Neutrino PhysicsNeutrino PhysicsCaren Hagner

Universität Hamburg

Caren Hagner

Universität Hamburg

Part 1: Neutrino oscillation in vacuum

Introduction: neutrino mass, mixing and oscillation

Atmospheric neutrinos and accelerator neutrinos

Part 1: Neutrino oscillation in vacuum

Introduction: neutrino mass, mixing and oscillation

Atmospheric neutrinos and accelerator neutrinos

Some Historical RemarksSome Historical Remarks

• 1930: neutrino postulated by Pauli (massless, neutral)

• 1956: neutrino ve detected by Reines and Cowan

• 1957: Wu discovered parity violation in weak interaction

• 1958: Goldhaber experiment neutrinos are left handed anti-neutrinos right handed

• 1930: neutrino postulated by Pauli (massless, neutral)

• 1956: neutrino ve detected by Reines and Cowan

• 1957: Wu discovered parity violation in weak interaction

• 1958: Goldhaber experiment neutrinos are left handed anti-neutrinos right handed

nepve

3 Neutrino Flavors3 Neutrino Flavors

• 1960: B. Pontecorvo and M. Schwartz proposed neutrino beam (from accelerated protons) → discovery of vμ at AGS in Brookhaven by Ledermann, Schwartz and Steinberger

• LEP measurement of Z0 decay width:→ 3 active neutrino flavors (mv < 80 GeV): Nv = 3.00±0.06 ve, vμ, vτ

• 2000: vτ detected by DONUT experiment

• 1960: B. Pontecorvo and M. Schwartz proposed neutrino beam (from accelerated protons) → discovery of vμ at AGS in Brookhaven by Ledermann, Schwartz and Steinberger

• LEP measurement of Z0 decay width:→ 3 active neutrino flavors (mv < 80 GeV): Nv = 3.00±0.06 ve, vμ, vτ

• 2000: vτ detected by DONUT experiment

Neutrinos in the Standard ModelNeutrinos in the Standard Model

LLLb

t

s

c

d

u

LLL

e

e

RRRRRR btscdu ,,,,, RRRe ,,

• No right handed neutrinos

• Neutrinos are massless

• Le, Lμ, Lτ conserved

• No right handed neutrinos

• Neutrinos are massless

• Le, Lμ, Lτ conserved

??

Super-Kamiokande

atmospheric neutrinosaccelerator neutrinos

JAPANKamLAND

reactor neutrinos

JAPANCANADA

solar neutrinos

SNO

Important experimental results in recent years

ve→vμ,τ

OscillationΔm2 ≈ 8·10-5 eV2

vμ→v,(s)

Oscillation Δm2 ≈ 2·10-3 eV2

Neutrino Oscillations were observed→ Neutrinos have mass!

Neutrino Oscillations are a consequence of

neutrino mass and mixing

Neutrino Oscillations are a consequence of

neutrino mass and mixing

What is neutrino mixing? → compare to quark CKM mixingWhat is neutrino mixing? → compare to quark CKM mixing

b

t

s

c

d

u

ee

Quark and Lepton Mixing:Eigenstates of weak interaction ≠ Eigenstates of mass

bsd ,, bsd ,, bsd ,,

mass eigenstates

mass eigenstates 321 ,, 321 ,, 321 ,,

Quark - Mixing

Neutrino - Mixing

b

s

d

VVV

VVV

VVV

b

s

d

tbtstd

cbcscd

ubusud

Quark-Mixing Quark-Mixing

Cabbibo-Kobayashi-Maskawa (CKM) Matrix

• 3 mixing angles

• 1 phase: ei

CP-violation

BELLE, BABAR,CLEO,…

in precision measurement phase

b

t

s

c

d

u

b

t

s

c

d

u

b

s

d

VVV

VVV

VVV

b

s

d

tbtstd

cbcscd

ubusud

Hierarchy in Quark MixingHierarchy in Quark Mixing

• of masses: md « ms « mb

• of mixing angles: s12 = λ, s23 ≈ λ2, s13 ≈ λ3

• of masses: md « ms « mb

• of mixing angles: s12 = λ, s23 ≈ λ2, s13 ≈ λ3

b

s

d

cs

sc

ces

esc

cs

sc

b

s

d

i

i

100

0

0

0

010

0

0

0

001

'

'

'

1212

1212

1313

1313

2323

2323

Neutrino mass and mixingNeutrino mass and mixing

Neutrino mixing!Neutrino mixing!

