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(C) Other neutrino mixing results

The LSND collaboration reported in AGUILAR 2001 a signal which is consistent with

{\overset{―}{ν}}_{μ}

\to

{\overset{―}{ν}}_{e}

oscillations. In a three neutrino framework, this would be a measurement of

θ_{12}

and

Δ m_{21}^{2}

. This does not appear to be consistent with most of the other neutrino data. The following listings include results from

ν_{μ}

\to

ν_{e}

,

{\overset{―}{ν}}_{μ}

\to

{\overset{―}{ν}}_{e}

appearance and

ν_{μ}

,

{\overset{―}{ν}}_{μ}

,

ν_{e}

, and

{\overset{―}{ν}}_{e}

disappearance experiments, and searches for

C P T

violation.

Search for $ν_{μ}$ or $ν_{e}$ $\to$ $ν_{s}$

VALUE

CL%

DOCUMENT ID

TECN

COMMENT

• • We do not use the following data for averages, fits, limits, etc. • •

< 5 \times 10^{- 4}

95

^{} T

β

decay

< 0.05

95

STEREO

< 0.02

95

SPEC

^{} T

β

decay

< 0.0035

95

RENO, NEOS

0.42

_{- 0.17}^{+ 0.15}

68

BEST

< 0.05

95

PROSPECT

< 0.005

95

Neutrino-4

< 0.008

95

DANSS

< 0.01

90

DANSS

< 0.06

90

STEREO

< 0.1

95

PROSPECT

< 0.4

90

ICCB

IceCube-DeepCore

< 8 \times 10^{- 3}

95

T

β

decay

< 0.01

90

NEOS

< 0.02

90

ICCB

IceCube

< 4.5 \times 10^{- 4}

95

MINOS, DayaBay

< 0.086

95

MINS

< 0.011

95

DAYA

MCRO

matter effects

SKAM

neutral currents + matter effects

¹	AKER 2023 assume a 3+1 neutrino mixing model, use low-rate commissioning data of the KATRIN tritium $β$ decay experiment to place a limit on sin $^{2} (θ_{14})$ for a admixture sterile neutrino mass m $_{4}$ of $\sim$ 300 eV.

²

ALMAZAN 2023 use inverse beta decay data collected by the STEREO experiment, placed 9 to 11 m from the ILL research reactor, to search for

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations. The ILL research reactor uses highly enriched

^{235} U

fuel. No indication of the oscillation to sterile neutrinos is found, the stated limit on sin

^{2} (2 θ_{14})

correspond to

Δ

m

_{41}^{2}

\sim

1 eV

^{2}

where the exclusion is maximal. Supersedes ALMAZAN 2018.

³

AKER 2022A uses the first two science runs of the KATRIN tritium

β

decay neutrino mass experiment to search for an admixture of sterile neutrinos. No evidence is found for a spectral anomaly, indicating such admixture. The resulting limit is on sin

^{2} (2 θ_{14})

for sterile neutrino masses m

_{4}

<

40 eV. It is most restrictive at

Δ

m

_{41}^{2}

\sim

400 eV

^{2}

. A 3+1 model is assumed.

⁴

ATIF 2022 report results from the combined analysis of the RENO (419 m) and NEOS (24 m) experiments data, collected at the Hanbit Nuclear Power Plant. Results, in terms of sin

^{2} (2 θ_{14})

, constrain for

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations. The authors report both excluded and allowed parameter combinations. The exclusion result reported here is based on the Feldman-Cousins method and for

Δ

m

_{41}^{2}

≃

0.55

eV

^{2}

. Part of the allowed area is excluded by the STEREO and PROSPECT experiments.

⁵

BARINOV 2022A report an event deficit observed using the segmented Baksan Ga neutrino detector, exposed to a 3.4 MCi

^{51} Cr

source. Equal suppression factors are observed for the inner and outer segments. The deficit is interpreted as evidence for oscillations to sterile neutrinos. The result is in terms of sin

^{2} (2 θ_{14})

, for a best fit of

Δ

m

_{41}^{2}

=3.3

_{- 2.3}^{+ \infty}

eV

^{2}

. Some, but not all, of the allowed neutrino parameter space conflicts with other experiments.

