JUNO Oscillation Physics

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Jinnan Zhang ^1,²

On behalf of the JUNO collaboration

August 30, 2021

17th International Conference on Topics in Astroparticle and Underground Physics

Online

E-mail: [email protected] ¹Institute of High Energy Physics, Beijing, China

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Outline

• JUNO experiment

• Multi-purpose liquid scintillator detector

• Neutrino mixing and oscillation

• Oscillation physics at JUNO

• Reactor neutrino: _𝑒𝑒̅𝜈𝜈

• Atmospheric neutrino: 𝜈𝜈_𝜇𝜇, _𝜇𝜇̅𝜈𝜈 , 𝜈𝜈_𝑒𝑒, _𝑒𝑒̅𝜈𝜈

• ⁸B solar neutrino: 𝜈𝜈_𝑒𝑒

• Summary

JUNO Oscillation Physics - TAUP 2021 2

Jinnan Zhang (IHEP)

JUNO Central detector

JUNO experimental hall

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JUNO Experiment: Layout

• A multi-purpose liquid scintillator experiment in China:

• Reactor �𝝂𝝂_𝒆𝒆 ~ 𝟔𝟔𝟔𝟔/𝐝𝐝𝐝𝐝𝐝𝐝

• Atmospheric 𝝂𝝂’s: several/day

• Solar 𝝂𝝂_𝒆𝒆 ~ 10-1000/day

• Supernova 𝜈𝜈’s ~ 10⁴ in 10 s for 10 kpc

• DSNB 2-4 IBD/year

• Geo-𝜈𝜈’s 1-2/day

• Optimized baseline for neutrino mass ordering determination with reactor ̅𝜈𝜈_𝑒𝑒

Figure: Setup of JUNO experiment, with the main 20-kton JUNO detector and satellite 2.8-ton TAO detector.

Jiangmen Underground Neutrino Observatory

Kaiping, Jiangmen city, Guangdong Province

~700 m underground

See also Giulio Settanta’s talk: “JUNO Non-oscillation Physics”

This talk

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JUNO Experiment: Detector

Jinnan Zhang (IHEP) JUNO Oscillation Physics - TAUP 2021 4

• A multi-purpose liquid scintillator experiment.

• Energy resolution < 3%/ 𝑬𝑬 𝐌𝐌𝐌𝐌𝐌𝐌 :

• ~78% PMT coverage, ~1350 PE/MeV:

• 5000 Hamamatsu 20′′ dynode-PMTs

• 12612 NNVT 20′′ MCP-PMTs

• 25600 HZC 3′′ PMT

• Large target volume:

• 20-kton LAB-based liquid scintillator

• Energy scale uncertainty <1%

• JHEP03(2021)004: “Calibration strategy of the JUNO experiment”

• Background control

• arXiv:2107.03669: “Radioactivity control strategy for the JUNO detector”

43.5 m

See also Zhimin Wang’s talk: “JUNO Detector Design

& Status”

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Neutrino Mixing Open Question

1 2 3

µ µ µ

µ

τ τ

ν ν ν

ν

ν ν

  

 

 

 

=  

 

 

 

 

 

  

e e e

e U U U

U U U U U U

θ₂₃ ~ 49°

Atmospheric Accelerator

θ₁₂ ~ 34°

Solar Reactor

0νββ θ₁₃ ~ 9°

Reactor Accelerator

Mass eigenstates Flavor

eigenstates

Pontecorvo-Maki- Nakagawa-Sakata (PMNS) mixing matrix

parametrization

𝑈𝑈 = 1 0 0

0 𝑐𝑐₂₃ 𝑠𝑠₂₃ 0 −𝑠𝑠₂₃ 𝑐𝑐₂₃

𝑐𝑐₁₃ 0 𝑠𝑠₁₃𝑒𝑒^{−𝑖𝑖𝛿𝛿}^{𝐶𝐶𝐶𝐶}

0 1 0

−𝑠𝑠₁₃𝑒𝑒^{𝑖𝑖𝛿𝛿}^{𝐶𝐶𝐶𝐶} 0 𝑐𝑐₁₃

𝑐𝑐₁₂ 𝑠𝑠₁₂ 0

−𝑠𝑠₁₂ 𝑐𝑐₁₂ 0

0 0 1

𝑒𝑒^{𝑖𝑖𝜂𝜂}¹ 0 0 0 𝑒𝑒^{𝑖𝑖𝜂𝜂}² 0

0 0 1

• Neutrino mass ordering

:

Whether 𝝂𝝂

_𝟑𝟑

mass eigenstate is

heavier or lighter than the 𝝂𝝂

_𝟏𝟏

and 𝝂𝝂

_𝟐𝟐^?

• 𝜈𝜈₁ has the largest component of the 𝜈𝜈_𝑒𝑒.

• 𝜈𝜈₃ has the smallest component of the 𝜈𝜈_𝑒𝑒.

𝑃𝑃(𝜈𝜈_𝛼𝛼 → 𝜈𝜈_𝛽𝛽) = | 𝜈𝜈_𝛽𝛽 𝜈𝜈_𝛼𝛼 𝑡𝑡 |² = �

𝑖𝑖=1 3

�

𝑗𝑗=1 3

𝑈𝑈_{𝛼𝛼𝑖𝑖}^∗ 𝑈𝑈_{𝛽𝛽𝑗𝑗} 𝜈𝜈_𝑗𝑗 𝜈𝜈_𝑖𝑖 𝑡𝑡

Neutrino oscillation: 2

JHEP09(2020)178

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Reactor 𝑒𝑒 ̅𝜈𝜈 : Source and Oscillation

• Source^:reactor antineutrino from fission of four isotopes:

• ²³⁵U, ²³⁸U, ²³⁹Pu, and ²⁴¹Pu

• Major: 6 YJ cores, 4 → 2 TS cores

Table: Thermal power and baseline to the JUNO detector for the Yangjiang (YJ), Taishan (TS), Daya Bay (DYB), and Huizhou (HZ) reactor cores.

Oscillation

Inverse Beta Decay

Delayed signal

~200 𝜇𝜇s as tag

The energy resolution is one of the key factors for determining neutrino mass ordering (NMO).

[1]. Oscillation in matter with effective oscillation parameters (j.physletb.2020.135354).

J. Phys. G43:030401 (2016) → arXiv:2104.02565

• Oscillation: _𝑒𝑒_̅𝜈𝜈 survival probability in vacuum ¹ :

𝑃𝑃_�𝜈𝜈_𝑒𝑒_{→�𝜈𝜈}_𝑒𝑒 = 1−cos⁴𝜃𝜃₁₃sin² 2𝜃𝜃₁₂sin^{2 Δ𝑚𝑚}_4𝐸𝐸¹²² ^𝐿𝐿

−sin²2𝜃𝜃₁₃ cos²𝜃𝜃₁₂sin²Δ𝑚𝑚₃₁² 𝐿𝐿

4𝐸𝐸 + sin²𝜃𝜃₁₂sin²Δ𝑚𝑚₃₂² 𝐿𝐿 4𝐸𝐸 .

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Reactor 𝑒𝑒 ̅𝜈𝜈 : Detector Response

Due to the nucleon recoil,

positron energy 𝐸𝐸_𝑒𝑒⁺(𝐸𝐸_𝜈𝜈) has a width:

Nucleon recoil is not negligible

Inverse Beta Decay

• Energy nonlinearity (NL) of liquid scintillator (LS) [j.nima.2019.06.031]:

𝑓𝑓_{𝑁𝑁𝐿𝐿} 𝐸𝐸_dep ≡ 𝐸𝐸_vis/𝐸𝐸_dep.

𝑒𝑒⁺ deposited energy: E_{𝑑𝑑𝑒𝑒𝑑𝑑} ∝ 𝐸𝐸_𝑒𝑒⁺ + 0.511 MeV. Visible energy 𝐸𝐸_vis ∝ 𝑁𝑁_{𝑃𝑃𝐸𝐸}.

