arXiv subjects

G. Sanchez Garcia

Publications and source records attributed to G. Sanchez Garcia.

At least 19 recordsLinked to original sources

arXiv2026

Refined extraction of electroweak and nuclear parameters from germanium CE$ν$NS data

We present a combined analysis of recent CE$ν$NS data on germanium from two complementary experiments: COHERENT, which uses neutrinos from pion decay at rest, and CONUS+, which detects reactor antineutrinos. Exploiting the complementarity of these two datasets in a joint statistical analysis, we extract the germanium root-mean-square neutron radius and neutron skin with improved precision, disentangling spectral shape distortions from overall normalizations and reducing systematic uncertainties. We also determine the weak mixing angle at low momentum transfer, providing a test of the Standard Model in a less-explored kinematic regime. A key systematic uncertainty in CE$ν$NS ionization measurements is the nuclear quenching factor; we therefore present our results as a function of variations of the Lindhard model. For the nuclear form factor, we adopt the analytical Klein-Nystrand parametrization and benchmark it against predictions from the large-scale nuclear Shell Model, assessing the impact of nuclear structure uncertainties on our results. Our analysis demonstrates the power of combining datasets across different neutrino sources to maximize sensitivity to both nuclear and electroweak physics.

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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.

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arXiv2026

Constraints on Light Sterile Neutrinos and Scalar Non-Standard Interactions Using the First Reactor Antineutrino Oscillation Results at JUNO

Constraints on light sterile neutrinos and scalar non-standard neutrino interactions are obtained from the first reactor antineutrino results reported by JUNO. The analysis is based on a spectral $χ^2$ fit to the prompt-energy distribution corresponding to 59.1 days of data, including full three-flavor oscillations extended to a $3+1$ framework and effective scalar NSI contributions. The reactor flux is modeled using the Daya Bay measured spectrum, and systematic uncertainties are accounted for through a set of nuisance parameters describing reactor flux normalization, spectral shape, background normalization, and detector response. It is found that JUNO is already sensitive to light sterile neutrinos in the mass-splitting range $10^{-5} \lesssim Δm^2_{41}/\text{eV}^2 \lesssim 10^{-2}$, probing mixing amplitudes down to $\sin^2 2θ_{14} \sim \mathcal{O}(10^{-1})$. In addition, a constraint on the scalar NSI parameter $|η_{ee}| < \mathcal{O}(10^{-2})$ is obtained, with correlations with solar oscillation parameters. These results demonstrate the potential of JUNO to probe small deviations from the Standard Model resulting from new physics through precision measurements, with significant improvements expected as statistics and systematic control improve.

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arXiv2026

Sensitivity to sub-GeV dark matter in forthcoming spallation-source neutrino experiments

Sub-GeV thermal dark matter weakly interacting with the Standard Model through vector-portal mediators provides a well-motivated and predictive framework that remains challenging to probe with conventional direct detection experiments. Motivated by the rapid development of neutrino facilities based on spallation neutron sources, we study the sensitivity of future coherent elastic neutrino-nucleus scattering experiments to light dark matter produced in neutral pion decays. We consider scalar dark matter interactions mediated by two different vector portals, a generic dark photon and a baryophilic vector mediator. The neutral pion yield is calculated through a GEANT4 simulation and the results are compared with those obtained with the Sandford-Wang parametrization. We show that predictions based on either approach do not produce significant differences. Our results demonstrate that upcoming low-threshold neutrino detectors at the European Spallation Source (ESS), the Japan Proton Accelerator Research Complex (J-PARC) and the China Spallation Neutron Source (CSNS) may test regions in parameter space not yet explored, or be competitive with existing bounds. We point out that these facilities will strengthen the global experimental program searching for secluded sectors.

