Search for light sterile neutrinos with ANTARES and KM3NeT/ORCA telescopes

A. Domi1,2, J. A. B. Coelho3, T. Thakore4, for the ANTARES and KM3NeT Collaborations

1 Università degli Studi di Genova, Genoa (Italy) - [email protected] 2 INFN-Genova, Genoa (Italy) 3 LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay (France) - [email protected] 4

University of Cincinnati, Ohio (United States) - [email protected]

VLVnT Workshop - 19/05/2021 1 Where are we with light sterile neutrinos? • Majority of experiments have confrmed the 3 favour neutrino oscillations. • In parallel, anomalies observed in some oscillation experiments: Anomalies in Short baseline (SBL) Ref: Prog.Part.Nucl.Phys. 111 (2020) 103736 experiments

•LSND: �� -> �e

•MINIBooNE: �� -> �e / �� -> �e

Gallium Anomalies: �e disappearance

Reactor anomalies: e disappearance � Disagreement between appearance and disappearance NO ANOMALIES observed in / disappearance. Further observations needed! �� �� 2 Where are we with light sterile neutrinos? Cosmology

• Constrains the efective number of relativistic species (Nef) in our universe.

• A SBL neutrino would require Nef=4.

• Measured Nef compatible with 3. -> Tension with SBL anomalies. • Tension relaxes when cosmological data are combined with astrophysical data. • Cosmological data alone can be compatible with

• an eV-mass sterile neutrino only if its contribution to Nef is very small,

• a larger Nef only if it comes from a nearly massless sterile particle.

We need further observations: neutrino telescopes make it possible! 3 Sterile Neutrinos

• Oscillations in the presence of sterile neutrinos are solutions of:

2 • Adding one sterile neutrino introduces 6 more free parameters: �m41 , 3 mixing angles (�14,�24,�34) and 2 more CP phases (�14, �24).

4 Sterile Neutrinos Solutions of Hef: resonances and �24 impact

EFFECT OF THE 4 RESONANCES IN THE AMPLITUDES Eigenvalues (in matter)

4 RESONANCES IN THE EIGENVALUES IMPACT OF �24 IN EIGENVALUES AND EFFECTIVE AMPLITUDES 5 Sterile Neutrinos

NMO and �24 degeneracy for E� > 10 GeV

• Resonance: Vn ~ �31 / ε • Resonance conditions:

1 • Possible for: No Sterile 0.9 NO, δ24 = 0° 0.8 IO, δ24 = 180° • neutrinos: 0.7

µ 0.6 ν

→

µ 0.5 ν

P 0.4 • antineutrinos: 0.3 0.2

0.1

0 10 102 Eν [GeV] 6 ANTARES Neutrino Telescope 12 lines -> 350 m height instrumented area 0.1 km2

~2500 m deep in the Mediterranean Sea.

Running since 2007 (completed in 2008).

25 units for each line 7 KM3NeT Neutrino Telescope 18 DOMS with 31 3’’ PMTs FOR EACH LINE

ORCA: 1 DENSE BUILDING BLOCK OPTIMISED FOR INTERMEDIATE ENERGIES (1-100 GEV) 20 m

ARCA: 2 SPARSE BUILDING BLOCKS OPTIMISED FOR HIGH ENERGIES (>1 TEV) 8 Deep Water Neutrino Telescopes NEUTRINO EVENT TOPOLOGIES

Tracks: ��CC, ��CC (�→�) Showers: �eCC, �NC, ��CC (�→�)

L ～ 4 m x E/GeV L ～ 0.9 + 0.36 ln(E/GeV) m

9 Neutrino telescopes: sterile neutrino search

Source: Atmospheric neutrinos.

The possible presence of a light sterile neutrino afects the oscillation pattern through the Earth.

STANDARD 3 � CASE STERILE NEUTRINO

Animation Ref: J. A. B. Coelho - http:// www.apc.univ-paris7.fr/ Downloads/antares/Joao/ animations/ 10 ANTARES & ORCA J. High Energ. Phys. 2019, 113 (2019). EVENT SELECTION

• ANTARES: only tracks used in the analysis. • Selection based on quality cuts of 2 reconstructions (A & B).

