The PandaX-4T and XENONnT experiments present indications of Coherent Elastic Neutrino Nucleus Scattering (CE$\textit{ν}$NS) from B solar neutrinos at 2.6$\textit{σ}$ and 2.7$\textit{σ}$, respectively. This constitutes the first observation of the neutrino “floor” or “fog”, an irreducible background that future dark matter searches in terrestrial detectors will have to contend with. Here, we first discuss the contributions from neutrino–electron scattering and from the Migdal effect in the region of interest of these experiments, and we argue that they are non-negligible. Second, we make use of the recent PandaX-4T and XENONnT data to derive novel constraints on light scalar and vector mediators coupling to neutrinos and quarks. We demonstrate that these experiments already provide world-leading laboratory constraints on new light mediators in some regions of parameter space.

Spain

Pablo Blanco-Mas

Pilar Coloma

United States

Gonzalo Herrera

Patrick Huber

Switzerland

Germany

Joachim Kopp

Ian Shoemaker

Zahra Tabrizi

Clarity through the neutrino fog: constraining new forces in dark matter detectors

Deviations from unitarity of the CKM matrix in the quark sector are considered excellent windows to probe physics beyond the Standard Model. In its leptonic counterpart, the PMNS matrix, these searches are particularly motivated, as the new physics needed to generate neutrino masses often leads to non-unitary mixing among the standard neutrinos. It is then interesting to consider how neutrino oscillations are affected in such scenario. This simple question is, however, subject to several subtleties: What is the correct way to define oscillation probabilities for a non-unitary mixing matrix? Do these probabilities add up to one? Does a non-unitary mixing matrix lead to observable flavor transitions at zero distance? What is the interplay between unitarity constraints obtained from neutrino oscillations and from electroweak precision data? This work aims to shed light on these issues and to clarify the corresponding misconceptions commonly found in the literature. We also compile updated bounds from neutrino oscillation searches to compare with those from flavour and electroweak precision observables.

Sweden

Mattias Blennow

Enrique Fernández-Martínez

Josu Hernández-García

Jacobo López-Pavón

Xabier Marcano

Daniel Naredo-Tuero

France

Salvador Urrea

Misconceptions in neutrino oscillations in presence of non-unitary mixing

We analyze how neutrino oscillation and coherent elastic neutrino-nucleus scattering data impact the global SMEFT fit. We first review the mapping between the SMEFT parameters and the so-called NSI framework, commonly considered in the neutrino literature. We also present a detailed discussion of how the measurements for the normalization of neutrino fluxes and cross sections, that will also be affected by the new physics, indirectly impact the measured oscillation probabilities. We then analyze two well-motivated simplified scenarios. Firstly, we study a lepton flavour conserving case, usually assumed in global SMEFT analyses, showing the complementarity of neutrino oscillation and CE$\textit{ν}$NS experiments with other low-energy observables. We find that the inclusion of neutrino data allows to constrain previously unbounded SMEFT operators involving the tau flavour and confirm the improvement of the constraint on a combination of Wilson coefficients previously identified. Moreover, we find that neutrino oscillation constraints on NSI are improved when embedded in the global SMEFT framework. Secondly, we study a lepton flavour violating scenario and find that neutrino data also improves over previously derived global constraints thanks to its sensitivity to new combinations of Wilson coefficients.

Improving the global SMEFT picture with bounds on neutrino NSI

The upcoming European Spallation Source (ESS) will soon provide the most intense neutrino source in the world. We propose the Search for Hidden Neutrinos at the ESS (SHiNESS) experiment, highlighting its unique opportunities to search for the existence of sterile neutrinos across a wide range of scales: anomalous oscillations at short baselines; non-unitarity mixing in the active neutrino sector; or an excess of events with multiple leptons in the final state, produced in the decay of heavy neutrinos. The baseline design of the detector comprises an active volume filled with 42 ton of liquid scintillator, located 25 m far from the ESS beam target. We show that SHiNESS will be able to considerably improve current global limits for the three cases outlined above. Although in this work we focus on new physics in the neutrino sector, the proposed setup may also be used to search for signals from weakly interacting particles in a broader context.

