NEUTRINO OSCILATIONS

Tópicos Avançados deFísica de Partículas

e Astropatrículas

Sofia Andringa, LIP (sofia@lip.pt) Novembro 2016

Discovery withNatural Sources

Confirmation w/human-made

High precisionexperiments

oscillationsand mass

closing thecircle of 3

open questions

What are neutrinos? elementary particles, like electrons, but with neutral electrical charge* “undetectable” particles keeping energy conservation in decays

have only nuclear weak interactions

* mean free path of 10¹ m in water⁹* 1 of 10¹ interact in 1m of water⁹

detected 25 years after first proposal

(Z,A) –> (Z+1,A) + M(Z,A) = M(Z+1,A) + E

n –> p + e + v ⁻

Electron kinetic energy (MeV)

Inte

nsity

in e

lect

rons

3 types of neutrinosEletron neutrino (1956)

Muon neutrino (1962)

Tau neutrino (2000)

Lepton Universalitychecked at LEP

Same NC interaction for all neutrino; CC needs E > lepton mass(also more interactions fore with electrons in dense matter)

neutrinos and weak interaction

np

K2K

neutrinos and weak interaction

sources of neutrinos

Main nuclear fusion process in the Sun is

2e + 4p -> ⁻⁴He + 2 + 27 MeV

From measured luminosity:~ 60 billion / (cm² s)

First counting experiments:

³ Cl -> ³ Ar (E>0.8 MeV) : 0.34 x SSM⁷ ⁷[only secondary processes]

⁷¹Ga -> ¹Ge (E>0.2 KeV) : 0.58 x SSM⁷[including main fusion process]

the solar neutrino problem

underground telescopes

the Super Kamiokande detector50,000 ton water Cherenkov detector

11,000 PMT 50 cm (+ 2 000 PMTs in OD)

１０００ｍ underground

in Mozumi mine,

Kamioka, Japan３９ｍ

４２

ｍ

Succeeds to KamiokaNDE detector which saw SN1987A

solar, atmospheric and beam neutrinos in SK since 1996

SKI 1996-2001 SKII 2002-2005 (half coverage)SKIII 2006-2008 (full coverage)SKIV 2009-now (new electronics)Solar + Atmospheric + K2K + T2K

the Super Kamiokande detector

from Nature @ Super Kamiokande500 days + nights exposure

Flux lower than Solar e

compatible with SNO's results

higher energy but lower fluxe ~ 2 in all directions

Solar e@ MeV

Atmospherice e

@ GeV

GeV events at Super Kamiokande

e

l l = e,

p, n, ,...

identifying electrons and muons

l l = e, Kinematics of e/ give energy and direction

no charge measurement

muon neutrino disappearence

10 kmcos =1

10 000 kmcos =-1

e e

/ e ~ 2

Fluxes confirmed bye

first measurement of oscillations

expected from cosmic ray fluxesconfirmed by electron measurements

fit with 1 - sin²2 sin²(1.27 m² L/E)

1 10 100 1000 km

@GeV

first measurement of oscillations

No time to change Fast change

1 - sin²2 sin²(1.27 m² L/E)maximal amplitude atL ~ 500 km / E ~ 1 GeV

new results

1 10 100 1000 km

@GeV

vacuum oscillations: 2 case1. Flavor states as a function of mass states – rotation matrix in 2. Time evolution for each mass state – Schrödinger equation

3. Same energy (E) at production – Taylor expansion around m~04. Probability to find different flavor – function of time, E, m,

from Nature @ Super Kamiokande500 days + nights exposure

Flux lower than Solar e

compatible with SNO's results

higher energy but lower fluxe ~ 2 in all directions

Solar e@ MeV

Atmospherice e

@ GeV

from the Sun @ SNOSudbury Neutrino Observatory: 1 kton of (salted) heavy water, viewed by 9000 PMTs

Electron-scattering + e -> + eas in H2O: 0.50 x SSM

Charged Currents + d(p,n) -> e + p + ponly e: 0.35 x SSM

Neutral Currents + d(p,n) -> + p + nall x: 1.00 x SSM

Sudbury Neutrino Observatory is a (Salted) Heavy Water Detector:

CC measure electron neutrinos; NC measure all neutrino types

CC / NC / ES / backgrounds

CC / NC = 0.35 ! NC/Solar Model = 1.00 !--> electron neutrinos oscillate and arrive as other neutrino types

1st “neutrino appearance”!Confirmation of Solar Model!

