Broad Overview of Neutrino Physics
International Workshop：
Neutrino Research and Thermal Evolution of the Earth
Oct. 20, 2016
Itaru Shimizu (Tohoku Univ.)

Contents• Introduction to neutrino physics• Neutrino oscillation• Double beta decay• Open questions about neutrino• Neutrino astrophysics

What is Neutrino?

ElectronNeutrinoνno electric chargeFermilabelementary particles = fundamental constituent of matter

only “weak interaction”

Neutrino Hypothesis

frequency (probability)

Neutrino is light neutral particle suggested by W. Pauliin 1930 to explain the continuous energy spectrum ofemitted electron in β-decay

averageenergyelectronelectronmaximumenergyelectron energy

anti-neutrino

W. Pauli

energy is split between
the neutrino and electron

For the case of no neutrino emission, the electronenergy becomes constant (maximum)

Neutrinos slip out of the detector because of the weak interaction

Neutrino Detection
Neutrinos react so seldom with matter (high permeability)ν̄e + p → e+ + n
need thickness of 20 light-year
in water to react~ 1000In those days, people thought the neutrino detection is experimentally impossible …

Intense production of neutrinos bynuclear reactor and developmentof detection technique

In 1953, neutrinos are detected by
Reines and Cowan finally!

Neutrino in Standard Model• Mass of neutrino is zero• 3 flavor lepton number (e, νe) (μ, νμ) (τ, ντ) isconserved• All neutrinos are left-handed, andall anti-neutrinos are right-handed• Neutrino and anti-neutrino can be distinguished
2 component neutrino model
left-handed

right-handed
spinspinννNeutrino Oscillation

Assuming1. Neutrinos have tiny masses (beyond Standard Model)
2. Flavor (weak) states are superpositions of mass states|⌫↵ >=flavor

XMNS (Maki-Nakagawa-Sakata) Matrix

U↵i |⌫i >massi
no diagonal unitary matrix

flavor oscillations must exist as neutrinos propagate
2 flavor caseP (⌫e ! ⌫e )ν22[eV]L[m]1.27m22)P (⌫e ! ⌫µ ) = sin 2✓ sin (E[MeV]

amplitude frequency- L / E depends on the condition of experiments- Disappearance or Appearance
P (⌫e ! ⌫µ )wikipedia

Where are neutrinos coming from?
Neutrino Energy v.s. Flux
Big Bang(background)
Solar

KamLAND
Supernova

Supernova(background)

P. Lipari, Introduction to Neutrino Physics (2002)~20 orders ofmagnitude!

Naturalneutrinos
Atmospheric
Man-made +Reactorneutrinos
AstrophysicalMan-made +Accelerator
neutrinos

ReactorEarth (geo)neutrino flux &neutrino energyMan-made Neutrino
Accelerator

Reactor

25GW, the world strongest KashiwazakiKariwa reactor complex

π → µ + νµ++235

etc.

expensive!

U + n → X + Y + 6.1e− + 6.1ν̄e + 2.5n + 202 MeV
also 239 Pu, 238 U, 241 Pu

no charge

electron anti-neutrinos are emitted

Well-controlled man-made sources are more appropriate
for a precise investigation of the neutrino property

KamLAND
operated since 2002

low BG~10−5neutrino
ニュートリノ cosmic-ray
宇宙線

1,000 mdepthlarge volume
13 m

1,000 ton Liquid Scintillator
Dodecane (80%) Pseudocumene (20%) PPO (1.36 g/l)

18 m~500 p.e./MeV

high light yield

1,325 17 inch + 554 20 inch PMTs

Reactor Neutrino
2 flavor neutrino oscillation (disappearance)x109Pu239

5000

U238

12Fission number flux(10P (⌫e ! ⌫e ) = 1

U235

6000
6泊

Pu241

4000
43000

1000

000100 200 300 400 500 600 700 800 900 1000
距離（km)
distance
(km)

