Towards Resolving the Gallium Anomaly

Abstract

A series of experiments studying neutrinos from intense radioactive sources have reported a deficit in the measured event rate which, in combination, has reached a statistical significance of $\sim 5\sigma$. In this paper, we explore avenues for explaining this anomaly, both within the Standard Model and beyond. First, we discuss possible biases in the predicted cross section for the detection reaction ${\nu }_e{+}^{71}\text{Ga}\to e^{-}{+}^{71}\text{Ge}$, which could arise from mismeasurement of the inverse process, ${}^{71}\text{Ge}$ decay, or from the presence of as yet unknown low-lying excited states of ${}^{71}\text{Ga}$. The latter would imply that not all ${}^{71}\text{Ge}$ decays go to the ground state of ${}^{71}\text{Ga}$, so the extraction of the ground state-to-ground state matrix element relevant for neutrino capture on gallium would be incorrect. Second, we scrutinize the measurement of the source intensity in gallium experiments, and we point out that a $\sim 2\%$ error in the branching ratios for ${}^{51}\text{Cr}$ decay would be enough to explain the anomaly. Third, we investigate the calibration of the radiochemical germanium extraction efficiency as a possible origin of anomaly. Finally, we outline several new explanations beyond the Standard Model, including scenarios with sterile neutrinos coupled to fuzzy dark matter or to dark energy, as well as a model with decaying sterile neutrinos. We critically assess the viability of these scenarios, and others that have been proposed, in a summary table.

arXiv comment19 pages, 5 figures, matches published version in JHEP

References in corpus (79)