• ORCA: Random Decision Forest classifer with binary decision trees trained to classify: Method A • neutrinos vs atmospheric muons • neutrinos vs noise • tracks vs showers: 3 topologies based on track_score p: Tracks (track preselection & p > 0.7), Intermediates (shower preselection & 0.3 < p ≤ 0.7), Showers (shower preselection & p ≤ 0.3). arXiv:2103.09885 (2021). 11 Sterile Neutrino: Impact on event distributions Example plots for KM3NeT/ORCA - Same principle for ANTARES

Signed χ2 for tracks, total χ2 = 251 Signed χ2 for intermediates, total χ2 = 69 Signed χ2 for showers, total χ2 = 62 0 0 0 3 3 3 −0.1 −0.1 −0.1 −0.2 2 −0.2 2 −0.2 2 −0.3 −0.3 −0.3 1 1 1

−Z 0.4 −Z 0.4 −Z 0.4 θ θ θ −0.5 0 −0.5 0 −0.5 0 cos −0.6 cos −0.6 cos −0.6 −1 −1 −1 −0.7 −0.7 −0.7 −0.8 −2 −0.8 −2 −0.8 −2 −0.9 −0.9 −0.9 −3 −3 −3 −1 −1 −1 10 102 10 102 10 102 Eν [GeV] Eν [GeV] Eν [GeV]

active-sterile parameters: 12 Sterile Neutrino: Impact on event distributions Example plots for KM3NeT/ORCA

Majority of the impact below ANTARES energy threshold (~20 GeV)!

Signed χ2 for tracks, total χ2 = 3 Signed χ2 for intermediates, total χ2 = 69 Signed χ2 for showers, total χ2 = 171 0 1.5 0 1.5 0 1.5 −0.1 −0.1 −0.1 −0.2 1 −0.2 1 −0.2 1 −0.3 −0.3 −0.3 0.5 0.5 0.5

−Z 0.4 −Z 0.4 −Z 0.4 θ θ θ −0.5 0 −0.5 0 −0.5 0 cos −0.6 cos −0.6 cos −0.6 −0.5 −0.5 −0.5 −0.7 −0.7 −0.7 −0.8 −1 −0.8 −1 −0.8 −1 −0.9 −0.9 −0.9 −1 −1.5 −1 −1.5 −1 −1.5 10 102 10 102 10 102 Eν [GeV] Eν [GeV] Eν [GeV]

active-sterile parameters: 13 Sterile Neutrino: Impact on event distributions Example plots for KM3NeT/ORCA

Majority of the impact below ANTARES energy threshold (~20 GeV)!

Signed χ2 for tracks, total χ2 = 238 Signed χ2 for intermediates, total χ2 = 136 Signed χ2 for showers, total χ2 = 145 0 0 0 8 8 8 −0.1 −0.1 −0.1 6 6 6 −0.2 −0.2 −0.2 −0.3 4 −0.3 4 −0.3 4 2 2 2 −Z 0.4 −Z 0.4 −Z 0.4 θ θ θ −0.5 0 −0.5 0 −0.5 0 cos cos cos −0.6 −2 −0.6 −2 −0.6 −2 −0.7 −4 −0.7 −4 −0.7 −4 −0.8 −0.8 −0.8 −6 −6 −6 −0.9 −0.9 −0.9 −8 −8 −8 −1 −1 −1 10 102 10 102 10 102 Eν [GeV] Eν [GeV] Eν [GeV]

active-sterile parameters: 14 ANTARES ANALYSIS DATA: from 2007 to 2016 - 2830 days ONLY TRACK-LIKE EVENTS FITTED IN THE ANALYSIS MC: events passing the cuts assuming NO OSCI = 7590 (720 less with OSCI) DATA: events passing the cuts = 7710 J. High Energ. Phys. 2019, 113 (2019).

15 ANTARES: Upper limits on active-sterile mixing angles DATA: from 2007 to 2016 - 2830 days J. High Energ. Phys. 2019, 113 (2019).

This work NH 24 θ This work NH, δ24 = 0° 2

IceCube (2017) NH, δ24 = 0° IceCube (2017) IH, δ = 0°

cos 24 SK (2015) NH, = 0 34 δ24 ° θ 2 �24 and NMH sin 10−1 degeneracy allows for direct comparison �24 FREE -> LESS STRINGENT between LIMITS. NH & �24 FREE with 10−2 IH & �24 = 0

−3 −2 −1 10 10 10 2 sin θ24 16 KM3NeT/ORCA Sensitivity Study 3 years of assumed data taking

The analysis with ORCA fts track, intermediate and shower-like events.