3

2

1

321

321

321

UUU

UUU

UUU eeee

3 massive neutrinos: ν1, ν2, ν3 with masses: m1,m2,m3

Flavor-Eigenstates ve,vμ,vτ ≠ Mass-EigenstatesFlavor-Eigenstates ve,vμ,vτ ≠ Mass-Eigenstates

Historical remarkHistorical remark

• 1957-58: B. Pontecorvo proposed neutrino oscillations(because only ve was known, he thought of v ↔ anti-v)

• 1962 Maki, Nakagawa, Sakatadescribed the 2 flavor mixing and discussed neutrino flavor transition

• 1967 full discussion of 2 flavor mixing,possibility of solar neutrino oscillations,question of sterile neutrinos by B. Pontecorvo

• 1957-58: B. Pontecorvo proposed neutrino oscillations(because only ve was known, he thought of v ↔ anti-v)

• 1962 Maki, Nakagawa, Sakatadescribed the 2 flavor mixing and discussed neutrino flavor transition

• 1967 full discussion of 2 flavor mixing,possibility of solar neutrino oscillations,question of sterile neutrinos by B. Pontecorvo

Parametrization of Neutrino MixingParametrization of Neutrino Mixing

3

2

1

132313231223121323122312

132313231223121323122312

1313121312

21

21

21

][

][

iiii

iiii

iiie

ecceescsscesccss

ecseesssccessccs

eesecscc

Pontecorvo-Maki-Nakagawa-Sakata (PMNS) Matrix: • 3 Mixing angles: θ12, θ23, θ13

• 1 Dirac-Phase (CP violating): δ

Pontecorvo-Maki-Nakagawa-Sakata (PMNS) Matrix: • 3 Mixing angles: θ12, θ23, θ13

• 1 Dirac-Phase (CP violating): δ

If neutrinos are Majorana particles:• 2 additional Majorana-Phases (CPV): α1, α2

3

2

1

1212

1212

1313

1313

2323

2323

100

0

0

0

010

0

0

0

001

cs

sc

ces

esc

cs

sci

ie

θsolθ13, δθatm

Neutrino mixing anglesNeutrino mixing angles

v1

v2

v3

ve

vμ

vτ

θ12θ12ve

vμ

vτ

θ13

θ12

vτ

vμ

ve

θ23

θ13ve

vμ

vτ

3

2

1

1212

1212

1313

1313

2323

2323

100

0

0

0

010

0

0

0

001

cs

sc

ces

esc

cs

sci

ie

Solar and reactor experiments

θ12: 29o - 39oθ13<13o, δ ?

Unknown (CHOOZ)

Θ23: 34o - 58o

Atmospheric and accelerator

Neutrino OscillationsNeutrino Oscillations

3

2

2323

2323

cossin

sincos

Flavor eigenstates vμ, vτ Mass eigenstates v2,v3 with m2, m3

W

vμ

μ

source createsflavor-eigenstates

vτ

W

τ

p,n hadrons

detector seesflavor-eigenstates

v2

v3

propagation determined bymass-eigenstates

23,2

23,23,2 mpE

slightly different frequencies→ phase difference changes

General derivation of oscillation formula:

3

1kkk vUv

α = e, μ, τ

k = 1, 2, 3

kv neutrinos with negative helicity, mass mk, momentum pand energy

p

mpmpE k

kk 2

222

ktiE

k vetv k)(

3

1

*)(k

ktiE

k vUeUtv k

3

1

)(k

ktiE

k veUtv k now change to flavor base

→

vvA is the amplitude for the transition vα→ vβ at time t

General derivation of oscillation formula:

23

1

*2

)(

kk

tiEkvvvv UeUtAP k

ji

ijjjii

ji

ijjjiivv

E

LmUUUU

E

LmUUUUP

2sin)(2

4sin)(4

2**

22**

3

1

*

kkkUU using and

222jkkj mmm

2 Flavor Neutrino Oscillations2 Flavor Neutrino Oscillations

23

22

2 mmm 23

22

2 mmm

oszL

xP

223

2 sin)2(sin)(

Oscillation probability

)eV (in

GeV) (in48.2km) in(

22m

ELosz

)eV (in

GeV) (in48.2km) in(

22m

ELosz

Pro

babili

ty t

o fi

nd

vτ

Distance x in Losz

Losz, Δm2 sin2(2θ)

Pro

babili

ty t

o fi

nd

vμ

oszL

xP

223

2 sin)2(sin1)(

Survival probability

appearance

disappearance

Primary cosmic ray

N

N

K

π

π

μ

ν

π

#(vμ) / #(ve) ≈ 2

atmospheric neutrinos

Atmospheric Neutrino HistoryAtmospheric Neutrino History

•In less than two decades, atmospheric neutrinos have gone from being “anomalous” to being one of our main tools for theexploration of the lepton sector.

