The determination of the neutrino mass ordering is one of the flagship goals in particle physics. A well-known and powerful synergy emerges when combining high-precision measurements of the effective atmospheric mass-squared splitting from electron antineutrino disappearance in reactor experiments with that from muon (anti)neutrino disappearance in accelerator-based long-baseline experiments. To fully exploit this synergy, percent-level precision in the atmospheric mass splitting is required—a target that JUNO is expected to achieve within a few months of data taking. This motivated the formulation of a mass ordering sum rule for neutrino disappearance channels, which shows that by combining data from T2K and NOvA with JUNO after one year of operation, the neutrino mass ordering can be determined at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> confidence level. Since JUNO has recently started taking data, it is timely to ask whether this sum rule remains robust in the presence of new physics. We identify the necessary conditions for new physics to affect the sum rule and demonstrate that, in some cases, such effects could lead to an incorrect inference of the mass ordering. As concrete examples, we consider scalar nonstandard interactions (SNSI) and neutrinos coupled to an ultralight scalar field. We find that, for SNSI, current constraints render any modification of the sum rule negligible, whereas in the latter case, the inference of the ordering requires caution. Nevertheless, these effects can be disentangled, illustrating how the sum rule can also be used to search for new physics.

United States

Brazil

Gustavo F.S. Alves

Hiroshi Nunokawa

Renata Zukanovich Funchal

Impact of new physics on the JUNO-long-baseline synergy in the neutrino mass ordering determination

A black hole is expected to end its lifetime in a cataclysmic runaway burst of Hawking radiation, emitting all standard model particles with ultrahigh energies. Thus, the explosion of a nearby primordial black hole (PBH) has been proposed as a possible explanation for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>220</mn><mtext> </mtext><mtext> </mtext><mi>PeV</mi></math> neutrino-like event recently reported by the KM3NeT Collaboration. If the event originated from a PBH, the source would need to lie at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mn>1</mn><mi>–</mi><mn>7</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>pc</mi></mrow></math>—depending on the assumed effective area—thus within the Solar System. At such proximity, the resulting flux of gamma rays and cosmic rays would be detectable at Earth. By incorporating the time-dependent field of view of gamma-ray observatories, we show that LHAASO should have recorded <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mn>8</mn></msup><mo stretchy="false">)</mo></math> events between fourteen and seven hours prior to the KM3NeT detection. IceCube and KM3NeT itself should likewise have detected of order a few hundred events in the range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi><mo>≲</mo><msub><mrow><mi>E</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo>≲</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>PeV</mi></mrow></math> during the 24 h preceding the burst. The absence of any such multimessenger signal, particularly in gamma-ray data, strongly disfavors the interpretation of the KM3-230213A event as arising from evaporation in a minimal four-dimensional Schwarzschild scenario.

Lua F.T. Airoldi

Spain

Yuber F. Perez-Gonzalez

Gabriel M. Salla

Could a Primordial Black Hole Explosion Explain the Extremely High-Energy KM3NeT Neutrino Event?

We revisit, reformulate, and extend a method for determining the neutrino mass ordering by using precision measurements of the atmospheric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msup><mi>m</mi><mn>2</mn></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">s</mi></math> in both electron and muon neutrino disappearance channels, first proposed by the authors in 2005 [H. Nunokawa et al., <a href="http://dx.doi.org/10.1103/PhysRevD.72.013009">Phys. Rev. D 72, 013009 (2005)</a>]. The mass ordering is a very important outstanding question for our understanding of the elusive neutrino and determination of the mass ordering has consequences to particle physics, nuclear physics, and cosmology. The JUNO reactor experiment will start data taking this year, and the precision of the atmospheric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msup><mi>m</mi><mn>2</mn></msup><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">s</mi></math> from electron antineutrino measurements will improve by a factor of 3 from Daya Bay’s 2.4% to 0.8% within a year. This measurement, when combined with the atmospheric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msup><mi>m</mi><mn>2</mn></msup></math>’s measurements from T2K and NOvA for muon neutrino disappearance, will contribute substantially to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msup><mi>χ</mi><mn>2</mn></msup></math> between the two remaining neutrino mass orderings. In this paper we derive for the first time a mass ordering sum rule that can be used to address the possibility that JUNO’s atmospheric <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msup><mi>m</mi><mn>2</mn></msup></math>’s measurement, when combined with other experiments in particular T2K and NOvA, can determine the neutrino mass ordering at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>3</mn><mi>σ</mi></mrow></math> confidence level within one year of operation. For a confidence level of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>5</mn><mi>σ</mi></mrow></math> in a single experiment, we will have to wait until the middle of the next decade when the DUNE experiment is operating.