17 2 KM3NeT/ORCA: Sensitivity to �24-�34 in the large �m41 limit 3 years of data taking

24 99% C.L. θ 2 KM3NeT/ORCA, truth=NO, δ24 FREE

cos KM3NeT/ORCA, truth=IO, δ24 FREE 34

θ ANTARES (2019), NO, δ24 FREE 2

IceCube (2017), IO, δ24 = 0° sin and NMO SK (2015), NO, δ24 = 0° �24 10−1 degeneracy allows for direct comparison LETTING �24 FREE WORSENS between THE SENSITIVITY. NO & �24 FREE with 10−2 IO & �24 = 0

−3 2 1 10 10− 2 10− sin θ24 18 2 KM3NeT/ORCA: Sensitivity to �24 for different �m41 values 3 years of data taking 10

1

10−1 ] 2

[eV −2 10 Cosmology (2020), 95% C.L. 2 41 �14, �34, �24, �34 FREE m

Δ IN THE ANALYSIS. 10−3 99% C.L. KM3NeT/ORCA, truth=NO −4 KM3NeT/ORCA, truth=IO 10 IceCube (2020), NO SK (2015), NO MINOS/MINOS+ (2020), NO 10−5 10−3 10−2 10−1 1 2 sin θ24 19 2 KM3NeT/ORCA: Sensitivity to �24 for different �m41 values 3 years of data taking 10

1

10−1 ] 2

[eV −2 10 Cosmology (2020), 95% C.L. 2 41

m Low frequency Δ (LF) region 10−3 99% C.L. KM3NeT/ORCA, truth=NO −4 KM3NeT/ORCA, truth=IO 10 IceCube (2020), NO SK (2015), NO MINOS/MINOS+ (2020), NO 10−5 10−3 10−2 10−1 1 2 sin θ24 20 KM3NeT/ORCA: LF region

With ORCA we have 2 advantages with respect to MINOS:

a longer baseline.

Earth’s matter efects can not be neglected.

1.0 No Sterile U = 0.1, U = 0, m2 = 0.1 µ4 τ4 Δ 14 U = 0.1, U = 0, m2 = 1e-3 µ4 τ4 Δ 14 U = 0.1, U = 0, m2 = 1e-4 µ4 τ4 Δ 14 0.8 µ

ν 0.6 -> µ ν P 0.4

0.2

0.0 1 10 102 E [GeV] 21 2 2 KM3NeT/ORCA: Sensitivity to �14 and |U�e| for different �m41 values 3 years of data taking

10 Neutrino-4 (2020), 99.73% C.L. 10 99% C.L. Global Fit (2019), 99% C.L. Reactors Global Fit (2020), 99% C.L. KM3NeT/ORCA, truth=NO 1 1 KM3NeT/ORCA, truth=IO Daya Bay+Bugey-3+MINOS (2020), NO ] ] 2

2 1 10−1 10− [eV [eV 2 41 2 41

m −2 m −2 10 Δ

Δ 10 95% C.L. KM3NeT/ORCA, truth=NO −3 10−3 KM3NeT/ORCA, truth=IO 10 STEREO (2020), NO LSND (2001), 99% C.L. Daya Bay+Bugey-3 (2020), NO MiniBooNE (2020), 99% C.L. Cosmology (2020) −4 −4 10 10 −6 −5 −4 −3 −2 −1 −4 −3 −2 −1 10 10 10 10 10 10 1 10 10 10 10 1 2 2 2 2 sin 2θµe = 4|U | |U | sin θ14 e4 µ4

�24, �34, �24, �34 FREE �34, �24, �34 FREE 22 2 KM3NeT/ORCA: Sensitivity to �34 for different �m41 values 3 years of data taking 10 99% C.L.

KM3NeT/ORCA, truth=NO

1 KM3NeT/ORCA, truth=IO

IceCube (2017), NO

SK (2015), NO ] 2 10−1 [eV 2 41

m −2 14, 24, 24, 34 FREE Cosmology (2020), 95% C.L. � � � �

Δ 10

10−3

10−4 10−3 10−2 10−1 1 2 sin θ34 23 Summary and Conclusions

• ANTARES shows very stringent upper limits on the active-sterile mixing angles with ~10 years of data [J. High Energ. Phys. 2019, 113 (2019)].

• KM3NeT/ORCA shows a high potential to probe the 3+1 model parameters in a wide range of sterile masses, after 3 years of data taking.

…. ORCA is now under construction and 6 DUs are already taking data!

The deployment of 6 more lines this year is foreseen.

24