NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
Abstract
Parallel talk presented at the XXI International Workshop on Neutrino Telescopes - Padova 29 September - 3 October 2025 (https://agenda.infn.it/event/44606/) On behalf of the JUNO Collaboration Abstract: The Jiangmen Underground Neutrino Observatory (JUNO) is a next-generation neutrino experiment in South China that is currently in the final stages of commissioning. Situated beneath 650 meters of rock overburden (1800 meters water equivalent), JUNO’s central detector features a 20-kiloton liquid scintillator target enclosed within a 35.4-meter-diameter acrylic sphere. It achieves a remarkable 78% photocathode coverage through a hybrid array of 17,612 large (20-inch) and 25,600 small (3-inch) photomultiplier tubes. This extensive coverage is essential to meet the experiment’s goal of an unprecedented energy resolution of 3% at 1 MeV.JUNO’s primary objective is to determine the neutrino mass ordering (NMO) using reactor antineutrinos. However, it also has the potential to probe atmospheric neutrino oscillations through matter effects, offering an independent sensitivity to NMO. When combined, these measurements can enhance JUNO’s overall sensitivity. Notably, JUNO will be the first experiment to explore GeV-scale atmospheric neutrino oscillations using a large, homogeneous liquid scintillator detector. In contrast to conventional water Cherenkov detectors, JUNO’s liquid scintillator requires the development of novel reconstruction techniques to identify neutrino flavors, differentiate between neutrinos and antineutrinos, and reconstruct particle direction and energy in the GeV range.This talk will be focused on recent advancements toward these goals, including progress in reconstructing the energy and direction of atmospheric neutrinos, identifying neutrino flavor and type, and suppressing background events. Preliminary sensitivity studies will also be discussed.
Full text
VANESSA CERRONE on behalf of the JUNO collaboration [email protected] XXI International Workshop on Neutrino Telescopes, Sep 29th – October 3rd , 2025, Padova NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
JUNO AT A GLANCE 1 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO PPNP 123 (2022): 103927 Yangjiang 52.5 km 52.5 km 736.0 m 6x 2.9 GWth Taishan 252.5 m 2x 4.6 GWth JUNO Overburden ~650 m (1800 m.w.e.) Vertical shaft 563 m Slope tunnel 1265 m ◿ 42% The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton multi-purpose liquid scintillator detector . It sits at a baseline of about 52.5 km from eight nuclear reactors in the Guangdong Province of South China. 26.6 GWth
JUNO STATUS (2024 - TODAY) 2 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO 2024, Dec 18th Start of Water Filling 2025, Jan TT installation started 2025, Feb 1st End of Water Filling 2025, Feb 8th Start of LS Filling Water Phase Mixed Phase 2025, Aug 22nd End of LS Filling 2025, June 2025, Aug 26th Start of Data Taking Full detector calibration Scheme from A. Garfagnini @ TAUP 2025
JUNO KEY EXPERIMENTAL FEATURES 3 Central detector (CD) ✶ 20 kton of liquid scintillator ✶ 17612 20” large-PMTs and 25600 3” small-PMTs à 78% photo-coverage ✶Earth’s magnetic field compensation coils Water Cherenkov Detector (WCD) ✶35 kton of high pure water as shield ✶2400 20” large-PMTs for active veto Top Tracker (TT) ✶3 plastic scintillator layers (coverage ~30% of muons) Calibration system ✶More than 6 sources + laser 35.4 m 44 m PPNP 123 (2022): 103927 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO More details in M. Sisti talk
JUNO PHYSICS PROGRAM 4 JUNO has a rich physics program and will detect neutrinos from several sources. Neutrino oscillations Neutrinos as a probe Reactor !𝜈!#Atmospheric 𝜈/ !𝜈 Solar 𝜈! Supernovae Geo-neutrinos BSM physics VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
JUNO PHYSICS PROGRAM 5 JUNO has a rich physics program and will detect neutrinos from several sources. Neutrino oscillations Reactor !𝜈!#Atmospheric 𝜈/ !𝜈 Solar 𝜈! Supernovae Geo-neutrinos BSM physics Neutrinos as a probe Han Zhang’s talk VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
JUNO PHYSICS PROGRAM 6 JUNO has a rich physics program and will detect neutrinos from several sources. Neutrino oscillations Reactor !𝜈!#Atmospheric 𝜈/ !𝜈 Solar 𝜈! Supernovae Geo-neutrinos BSM physics Neutrinos as a probe In this presentation focus on atmospheric neutrinos VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
⇠ m2 31 ⇠sin22✓13 0 5 10 15 20 25 Events [MeV°1] £103No oscillations£1/7 Normal Ordering Inverted Ordering Only solar term: sin2µ12 =0.282, sin2µ13 =0 2345678 Neutrino energy [MeV] 0.0 0.5 1.0 Survival probability ⇠sin22✓12 ⇠m2 21 7 WHY ATMOSPHERIC NEUTRINOS IN JUNO? ✶ Atmospheric neutrinos provide independent sensitivity to NMO via matter effects ✶Combining reactor antineutrinos and atmospheric neutrinos oscillations can maximize JUNO NMO sensitivity VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO 100101 Energy [GeV] °1.0 °0.8 °0.6 °0.4 °0.2 0.0 cos µz Normal ordering 100101 Energy [GeV] °1.0 °0.8 °0.6 °0.4 °0.2 0.0 cos µz Normal ordering 0.0 0.1 0.2 0.3 0.4 0.5 0.6 P(∫µ!∫e) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 P(¯∫µ!¯∫e) 0 2º 0 2º 0 2º ¢m2 21 '7.5£10°5eV2 ¢m2 32 '2.5£10°3eV2 0 2º 0 2º 0 2º ¢m2 31 '2.5£10°3eV2 ¢m2 21 '7.5£10°5eV2 ∫1 ∫2 ∫3 ∫3 ∫1 ∫2 Normal Ordering: m1<m 2<m 3Inverted Ordering: m3<m 1<m 2 ∫e∫µ∫ø Reactor % 𝝂𝒆#: NMO sensitivity through interference, oscillations by small and large mass splittings Atmospheric 𝝂/% 𝝂 : NMO sensitivity through matter effects, MSW effect