⁶

ANDRIAMIRADO 2021 reports a search for

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations at the HFIR research reactor, at baselines from 6.7 to 9.2 m. The reactor has a

^{235} U

core. 4 tons of

^{6} Li

-doped liquid scintillator are used in a segmented detector. Oscillations into sterile neutrinos are disfavored. The stated limit for sin

^{2} (2 θ_{14})

is for

Δ

m

_{41}^{2}

\sim

2 eV

^{2}

where the sensitivity is maximal.

⁷

SEREBROV 2021 searches for

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations with a moveable detector with baseline

6 - 12

m from the SM-3 research reactor with highly enriched

^{235} U

fuel. Analyzing the

L / E

dependence a

χ^{2}

minimum is found at

Δ

m

_{41}^{2}

=

7.3

\pm 0.13

\pm 1.16

eV

^{2}

and sin

^{2} (2 θ_{14})

=

0.36

\pm 0.12

. The quoted limit of 0.005 for sin

^{2} (2 θ_{14})

corresponds to

Δ

m

_{41}^{2}

\sim

2 eV

^{2}

. This is the result from 720 days of reactor ON and 860 days of reactor OFF measurements. The significance of the

χ^{2}

minimum is 2.9

σ

. Supersedes SEREBROV 2020, SEREBROV 2019 and SEREBROV 2018A.

⁸

SKROBOVA 2020 searches for

{\overset{―}{ν}}_{e} - {\overset{―}{ν}}_{s}

oscillations using the DANSS detector at 10.7, 11.2, and 12.7 m from the 3.1 GW

_{t h}

power reactor. The DANSS detector is highly segmented and moveable; the positions are changed usually 3 times a week. The analysis is based on the ratio of the events at top and bottom position; the middle position is used for checks of consistency. No evidence for sterile neutrinos is found. The quoted limit 0.008, the smallest excluded sin

^{2} (2 θ_{14})

, corresponds to

Δ

m

_{41}^{2}

\sim

1.0 eV

^{2}

. Supersedes ALEKSEEV 2018.

⁹

ALEKSEEV 2018 searches for

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations using the DANSS detector at 10.7, 11.2, and 12.7 m from the 3.1 GW

_{t h}

power reactor. The DANSS detector is highly segmented and moveable; the positions are changed usually 3 times a week. The analysis is based on the ratio of the events at top and bottom position; the middle position is used for checks of consistency. The best fit point is at

Δ

m

_{41}^{2}

= 1.4 eV

^{2}

and sin

^{2} (2 θ_{14})

= 0.05 with

Δ χ^{2}

= 13.1 (statistical errors only) compared to the fit with 3 active neutrinos only. The quoted limit of 0.01 for sin

^{2} (2 θ_{14})

corresponds to

Δ

m

_{41}^{2}

\sim

1.0 eV

^{2}

. Superseded by SKROBOVA 2020.

¹⁰

ALMAZAN 2018 searches for the

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations with baseline from 9.4 to 11.1 m from the ILL research reactor with highly enriched

^{235} U

fuel. The STEREO detector consists of six separated cells with

^{} Gd

loaded scintillator, with 15 m water equivalent overburden. The detected rate is

396.3

\pm 4.7

{\overset{―}{ν}}_{e}

/day with signal to background ratio of about 0.9. The reported results corresponds to 66 days of reactor-on. The analysis uses the relative rates normalized to the cell number 1. No indication of the oscillation to the sterile neutrinos is found, the stated limit on sin

^{2} (2 θ_{14})

correspond to

Δ

m

_{41}^{2}

\sim

3.5 eV

^{2}

where the exclusion is maximal. Superseded by ALMAZAN 2023.