女川
福島第一

柏崎刈羽

福島第二
志賀180km

東海第二

敦賀 ふげん
高浜
島根

美浜
大飯
浜岡

伊方

玄海

カムランド
KamLAND

KamLAND data
Neutrino oscillation with real reactor distribution

10.8
ILL
Goesgen
Savannah River
Palo Verde
CHOOZ
Bugey
Rovno
Krasnoyarsk

0.6
0.4
0.2
010

川内

2
2
[eV]l[m]1.27m22)sin 2✓ sin (E[MeV]

previousreactor experiments1.2

2000
2Survival Probability

2fission/cm )7000-310-2

10-1

2 cycle of oscillation
11020304050607080

L 0/E (km/MeV)

strong evidence of neutrino oscillation
If mass of neutrino is zero, this quantum interference is not allowed
Neutrino oscillation experiments require 3 different mass states

Neutrino has nonzero mass

MNSMatrix

Neutrino Oscillation Experiments
3 flavor oscillation

relative m2 normalmass
3Δm322
Δm21

12
1

3

1

mass hierarchy

BorexinoSNO

2

10MINOS3

not determinedDataOsc. e CC
µ+µ CC
e CCNC

32m2atm2m2J

θ12not determined
T2K
Number of events /(250 MeV)Super-K

θ13 CP phase

01000

2000

3000

Reconstructed  energy (MeV)

KamLAND

Daya-Bey

KamLAND data
Neutrino oscillation with real reactor distribution

previous
reactor experiments

1.2Survival Probability

θ23m2Jm2atm

2mixing

inverted degenerated

10.8
ILL
Goesgen
Savannah River
Palo Verde
CHOOZ
Bugey
Rovno
Krasnoyarsk

0.6
0.4
0.2
010-310-210-111020304050

L 0/E (km/MeV)

607080Neutrino in Standard Model• Mass of neutrino is zero• 3 flavor lepton number (e, νe) (μ, νμ) (τ, ντ) isconserved• All neutrinos are left-handed, andall anti-neutrinos are right-handed• Neutrino and anti-neutrino can be distinguished ?
Dirac neutrino

4 chiral partner must exist for neutrino and anti-neutrino
2 component neutrino model

weak interaction

weak interaction

no weak interaction

no weak interaction

left-handed

right-handed

left-handed

right-handed

spinspinννspinspinννNeutrino in Standard Model• Mass of neutrino is zero• 3 flavor lepton number (e, νe) (μ, νμ) (τ, ντ) isconserved• All neutrinos are left-handed, andall anti-neutrinos are right-handed• Neutrino and anti-neutrino can be distinguished ?
Majorana neutrino

4 chiral partner must exist for neutrino and anti-neutrino
2 component neutrino model

weak interaction

weak interaction

no weak interaction

no weak interaction

left-handed

right-handed

left-handed

right-handed

spin

spin

ν=ν
light neutrino

spin

spin

ν=ν
heavy neutrino

Light Neutrino Massmass = energy

Particle mass
neutrinos are extraordinary light( 3) <1 <electron

2 < ( 3)

1 eV energy

Seesaw mechanism
Mass of existing
light neutrino

Light2DM
Mν =MN

Masses of quarks
and charged leptons

νHeavyMass of heavy neutrino

The mass of heavy neutrino can be as heavy as 1023 eV!
(1010 times of energy attained by world’s largest accelerator)

Heavy neutrino (just below GUT scale) naturally explains“finite but light neutrino mass”

NMatter Dominated Universepresent- significant asymmetry between
matter and anti-matter- neutrinos and photons are
the most abundant particle

neutrinos / nucleon ~ 109Neutrinos may play a key role to explain matter/anti-matter asymmetry

Matter Production
Leptogenesis theory

violation of B−LThree Sakharov conditions

A. Ibarra, Leptogenesis, INSS 2012

CP violating decay of heavy neutrino explains“matter dominance in the universe”

Neutrinoless Double-Beta Decay
Nucleus ββ-decay emitting two electrons(Z, A)0νββ(Z + 2, A) + 2e2νββN̄L NMneutrinoless double
beta-decay

H0elepton number violation

Majo
Mecrana M
hani asssm¯RRH0L136-136Xen

ΔL = 2e-n=¯Cs× β-decay
ββ-decay

2.46 MeV136Ba

0νββsum energy for two electrons / Q

Require the neutrino Majorana nature● Heavy neutrino naturally explains “finite but light neutrino mass”● CP violating decay of heavy neutrino explains “matter dominance inthe universe” (Leptogenesis theory)

Light Majorana Neutrino Exchangemass mechanism

Effective neutrino mass <mββ>np222= |Ue1 | m1 + |Ue2 | ei 1 m2 + |Ue3 | ei 1 m3

- Unknown parameters : α1, α2, mmin

W-- Mass hierarchy is not determined

νe,Rν e,Le-L- Cancellations due to CP phases (α1, α2)e -L

How to measure <mββ>?