• Energy resolution (Res) [JHEP03(2021)004]:

𝜎𝜎/𝐸𝐸_vis = 𝑎𝑎/ 𝐸𝐸_vis ²+𝑏𝑏²+ 𝑐𝑐/𝐸𝐸_vis ²

See also “Energy Response Model for JUNO

Experiment” by Miao Yu Delayed signal

~200 𝜇𝜇sas tag

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Reactor 𝑒𝑒 ̅𝜈𝜈 : Signal and Background

• Event selection and background suppression:

• With fiducial volume, energy selection, time coincidence, vertex correlation, and muon veto

• ~82% efficiency for IBD events

Table: The estimated background for reactor _𝑒𝑒̅𝜈𝜈 events, based on the

measurement and simulation.

arXiv:2104.02565

JUNO Simulation Preliminary

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Reactor 𝑒𝑒 ̅𝜈𝜈 : JUNO-TAO Spectrum Reference

• Taishan Antineutrino Observatory:

• Satellite detector for JUNO

• ~30 m from reactor core

• ~2000 IBD events/day

• Run @ -50 ℃

• Energy resolution ~2% @1 MeV

• Physics goals:

• Reference for reactor _𝒆𝒆̅𝜈𝜈 spectrum

• Sterile neutrino measurement:

• Sensitive range: 0.5 eV² < Δ𝑚𝑚₄₁² < 5 eV²

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Reactor 𝑒𝑒 ̅𝜈𝜈 : Neutrino Mass Ordering

• Neutrino mass ordering (NMO):

Δ𝜒𝜒

²

= 𝜒𝜒

_{𝑚𝑚𝑖𝑖𝑚𝑚}²

NO − 𝜒𝜒

_{𝑚𝑚𝑖𝑖𝑚𝑚}²

IO ;

• Median sensitivity > 3 𝝈𝝈 in 6 years with only JUNO data.

With external Δ𝑚𝑚

₃₂²

/Δ𝑚𝑚

₃₁²

constraint:

• JUNO sensitivity ~ 𝟒𝟒𝝈𝝈 in 6 years or 𝟑𝟑𝝈𝝈 in less than 6 years

• Great potential in combining with accelerator or atmospheric experiment:

• PhysRevD.101.032006, PhysRevD.103.112010

• arXiv:2008.11280, arXiv:2108.06293

J. Phys. G43:030401 (2016)

A publication is coming soon on JUNO NMO sensitivity.

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Reactor

_𝑒𝑒

̅𝜈𝜈 : Precision Measurement of Oscillation Parameters

• Precision measurement of oscillation parameters:

Relative

Precision (%) sin²𝜃𝜃₁₂ Δm₂₁² sin²𝜃𝜃₁₃ Δm₃₁² /Δm₃₂² Current global fit

(Nufit 5.0) [1] 4.0 2.8 2.8 1.1

PDG2020 [2] 4.2 2.4 3.2 1.4

JUNO 6 years 0.5 0.3 12 0.2

• JUNO will dominant the precision of Δ𝑚𝑚₃₁² /Δ𝑚𝑚₃₂² , Δ𝑚𝑚₂₁² , and sin² 𝜃𝜃₁₂

in 1 year

• To sub-percent level in 1-2 years

A publication on the precision measurement of the oscillation parameters is coming soon.

JUNO Simulation Preliminary

[1]. JHEP09(2020)178 [2]. PTEP 2020 (2020) 8, 083C01

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Atmospheric 𝜈𝜈′ s at JUNO

J. Phys. G43:030401 (2016)

JUNO

• Atmospheric neutrinos:

• 𝜈𝜈_𝜇𝜇/𝜈𝜈_𝑒𝑒 identification

• 𝜈𝜈/ ̅𝜈𝜈 classification

• 𝜇𝜇 direction 𝜎𝜎_𝜃𝜃_𝜇𝜇 < 1^∘ for 𝐿𝐿_𝜇𝜇 >5 m

• Energy resolution ~1% @ 1 GeV

• NMO sensitivity potential:

• >1𝝈𝝈 in 6 years

• With 𝜈𝜈_𝜇𝜇/ _𝜇𝜇̅𝜈𝜈 CC and 𝜈𝜈_𝑒𝑒/ _𝑒𝑒̅𝜈𝜈 CC events

• 𝜃𝜃₂₃ octant determination

• Complementary measurement for 𝛿𝛿_{𝐶𝐶𝑃𝑃}

Energy and zenith angle distribution

arXiv: 2103.09908

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Solar 𝜈𝜈 𝑒𝑒 Measurement

•

⁸

B solar neutrino

• Main channel 𝜈𝜈-e ES: 𝜈𝜈_𝛼𝛼 + 𝑒𝑒⁻ → 𝜈𝜈_𝛼𝛼 + 𝑒𝑒⁻

• Radioactivity: 10⁻¹⁷ g/g U/Th

• Signal/background (10 years): 60000/30000

• Physics:

• 0.9% sensitivity day-night-asymmetry (SK 1.1%)

• 20% precision of Δ𝑚𝑚₂₁² , 8% precision of sin² 𝜃𝜃₁₂

• Solar neutrino flux measurement

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Summary

• Multipurpose experiment JUNO:

• Neutrino mass ordering determination:

• > 3𝜎𝜎 in 6 years with only reactor _𝑒𝑒̅𝜈𝜈

• > 1𝜎𝜎 with JUNO atmospheric neutrinos

• Precision measurement of oscillation parameters

• Sub-percent for Δ𝑚𝑚₃₁² /Δ𝑚𝑚₃₂² , Δ𝑚𝑚₂₁² , and sin² 𝜃𝜃₁₂ with reactor _𝑒𝑒̅𝜈𝜈

• 𝜃𝜃₂₃ octant with atmospheric neutrinos

• Independent Δ𝑚𝑚₂₁² and sin²𝜃𝜃₁₂ measurement with solar ⁸B neutrino

• TAO detector

• High precision reactor neutrino spectrum

• Sterile neutrino exploration

• JUNO will start operation in 2023

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Thank you for your attention!

Jinnan Zhang IHEP, Beijing, China

Other JUNO talks:

#31. JUNO Detector Design & Status

#273. JUNO Non-oscillation Physics

Posters:

#142. The JUNO OSIRIS detector

#172. Energy Response Model for JUNO Experiment

#244. Characterization of the JUNO Large-PMT readout electronics

#290. Detection of Core-Collapse Supernova Neutrino at JUNO

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Backup

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JUNO reactor 𝑒𝑒 ̅𝜈𝜈 analysis input update

• Bad news

• Two of Taishan reactor cores will not be build

• Reactor flux decreased by ~ 25%

• Experiment hall shifted by ~ 60 m

• Comic muon flux increased by ~ 30%

• Good news

• Background control: more realistic with measurement and simulation

• Optimized event selection and muon veto strategies:

• IBD selection efficiency: 73%→ ~ 82%

• Higher 20-inch PMT photon detection efficiency:

• ~𝟐𝟐𝟐𝟐𝟐 → ~𝟐𝟐𝟐𝟐𝟐

• More realistic PMT and liquid scintillator optical model

• Combined analysis with TAO

Comparing to J. Phys.

G43:030401 (2016)

Better energy resolution

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Systematic uncertainties

Figure: The systematic uncertainties that will distort the measured spectrum.

• The uncertainty of energy scale,

background, spent nuclear fuel, and non-equilibrium correction may

have close pattern as oscillation.

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Systematic uncertainty breakdown

Table: List of reactor _𝑒𝑒̅𝜈𝜈 analysis systematic uncertainties.

The dominant syst. for precision measurement:

• Δ𝑚𝑚₃₁² /Δ𝑚𝑚₃₂² : reactor spectrum shape

• Δ𝑚𝑚₂₁² : background, non-equilibrium effect

• sin² 𝜃𝜃₁₂ , sin² 𝜃𝜃₁₃: normalization rate