• The Reactor Antineutrino Anomaly
• Improved Predictions of Reactor Antineutrino Spectra
• The Search for Heavy Majorana Neutrinos
• Measurement of the solar neutrino capture rate with gallium metal. III: Results for the 2002--2007 data-taking period
• Reanalysis of the GALLEX solar neutrino flux and source experiments
• Measurement of the Solar Neutrino Capture Rate by the Russian-American Gallium Solar Neutrino Experiment During One Half of the 22-Year Cycle of Solar Activity
• Statistical Significance of the Gallium Anomaly
• Dark Light, Dark Matter and the Misalignment Mechanism
• Updated global analysis of neutrino oscillations in the presence of eV-scale sterile neutrinos
• Unitarity of the Leptonic Mixing Matrix
• Strong bound on canonical ultra-light axion dark matter from the Lyman-alpha forest
• Cosmic Acceleration from Abelian Symmetry Breaking
• Lyman-alpha Constraints on Ultralight Scalar Dark Matter: Implications for the Early and Late Universe
• A ménage à trois of eV-scale sterile neutrinos, cosmology, and structure formation
• Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun
• Gallium Solar Neutrino Experiments: Absorption Cross sections, Neutrino spectra, and Predicted Event Rates
• Updated Global 3+1 Analysis of Short-BaseLine Neutrino Oscillations
• Constraining the Self-Interacting Neutrino Interpretation of the Hubble Tension
• Diffractive-Like (or Parametric-Resonance-Like?) Enhancement of the Earth (Day-Night) Effect for Solar Neutrinos Crossing the Earth Core
• Neutrinoless double beta decay versus other probes of heavy sterile neutrinos
• How secret interactions can reconcile sterile neutrinos with cosmology
• Results from the Baksan Experiment on Sterile Transitions (BEST)
• Parametric resonance of neutrino oscillations and passage of solar and atmospheric neutrinos through the earth
• Dark energy as a massive vector field
• Unitarity and the three flavour neutrino mixing matrix
• Thermalisation of light sterile neutrinos in the early universe
• Short-Baseline Active-Sterile Neutrino Oscillations?
• Explaining LSND by a decaying sterile neutrino
• Updated determination of the solar neutrino fluxes from solar neutrino data
• The Neutrino Magnetic Moment Portal: Cosmology, Astrophysics, and Direct Detection
• Neutrino Oscillations as a Probe of Light Scalar Dark Matter
• Reactor antineutrino anomaly in light of recent flux model refinements
• Fuzzy Dark Matter and Non-Standard Neutrino Interactions
• Sterile Neutrinos with Secret Interactions - Lasting Friendship with Cosmology
• Effect of Gravitational Focusing on Annual Modulation in Dark-Matter Direct-Detection Experiments
• Cosmological constraints on neutrino self-interactions with a light mediator
• Distorted Neutrino Oscillations From Ultralight Scalar Dark Matter
• Short-Baseline Electron Neutrino Disappearance, Tritium Beta Decay and Neutrinoless Double-Beta Decay
• Sterile Neutrinos or Flux Uncertainties? - Status of the Reactor Anti-Neutrino Anomaly
• Revisiting Neutrino Self-Interaction Constraints from $Z$ and $\tau$ decays
• Sterile Neutrinos with Secret Interactions -- Cosmological Discord?
• A small cosmological constant from Abelian symmetry breaking
• Stereo neutrino spectrum of 235U fission rejects sterile neutrino hypothesis
• The gallium anomaly revisited
• Decaying Sterile Neutrinos and the Short Baseline Oscillation Anomalies
• Neutrinos in Large Extra Dimensions and Short-Baseline ${\nu }_e$ Appearance
• Unveiling secret interactions among sterile neutrinos with big-bang nucleosynthesis
• Cosmic microwave background constraints on secret interactions among sterile neutrinos
• Statistical significance of the sterile-neutrino hypothesis in the context of reactor and gallium data
• Sterile Neutrinos and the Global Reactor Antineutrino Dataset
• Current and Future Neutrino Oscillation Constraints on Leptonic Unitarity
• Cross Section Uncertainties in the Gallium Neutrino Source Experiments
• On The Decaying-Sterile Neutrino Solution to the Electron (Anti)Neutrino Appearance Anomalies
• Large Extra Dimensions and neutrino experiments
• Ultra-light scalar saving the 3+1 neutrino scheme from the cosmological bounds
• BEST Impact on Sterile Neutrino Hypothesis
• Bulk Neutrinos as an Alternative Cause of the Gallium and Reactor Anti-neutrino Anomalies
• Combining Sterile Neutrino Fits to Short Baseline Data with IceCube Data
• Implications of the GALLEX Source Experiment for the Solar Neutrino Problem
• Cosmology-friendly time-varying neutrino masses via the sterile neutrino portal
• Gravitational Focusing of Wave Dark Matter
• Sterile Neutrino Searches with MicroBooNE: Electron Neutrino Disappearance
• Revised neutrino-gallium cross section and prospects of BEST in resolving the Gallium anomaly
• Direct determination of the solar neutrino fluxes from solar neutrino data
• Leptonic Unitarity Triangles
• Gallium Anomaly: Critical View from the Global Picture of ${\nu }_e$ and ${\bar{\nu }}_e$ Disappearance
• Model Independent Bounds on the Non-Oscillatory Explanations of the MiniBooNE Excess
• Global oscillation data analysis on the $3\nu$ mixing without unitarity
• New oscillation and scattering constraints on the tau row matrix elements without assuming unitarity
• Statistical Significance of Reactor Antineutrino Active-Sterile Oscillations
• An Altarelli Cocktail for the MiniBooNE Anomaly?
• Constraints on Decaying Sterile Neutrinos from Solar Antineutrinos
• Parametric resonance in neutrino oscillations induced by ultra-light dark matter and implications for KamLAND and JUNO
• Impact of Wave Packet Separation in Low-Energy Sterile Neutrino Searches
• Distortion of neutrino oscillations by dark photon dark matter
• Energy-Dependent Neutrino Mixing Parameters at Oscillation Experiments
• Addressing the Short-Baseline Neutrino Anomalies with Energy-Dependent Mixing Parameters
• Measurement of neutrino source activity in the experiment BEST by calorimetric method
• Production of the artificial 51Cr neutrino source in the BEST project

Cited by in corpus (9)

• Anomalies in Particle Physics
• Sterile Neutrino Shape-shifting Caused by Dark Matter
• Solar fusion III: New data and theory for hydrogen-burning stars
• Neutrino Constraints and the ATOMKI X17 Anomaly
• Status of Direct Determination of Solar Neutrino Fluxes after Borexino
• New Measurements of ${}^{71}$Ge Decay: Impact on the Gallium Anomaly
• Search for Hidden Neutrinos at the European Spallation Source: the SHiNESS experiment
• Solar Model Independent Constraints on the Sterile Neutrino Interpretation of the Gallium Anomaly
• Sterile sector impacting the correlations and degeneracies among mixing parameters at the Deep Underground Neutrino Experiment