Stephen J. Parke

Mass ordering sum rule for the neutrino disappearance channels in T2K, NOvA, and JUNO

In this Letter we show that pseudoscalar meson leptonic decay data can be used to set stringent limits on the mass <math><msub><mi>m</mi><msub><mi>W</mi><mi>R</mi></msub></msub></math> of a right-handed vector boson, such as the one that appears in left-right symmetric models. We have shown that for a heavy neutrino with a mass <math><msub><mi>m</mi><mi>N</mi></msub></math> in the range <math><mrow><mn>50</mn><mo>&lt;</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>N</mi></mrow></msub><mo>/</mo><mi>MeV</mi><mo>&lt;</mo><mn>1900</mn></mrow></math> one can constraint <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><msub><mrow><mi>W</mi></mrow><mrow><mi>R</mi></mrow></msub></mrow></msub><mo>≳</mo><mo>(</mo><mn>4</mn><mi>–</mi><mn>19</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> at 90% CL. This provides the most stringent experimental limits on the <math><msub><mi>W</mi><mi>R</mi></msub></math> mass to date for this heavy neutrino mass range.

Gustavo F. S. Alves

Chee Sheng Fong

Luighi P. S. Leal

Limits on <math><mrow><msub><mrow><mi>W</mi></mrow><mrow><mi>R</mi></mrow></msub></mrow></math> from Meson Decays

We investigate the possibility of using the Short-Baseline Near Detector (SBND) at Fermilab to constrain lepton flavor violating decays of pions and kaons. We study how to leverage SBND-PRISM, the use of the neutrino beam angular spread to mitigate systematic uncertainties, to enhance this analysis. We show that SBND-PRISM can put stringent limits on the flavor violating branching ratios <math><mi>BR</mi><mo>(</mo><msup><mi>π</mi><mo>+</mo></msup><mo>→</mo><msup><mi>μ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>e</mi></msub><mo>)</mo><mo>=</mo><mspace></mspace><mn>8.9</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math>, <math><mrow><mi>BR</mi><mo>(</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>→</mo><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msub><mrow><mi>ν</mi></mrow><mrow><mi>e</mi></mrow></msub><mo>)</mo><mo>=</mo><mn>3.2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math>, improving previous constraints by factors 9 and 1.25, respectively. We also estimate the SBND-PRISM sensitivity to lepton number violating decays, <math><mi>BR</mi><mo>(</mo><msup><mi>π</mi><mo>+</mo></msup><mo>→</mo><msup><mi>μ</mi><mo>+</mo></msup><msub><mover><mi>ν</mi><mo>¯</mo></mover><mi>e</mi></msub><mo>)</mo><mo>=</mo><mn>2.1</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>3</mn></mrow></msup></math> and <math><mrow><mi>BR</mi><mo>(</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>→</mo><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>e</mi></mrow></msub><mo>)</mo><mo>=</mo><mn>7.4</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math>, though not reaching previous Big European Bubble Chamber limits. Last, we identify several ways how the SBND collaboration could improve this analysis.

Pedro A. N. Machado

Could SBND-PRISM probe lepton flavor violation?

Axionlike particles are among the most studied extensions of the standard model. In this Letter we study the bounds that the ArgoNeuT experiment can put on the parameter space of two specific scenarios: leptophilic axionlike particles and Majorons. We find that such bounds are currently the most constraining ones in the (0.2–1.7) GeV mass range.

