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Neutrino Physics. Part 1: Neutrino oscillation in vacuum Introduction: neutrino mass, mixing and oscillation Atmospheric neutrinos and accelerator neutrinos. Caren Hagner Universität Hamburg. n. Some Historical Remarks. 1930: neutrino postulated by Pauli (massless, neutral)

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neutrino physics

Neutrino Physics

  • Part 1: Neutrino oscillation in vacuum
    • Introduction: neutrino mass, mixing and oscillation
    • Atmospheric neutrinos and accelerator neutrinos

Caren Hagner

Universität Hamburg

some historical remarks

n

Some 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
3 neutrino flavors
3 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: vτdetected by DONUT experiment
neutrinos in the standard model
Neutrinos in the Standard Model

?

  • No right handed neutrinos
  • Neutrinos are massless
  • Le, Lμ, Lτconserved
slide5

Neutrino Oscillations were observed→ Neutrinos have mass!

JAPAN

JAPAN

CANADA

SNO

KamLAND

Super-Kamiokande

vμ→v,(s)

OscillationΔm2 ≈ 2·10-3 eV2

ve→vμ,τ

OscillationΔm2 ≈ 8·10-5 eV2

atmospheric neutrinosaccelerator neutrinos

reactor neutrinos

solar neutrinos

Important experimental results in recent years

slide6

Neutrino Oscillations are a consequence of

neutrino mass and mixing

What is neutrino mixing?→ compare to quark CKM mixing

slide7

mass eigenstates

mass eigenstates

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

Neutrino - Mixing

Quark - Mixing

quark mixing

Cabbibo-Kobayashi-Maskawa (CKM) Matrix

  • 3 mixing angles
  • 1 phase: ei CP-violation

BELLE, BABAR,CLEO,…

Quark-Mixing

in precision measurement phase

hierarchy in quark mixing
of masses: md « ms « mb

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

Hierarchy in Quark Mixing
neutrino mass and mixing

Neutrino mixing!

Neutrino mass and mixing

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

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

historical remark
Historical 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
parametrization of neutrino mixing
Parametrization of Neutrino Mixing
  • Pontecorvo-Maki-Nakagawa-Sakata (PMNS) Matrix:
  • 3 Mixing angles: θ12, θ23, θ13
  • 1 Dirac-Phase (CP violating): δ

θsol

θ13, δ

θatm

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

v3

θ23

v2

ve

ve

θ12

θ12

θ12

v1

θ12: 29o - 39o

ve

θ13

θ13

ve

Solar and reactor experiments

Θ23: 34o - 58o

θ13<13o, δ ?

Atmospheric and accelerator

Unknown (CHOOZ)

Neutrino mixing angles
neutrino oscillations

propagation determined bymass-eigenstates

source createsflavor-eigenstates

detector seesflavor-eigenstates

v2

τ

v3

W

W

μ

p,n

hadrons

slightly different frequencies→ phase difference changes

Neutrino Oscillations

Mass eigenstates v2,v3with m2, m3

Flavor eigenstates vμ, vτ

general derivation of oscillation formula

k = 1, 2, 3

α = e, μ, τ

neutrinos with negative helicity, mass mk, momentum pand energy

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

General derivation of oscillation formula:

now change to flavor base →

2 flavor neutrino oscillations

Oscillation probability

Probability to find vμ

Probability to find vτ

disappearance

Survival probability

Losz, Δm2

sin2(2θ)

appearance

Distance x in Losz

2 Flavor Neutrino Oscillations
slide18

Primary cosmic ray

π

π

N

N

π

K

ν

μ

atmospheric neutrinos

#(vμ) / #(ve) ≈ 2

atmospheric neutrino history
Atmospheric 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!”
oscillation of atmospheric neutrinos

L ≈ 20 km

atmosphericneutrinos:Ev in GeV range

L ≈ 13000 km

Oscillation of atmospheric neutrinos

Oscillation probabilityvaries with zenith angle θ

θ

super kamiokande
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
slide24

electron event

myon event

Super-Kamiokande

50kt H2O

12000 PMTs

superk atmospheric neutrinos

without oscillation

oscillation (best fit)

data

SuperK – atmospheric neutrinos

e–like events

μ–like events

νμ

νe

μ

e

atmospheric neutrinos analysis neutrino oscillation full sk i data set
Atmospheric neutrinos:Analysis neutrino oscillation (full SK-I data set)

E.Kearns Neutrino2004

Confirmed by MACRO, SOUDAN

first evidence of oscillation pattern

Oscillation dip!(?)

First evidence of oscillation pattern?
  • oscillation
  • decay
  • decoherence

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

super kamiokande accident 2001
Super-Kamiokande: Accident 2001

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

neutrino beams

Decay Pipe

Focusing

Devices

m

Proton

Beam

Target

nm

p,K

Beam Dump

  • Beam composition (typical example):
  • dominantly vμ
  • contamination from vμ(≈6%), ve (≈0.7%), ve (≈0.2%)
  • vτ≲ 10-6
Neutrino beams

few GeV

few 100 GeV

slide39

K2K

250km

the k2k experiment

Super-Kamiokande I

Inner detector

41.4m

1114620” PMTs

Outer detector

18858” PMTs

39m

Super-Kamiokande II

  • Removed Lead Glass detector
  • Installed SciBar and Electron
  • Catcher (Oct.2003~)
The K2K experiment

K2K-I

Mar.1999 ~ Jul.2001

near neutrino detectors

Muon range

detector

K2K-II

Dec.2002~

Upgrade of near neutrino detectors

k2k accelerator experiment
K2K accelerator experiment

Super-Kfar detector50 kton

Near Detector1 ton

νμ, <Eν>=1.3 GeV

KEK

300m

250km

Goal: 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:

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

first hint f or typical deformation of energy spectrum
First hint for typical deformation of energy spectrum

without oscillationbest fit oscillation

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