Logo image
Back
White paper on light sterile neutrino searches and related phenomenology
Journal article   Open access   Peer reviewed

White paper on light sterile neutrino searches and related phenomenology

M. A. Acero, C. A. Arguelles, M. Hostert, D. Kalra, G. Karagiorgi, K. J. Kelly, B. R. Littlejohn, P. Machado, W. Pettus, M. Toups, …
Journal of physics. G, Nuclear and particle physics, Vol.51(12), 120501
12/01/2024
DOI: 10.1088/1361-6471/ad307f
url
https://doi.org/10.1088/1361-6471/ad307fView
Published (Version of record) Open Access

Abstract

Executive summary Several decades of a rich and diverse program of experimental neutrino measurements have provided an increasingly clearer picture of the elusive neutrino sector, and uncovered physics not predicted by the Standard Model (SM), such as the existence of nonzero neutrino masses implied by the surprising discovery of neutrino flavor mixing. This foundational discovery represented a welcome resolution to decades-long experimental anomalies associated with solar and atmospheric neutrino measurements. Alongside this foundational discovery, experimental neutrino anomalies have been observed that still remain unresolved, and have served as primary drivers in the development of a vibrant short-baseline neutrino program, and in the launch of a multitude of complementary probes within a large variety of other experiments. Two of these anomalies arise from the apparent oscillatory appearance of electron (anti)neutrinos in relatively pure muon-(anti)neutrino beams originating from charged-pion decay-at-rest, specifically the LSND Anomaly, and from charged-pion decay-in-flight, the MiniBooNE Low-Energy Excess. Two other anomalies are associated with an overall normalization discrepancy of electron (anti)neutrinos expected both from conventional fission reactors, the Reactor Neutrino Anomaly, and in the radioactive decay of Gallium-71, the Gallium Anomaly. In these two latter cases, no oscillatory signature is observed, but the overall normalization deficit can be ascribed to rapid oscillations that are averaged out and appear as an overall deficit. Historically, these anomalies were first interpreted as oscillations due to the existence of light sterile neutrinos that mix with the three SM neutrinos. This interpretation requires an oscillation frequency Δm2 ≳ 1 eV2, implying the addition of at least one neutrino to the three-flavor mixing paradigm. This new neutrino would have to be a SM gauge singlet, thus it is referred to as sterile, as LEP measurements of the invisible decay width of the Z boson show only three neutrinos couple to the Z boson. However, this purely oscillatory interpretation is disfavored by several other direct and indirect experimental tests. Consequently, recent years have seen accelerating theoretical interest in more complex Beyond the Standard Model (BSM) flavor transformation and hidden-sector particle production as explanations for the anomalies. Experimental interest in testing a more diverse set of interpretations has also been growing, as well as motivation to probe deeper into potential conventional explanations. The discovery of new physics associated with these anomalies would be groundbreaking, and would have profound implications not only for particle physics but also for astrophysics and cosmology. This white paper provides a comprehensive review of our present understanding of the experimental neutrino anomalies, charting the progress achieved over the last decade at the experimental and phenomenological level, and sets the stage for future programmatic prospects in addressing the anomalies. In a similar spirit to the ‘Light Sterile Neutrinos: A White Paper’ document from a decade ago [1], this new white paper is purposed to serve as a guiding and motivational ‘encyclopedic’ reference, with emphasis on needs and options for future exploration that may lead to the ultimate resolution of the anomalies.
 Physical Sciences Physics Physics, Nuclear Physics, Particles & Fields Science & Technology

Details

Metrics

17 Record Views
39 Times Cited - Web of Science
Logo image