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arXiv2026

Generalized Neutrino Interactions: constraints and parametrizations

Generalized neutrino interactions (GNI) are emerging as a convenient framework for describing effective scalar, vector, and tensor interactions. Such interactions arise naturally from extensions of the Standard Model that aim to explain neutrino properties and their mass origin. In this paper, we carefully study the two more common parametrizations for GNI and how to relate them. This allows us to compare bounds obtained from CEvNS and deep-inelastic scattering under the same footing. In addition, we present the current bounds from CEvNS measurements by COHERENT and compare them to those obtained from deep inelastic scattering on the same level. Our results focus on neutrino-quark interactions, and illustrate the complementarity between experiments working at different scales for GNI, showing that scalar interactions are better constrained by low-energy experiments like COHERENT, while tensor interactions are robustly constrained from deep inelastic scattering.

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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.

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arXiv2025

Collider signatures of fermionic scotogenic dark matter

Weakly interacting massive particles (WIMPs) constitute a paradigm in the search for particle dark matter. In contrast to supersymmetry (SUSY), we explore the possibility that WIMP dark-matter acts as mediator of neutrino mass generation. We examine in detail the phenomenology of fermionic dark matter in the revamped (or singlet-triplet) scotogenic model and study its collider implications. Unlike SUSY WIMP dark-matter, collider searches for the Lightest Scotogenic Particle (LSP) at LHC/LHC-HL are strongly complementary to charged lepton flavor violation probes and dark matter studies.

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arXiv2024

Exploring the Sensitivity to Non-Standard Neutrino Interactions of NaI and Cryogenic CsI Detectors at the Spallation Neutron Source

After the first observation of coherent elastic neutrino-nucleus scattering (CE$ν$NS) by the COHERENT collaboration, many efforts are being made to improve the measurement of this process, making it possible to constrain new physics in the neutrino sector. In this paper, we study the sensitivity to non-standard interactions (NSIs) and generalized neutrino interactions (GNIs) of two experimental setups at the Spallation Neutron Source at Oak Ridge National Laboratory: a NaI detector with characteristics similar to the one that is currently being deployed there, and a cryogenic CsI detector proposed at the same facility. We show that a combined analysis of the data from these detectors, whose target nuclei have significantly different proton-to-neutron ratios, could help to partially break the parameter degeneracies arising from the interference between the Standard Model and NSI contributions to the CE$ν$NS cross section, as well as between different NSI parameters. By contrast, only a slight improvement over the current CsI constraints is expected for parameters that do not interfere with the SM contribution.

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arXiv2024

Probing neutrino millicharges at the European Spallation Source

We study the potential of a set of future detectors, proposed to be located at the European Spallation Source (ESS), to probe neutrino millicharges through coherent elastic neutrino-nucleus scattering. In particular, we focus on detectors with similar characteristics as those that are under development for operation at the ESS, including detection technologies based on cesium iodine, germanium, and noble gases. Under the considered conditions, we show that the Ge detector, with a lighter nuclear target mass with respect to CsI and to a noble gas like Xe, is more efficient to constrain neutrino millicharges, reaching a sensitivity of $\sim 10^{-9}e$ for diagonal neutrino millicharges, and $\sim 10^{-8}e$ for the transition ones. In addition, we study the effects of including electron scattering processes for the CsI detector, achieving an expected sensitivity of $\sim 10^{-10} e$ for the diagonal millicharges.

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arXiv2024

A neutrino window to scalar leptoquarks: from low energy to colliders

Leptoquarks are theorized particles of either scalar or vector nature that couple simultaneously to quarks and leptons. Motivated by recent measurements of coherent elastic neutrino-nucleus scattering, we consider the impact of scalar leptoquarks coupling to neutrinos on a few complementary processes, from low energy to colliders. In particular, we set competitive constraints on the typical mass and coupling of scalar leptoquarks by analyzing recent COHERENT data. We compare these constraints with bounds from atomic parity violation experiments, deep inelastic neutrino-nucleon scattering and LHC data. Our results highlight a strong complementarity between different facilities and demonstrate the compelling power of coherent elastic neutrino-nucleus scattering experiments to probe leptoquark masses in the MeV-GeV range. Finally, we also present prospects for improving current bounds with future upgrades of the COHERENT detectors and the planned European Spallation Source.