from the Sun @ SNO

- only electron neutrinos can be produced in nuclear fusion- but different neutrino types detected upon arrival at Earth* most neutrinos leave the Sun is the same effective mass state * the “survival probability” depends on neutrino energy/solar density

the solar neutrino problem solution

Oscillations in MatterMSW (Mikheyev-Smirnov-Wolfstein) effect

For propagation, only energy and mass are relevantFor interaction, only the energy and flavor are relevant

(E, M)E²=P²+M² = (Mx²-My²)/E

VeVV

oscillations and mass

Each mass has a combination of different interaction flavorsand each flavor has a combination of the different masses

(interaction in matter can be seen as inducing an effective mass)

L = c.Time

Mx and My

at productionand detection

L = c.Time

Discovery withNatural Sources

Confirmation w/human-made

High precisionexperiments

oscillationsand mass

closing thecircle of 3

open questions

flavor change + L/E dependence => mass

* Fix large propagation Length to see oscillation pattern in Energy

* First experimental discoveries of neutrinos used artificial sourcesNuclear reactor's e =/= Particle accelerator's

Nuclear fission (& fusion) @ MeV Pion production & decay@ GeV

K2K – 250 km from KEK to Kamioka

~10² protons on target between 1999 and 2004⁰(pion, kaon production in target studied at CERN)

muon neutrinos from positive pion decays,energy spectrum similar to the atmospheric one

The first Long Base Line experiment, 250 km from KEK to Kamioka

K2K, near detectors at KEK

Flux at 250 m much larger than at 250 km!!

Check muon neutrino beam (and contamination)Measure the resulting /e and other particlesStudy neutrino interactions (and nuclear effects)

K2K, near detectors at KEK

Flux at 250 m much larger than at 250 km!!

Check muon neutrino beam (and contamination)Measure the resulting /e and other particlesStudy neutrino interactions (and nuclear effects)

interactions @ 1 GeV

K2K

(Quasi)Elastic to Deep Inelasticp, , p / n, many , ...

1ktT, SK see mostly , e, , ...⁰

CC protons measured in ND detectors production in charged/neutral currents

(Quasi-)elastic interactions dominate

Needed for energy and direction in SK

n (N)

confirmation of oscillationspulsed beam events selectedwith neutrino time of flight:

107 seen for 150.9 expected (if there was no oscillation)

Oscillation pattern in E spectrum

location of the minimum m²flux reduction from sin²2

1 - sin²2 sin²(1.27 m² L/E)

@ 250 m@ 250 km

“atmospheric” oscillations

2010

Oscillations confirmed: beam disappearance compatible with in cosmic rays

1 - sin²2 sin²(1.27 m² L/E)

- fixed Length, selected Energies

- pure beams and near detectors

- measurements on interactions

2010 MINOS, magnetizedFar (+ Near) Detector730 km (E ~ 3 GeV),also atmospheric

“atmospheric” oscillationsOscillations confirmed: beam disappearance compatible with in cosmic rays

Precise L/E to measure phase; large fluxes to measure amplitude

1 - sin²2 sin²(1.27 m² L/E)

“atmospheric” oscillations

beam disappearance ~

~ beam disappearance

Very precise |m2|

Maximal mixing!?

and sharelarge % of m2, m3

e has more m1, m2

( )

T2K – from Tokay to Kamioka

Optimal beam energy for oscillation and resolution0.6 GeV 2.5º off-axis from parent direction

Reduce beam contaminationEnhance quasi-elastic interactions

disappearance

e appearence

On-axis and off-axis ND280m detector complex

selecting muon neutrinos1 Cherenkov ring e-like / -like late decay e signal

Neutrino energy position x,y position z,R

selecting electron neutrinos1 Cherenkov ring e-like / -like

late decay e signal

visible energy

neutrino energy not ⁰

recent results from T2KNeutrino mode446 from beam120

28 e (5 from beam)

not visible

and

e appearance!

