Neutrino Experiments

Overview

Liangjian WenInstitute of High Energy Physics, CAS

Jun. 7, 2021

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Xing，Phys. Rep. 854(2020)1

Quark and Lepton Mass Spectra

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|𝑈| =

CKM

Hierarchy!

|𝑉| =

PMNS

Approximate μ-τ symmetry?

Fundamental problem: neutrino absolute masses?Quarks vs. Leptons: A big puzzle of fermion flavor mixings

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Neutrino Mass & Flavor Mixing

M. V. Diwan et al (2016)

𝜽𝟏𝟑 ~ 𝟖. 𝟒∘

𝜽𝟏𝟐 ~ 𝟑𝟒∘

𝜽𝟐𝟑 ~ 𝟒𝟓∘ |𝚫𝒎𝟑𝟐𝟐 | ~ 𝟐. 𝟓 × 𝟏𝟎−𝟑 eV𝟐

𝚫𝒎𝟐𝟏𝟐 ~ 𝟖 × 𝟏𝟎−𝟓 eV𝟐

𝑉 =1 0 00 𝑐23 𝑠230 −𝑠23 𝑐23

𝑐13 0 𝑠13𝑒−𝑖𝛿

0 1 0−𝑠13𝑒

𝑖𝛿 0 𝑐13

𝑐12 𝑠12 0−𝑠12 𝑐12 00 0 1

𝑒𝑖𝜌 0 00 𝑒𝑖𝜎 00 0 1

Standard Parameterization of the PMNS Matrix

0ν2β, LNV?

𝜽𝟐𝟑 𝑶𝒄𝒕𝒂𝒏𝒕?

Daya Bay dominates the global precision

Daya Bay

Double Chooz RENO

𝜎𝑠𝑖𝑛22𝜃13

𝜎Δ𝑚

𝑒𝑒2

10−3eV

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end of DYB data taking @2020.12.12

𝑃 𝜈𝑒 → 𝜈𝑒 = 1 − sin2 2𝜃13 cos2 𝜃12 sin2 Δ31 + sin2 𝜃12 sin

2 Δ32 − cos4 𝜃13 sin2 2𝜃12 sin

2 Δ21

≈ 1 − sin2 2𝜃13 sin2 Δ𝑒𝑒 − cos4 𝜃13 sin

2 2𝜃12 sin2 Δ21 Δ𝑖𝑗 = Δ𝑚𝑖𝑗

2 𝐿

4𝐸

sin22θ13 uncertainty 3.4%➔2.7% Δm2ee uncertainty 2.8% ➔ 2.1%

𝐬𝐢𝐧𝟐𝟐𝜽𝟏𝟑 = 𝟎. 𝟎𝟖𝟓𝟔 ± 𝟎. 𝟎𝟎𝟐𝟗

∆𝒎𝒆𝒆𝟐 = 𝟐. 𝟓𝟐 ± 𝟎. 𝟎𝟕 × 𝟏𝟎−𝟑 eV2

∆𝑚322 = 2.47 ± 0.07 × 10−3 eV2 (NO)

∆𝑚322 = −2.58 ± 0.07 × 10−3 eV2 (IO)

θ13

Daya Bay

RENO

Double Chooz

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θ12 & Δm221

SK+SNO fit disfavors the KamLANDbest fit value at ~1.4σ (was ~2σ)

θ12 : dominated by solar neutrino dataΔm2

21: better measured by reactor

• Precise measurement of spectrum at the vacuum-to-matter transition region

• Measurement of Day/Night asymmetry

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θ23 & Δm232

Run 1-9 analysis: PRD 103, L011101 (2021)

Run 1-10 analysis:• Upper octant preference

(77.1% prob) from νe samples• Normal ordering preferred at

80.8%

• Data prefers first octant • Contours for θ23

significantly more constraining

• Slight preference for upper octant, normal hierarchy (1.0 σ)

𝐬𝐢𝐧𝟐 𝜽𝟐𝟑 = 𝟎. 𝟓𝟕−𝟎.𝟎𝟑+𝟎.𝟎𝟒

∆𝑚322 = 2.41 ± 0.07 × 10−3 eV2 (NO)

θ23 octant significantly affect the NMO determination in atmospheric experiments. 6

θ23 & Δm232

Run 1-9 analysis: PRD 103, L011101 (2021)

Run 1-10 analysis:• Upper octant preference

(77.1% prob) from νe samples• Normal ordering preferred at

80.8%

• Data prefers first octant • Contours for θ23

significantly more constraining

• Slight preference for upper octant, normal hierarchy (1.0 σ)