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arXiv2023

Probing nuclear properties and neutrino physics with current and future CEνNS experiments

The recent observation of Coherent Elastic Neutrino Nucleus Scattering (CEνNS) with neutrinos from pion decay at rest (π-DAR) sources by the COHERENT Collaboration has raised interest in this process in the search for new physics. Unfortunately, current uncertainties in the determination of nuclear parameters relevant to those processes can hide new physics effects. This is not the case for processes involving lower-energy neutrino sources such as nuclear reactors. Note, however, that a CEνNS measurement with reactor neutrinos depends largely on the determination of the quenching factor, making its observation more challenging. In the upcoming years, once this signal is confirmed, a combined analysis of π-DAR and reactor CEνNS experiments will be very useful to probe particle and nuclear physics, with a reduced dependence on the nuclear uncertainties. In this work, we explore this idea by simultaneously testing the sensitivity of current and future CEνNS experiments to neutrino non-standard interactions (NSI) and the neutron root mean square (rms) radius, considering different neutrino sources as well as several detection materials. We show how the interplay between future reactor and accelerator CEνNS experiments can help to get robust constraints on the neutron rms, and to break degeneracies between the NSI parameters. Our forecast could be used as a guide to optimize the experimental sensitivity to the parameters under study.

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arXiv2023

Physics implications of a combined analysis of COHERENT CsI and LAr data

The observation of coherent elastic neutrino nucleus scattering has opened the window to many physics opportunities. This process has been measured by the COHERENT Collaboration using two different targets, first CsI and then argon. Recently, the COHERENT Collaboration has updated the CsI data analysis with a higher statistics and an improved understanding of systematics. Here we perform a detailed statistical analysis of the full CsI data and combine it with the previous argon result. We discuss a vast array of implications, from tests of the Standard Model to new physics probes. In our analyses we take into account experimental uncertainties associated to the efficiency as well as the timing distribution of neutrino fluxes, making our results rather robust. In particular, we update previous measurements of the weak mixing angle and the neutron root mean square charge radius for CsI and argon. We also update the constraints on new physics scenarios including neutrino nonstandard interactions and the most general case of neutrino generalized interactions, as well as the possibility of light mediators. Finally, constraints on neutrino electromagnetic properties are also examined, including the conversion to sterile neutrino states. In many cases, the inclusion of the recent CsI data leads to a dramatic improvement of bounds.

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arXiv2023

Constraining Non-Standard Interactions with Coherent Elastic Neutrino-Nucleus Scattering at the European Spallation Source

The European Spallation Source (ESS), currently under construction in Sweden, will provide an intense pulsed neutrino flux allowing for high-statistics measurements of coherent elastic neutrino-nucleus scattering (CEνNS) with advanced nuclear recoil detectors. In this paper, we investigate in detail the possibility of constraining non-standard neutrino interactions (NSIs) through such precision CEνNS measurements at the ESS, considering the different proposed detection technologies, either alone or in combination. We first study the sensitivity to neutral-current NSI parameters that each detector can reach in 3 years of data taking. We then show that operating two detectors simultaneously can significantly improve the expected sensitivity on flavor-diagonal NSI parameters. Combining the results of two detectors turns out to be even more useful when two NSI parameters are assumed to be nonvanishing at a time. In this case, suitably chosen detector combinations can reduce the degeneracies between some pairs of NSI parameters to a small region of the parameter space.

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arXiv2022

High-energy colliders as a probe of neutrino properties

The mediators of neutrino mass generation can provide a probe of neutrino properties at the next round of high-energy hadron (FCC-hh) and lepton colliders (FCC-ee/ILC/CEPC/CLIC). We show how the decays of the Higgs triplet scalars mediating the simplest seesaw mechanism can shed light on the neutrino mass scale and mass-ordering, as well as the atmospheric octant. Four-lepton signatures at the high-energy frontier may provide the discovery-site for charged lepton flavour non-conservation in nature, rather than low-energy intensity frontier experiments.

