arXiv subjects

N. Rojas

Publications and source records attributed to N. Rojas.

6 recordsLinked to original sources

arXiv2020

Majoron Dark Matter From a Spontaneous Inverse Seesaw Model

The generation of neutrino masses by inverse seesaw mechanisms has advantages over other seesaw models since the potential new physics can be produced at the TeV scale. We propose a model that generates the inverse seesaw mechanism via spontaneous breaking of the lepton number, by extending the Standard Model with two scalar singlets and two fermion singlets both charged under lepton number. The model gives rise to a massless Majoron and a massive pseudoscalar which we dub as massive Majoron, which corresponds to the Nambu-Goldstone boson of the breaking of lepton number. If the massive Majoron is stable in cosmological time, it might play the role of a suitable Dark Matter candidate. In this scenario, we examine the model with a massive Majoron in the keV range. In this regime, its decay mode to neutrinos is sensitive to the ratio between the vevs of the new scalars ($ω$), and it vanishes when $ ω\simeq \sqrt{2/3}$, which is valid within a large region in the parameter space. On the other hand, the cosmological lifetime for the Dark Matter candidate places constraints on its mass via scalar decays. In addition, simple mechanisms that explain the Dark Matter relic abundance within this context and plausible modifications to the proposed setup are briefly discussed.

hep-ph↗

arXiv2019

CP violating effects in coherent elastic neutrino-nucleus scattering processes

The presence of new neutrino-quark interactions can enhance, deplete or distort the coherent elastic neutrino-nucleus scattering (CEvNS) event rate. The new interactions may involve CP violating phases that can potentially affect these features. Assuming light vector mediators, we study the effects of CP violation on the CEvNS process in the COHERENT sodium-iodine, liquid argon and germanium detectors. We identify a region in parameter space for which the event rate always involves a dip and another one for which this is never the case. We show that the presence of a dip in the event rate spectrum can be used to constraint CP violating effects, in such a way that the larger the detector volume the tighter the constraints. Furthermore, it allows the reconstruction of the effective coupling responsible for the signal with an uncertainty determined by recoil energy resolution. In the region where no dip is present, we find that CP violating parameters can mimic the Standard Model CEvNS prediction or spectra induced by real parameters. We point out that the interpretation of CEvNS data in terms of a light vector mediator should take into account possible CP violating effects. Finally, we stress that our results are qualitatively applicable for CEvNS induced by solar or reactor neutrinos. Thus, the CP violating effects discussed here and their consequences should be taken into account as well in the analysis of data from multi-ton dark matter detectors or experiments such as CONUS, $ν$-cleus or CONNIE.

hep-ph↗

arXiv2018

COHERENT analysis of neutrino generalized interactions

Effective neutrino-quark generalized interactions are entirely determined by Lorentz invariance, so they include all possible four-fermion non derivative Lorentz structures. They contain neutrino-quark non-standard interactions as a subset, but span over a larger set that involves effective scalar, pseudoscalar, axial and tensor operators. Using recent COHERENT data, we derive constraints on the corresponding couplings by considering scalar, vector and tensor quark currents and assuming no lepton flavor dependence. We allow for mixed neutrino-quark Lorentz couplings and consider two types of scenarios in which: (i) one interaction at the nuclear level is present at a time, (ii) two interactions are simultaneously present. For scenarios (i) our findings show that scalar interactions are the most severely constrained, in particular for pseudoscalar-scalar neutrino-quark couplings. In contrast, tensor and non-standard vector interactions still enable for sizable effective parameters. We find as well that an extra vector interaction improves the data fit when compared with the result derived assuming only the standard model contribution. In scenarios (ii) the presence of two interactions relaxes the bounds and opens regions in parameter space that are otherwise closed, with the effect being more pronounced in the scalar-vector and scalar-tensor cases. We point out that barring the vector case, our results represent the most stringent bounds on effective neutrino-quark generalized interactions for mediator masses of order $\sim 1\,$GeV. They hold as well for larger mediator masses, case in which they should be compared with limits from neutrino deep-inelastic scattering data.

hep-ph↗

arXiv2017

Neutrino non-standard interactions and dark matter searches with multi-ton scale detectors

Future dark matter (DM) direct detection searches will be subject to irreducible neutrino backgrounds that will challenge the identification of an actual WIMP signal in experiments without directionality sensitivity. We study the impact of neutrino-quark non-standard interactions (NSI) on this background, assuming the constraints from neutrino oscillations and the recent COHERENT experiment data, which are relevant for NSI mediated by light mediators, $m_{\rm med} \lesssim{\cal O}$(GeV). We calculate the expected number of neutrino-nucleus elastic scattering events in a Xe-based ton-size dark matter detector, including solar neutrino fluxes from the $pp$ chain and CNO cycle as well as sub-GeV atmospheric fluxes and taking into account NSI effects in both propagation and detection. We find that sizable deviations from the standard model expectation are possible, but are more pronounced for flavor-diagonal couplings, in particular for electron neutrinos. We show that neutrino NSI can enhance or deplete the neutrino-nucleus event rate, which may impact DM searches in multi-ton detectors.

hep-ph↗

arXiv2013

WIMP dark matter as radiative neutrino mass messenger

The minimal seesaw extension of the Standard SU(3) x SU(2) x U(1) Model requires two electroweak singlet fermions in order to accommodate the neutrino oscillation parameters at tree level. Here we consider a next to minimal extension where light neutrino masses are generated radiatively by two electroweak fermions: one singlet and one triplet under SU(2). These should be odd under a parity symmetry and their mixing gives rise to a stable weakly interactive massive particle (WIMP) dark matter candidate. For mass in the GeV-TeV range, it reproduces the correct relic density, and provides an observable signal in nuclear recoil direct detection experiments. The fermion triplet component of the dark matter has gauge interactions, making it also detectable at present and near future collider experiments.

hep-ph↗

arXiv2008

Faithful representations of minimal dimension of current Heisenberg Lie algebras

Given a Lie algebra $\mathfrak{g}$ over a field of characteristic zero $k$, let $μ(\mathfrak{g})=\min\{\dim π: π\text{is a faithful representation of}\mathfrak{g}\}$. Let $\mathfrak{h}_{m}$ be the Heisenberg Lie algebra of dimension $2m+1$ over $k$ and let $k[t]$ be the polynomial algebra in one variable. Given $m\in\mathbb{N}$ and $p\in k[t]$, let $\mathfrak{h}_{m,p}=\mathfrak{h}_m\otimes k[t]/(p)$ be the current Lie algebra associated to $\mathfrak{h}_m$ and $k[t]/(p)$, where $(p)$ is the principal ideal in $k[t]$ generated by $p$. In this paper we prove that $ mu(\mathfrak{h}_{m,p}) = m °p + \left \lceil 2\sqrt{°p} \right\rceil$.

math.RT↗