𝐬𝐢𝐧𝟐 𝜽𝟐𝟑 = 𝟎. 𝟓𝟕−𝟎.𝟎𝟑+𝟎.𝟎𝟒

∆𝑚322 = 2.41 ± 0.07 × 10−3 eV2 (NO)

θ23 octant significantly affect the NMO determination in atmospheric experiments. 7

• Best-fit δ = 0.82 π• Exclude ΙΗ δ = π/2 at >3σ• Disfavor NH δ = 3π/2 at ~2σ

NOνA

• δ = - π/2 favored• Large range of values of δCP

around +𝜋/2 are excluded at 99.7%

T2K

Clear tension existsNOνA + T2K joint analysis is underway

The CP Phase

(Run 1-9)

Alex Himmel @ Neutrino 2020 8

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Fundamental problem: neutrino absolute masses?• Oscillation experiments sign of m2

31 , δCP = ?, precise PMNS

• 0νββ experiments = ?, effective neutrino mass

• β decay, cosmology … neutrino absolute mass

Xing，Phys. Rep. 854(2020)1

Quark and Lepton Mass Spectra

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∆𝒎𝟑𝟏𝟐 and ∆𝒎𝟑𝟐

𝟐

interference ()∆𝒎𝒆𝒆

𝟐 and ∆𝒎𝝁𝝁𝟐

differenceMatter Effect

AtmosphericReactorAccelerator

Future Neutrino Oscillation Experiments

NMO: fundamental ν property, imply different flavor structure, a model discriminatorStrategy: Complementary NMO determination in neutrino oscillations

Effective Parameters

𝜟𝒎𝒆𝒆𝟐 = 𝐜𝐨𝐬𝟐𝜽𝟏𝟐𝜟𝒎𝟑𝟏

𝟐 + 𝐬𝐢𝐧𝟐𝜽𝟏𝟐𝜟𝒎𝟑𝟐𝟐

𝜟𝒎𝝁𝝁𝟐 = 𝐬𝐢𝐧𝟐𝜽𝟏𝟐𝜟𝒎𝟑𝟏

𝟐 + 𝐜𝐨𝐬𝟐𝜽𝟏𝟐𝜟𝒎𝟑𝟐𝟐

+ 𝐜𝐨𝐬𝜹 𝐬𝐢𝐧𝜽𝟏𝟑 𝐬𝐢𝐧𝟐𝜽𝟏𝟐𝐭𝐚𝐧𝜽𝟐𝟑𝜟𝒎𝟐𝟏𝟐

𝜟𝒎𝒆𝒆𝟐 − |𝜟𝒎𝝁𝝁

𝟐 | = ±𝜟𝒎𝟐𝟏𝟐 (𝐜𝐨𝐬𝟐𝜽𝟏𝟐

− 𝐜𝐨𝐬𝜹 𝐬𝐢𝐧𝜽𝟏𝟑 𝐬𝐢𝐧𝟐𝜽𝟏𝟐𝐭𝐚𝐧𝜽𝟐𝟑)

Primary goals: ν mass ordering (NMO) and CP violation

δ CP : matter-antimatter asymmetryStrategy: Compare 𝑷(𝝂𝝁 → 𝝂𝒆) and 𝑷( 𝝂𝝁 → 𝝂𝒆) at Acc.

Neutrino Telescopes

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Jiangmen Underground Neutrino Observatory

• 20 kton liquid scintillator, 3% E reso, <1% E scale Uncer.

• Primary goals: ν mass ordering (3~4 σ, with 6 yrs data) & Precision measurement (<<1%)

• Rich physics: Supernova/Solar/Geo/Atmosphere neutrinos, nucleon decay

JUNO Physics Book, J. Phys. G43:030401 (2016)JUNO-TAO CDR: arXiv:2005.08745JUNO Physics and Detector, arXiv:2104.02565

Vertical shaft

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ν mass ordering at JUNO

• Independent on δ CP and θ23

3σ sensitivity (6 yrs of data taking)

• Further improvement with precise ∆𝒎𝝁𝝁𝟐

> 4σ (in 6 yrs) if 1% external ∆𝒎𝝁𝝁𝟐

𝐬𝐢𝐧𝟐𝜽𝟏𝟐 ∆𝒎𝟐𝟏𝟐 𝐬𝐢𝐧𝟐𝜽𝟏𝟑 ∆𝒎𝟑𝟏

𝟐 /∆𝒎𝟑𝟐𝟐

Direct Meas.(Dominant Expts.)