¹¹

ASHENFELTER 2018 searches for the

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

oscillations at baseline from 6.7 to 9.2 m from the 85 MW research reactor with pure

^{235} U

core. The segmented 4 ton

^{6} Li

-doped liquid scintillator is operated with about 1 m water equivalent overburden and recorded

25461

\pm 283

IBD events. No indication of oscillations into sterile neutrinos was observed. The stated limit for sin

^{2} (2 θ_{14})

is for

Δ

m

_{41}^{2}

\sim

2 eV

^{2}

where the sensitivity is maximal.

¹²

AARTSEN 2017B uses three years of upward-going atmospheric neutrino data in the energy range of 10-60 GeV to constrain their disappearance into light sterile neutrinos. The reported limit sin

^{2} θ_{24}

<

0.11 at 90

%

C.L. is for

Δ

m

_{41}^{2}

= 1.0 eV

^{2}

. We convert the result to sin

^{2} 2 θ_{24}

for the listing. AARTSEN 2017B also reports cos

^{2} θ_{24} \cdot

sin

^{2} θ_{34}

<

0.15 at 90

%

C.L. for

Δ

m

_{41}^{2}

= 1.0 eV

^{2}

.

¹³

ABDURASHITOV 2017 use the Troitsk nu-mass experiment to search for sterile neutrinos with mass 0.1 - 2 keV. We convert the reported limit from

U_{e 4}^{2} <

0.002 to sin

^{2} 2 θ_{14} <

0.008 assume

U_{e 4} \sim

sin

θ_{14}

. The stated limit corresponds to the smallest

U_{e 4}^{2}

. The exclusion curve begins at

U_{e 4}^{2}

of 0.02 for m

_{4}

= 0.1 keV.

¹⁴

KO 2017 reports on short baseline reactor oscillation search (

{\overset{―}{ν}}_{e}

\to

{\overset{―}{ν}}_{s}

), motivated be the so-called "reactor antineutrino anomaly". The experiment is conducted at 23.7 m from the core of unit 5 of the Hanbit Nuclear Power Complex in Korea. the reported limited on sin

^{2} (2 θ_{41})

for sterile neutrinos was determined using the reactor antineutrino spectrum determined by the Daya Bay experiment for

Δ

m

_{14}^{2}

around 0.55 eV

^{2}

where the sensitivity is maximal. A fraction of the parameter space derived from the "reactor antineutrino anomaly" is excluded by this work. Compared to reactor models an event excess is observed at about 5 MeV, in agreement with other experiments.

¹⁵

AARTSEN 2016 use one year of upward-going atmospheric muon neutrino data in the energy range of 320 GeV to 20 TeV to constrain their disappearance into light sterile neutrinos. Sterile neutrinos are expected to produce distinctive zenith distribution for these energies for 0.01

\leq Δ

m

^{2} \leq

10 eV

^{2}

. The stated limit is for sin

^{2} 2 θ_{24}

at

Δ

m

^{2}

around 0.3 eV

^{2}

.

¹⁶	ADAMSON 2016B combine the results of AN 2016B, ADAMSON 2016C, and Bugey-3 reactor experiments to constrain $ν_{μ}$ to $ν_{e}$ mixing through oscillations into light sterile neutrinos. The stated limit for sin $^{2} 2 θ_{μ e}$ is at $\| Δ$ m $_{41}^{2} \|$ = 1.2 eV $^{2}$ .

¹⁷

ADAMSON 2016C use the NuMI beam and exposure of

10.56 \times 10^{20}

protons on target to search for the oscillation of

ν_{μ}

dominated beam into light sterile neutrinos with detectors at 1.04 and 735 km. The reported limit sin

^{2} (θ_{24})

<

0.022 at 95

%

C.L. is for

| Δ

m

_{41}^{2} |

= 0.5 eV

^{2}

. We convert the result to sin

^{2} (2 θ_{24})

for the listing.

