unstable, with several of its decay properties predicted in terms of neutrino mixing angles. A smoking gun of this model in colliders is the presence of displaced vertices due to LSP decays in large parts of the parameter space. Read More

We analyze the production of multileptons in the simplest supergravity model with bilinear violation of R parity at the Fermilab Tevatron. Despite the small R-parity violating couplings needed to generate the neutrino masses indicated by current atmospheric neutrino data, the lightest supersymmetric particle is unstable and can decay inside the detector. This leads to a phenomenology quite distinct from that of the R-parity conserving scenario. Read More

The Higgs potential and the mass spectrum of the N=1 supersymmetric extension of a recently proposed one-family model based on the local gauge group $SU(3)_c \otimes SU(3)_L \otimes U(1)_X$, which is a subgroup of the electroweak-strong unification group $E_6$, is analyzed. In this model the slepton multiplets play the role of the Higgs scalars and no Higgsinos are needed, with the consequence that the sneutrino, the selectron and six other sleptons play the role of the Goldstone bosons. We show how the $\mu$ problem is successfully addressed in the context of this model which also predicts the existence of a light CP-odd scalar. Read More

A Majorana neutrino is characterized by just one flavor diagonal electromagnetic form factor: the anapole moment, that in the static limit corresponds to the axial vector charge radius . Experimental information on this quantity is scarce, especially in the case of the tau neutrino. We present a comprehensive analysis of the available data on the single photon production process $e^+ e^- -> \nu \bar\nu \gamma$ off Z-resonance, and we discuss the constraints that these measurements can set on for the tau neutrino. Read More

The straightforward supersymmetrization of the Standard Model (SM) results in a phenomenologically inconsistent theory in which Baryon number ($B$) and Lepton number ($L$) are violated by dimension 4 operators, inducing fast proton decay. Proton stability allows only for separate $L$ or $B$ violation and, if neutrinos are massive Majorana particles, $L$ violating terms must be present. In this thesis I will study a Supersymmetric Standard Model (SSM) realization with $B$ conservation and minimal $L$ violation. Read More

We discuss the phenomenology of the lightest stop in models where R-parity is broken by bilinear superpotential terms. In this class of models we consider scenarios where the R-parity breaking two-body decay ~t_1->\tau^+b competes with the leading three-body decays such as ~t_1->W^+b~\chi^0_1. We demonstrate that the R-parity violating decay can be sizable and in some parts of the parameter space even the dominant one. Read More

We study extensions of supersymmetric models without R-parity which include an anomalous U(1)_H horizontal symmetry. Bilinear R-parity violating terms induce a neutrino mass at tree level of approximately $(\theta^2)^\delta$ eV where $\theta\approx 0.22$ is the U(1)_H breaking parameter and $\delta$ is an integer number that depends on the horizontal charges of the leptons. Read More

We discuss the phenomenology of the lightest neutralino in models where an effective bilinear term in the superpotential parametrizes the explicit breaking of R-parity. We consider supergravity scenarios where the lightest supersymmetric particle (LSP) is the lightest neutralino and which can be explored at LEP2. We present a detailed study of the LSP decay properties and general features of the corresponding signals expected at LEP2. Read More

We discuss the phenomenology of the lightest stops in models where R-parity is broken by bilinear terms. In this class of models we consider scenarios where the R-parity breaking two-body decay stop_1 -> tau + b competes with the leading three-body decays stop_1 -> W^+ + b + neutralino_1, H^+ + b + neutralino_1, b slepton^+_i neutrino_l, b sneutrino_l l^+ (l=e, mu, tau). We demonstrate that the R-parity violating decay can be the dominant one. Read More

A non anomalous horizontal $U(1)_H$ gauge symmetry can be responsible for the fermion mass hierarchies of the minimal supersymmetric standard model. Imposing the consistency conditions for the absence of gauge anomalies yields the following results: i) unification of leptons and down-type quarks Yukawa couplings is allowed at most for two generations. ii) The $\mu$ term is necessarily somewhat below the supersymmetry breaking scale. Read More

We study the decays of the lightest top squark in supergravity models with and without R-parity. Using the simplest model with an effective explicit bilinear breaking of R-parity and radiative electroweak symmetry breaking we show that, below the threshold for decays into charginos $\tilde t_1\to c\chi^+_1$, the lightest stop decays mainly into third generation fermions, $\tilde t_1\to b\tau$ instead of the R-parity conserving mode $\tilde t_1\to c\chi^0_1$, even for tiny tau--neutrino mass values. Moreover we show that, even above the threshold for decays into charginos, the decay $\tilde t_1\to b\tau$ may be dominant. Read More

We present an outlook for possible discovery of supersymmetry with broken R-parity at Run II of the Tevatron. We first present a review of the literature and an update of the experimental bounds. In turn we then discuss the following processes: 1. Read More

We study unconventional decays of the top-quark and the top-squark in the framework of SUSY models with broken R-parity. The model under study is the MSSM with an additional bilinear term that breaks R-parity. In this model the top-squark behaves similar to a third generation leptoquark. Read More

We perform a careful study of the neutral scalar sector of a model which includes a singlet, a doublet, and a triplet scalar field under $SU(2)$. This model is motivated by neutrino physics, since it is simply the most general version of the seesaw model of neutrino mass generation through spontaneous violation of lepton number. The neutral Higgs sector contains three CP-even and one massive CP-odd Higgs boson $A$, in addition to the massless CP-odd majoron $J$. Read More

Affiliations: 1IFIC, Uni. Valencia-CSIC, 2IFIC, Uni. Valencia-CSIC, 3IFIC, Uni. Valencia-CSIC, 4IFIC, Uni. Valencia-CSIC

In the simplest scheme for neutrino masses invoking a triplet of Higgs scalars there are two CP-even neutral Higgs bosons $H_i$ (i=1,2) and one massive pseudoscalar $A$. For some choices of parameters, the lightest $H_1$ may be lighter than the Standard Model Higgs boson. If the smallness of neutrino mass is due to the small value of the triplet expectation value, as expected in a seesaw scheme, the Higgs bosons may decay dominantly to the invisible neutrino channel. Read More

We present the realization of a mechanism that generates all mases and mixing angles by using the top quark as seed in the context of an anomaly free abelian extension of the standard model. Read More