arXiv subjects

J. W. F. Valle

Publications and source records attributed to J. W. F. Valle.

At least 19 recordsLinked to original sources

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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arXiv2025

Axion framework with color-mediated Dirac neutrino masses

We propose a KSVZ-type axion framework in which vector-like quarks (VLQ) and colored scalars generate Dirac neutrino masses radiatively. The global Peccei-Quinn symmetry (under which the exotic fermions are charged) addresses the strong CP problem and ensures the Dirac nature of neutrinos. The axion also accounts for the observed cosmological dark matter. We systematically explore all viable VLQ representations. Depending on the specific scenario, the framework predicts distinct axion-to-photon couplings, testable through haloscope and helioscope experiments, as well as potentially significant flavor-violating quark-axion interactions.

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arXiv2024

Vector-Like Fermions and Inert Scalar Solutions to the Muon g-2 Anomaly and collider probes at the HL-LHC and FCC-hh

We examine simple models with an inert scalar and vector-like leptons that can explain the recent $g_μ-2$ measurement reported at FNAL. Prompted by this exciting result, we explore the viability of a simple interpretation and determine the required parameters. We also embed these models within a 3-3-1 gauge extension of the Standard Model (SM), showing that the $g_μ-2$ anomaly can be accommodated in agreement with current data. We also show how our theory can be tested at high-energy colliders such as HL-LHC and FCC-hh.

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arXiv2024

Axion Paradigm with Color-Mediated Neutrino Masses

We propose a generalized Kim-Shifman-Vainshtein-Zakharov-type axion framework in which colored fermions and scalars act as two-loop Majorana neutrino-mass mediators. The global Peccei-Quinn symmetry under which exotic fermions are charged solves the strong CP problem. Within our general proposal, various setups can be distinguished by probing the axion-to-photon coupling at helioscopes and haloscopes. We also comment on axion dark-matter production in the early Universe.

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arXiv2023

Dark-sector seeded solution to the strong CP problem

We propose a novel realization of the Nelson-Barr mechanism "seeded'' by a dark sector containing scalars and vector-like quarks. Charge-parity (CP) and a $\mathcal{Z}_8$ symmetry are spontaneously broken by the complex vacuum expectation value of a singlet scalar, leaving a residual $\mathcal{Z}_2$ symmetry that stabilizes dark matter (DM). A complex Cabibbo-Kobayashi-Maskawa matrix arises via one-loop corrections to the quark mass matrix mediated by the dark sector. In contrast with other proposals where non-zero contributions to the strong CP phase arise at the one-loop level, in our case this only occurs at two loops, enhancing naturalness. Our scenario also provides a viable weakly interacting massive particle scalar DM candidate.

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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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arXiv2022

Nonunitarity of the lepton mixing matrix at the European Spallation Source

If neutrinos get mass through the exchange of lepton mediators, as in seesaw schemes, the neutrino appearance probabilities in oscillation experiments are modified due to effective nonunitarity of the lepton mixing matrix. This also leads to new CP phases and an ambiguity in underpinning the ''conventional'' phase of the three-neutrino paradigm. We study the CP sensitivities of various setups based at the European spallation source neutrino super-beam (ESSnuSB) experiment in the presence of nonunitarity. We also examine its potential in constraining the associated new physics parameters. Moreover, we show how the combination of DUNE and ESSnuSB can help further improve the sensitivities on the nonunitarity parameters.

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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

Low-energy probes of sterile neutrino transition magnetic moments

Sterile neutrinos with keV-MeV masses and non-zero transition magnetic moments can be probed through low-energy nuclear or electron recoil measurements. Here we determine the sensitivities of current and future searches, showing how they can probe a previously unexplored parameter region. Future coherent elastic neutrino-nucleus scattering (CE$ν$NS) or elastic neutrino-electron scattering (E$ν$ES) experiments using a monochromatic $^{51}$Cr source can fully probe the region indicated by the recent XENON1T excess.