8 ATMOSPHERIC NEUTRINO OSCILLATIONS VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO 100101 Energy [GeV] °1.0 °0.8 °0.6 °0.4 °0.2 0.0 cos µz Normal ordering 100101 Energy [GeV] °1.0 °0.8 °0.6 °0.4 °0.2 0.0 cos µz Normal ordering 0.0 0.1 0.2 0.3 0.4 0.5 0.6 P(∫µ!∫e) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 P(¯∫µ!¯∫e) CMB 𝑃(𝜈#→ 𝜈!)(NO) 𝑃( !𝜈#→ !𝜈!)(NO) Flavor transition enhanced for neutrinos (antineutrinos) if NO (IO) Core to Mantle Boundary (CMB) ✶Atmospheric neutrinos (of several GeV) going through Earth’s matter undergo MSW effects ✶Neutrino oscillation probability 𝑃 = 𝑓 $ %, 𝐿 ∼ cosθ,depends on the neutrino energy, incident zenith angle 𝜃, and type/flavor à Neutrino directionality and flavor identification are critical
15 DIRECTION RECONSTRUCTION VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO ✶Both lepton and hadron information is used in the direction reconstruction ✶ Reconstructed neutrino direction less smeared from true neutrino direction compared with the charged lepton direction Phys.Rev.D 109 (2024) 5, 052005 ✶Compared with non-ML traditional methods: •Likelihood method based on light propagation model to get particle trajectory •Similar results, but ML works better for electron neutrinos PoS(ICRC2023)1189
16 ENERGY RECONSTRUCTION VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO ✶Preliminary results: for 𝐸𝜈 > 3 GeV: •Better than 6% resolution for electron neutrinos •Better than 8% resolution for muon neutrinos ✶Investigating two possible strategies for energy reconstruction: reconstruct the visible energy or the neutrino energy for FC CC events à detailed study is on-going for the impact on oscillation analysis WORK IN PROGRESS WORK IN PROGRESS
17 NEUTRINO FLAVOR IDENTIFICATION VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO Phys. Rev. D 112, 012018 (2025) ✶Event topology information reflected in the PMT waveforms ✶PMT waveforms are used to classify: 𝛍 -like, e-like and NC-like
18 NEUTRINO vs ANTINEUTRINO VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO Phys. Rev. D 112, 012018 (2025) ✶Antineutrinos transfer less energy to hadrons (less hadronic interaction): encoded in PMT waveform ✶Antineutrino interactions tend to produce more primary neutrons than neutrino interactions à statistically separate 𝜈 and $𝜈%adding neutron-capture information •Energy between 2-2.7 MeV •Time from prompt trigger between 10 𝜇s and 1 ms
19 TOWARDS AN UPDATED SENSITIVITY VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO ✶Recent updates in reconstruction and event identification ✶Re-evaluation of sensitivity in progress J. Phys. G. 43 030401 From Q. Yan talk at NuFact 2025
CONCLUSIONS 20 ✶First measurement of atmospheric neutrinos with a LS detector à sub-GeV to multi-GeV energy range ✶NMO through matter effects, complementary to reactor antineutrinos, boost the overall NMO sensitivity ✶New atmospheric neutrinos study in JUNO ongoing with the latest and more realistic detector response à paper coming soon •Progress in event reconstruction and identification •Crosschecked with ML and non-ML methods •Systematic uncertainties under study ✶Construction of the JUNO detector is fully completed à stay tuned for exciting physics results! VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
BACKUP 21 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
NEUTRINO vs ANTINEUTRINO 22 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
NEUTRINO vs ANTINEUTRINO 23 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
MAJOR IMPROVEMENTS IN DETECTOR RESPONSE 24 VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
STATUS OF 𝝂OSCILLATION PHYSICS 31 5 knowns: üΔ𝑚#$ #∼ 7.5 × 10%&eV# ü|Δ𝑚'$ #| ∼ 2.5 × 10%'eV# üsin#𝜃$# ∼ 0.3 üsin#𝜃#' ∼ 0.5 üsin#𝜃$' ∼ 0.02 5 known unknowns: ?Mass ordering: Δ𝑚#$ #> 0 but Δ𝑚'$ #≷ 0 ? ?Octant of 𝜃#': 𝜃#' ≷ 45º? ?CP phase 𝛿: 𝛿 not 0 or 𝜋 ? CP violation? ?Dirac or Majorana nature ?Absolute mass scale Cannot be probed with νoscillations JUNO will contribute to both the precision and discovery frontiers Precision measurement of three parameters: Δ𝑚#$ #, Δ𝑚'$ #, and sin#𝜃$# Mass ordering determination VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO
NEUTRINO SOURCES IN JUNO 32 Source Expected rate Energy range Reactor ~ 60 / day SN burst ~ 7300 @ 10 kpc in few s DSNB ~"2-4 / year Solar (8B ) O(100) / day Atmospheric ~"O(100) /year Geo-neutrinos ~"400 / year 0.1 110 102103104MeV Reactor $𝜈!%Atmospheric 𝜈/ $𝜈 Solar 𝜈! Supernovae Geo-neutrinos VANESSA CERRONE – NEUTRINO OSCILLATIONS WITH ATMOSPHERIC NEUTRINOS IN JUNO