arXiv subjects

Víctor Martín Lozano

Publications and source records attributed to Víctor Martín Lozano.

6 recordsLinked to original sources

arXiv2026

Searches for heavy neutral lepton decays at spallation neutron sources

Spallation neutron sources provide intense neutrino fluxes from pion and muon decay at rest, with energies in the few tens of MeV range. Experiments such as COHERENT exploit these fluxes to detect neutrinos via coherent elastic neutrino$\unicode{x2013}$nucleus scattering (CE$ν$NS). However, these facilities also offer a unique opportunity to produce and probe light, secluded, or weakly$\unicode{x2013}$coupled particles. In this work, we investigate the sensitivity of the Spallation Neutron Source at the Oak Ridge National Laboratory to heavy neutral leptons (HNLs) in the MeV$\unicode{x2013}$GeV mass range, as a case study. We consider HNL production in pion and muon decays at rest, followed by their decay into visible Standard Model particles within the detector volume. We analyze a range of current and proposed COHERENT detectors and evaluate their sensitivity to HNL mixing with muon and electron neutrinos, as well as to scenarios with mixed mixing. We find that existing detectors can set meaningful constraints, particularly for muon$\unicode{x2013}$flavor mixing, while future ton$\unicode{x2013}$scale realizations can probe previously unexplored regions of the parameter space. We further discuss prospects at other relevant spallation source facilities and comment on the complementarity of their projected sensitivities. Our results demonstrate that CE$ν$NS experiments at spallation neutron sources provide a powerful, complementary avenue for new physics searches beyond their primary role as neutrino detectors.

hep-ph↗

arXiv2025

Neutrino nonstandard interactions: Confronting COHERENT and LHC data

We study the complementarity between COHERENT and LHC searches in testing neutrino nonstandard interactions (NSIs) through the completion of the effective field theory approach within a $Z'$ simplified model. Our results show that LHC bounds are strongly dependent on the $Z'$ mass, with relatively large masses excluding regions in the parameter space that are allowed by COHERENT data and its future expectations. We demonstrate that the combination of low- and high-energy experiments results in a viable approach to break NSI degeneracies within the context of simplified models.

hep-ph↗

arXiv2025

Neutrino fog in the light dark sector: the role of isospin violation

Dark matter (DM) direct detection is now standing at an interesting juncture, where the Standard Model (SM) neutrino background and the upper bound on the DM signal cross section are starting to overlap in the DM mass region around 10 GeV. The neutrino floor, which defines the extent of the neutrino background, can be modified in different Beyond Standard Model (BSM) setups. We work in a simple BSM dark sector extension of the SM visible sector, where isospin-violating interactions occur naturally. In this model, both DM and neutrinos have, in general, isospin-violating (IV) interactions with nuclei, through a newly added local U(1) gauge boson $Z^{\prime}$. Depending on the choice of the model parameters, the coherent elastic neutrino-nucleus scattering (CE$\mathrmν$NS) cross section can either increase or decrease, shifting up or down the neutrino floor in the parameter space. The same is true for the DM experimental upper bound, whose change is driven exclusively by the IV parameter $f_n/f_p$. Several scenarios are constructed, based on the interplay between the two regions and the allowed parameter space left between them, and discussed. The potential observation of solar neutrinos in DM direct detection experiments is also discussed in the context of our framework.

hep-ph↗

arXiv2025

Exploring Dimuon Higgs Decay in an Extended Scotogenic Model

We investigate the dimuon Higgs decay $h \to μ^+μ^-$ in the context of an extended Scotogenic model. The model introduces a singlet complex scalar in addition to the standard Scotogenic scalar doublet and singlet fermions, charged under a dark $\mathbb{Z}_2$ symmetry. By exploring the one-loop contributions, we show that the model allows for sizable deviations in the Higgs dimuon decay rate, quantified by the quotient $R_{μμ} = \text{Br}(h \to μ^+μ^-)/\text{Br}(h \to μ^+μ^-)_{\text{SM}}$. Crucially, these deviations comply with experimental limits, including those on $\text{Br}(μ^{+} \to e^{+}γ)$ and $\text{Br}(h \to γγ)$. Such deviations can be tested and constrained by future precision measurements at the LHC.

hep-ph↗

arXiv2023

The ABC of RPV: Classification of R-Parity Violating Signatures at the LHC for Small Couplings

We perform a classification of all potential supersymmetric $R$-parity violating signatures at the LHC to address the question: are existing bounds on supersymmetric models robust, or are there still signatures not covered by existing searches, allowing LHC-scale supersymmetry to be hiding? We analyze all possible scenarios with one dominant RPV trilinear coupling at a time, allowing for arbitrary LSPs and mass spectra. We consider direct production of the LSP, as well as production via gauge-cascades, and find 6 different experimental signatures for the $LL\bar E$-case, 6 for the $LQ\bar D$-case, and 5 for the $\bar U\bar D\bar D$-case; together these provide complete coverage of the RPV-MSSM landscape. This set of signatures is confronted with the existing searches by \texttt{ATLAS} and \texttt{CMS}. We find all signatures have been covered at the LHC, although not at the sensitivity level needed to probe the direct production of all LSP types. For the case of a dominant $LL\bar E$-operator, we use \texttt{CheckMATE} to quantify the current lower bounds on the supersymmetric masses and find the limits to be comparable to or better than the $R$-parity conserving case. Our treatment can be easily extended to scenarios with more than one non-zero RPV coupling.

hep-ph↗

arXiv2022

A method for approximating optimal statistical significances with machine-learned likelihoods

Machine-learning techniques have become fundamental in high-energy physics and, for new physics searches, it is crucial to know their performance in terms of experimental sensitivity, understood as the statistical significance of the signal-plus-background hypothesis over the background-only one. We present here a simple method that combines the power of current machine-learning techniques to face high-dimensional data with the likelihood-based inference tests used in traditional analyses, which allows us to estimate the sensitivity for both discovery and exclusion limits through a single parameter of interest, the signal strength. Based on supervised learning techniques, it can perform well also with high-dimensional data, when traditional techniques cannot. We apply the method to a toy model first, so we can explore its potential, and then to a LHC study of new physics particles in dijet final states. Considering as the optimal statistical significance the one we would obtain if the true generative functions were known, we show that our method provides a better approximation than the usual naive counting experimental results.

hep-ph↗