4.7%(SNO)

2.5%(KamLAND)

3.2%(Daya Bay)

2.8%(Daya Bay/T2K/NOvA)

NuFIT 4.0% 2.8% 2.8% 1.1%

JUNO (6 yrs) < 0.6% < 0.6% ~ 10% < 0.6%

• Precision measurement to two oscillations and related ν mixing parameters

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• Mass ordering: 5𝝈 within the first 2-3 years, thanks to Earth’s matter effect• CPV discovery if true δCP = -π/2 with ~7 yrs exposure • CPV discovery for 50% of true δCP values with ~10 yrs exposure

ν:ν = 1:1

CP Violation Sensitivity Mass Ordering Sensitivity

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• Mass ordering: much less sensitivity due to much smaller matter effects• CPV discovery if true δCP = -π/2 with ~5 yrs exposure• CPV discovery for 50% of true δCP values with 5~10 yrs exposure

Reduction of sys. uncertainties has impact to CPV measurement various Near detectors

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• If NMO is unknown, beam only sensitivity degrades for some values of δCP

• Atmospheric neutrino: sensitive to NMO due to higher energy and large Earth’s matter effects

• Combination of beam and atmospheric neutrinos exclude wrong NMO at ~(4-6)𝝈, depending on θ23 value

10 years with 1.3MW, T2K 2018 systematic error

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KM3NeT

Neutrino Oscillations at Neutrino Telescopes

250k ν at 8 yrs

3 years of ORCA operation

For both IceCube-Gen2 (PRD 101 032006 (2020)) and ORCA (NeuTel talk), combination with JUNO results can significantly enhance the sensitivity

arXiv:2103.0988

ντ appearance normalisation

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Assess the absolute neutrino mass scale

Constraints on absolute neutrino masses Tritium β decays (95% C.L.)

𝒎𝜷 < 𝟏. 𝟏 𝐞𝐕 (KATRIN)

𝟐. 𝟏 𝐞𝐕 (Mainz & Troitzk) Neutrinoless double-β decays (90% C.L.)

𝒎𝜷𝜷 < 𝟎. 𝟎𝟔~𝟎. 𝟏𝟔 𝐞𝐕 (KamLAND-Zen)

𝟎. 𝟎𝟗~𝟎. 𝟐𝟗 𝐞𝐕 (EXO-200)𝟎. 𝟎𝟖~𝟎. 𝟏𝟖 𝐞𝐕 (GERDA)

Cosmological observations (95% probability)𝚺 < 𝟎. 𝟏𝟐 𝐞𝐕 (Planck, 2018)

𝜮 = 𝒎𝟏 +𝒎𝟐 +𝒎𝟑 [eV]

Co

smo

logical B

ou

nd

Tritium β decays (KATRIN)

Co

smo

logical B

ou

nd

IO

NO

Neutrinoless double-β decays

IO

NO

𝑚𝛽 = Σ𝑖 𝑈𝑒𝑖2𝑚𝑖

2 1/2[eV]

𝑚𝛽𝛽 = Σ𝑖𝑈𝑒𝑖2𝑚𝑖 [eV]

Capozzi et al., 2003.08511

Abazajian et al., 1907.04473

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4-week science run in 2019 (522 hr scanning):

m(ν)<1.1 eV (90% CL)

coincide with the target sensitivity:0.2 eV (90% CL, 5 yrs)

Phys. Rev. Lett. 123 (2019) 221802

background: 0.55 106 e-

Tritium β decays -- KATRIN

3H: super-allowed β-decay (T1/2 ~ 12.3 yrs, E0 ~ 18.56 keV)

neutrino mass square m2(νe)

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Next generation β-decay

Targeted sensitivity: 40 meV

30 yrs history of β-decay measurement

KATRIN will continue delivering world-leadingsensitivity

Cyclotron Radiation Emission Spectroscopy (CRES)

• Multi m3·yr effective exposure• High flux atomic tritium source• ~0.1 eV resolution• 10-7 field uniformity

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Neutrino-less Double Beta Decay

0νββ offers the most sensitive and only feasible probe to determine if neutrinos are Majorana neutrinos• Discovery of a new type of elementary particles• Discovery of LNV: a guide for theorists• MajoranaCP Phases

Determining the nature - Dirac or Majorana - of massive neutrinos is one of the most challenging and pressing problems in present day elementary particle physics

Schechter-Valle Theorem (1982) :if a 0 decay happens, there must be an effective Majoranamass term ( is of Majorana nature)