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arXiv2022

Towards deconstructing the simplest seesaw mechanism

The triplet or type-II seesaw mechanism is the simplest way to endow neutrinos with mass in the Standard Model (SM). Here we review its associated theory and phenomenology, including restrictions from $S$, $T$, $U$ parameters, neutrino experiments, charged lepton flavour violations as well as collider searches. We also examine restrictions coming from requiring consistency of electroweak symmetry breaking, i.e. perturbative unitarity and stability of the vacuum. Finally, we discuss novel effects associated to the scalar mediator of neutrino mass generation namely, (i) rare processes, e.g. $l_α\to l_βγ$ decays, at the intensity frontier, and also (ii) four-lepton signatures in colliders at the high-energy frontier. These can be used to probe neutrino properties in an important way, providing a test of the absolute neutrino mass and mass-ordering, as well as of the atmospheric octant. They may also provide the first evidence for charged lepton flavour violation in nature. In contrast, neutrino non-standard interaction strengths are found to lie below current detectability.

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arXiv2022

Novel approach for the study of coherent elastic neutrino-nucleus scattering

We propose the use of isotopically highly enriched detectors for the precise study of coherent-elastic neutrino-nucleus scattering (CEvNS). CEvNS has been measured for the first time in CsI and recently confirmed with a liquid argon detector. It is expected that several new experimental setups will measure this process with increasing accuracy. Taking Ge detectors as a working example, we demonstrate that a combination of different isotopes is an excellent option to do precision neutrino physics with CEvNS, test Standard Model predictions, and probe new physics scenarios. Experiments based on this new idea can make simultaneous differential CEvNS measurements with detectors of different isotopic composition. Particular combination of observables could be used to cancel systematic errors. While many applications are possible, we illustrate the idea with three examples: testing the dominant quadratic dependence on the number of neutrons, $N$, that is predicted by the theoretical models; constraining the average neutron root mean square (rms) radius; and testing the weak mixing angle and the sensitivity to new physics. In all three cases we find that the extra sensitivity provided by this method will potentially allow high-precision robust measurements with CEvNS and particularly, will resolve the characteristic degeneracies appearing in new physics scenarios.

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arXiv2021

Neutrino magnetic and electric dipole moments: From measurements to parameter space

Searches for neutrino magnetic moments/transitions in low energy neutrino scattering experiments are sensitive to effective couplings which are an intricate function of the Hamiltonian parameters. We study the parameter space dependence of these couplings in the Majorana (transitions) and Dirac (moments) cases, as well as the impact of the current most stringent experimental upper limits on the fundamental parameters. In the Majorana case we find that for reactor, short-baseline and solar neutrinos, CP violation can be understood as a measurement of parameter space vectors misalignments. The presence of nonvanishing CP phases opens a blind spot region where -- regardless of how large the parameters are -- no signal can be observed in either reactor or short-baseline experiments. Identification of these regions requires a combination of different data sets and allows for the determination of those CP phases. We point out that stringent bounds not necessarily imply suppressed Hamiltonian couplings, thus allowing for regions where disparate upper limits can be simultaneously satisfied. In contrast, in the Dirac case stringent experimental upper limits necessarily translate into tight bounds on the fundamental couplings. In terms of parameter space vectors, we provide a straightforward mapping of experimental information into parameter space.

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arXiv2020

Implications of the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) with Liquid Argon

The CENNS-10 experiment of the COHERENT collaboration has recently reported the first detection of coherent-elastic neutrino-nucleus scattering (CEvNS) in liquid Argon with more than $3 σ$ significance. In this work, we exploit the new data in order to probe various interesting parameters which are of key importance to CEvNS within and beyond the Standard Model. A dedicated statistical analysis of these data shows that the current constraints are significantly improved in most cases. We derive a first measurement of the neutron rms charge radius of Argon, and also an improved determination of the weak mixing angle in the low energy regime. We also update the constraints on neutrino non-standard interactions, electromagnetic properties and light mediators with respect to those derived from the first COHERENT-CsI data.

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