arXiv subjects

José Wudka

Publications and source records attributed to José Wudka.

9 recordsLinked to original sources

arXiv2020

Effective field theory analysis of dark matter-standard model interactions with spin one mediators

We analyze interactions between dark matter and standard model particles with spin one mediators in an effective field theory framework. In this paper, we are considering dark particles masses in the range from a few MeV to the mass of the $Z$ boson. We use bounds from different experiments: $Z$ invisible decay width, relic density, direct detection experiments, and indirect detection limits from the search of gamma-ray emissions and positron fluxes. We obtain solutions corresponding to operators with antisymmetric tensor mediators that fulfill all those requirements within our approach.

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arXiv2016

Dimension Seven Operators in Standard Model with Right handed Neutrinos

In this article we consider the Standard Model extended by a number of (light) right-handed neutrinos, and assume the presence of some heavy physics that cannot be directly produced, but can be probed by its low-energy effective interactions. Within this scenario, we obtain all the gauge-invariant dimension-seven effective operators, and determine whether each of the operators can be generated at tree-level by the heavy physics, or whether it is necessarily loop generated. We then use the tree-generated operators, including those containing right-handed neutrinos, to put limits on the scale of new physics $ Λ$ using low-energy measurements. We also study the production of same-sign dileptons at the Large Hadron Collider (LHC) and determine the constraints on the heavy physics that can be derived form existing data, as well as the reach in probing $ Λ$ expected from future runs of this collider.

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arXiv2016

Dark matter and the neutrino portal paradigm

A simple extension of the Standard Model (SM) that provides an explicit realization of the dark-matter (DM) neutrino-portal paradigm is presented. The leading interactions between the dark sector, containing scalars and relic fermions, and the SM involve neutrinos. This model meets all observational constraints.

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arXiv2016

A realistic model for Dark Matter interactions in the neutrino portal paradigm

We discuss a simple extension of the Standard Model (SM) that provides an explicit realization of the dark-matter (DM) neutrino-portal paradigm. The dark sector is composed of a scalar $ Φ$ and a Dirac fermion $ Ψ$, with the latter assumed to be lighter than the former. These particles interact with the SM through the exchange of a set of heavy Dirac fermion mediators that are neutral under all local SM symmetries, and also under the dark-sector symmetry that stabilizes the $ Ψ$ against decay. We show that this model can accommodate all experimental and observational constraints provided the DM mass is below $\sim 35\, \gev $ or is in a resonant region of the Higgs or $Z$ boson. We also show that if the dark scalar and dark fermion are almost degenerate in mass, heavier DM fermions are not excluded. We note that in this scenario DM annihilation in the cores of astrophysical objects and the galactic halo produces a monochromatic neutrino beam of energy $ \mfe $, which provides a clear signature for this paradigm. Other experimental signatures are also discussed.

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arXiv2013

The Bases of Effective Field Theories

With reference to the equivalence theorem, we discuss the selection of basis operators for effective field theories in general. The equivalence relation can be used to partition operators into equivalence classes, from which inequivalent basis operators are selected. These classes can also be identified as containing Potential-Tree-Generated (PTG) operators, Loop-Generated (LG) operators, or both, independently of the specific dynamics of the underlying extended models, so long as it is perturbatively decoupling. For an equivalence class containing both, we argue that the basis operator should be chosen from among the PTG operators, because they may have the largest coefficients. We apply this classification scheme to dimension-six operators in an illustrative Yukawa model as well in the Standard Model (SM). We show that the basis chosen by Grzadkowski {\it et. al.} \cite{Grzadkowski:2010es} for the SM satisfies this criterion. In this light, we also revisit and verify our earlier result \cite{Arzt:1994gp} that the dimension-six corrections to the triple-gauge-boson couplings only arise from LG operators, so the magnitude of the coefficients should only be a few parts per thousand of the SM gauge coupling if BSM dynamics respects decoupling. The same is true of the quartic-gauge-boson couplings.

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arXiv2013

Pionic Dark Matter

We study a phenomenological model where the lightest dark matter (DM) particles are the pseudo-Goldstone excitations associated with a spontaneously broken symmetry, and transforming linearly with respect to an unbroken group H. For definiteness we take H = SU(N) and assume the Goldstone particles are bosons; in parallel with QCD, we refer to these particles as dark-matter pions. This scenario is in contrast to the common assumption that DM fields transform linearly under the full symmetry of the model. We illustrate the formalism by treating in detail the case of H = SU(2), in particular we calculate all the interactions relevant for the Boltzmann equations, which we solve numerically; we also derive approximate analytic solutions and show their consistency with the numerical results. We then compare the results with the constraints derived from the cold DM and direct detection experiments and derive the corresponding restrictions on the model parameters.

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arXiv2010

Constraints on realistic Gauge-Higgs unified models

We investigate the general group structure of gauge-Higgs unified models. We find that a given embedding of the \sm\ gauge group will imply the presence of additional light vectors, except for a small set of special cases, which we determine; the arguments presented are independent of the compactification scheme. For this set of models we then find those that can both accommodate quarks and have a vanishing oblique T-parameter at tree-level. We show that none of the resulting models can have $|\sw| \sim1/2 $ (the sine of the weak-mixing angle) at tree-level and briefly discuss possible solutions to this problem.

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arXiv2009

A model for right-handed neutrino magnetic moments

A simple extension of the Standard Model providing Majorana magnetic moments to right-handed neutrinos is presented. The model contains, in addition to the Standard Model particles and right-handed neutrinos, just a singly charged scalar and a vector-like charged fermion. The phenomenology of the model is analysed and its implications in cosmology, astrophysics and lepton flavour violating processes are extracted. If light enough, the charged particles responsible for the right-handed neutrino magnetic moments could copiously be produced at the LHC.

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arXiv1996

Neutrino Oscillations in Strong Gravitational Fields

Neutrino oscillations in the presence of strong gravitational fields are studied. We look at very high energy neutrinos ($\sim $1 TeV) emanating from Active Galactic Nuclei (AGN). It is observed that spin flavor resonant transitions of such neutrinos may occur in the vicinity of AGN due to {\it gravitational} effects and due to the presence of a large magnetic field ($\sim $1 Tesla). A point to note is that matter effects (normal MSW transitions) become negligible in comparison o gravitational effects in our scenario.

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