2νββ 0νββ

Toward ton-scale 0νββ experiment

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• 136Xe (KamLAND-Zen): > 1026 yrs • 76Ge (GERDA) : > 1.8 x 1026 yrs • 130Te (CUORE) : > 3.2 x 1025 yrs

• ~100x improvement in T1/2

• Covers Inverted ν-mass ordering region

Present best Limits on T1/2

• 136Xe (nEXO) : T1/2 > 1028 yrs • 76Ge (LEGEND-1000) : T1/2 > 1028 yrs • 130Te (CUPID) : T1/2 > 1027 yrs

Future goal

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Further future: Towards the

1 meV sensitivity of |mββ|• Precise determination of the

lightest neutrino mass

• Constrain (m1, ρ, σ) to a very small parameter space

Cao et al., CPC 44 (2020) 031001

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For a none background-free experiment, use simple counting approach:

Plot remade from CPC 41 (2017) 053001

Driven factors of 0νββ Sensitivity

Detector Exposure

Detector Exposure Detector efficiency

Isotope abundance

Background in ROI* For 90% C.L, =1.64

Background Index (B.I.)

After the completion of the

primary physics goals, JUNO

can be upgraded by loading

0νββ isotope into LS, for

searching for 0νββ (~2030)Isotope mass (ton) <mββ>, meV

KamLAND-Zen 136Xe 1 61-165

EXO 136Xe 0.2 93-286

nEXO 136Xe 5 7-22

GERDA 76Ge 1 10-40

Majorana 76Ge 1 10-40

SNO+ 130Te 8 19-46

JUNO-ββ 136Xe 50 4-12

130Te 100-200 2-6 ？24

~102 tons of 0νββ target;

best LS shielding;

excellent energy resolution (3%/√E);

ultra-low background

Future prospect

of JUNO

The most sensitive to

probe the Majorana nature

of neutrinos, aiming at a

sensitivity level of |mββ|~

meV

Zhao et al., CPC 41 (2017) 053001

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Ambitious goal: Detection of Cosmic Neutrino Background, which can also probe neutrino mass

PTOLEMY – Another way to probe ν mass

Relic neutrino capture on -decaying nuclei

1962

Temperature today

Mean momentum today

At least 2 ’s cold today

NON-relativistic ’s!

Design: PPNP 106 (2019) 120

Physics: JCAP 07 (2019) 047

Challenges:3H amount, low background, energy resolution, …

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Discoveries on Solar-ν before 2021

7Be-ν: PRL 101, 091302 (2008)pep-ν: PRL 108, 051302 (2012)pp-ν: Nature 562 (2018) 7728CNO-ν: Nature 587 (2020) 577-582

PRL 89 (2002) 011301

Smoking gun evidence of solar-ν oscillation by SNOLater talk by Prof. Art McDonald“Twenty Years of Solar Neutrinos at SNO”

Borexino discovered 7Be, pep, pp, and CNO neutrinos, and its data allowed to probe the vacuum-matter transition

Current θ12 precision dominated by solar-ν data(SNO + Super-K)

LMA-MSW

1 s uncertainty

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Solar-ν after 2021

• Promising solar-ν spectroscopy (8B, 7Be, etc.)

• 8B ν-e ES: S/B = 60k/30k (10 yrs), Evis > 2 MeV

• 10-17 g/g LS radio-purity, optimized FV & muon veto

Day-Night-Asymmetry: 0.9% uncertainty

Upturn: test flat Pee >2σ if large 𝛥𝑚212 (7.5x10-5 eV2)

• Simultaneous solar 𝝂𝒆 and reactor 𝝂𝒆 meas.

• New flux meas. of 8B-ν

• 200 tons 13C

• Utilize 𝝂𝒆-13C CC & 𝝂-13C NC

130 evts/d/tank, Evis>4.5MeV

Challenge: radiological & cosmogenicbackgrounds

Chin. Phys. C 45 (2021) 023004

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Summary and Outlook

• Neutrino oscillation experiments have entered the precision

era, and mass ordering and δCP to be solved in 2030s or even

before (for ordering), which allows deep understanding of

leptonic flavor structure.

• The ultimate goal of neutrino physics is to understand the

origin of neutrino masses. Mass ordering, Majorana nature

and absolute mass are critical paths. Keep eyes on 0νββ.

• Many other important/exciting fields and experiments, e.g.,

astroparticle physics, neutrino cosmology, sterile neutrinos,

etc, are not covered in this talk.

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Thanks!