W-136Xenp
3

amplitude ~m2Ueimimi=1

effective neutrino mass

Possible contributions also from
Majoron, SUSY, right-handed current, ...

136Cs× single β-decay

doubleβ-decay

2.46 MeV

136Ba

determine the decay rate usinglarge number of ββ-decay nuclei

KamLAND-Zen
KamLAND-Zen

Kamioka Liquid Scintillator Anti-Neutrino Detector
Zero Neutrino Double Beta

Advantage of KamLAND- running detector : start quickly with relatively low cost
- big and pure : no BG from external gamma-rays- purification of LS, replacement of mini-balloon are possiblehigh scalability (a few ton of Xe)

Xe-LS
320 kgXe loaded

Inner Balloon(3.08 m diameter)

KamLAND-Zen expected sensitivity
Outer-LS
1 ktonXenon loaded LS (Xe-LS)
decane82%
pseudo-cumene 18%
PPO
2.7 g/literxenon
2.44 wt%

σE(2.5MeV) = 4%target ⟨mββ⟩ ~ 60 meV / 5 year

Nylon Film with Low Radioactivities
Class 1 cleanroom

Specially made 25 μm nylon film
for low radioactivities in U/Th/K
effect of ultrasonic cleaning

ultrasonic cleaning of film

U : 150 ! 2x10-12g/g
Th : 59 ! 3x10-12g/g
40K : 140 ! 2x10-12g/g
Class 10-100 cleanroom

heat welding of film

mini-balloon deployment

Data-taking restarted in September 2011

KamLAND-Zen Phase-II (2016)
Phase-II(a) Period-2104

Events/0.05MeV

103
102

Period-2 (263.8 days)
110m
Ag
Data
238
Total
U+232Th+210Bi
Total+210Po+85Kr+40K
IB/External(0νββ U.L.)136
Xe 2νββSpallation136
Xe 0νββ(90% C.L. U.L.)

KamLAND-Zen Phase-II search
after Xe-LS purification
found no significant 0νββ signal

10

obtain lower limit on half-life
Events/0.05MeV

1

Events/0.05MeV

10−1(b) Period-1

43212
3Visible Energy (MeV)

4

Half-life limit at 90% C.L.

14(c) Period-22νββT0ν1/2 > 1.9 × 1025 yrPhase-II

T0ν1/2 > 9.2 × 1025 yr

Spallation30νββ2(90% C.L.)

film BG

Combined T0ν1/2 > 1.07 × 1026 yr

10Phase-I

2.42.6
2.8
Visible Energy (MeV)

3Limits on Neutrino Mass
90% C.L. upper limit
CaZr NdTeSeCd
Te1Ge Mo

KamLAND-Zen (136Xe)〈mββ〉< 61-165 meVmlightest < 180-480 meV

10−1

including uncertainties fromCP phases and ν-osci. par.

KamLAND-Zen (136Xe)

NME calculations assuming gA ~ 1.27

IHm(eV)

Xesmall−210

SkM-HFB-QRPA (PRC87, 064302 (2013))
ISM (Nucl. Phys. A 818, 139 (2009))
QRPA (PRC 87, 045501 (2013))
SRQRPA (J. High Energy Phys. 02, 025 (2013))

NHpnQRPA (PRC 91, 024613 (2015))−3IBM-2 (PRC 91, 034304 (2015))

10large−4

10−3

10−2

10−1

10
mlightest (eV)50 100 150
A

EDF (PRL 105, 252503 (2010))

32Uei
mimi=1First search below 100 meV ~ near IH region

Prospects of KamLAND-Zen
103

KK claimratedKamLAND-Zen 400 (Phase-I + Phase-II)〈mββ〉< 61-165 meVgenenow@ 90% C.L.