¹⁸

AN 2016B utilize 621 days of data to place limits on the

{\overset{―}{ν}}_{e}

disappearance into a light sterile neutrino. The stated limit corresponds to the smallest sin

^{2} (2 θ_{14})

at

| Δ

m

_{41}^{2} |

\sim

3 \times 10^{- 2}

eV

^{2}

(obtained from Figure 3 in AN 2016B). The exclusion curve begins at

| Δ

m

_{41}^{2} | \sim 1.5 \times 10^{- 4}

eV

^{2}

and extends to

\sim 0.25

eV

^{2}

. The analysis assumes sin

^{2} (2 θ_{12})

=

0.846

\pm 0.021

,

Δ

m

_{21}^{2}

= (

7.53

\pm 0.18

)

\times 10^{- 5}

eV

^{2}

, and

| Δ

m

_{32}^{2} |

= (

2.44

\pm 0.06

)

\times 10^{- 3}

eV

^{2}

.

¹⁹

AMBROSIO 2001 tested the pure 2-flavor

ν_{μ}

\to

ν_{s}

hypothesis using matter effects which change the shape of the zenith-angle distribution of upward through-going muons. With maximum mixing and

Δ

m

^{2}

around

0.0024

eV

^{2}

, the

ν_{μ}

\to

ν_{s}

oscillation isdisfavored with 99

%

confidence level with respect to the

ν_{μ}

\to

ν_{τ}

hypothesis.

²⁰

FUKUDA 2000 tested the pure 2-flavor

ν_{μ}

\to

ν_{s}

hypothesis using three complementary atmospheric-neutrino data samples. With this hypothesis, zenith-angle distributions are expected to show characteristic behavior due to neutral currents and matter effects. In the

Δ

m

^{2}

and sin

^{2} 2 θ

region preferred by the Super-Kamiokande data, the

ν_{μ}

\to

ν_{s}

hypothesis isrejected at the 99

%

confidence level, while the

ν_{μ}

\to

ν_{τ}

hypothesis consistently fits all of the data sample.

EPJ C83 763

Search for keV-scale Sterile Neutrinos with first KATRIN Data

NAT 613 257

STEREO neutrino spectrum of

^{235}

U fission rejects sterile neutrino hypothesis

PR D105 072004

Improved eV-scale sterile-neutrino constraints from the second KATRIN measurement campaign

PR D105 L111101

Search for sterile neutrino oscillations using RENO and NEOS data

PR C105 065502

Search for electron-neutrino transitions to sterile states in the BEST experiment

PRL 128 232501

Results from the Baksan Experiment on Sterile Transitions (BEST)

PR D103 032001

Improved short-baseline neutrino oscillation search and energy spectrum measurement with the PROSPECT experiment at HFIR

PR D104 032003

Search for sterile neutrinos with the Neutrino-4 experiment and measurement results

IJMP A35 2044015

New results from the DANSS experiment

PL B787 56

Search for sterile neutrinos at the DANSS experiment

PRL 121 161801

Sterile Neutrino Constraints from the STEREO Experiment with 66 Days of Reactor-On Data

PRL 121 251802

First search for short-baseline neutrino oscillations at HFIR with PROSPECT

PR D95 112002

Search for Sterile Neutrino Mixing using Three Years of IceCube DeepCore Data

JETPL 105 753

First Measeurements in Search for keV-Sterile Neutrino in Tritium beta-Decay by Troitsk nu-Mass Experiment

PRL 118 121802

Sterile Neutrino Search at the NEOS Experiment

PRL 117 071801

Searches for Sterile Neutrinos with the IceCube Detector

PRL 117 151803

Search for Sterile Neutrinos Mixing with Muon Neutrinos in MINOS

PRL 117 151801

Limits on Active to Sterile Neutrino Oscillations from Disappearance Searches in the MINOS, Daya Bay, and Bugey-3 Experiments

PRL 117 151802

Improved Search for a Light Sterile Neutrino with the Full Configuration of the Daya Bay Experiment

PL B517 59

Matter Effects in Upward Going Muons and Sterile Neutrino Oscillations

PRL 85 3999

τ

Neutrinos Favored over Sterile Neutrinos in Atmospheric Muon Neutrino Oscillations

Except where otherwise noted, content of the 2024 Review of Particle Physics is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license. The publication of the Review of Particle Physics is supported by US DOE, MEXT (Japan), INFN (Italy) and CERN. Individual collaborators receive support for their PDG activities from their respective institutes or funding agencies. © 2024. See LBNL disclaimers.