Stefano Soleti

Juan Gómez Cadenas

Anatael Cabrera

Search for hidden neutrinos at the European Spallation Source: the SHiNESS experiment

Long-lived particles (LLPs) arise in many theories beyond the Standard Model. These may be copiously produced from meson decays (or through their mixing with the LLPs) at neutrino facilities and leave a visible decay signal in nearby neutrino detectors. We compute the expected sensitivity of the DUNE liquid argon (LAr) and gaseous argon near detectors (NDs) to light LLP decays. In doing so, we determine the expected backgrounds for both detectors, which have been largely overlooked in the literature, taking into account their angular and energy resolution. We show that searches for LLP decays into muon pairs, or into three pions, would be extremely clean. Conversely, decays into two photons would be affected by large backgrounds from neutrino interactions for both near detectors; finally, the reduced signal efficiency for <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> pairs leads to a reduced sensitivity for ND-LAr. Our results are first presented in a model-independent way, as a function of the mass of the new state and its lifetime. We also provide detailed calculations for several phenomenological models with axionlike particles (coupled to gluons, electroweak bosons, or quark currents). Some of our results may also be of interest for other neutrino facilities using a similar detector technology (e.g., MicroBooNE, SBND, ICARUS, or the T2K near detector).

Justo Martín-Albo

Discovering long-lived particles at DUNE

The exquisite capabilities of liquid Argon Time Projection Chambers make them ideal to search for weakly interacting particles in Beyond the Standard Model scenarios. Given their location at CERN the ProtoDUNE detectors may be exposed to a flux of such particles, produced in the collisions of 400 GeV protons (extracted from the Super Proton Synchrotron accelerator) on a target. Here we point out the interesting possibilities that such a setup offers to search for both long-lived unstable particles (Heavy Neutral Leptons, axion-like particles, etc) and stable particles (e.g. light dark matter, or millicharged particles). Our results show that, under conservative assumptions regarding the expected luminosity, this setup has the potential to improve over present bounds for some of the scenarios considered. This could be done within a short timescale, using facilities that are already in place at CERN, and without interfering with the experimental program in the North Area at CERN.

Laura Molina-Bueno

New physics searches using ProtoDUNE and the CERN SPS accelerator

We derive new constraints on effective four-fermion neutrino non-standard interactions with both quarks and electrons. This is done through the global analysis of neutrino oscillation data and measurements of coherent elastic neutrino-nucleus scattering (CEνNS) obtained with different nuclei. In doing so, we include not only the effects of new physics on neutrino propagation but also on the detection cross section in neutrino experiments which are sensitive to the new physics. We consider both vector and axial-vector neutral-current neutrino interactions and, for each case, we include simultaneously all allowed effective operators in flavour space. To this end, we use the most general parametrization for their Wilson coefficients under the assumption that their neutrino flavour structure is independent of the charged fermion participating in the interaction. The status of the LMA-D solution is assessed for the first time in the case of new interactions taking place simultaneously with up quarks, down quarks, and electrons. One of the main results of our work are the presently allowed regions for the effective combinations of non-standard neutrino couplings, relevant for long-baseline and atmospheric neutrino oscillation experiments.

M. Gonzalez-Garcia

Michele Maltoni

João Pinheiro

Global constraints on non-standard neutrino interactions with quarks and electrons

Erratum to: Constraining new physics with Borexino Phase-II spectral data

Erratum to: Neutrino oscillation constraints on U(1)′ models: from non-standard interactions to long-range forces

We point out that right-handed neutrinos can resolve the tension between the latest CDF II measurement of <math><msub><mi>M</mi><mi>W</mi></msub></math> and the SM. Integrating out the new states yields a single <math><mi>d</mi><mo>=</mo><mn>6</mn></math> operator, which translates into a nonunitary leptonic mixing matrix. This alters the extraction of <math><msub><mi>G</mi><mi>F</mi></msub></math> from muon decay and increases the prediction for <math><msub><mi>M</mi><mi>W</mi></msub></math>, in line with the CDF II result. We find that this explanation worsens the so-called Cabibbo anomaly, which could still be explained through the same <math><mi>d</mi><mo>=</mo><mn>6</mn></math> operator if it is not generated by right-handed neutrinos. Exploiting the flavor dependence, a common explanation of both anomalies would a priori be possible, but is ruled out by weak universality constraints.

Manuel González-López

Right-handed neutrinos and the CDF II anomaly