ve

uncertainty of nuclear matrix elementin102

KamLAND-Zendertedhmi[meV]0νββ search sensitivity can be enhanced byvarious KamLAND-Zen upgrade plansnext phase KamLAND-Zen 800 (750 kg Xe),

Xe-LS
Outer-LShigh purity mini-balloon
next plan

dream

Super-KamLAND-Zen

water or LS

PLANCK

Xe-LS102103⌃m⌫ [meV]

Xe concentration (wt%)(CMB + BAO + H0 + SPTCL)

cosmology

alnorm10

KamLAND2-Zen 1000 kg, high light yield LS
pressurized XeσE(2.5MeV) = 4% → 1.8%

3% → 12%Outer-LSXe partial pressure (MPa)increase decay target nuclei by pressurized Xe

4 times at 30 m depthKamLAND2-Zen
General-purpose
larger craneaccommodate various devices
strengthen floor
CaF2, CdWO4, NaI, …
enlarge opening

High performance
Winstone Cone

High Q.E. PMT1000 kg enriched Xe

17”Φ→20”Φ, ε=22% → 30%

Photo-coverage > x2

x1.9

Light Collection Eff. > x1.8

New Liquid Scintillator

x1.4

KamLAND liquid scintillator 8,000 photon/MeV
typical liquid scintillator
12,000 photon/MeVσ(2.6MeV)= 4% → < 2.5％
naive calc. < 2%target ⟨mββ⟩ ~ 20 meV / 5 year

Open Questions• CP phase (δ)ν oscillation

Is phase δ violating CP symmetry non-zero?

• Mass hierarchy• Sterile neutrino• Absolute mass scale• Dirac or Majorana

ν oscillation, 0νββ decayν1 < ν2 << ν3, ν3 < ν1 << ν2, ν1 ~ ν2 ~ ν3 ?

ν oscillation, cosmology

Is there 4th sterile neutrino?

ν?

β-decay, 0νββ decay, cosmology
What is the absolute neutrino mass scale?
0νββ decay

Is neutrino Dirac particle or Majorana particle?

Current & Future experiments
ν oscillation
KamLAND, Borexino, Super-K, SNO, T2K, MINOS, NOVA, LBNE, OPERA, Double-Chooz, Daya Bay,RENO, Nucifer, Stereo, CeLAND, SOX, Sage2, LENS, IsoDAR, MicroBooNE, ICARUS, …

0νββ decay
KamLAND-Zen, EXO, GERDA, CUORE, SuperNEMO, SNO+, CANDLES, MOON, DCBA, Majorana,Lucifer, AMORE, COBRA, NEXT, …

β decay
KATRIN, Project 8

Many experiments to answer the open questions!

Neutrino Astrophysics
Neutrino Energy v.s. Flux

Solar neutrino

Big Bang(background)
Solar
Supernova

ReactorEarth (geo)Supernova(background)AtmosphericSuper-K

Supernova neutrino

Astrophysical

Kamiokande, 1987A

P. Lipari, Introduction to Neutrino Physics (2002)

Astrophysical neutrino

IceCube, Neutrino 2014

Relic Supernova Neutrino
predicted flux

GADZOOKS!
low background Super-K (50 kton)

Hyper-K 10 years

Gd loaded
Water

Hyper-K (1 Mton)

high statistics

Letter of Intent (2011)

Investigation ofstar formation history

Size of Super-K

Neutrino Radiography
IceCubeHyper-K

Detector

oscillationin matter
absorptionpreliminary

Hoshina, Neutrino GeoScience (2013)

ν~ TeVν ~ GeV

Letter of Intent (2011)

Size of Super-K
Investigation of density andchemical composition of the Earth’s core

Summary• Neutrinos have been played a key role to develop
particle physics so far.

• Discovery of the neutrino mass and mixing from thestudies for the last few decades is a revolution.

• Future prospects of neutrino physics are very exciting!
• Furthermore, neutrinos will be essential to reveal thehistory of the Universe and the Earth.
Let’s pay great attention to the next geo neutrino talk!