Anti-neutrino mode

more difficult beam,and less statistics

compatible w/

e lacking statistics

Discovery withNatural Sources

Confirmation w/human-made

High precisionexperiments

oscillationsand mass

closing thecircle of 3

open questions

flavor change + L/E dependence => mass

* Fix large propagation Length to see oscillation pattern in Energy

* First experimental discoveries of neutrinos used artificial sourcesNuclear reactor's e =/= Particle accelerator's

Nuclear fission (& fusion) @ MeV Pion production & decay@ GeV

KamLANDLiquid scintillator Anti- Detectorin the old KamiokaNDE cavern

50% of all reactors in Japan 150km - 250km of Kamioka

calibration

OD

1 kton LSballoon

PMTsand buffer oil

e + p -> e + n⁺- only electron anti-nu- coincidence tagging

KamLAND measurementsDiscovery of geo-neutrinos!

solving the Solar Neutrino Problemopens the way to study natural sources

(ex: Borexino does solar + geo)

still backgrounds at low energy several purification campaigns

e + p -> e + n⁺- only electron anti-nu- coincidence tagging

Oscillations by KamLANDAmplitude sin²2 fixed by NaturePhase sin²(1.27 m² L/E) [eV²] [km]/[GeV]

maximized for =(1+2k) /2

m² for e disappearance ~ 10 ² ⁻ m² for disappearancelarge but non maximal mixing => different oscillation parameters

for different mass combinations

“solar” oscillationsSolar oscillations enhanced by matter effects in the SunConfirmed by vacuum oscillations of reactor in the Earth

Vacuum L/E signature gives best result on |m²|

Oscillation parameters arecompatible for and

Two very complementary independent measurements

P = 1 - sin²(2).x sin² (1.27 L/E.m²/x)x(2,m²,electron density)

Matter effects in the Sun, break degeneracy in /m²

closing the circle on 3 neutrinosOscillation frequencies depend of squared mass differencesOscillation amplitudes depend on similarity of mass mixing in each flavor

3 flavors of neutrinos ( & anti-neutrinos ) for 3 mass values

Sun

solar oscillations (12)m²~10 eV², ⁻⁵ ~30º

Reactor

Cosmic rays &Accelerators

atmospheric oscillations (23)m²~10 ³ eV², ⁻ ~45ºsmall oscillations (13)

m²~10 ³ eV², ⁻ <10º

E ~ MeV E ~ GeV

+ Tau identification onlyat very high energy

Needs very high fluxes

1 km / 100 km 250 km250 km / 700 km

Daya Bay in China1, 2, 4 .... in total 8 neutrino detectors

All very precisely equal at different distances from

large nuclear reactor cores

Daya Bay

1 far and 2 near detector halls4 near + 4 far equal detectorsinter-calibration is crucial

Energy spectrum

1579 m

561 m

512 m

checking the reactor spectrum

Oscillations

New mixing angle much smaller than solar/atmospheric mixing(small number of e in T2K's )

2 methods to tag neutrons

Daya Bay + RENO + DChooz

Atmospheric Solar

Juno

directly see pattern of subdominant oscillations?

The challenge is energy resolution

m12 + m23

Mass HierarchyJUNO

Discovery withNatural Sources

Confirmation w/human-made

High precisionexperiments

oscillationsand mass

closing thecircle of 3

open questions

* Seen L/E pattern for three sets of neutrino oscillation parameters * Can not use simplified two-neutrino oscillation formula anymore

e

1 0 00 c23 s23

0 -s23 c23

c13 0 s13 e⁻i

0 1 0-s13 ei0 c13

c12 s12 0 -s12 c12 0 0 0 1

m² = 7.5 + 0.2 x 10 eV²⁻⁵Solar = 30º-35º

m²| = 2.24 + 0.06 x10 ³ eV²⁻Atmospheric= 40º-50º <~ 10º & =?

Matrix values range 0.15 – 0.85, 1%-6% uncertainty

m²

m²|

Largest angle is 45º Largest angle is 13ºHaving 3 mixing angles allows for CP-violation (GIM mechanism)

|Ue1| |Ue2| |Ue3||U1| |U2| |U3||U1| |U2| |U3|

0.82 0.55 0.150.35 0.70 0.610.44 0.45 0.77

|Vud| |Vus| |Vub||Vcd| |Vcs| |Vcb||V td| |V ts| |V tb|

0.97 0.23 0.000.23 0.97 0.040.01 0.04 1.00[ ] [ ]

Pontecorvo-Maki- Cabibbo-Kobayashi--Nakagawa-Sakata -Maskawa

Mixing matrices: Neutrinos and Quarks

recent results from T2KNeutrino mode

Anti-neutrino mode

Hints of CP violation in T2K

H.A. Tanaka, T2K @ Neutrino 2016

1 relevant phase2 mixing angles

3 mixing angles

matter effectschange up to 10%

odd CP phase change up to 30%

Joining disappearance + appearance+ neutrino and anti-neutrino beams+ the results from other experiments

Can neutrinos help to explainmatter/anti-matter asymmetry?