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arXiv2021

2020 Global reassessment of the neutrino oscillation picture

We present an updated global fit of neutrino oscillation data in the simplest three-neutrino framework. In the present study we include up-to-date analyses from a number of experiments. Concerning the atmospheric and solar sectors, we give updated analyses of DeepCore and SNO data, respectively. We have also included the latest electron antineutrino data collected by the Daya Bay and RENO reactor experiments, and the long-baseline T2K and NO$ν$A measurements. These new analyses result in more accurate measurements of $θ_{13}$, $θ_{12}$, $Δm_{21}^2$ and $|Δm_{31}^2|$. The best fit value for the atmospheric angle $θ_{23}$ lies in the second octant, but first octant solutions remain allowed at $\sim2.4σ$. Regarding CP violation measurements, the preferred value of $δ$ we obtain is 1.08$π$ (1.58$π$) for normal (inverted) neutrino mass ordering. The global analysis prefers normal neutrino mass ordering with 2.5$σ$. This preference is milder than the one found in previous global analyses. The new results should be regarded as robust due to the agreement found between our Bayesian and frequentist approaches. Taking into account only oscillation data, there is a weak/moderate preference for the normal neutrino mass ordering of $2.00σ$. While adding neutrinoless double beta decay from the latest Gerda, CUORE and KamLAND-Zen results barely modifies this picture, cosmological measurements raise the preference to $2.68σ$ within a conservative approach. A more aggressive data set combination of cosmological observations leads to a similar preference, namely $2.70σ$. This very same cosmological data set provides $2σ$ upper limits on the total neutrino mass corresponding to $\sumν<0.12$ ($0.15$)~eV for normal (inverted) neutrino mass ordering.

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arXiv2020

Future CEvNS experiments as probes of lepton unitarity and light-sterile neutrinos

We determine the sensitivities of short-baseline coherent elastic neutrino-nucleus scattering (CE$ν$NS) experiments using a pion decay at rest neutrino source as a probe for nonunitarity in the lepton sector, as expected in low-scale type-I seesaw schemes. We also identify the best configuration for probing light sterile neutrinos at future ton-scale liquid argon CE$ν$NS experiments, estimating the projected sensitivities on the sterile neutrino parameters. Possible experimental setups at the Spallation Neutron Source, Lujan facility and the European Spallation Source are discussed. Provided that systematic uncertainties remain under control, we find that CE$ν$NS experiments will be competitive with oscillation measurements in the long run.

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arXiv2020

Minimal scoto-seesaw mechanism with spontaneous CP violation

We propose simple scoto-seesaw models to account for dark matter and neutrino masses with spontaneous CP violation. This is achieved with a single horizontal $\mathcal{Z}_8$ discrete symmetry, broken to a residual $\mathcal{Z}_2$ subgroup responsible for stabilizing dark matter. CP is broken spontaneously via the complex vacuum expectation value of a scalar singlet, inducing leptonic CP-violating effects. We find that the imposed $\mathcal{Z}_8$ symmetry pushes the values of the Dirac CP phase and the lightest neutrino mass to ranges already probed by ongoing experiments, so that normal-ordered neutrino masses can be cornered by cosmological observations and neutrinoless double beta decay experiments.

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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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arXiv2020

XENON1T signal from transition neutrino magnetic moments

The recent puzzling results of the XENON1T collaboration at few keV electronic recoils could be due to the scattering of solar neutrinos endowed with finite Majorana transition magnetic moments (TMMs). Within such general formalism, we find that the observed excess in the XENON1T data agrees well with this interpretation. The required TMM strengths lie within the limits set by current experiments, such as Borexino, specially when one takes into account a possible tritium contamination.

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arXiv2019

Probing neutrino transition magnetic moments with coherent elastic neutrino-nucleus scattering

We explore the potential of current and next generation of coherent elastic neutrino-nucleus scattering (CE$ν$NS) experiments in probing neutrino electromagnetic interactions. On the basis of a thorough statistical analysis, we determine the sensitivities on each component of the Majorana neutrino transition magnetic moment (TMM), $\left \vert Λ_i \right \vert$, that follow from low-energy neutrino-nucleus experiments. We derive the sensitivity to neutrino TMM from the first CE$ν$NS measurement by the COHERENT experiment, at the Spallation Neutron Source. We also present results for the next phases of COHERENT using HPGe, LAr and NaI[Tl] detectors and for reactor neutrino experiments such as CONUS, CONNIE, MINER, TEXONO and RED100. The role of the CP violating phases in each case is also briefly discussed. We conclude that future CE$ν$NS experiments with low-threshold capabilities can improve current TMM limits obtained from Borexino data.

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arXiv2018

Neutrinos and the challenges of particle physics

I present a grand view of some of the main particle physics challenges from a neutrino perspective. After a brief review of the current status of neutrino physics, I illustrate the possible role neutrinos can play in the elucidation of various puzzles in particle physics and cosmology, for which the Standard Model offers no answer.

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arXiv2018

Bound-state dark matter with Majorana neutrinos

We propose a simple scenario in which dark matter (DM) emerges as a stable neutral hadronic thermal relics, its stability following from an exact $\operatorname{U}(1)_D$ symmetry. Neutrinos pick up radiatively induced Majorana masses from the exchange of colored DM constituents. There is a common origin for both dark matter and neutrino mass, with a lower bound for neutrinoless double beta decay. Direct DM searches at nuclear recoil experiments will test the proposal, which may also lead to other phenomenological signals at future hadron collider and lepton flavour violation experiments.

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