Enrico Bertuzzo

Ana Luisa Foguel

New Limits on Leptophilic Axionlike Particles and Majorons from ArgoNeuT

The flagship measurement of the JUNO experiment is the determination of the neutrino mass ordering. Here we revisit its prospects to make this determination by 2030, using the current global knowledge of the relevant neutrino parameters as well as current information on the reactor configuration and the critical parameters of the JUNO detector. We pay particular attention to the nonlinear detector energy response. Using the measurement of <math><mrow><msub><mrow><mi>θ</mi></mrow><mrow><mn>13</mn></mrow></msub></mrow></math> from Daya Bay, but without information from other experiments, we estimate the probability of JUNO determining the neutrino mass ordering at <math><mo>≥</mo><mrow><mn>3</mn><mi>σ</mi></mrow></math> to be 31% by 2030. As this probability is particularly sensitive to the true values of the oscillation parameters, especially <math><mi>Δ</mi><msubsup><mi>m</mi><mn>21</mn><mn>2</mn></msubsup></math>, JUNO’s improved measurements of <math><msup><mi>sin</mi><mn>2</mn></msup><msub><mi>θ</mi><mn>12</mn></msub></math>, <math><mi>Δ</mi><msubsup><mi>m</mi><mn>21</mn><mn>2</mn></msubsup></math> and <math><mo>|</mo><mi>Δ</mi><msubsup><mi>m</mi><mrow><mi>e</mi><mi>e</mi></mrow><mn>2</mn></msubsup><mo>|</mo></math>, obtained after a couple of years of operation, will allow an updated estimate of the probability that JUNO alone can determine the neutrino mass ordering by the end of the decade. Combining JUNO’s measurement of <math><mo>|</mo><mi>Δ</mi><msubsup><mi>m</mi><mrow><mi>e</mi><mi>e</mi></mrow><mn>2</mn></msubsup><mo>|</mo></math> with other experiments in a global fit will most likely lead to an earlier determination of the mass ordering.

Colombia

David V. Forero

Italy

Christoph A. Ternes

JUNO’s prospects for determining the neutrino mass ordering

We inspect recently updated neutrino oscillation data—specifically coming from the Tokai to Kamioka and NuMI Off-axis <math><msub><mi>ν</mi><mi>e</mi></msub></math> Appearance experiments—and how they are analyzed to determine whether the neutrino mass ordering is normal (<math><msub><mi>m</mi><mn>1</mn></msub><mo>&lt;</mo><msub><mi>m</mi><mn>2</mn></msub><mo>&lt;</mo><msub><mi>m</mi><mn>3</mn></msub></math>) or inverted (<math><msub><mi>m</mi><mn>3</mn></msub><mo>&lt;</mo><msub><mi>m</mi><mn>1</mn></msub><mo>&lt;</mo><msub><mi>m</mi><mn>2</mn></msub></math>). We show that, despite previous results giving a strong preference for the normal ordering, with the newest data from T2K and NOvA, this preference has all but vanished. Additionally, we highlight the importance of this result for nonoscillation probes of neutrinos, including neutrinoless double beta decay and cosmology. Future experiments, including JUNO, DUNE, and T2HK will provide valuable information and determine the mass ordering at a high confidence level.

Kevin J. Kelly

Puerto Rico

Neutrino mass ordering in light of recent data

Novel leptophilic neutral currents can be tested at upcoming neutrino oscillation experiments using two complementary processes, neutrino trident production and neutrino-electron (<math><mi>ν</mi><mo>−</mo><mi>e</mi></math>) elastic scattering. Considering generic anomaly-free <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> extensions of the Standard Model, we discuss the characteristics of <math><mi>ν</mi><mo>−</mo><mi>e</mi></math> scattering as well as <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> and <math><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> trident production at the DUNE near detector in the presence of such beyond the Standard Model scenarios. We then determine the sensitivity of DUNE in constraining the well-known <math><msub><mi>L</mi><mi>e</mi></msub><mo>−</mo><msub><mi>L</mi><mi>μ</mi></msub></math> and <math><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></math> models. We conclude that DUNE will be able to probe these leptophilic models with unprecedented sensitivity, covering unproved explanations of the <math><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><msub><mo>)</mo><mi>μ</mi></msub></math> discrepancy.

United Kingdom

Peter Ballett

Matheus Hostert

Silvia Pascoli

Zahra Tabrizi

<math><msup><mi>Z</mi><mo>′</mo></msup><mrow><mi>s</mi></mrow></math> in neutrino scattering at DUNE

Neutrinos may be the harbingers of new dark sectors, since the renormalizable neutrino portal allows for their interactions with hidden new physics. We propose here to use this fact to connect the generation of neutrino masses to a light dark sector, charged under a new <math><mi>U</mi><msub><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><mi>D</mi></mrow></msub></math> dark gauge symmetry. We introduce the minimal number of dark fields to obtain an anomaly free theory with spontaneous breaking of the dark symmetry, and obtain automatically the inverse seesaw Lagrangian. In addition, the so-called μ-term of the inverse seesaw is dynamically generated and technically natural in this framework. As a bonus, the new light dark gauge boson can provide a possible explanation to the MiniBooNE anomaly.