• 1980s – 1990s: Skepticism was rampant!• “Neutrino experiments are hard!”• “Cosmic ray experiments are hard!”• “Oscillation experiments are hard!”

•In less than two decades, atmospheric neutrinos have gone from being “anomalous” to being one of our main tools for theexploration of the lepton sector.

• 1980s – 1990s: Skepticism was rampant!• “Neutrino experiments are hard!”• “Cosmic ray experiments are hard!”• “Oscillation experiments are hard!”

Oscillation of atmospheric neutrinosOscillation of atmospheric neutrinos

]GeV[

]km[]eV[27.1sin2sin)(

2222

E

LmP atm

atmx

L ≈ 20 km

L ≈ 13000 km

atmosphericneutrinos:

Ev in GeV range

Oscillation probabilityvaries with zenith angle θ θ

Super-Kamiokande

• solar neutrinos (8B ve few MeV)

• atmospheric neutrinos (vμ, ve few GeV)

• K2K accelerator neutrinos (vμ 1 GeV)

• start ~2009: T2K off-axis super neutrino beam

electron event

myon event

50kt H2O

12000 PMTs12000 PMTs

Super-Kamiokande

SuperK – atmospheric neutrinosSuperK – atmospheric neutrinos

e–like events μ–like events

without oscillationoscillation (best fit)

data

νe

e

νμ

μ

Atmospheric neutrinos:Analysis neutrino oscillation (full SK-I data set)

Atmospheric neutrinos:Analysis neutrino oscillation (full SK-I data set)

Confirmed by MACRO, SOUDAN

E.Kearns Neutrino2004

Analysis of eventswith high L/E resolution

First evidence of oscillation pattern? First evidence of oscillation pattern?

Oscillation dip!(?)

“EVIDENCE FOR AN OSCILLATORY SIGNATURE IN ATMOSPHERIC NEUTRINO OSCILLATION.”Super-Kamiokande Apr 2004., Submitted to Phys.Rev.Lett., hep-ex/0404034

“EVIDENCE FOR AN OSCILLATORY SIGNATURE IN ATMOSPHERIC NEUTRINO OSCILLATION.”Super-Kamiokande Apr 2004., Submitted to Phys.Rev.Lett., hep-ex/0404034

• oscillation

• decay

• decoherence

from L/E analysisfrom L/E analysis

Super-Kamiokande: Accident 2001Super-Kamiokande: Accident 2001

Accident Nov 21, 2001:~7000 of 12000 PMT’simploded in chain reaction

Neutrino beamsNeutrino beams

ProtonBeam

TargetFocusingDevices

Decay Pipe

Beam Dump

,K

few 100 GeV

few GeV

Beam composition (typical example):

• dominantly vμ

• contamination from vμ (≈6%), ve (≈0.7%), ve (≈0.2%)

• vτ ≲ 10-6

Beam composition (typical example):

• dominantly vμ

• contamination from vμ (≈6%), ve (≈0.7%), ve (≈0.2%)

• vτ ≲ 10-6

250km

K2K

The K2K experiment

Muon range

detector

K2K-I Mar.1999 ~ Jul.2001near neutrino detectors

39m

41.4

m

Super-Kamiokande I

Outer detector

Inner detector

1885 8” PMTs

11146 20” PMTs

K2K-II Dec.2002~Upgrade of near neutrino detectors

•Removed Lead Glass detector•Installed SciBar and Electron

Catcher (Oct.2003~)

Super-Kamiokande II

K2K accelerator experimentK2K accelerator experimentNear

Detector1 ton

KEK

300m250km

νμ, <Eν>= 1.3 GeV

νμ, <Eν>= 1.3 GeV

Super-Kfar detector

50 kton

Goal: 1.0×1020 POT = 200 neutrino events in SKGoal: 1.0×1020 POT = 200 neutrino events in SK

Data (06/1999 – 02/2004): 8.9·1019 POT events in “Far Detector” :expected without oscillation:

Data (06/1999 – 02/2004): 8.9·1019 POT events in “Far Detector” :expected without oscillation:

1086.110.109.150

Probability for no oscillation: <0.01%Neutrino oscillation confirmed with 3.9σ!

)eV (in

GeV) (in48.2km) in(

22m

ELosz

First hint for typical deformation of energy spectrum First hint for typical deformation of energy spectrum

without oscillationbest fit oscillation