Neutrino properties, Neutrino properties, oscillations, present statusoscillations, present status

Gaston WilquetIIHE - Université Libre de Bruxelles

1

Urs Fest, Bern, 21/1/2011

2

A very brief history of the neutrinosA very brief history of the neutrinos

Neutrino MixingNeutrino Mixing

Neutrino nature: Dirac or Majorana particle? Neutrino-less Neutrino nature: Dirac or Majorana particle? Neutrino-less -decay-decay

Direct mass measurementsDirect mass measurements

Neutrino oscillations – phenomenologyNeutrino oscillations – phenomenology

First evidences of neutrino oscillations: a selectionFirst evidences of neutrino oscillations: a selection

Observation of neutrino oscillations at reactors and accelerators: a selectionObservation of neutrino oscillations at reactors and accelerators: a selection

Near future (current decade) as conclusionsNear future (current decade) as conclusions

I shall not talk about the OPERA experiment: see next talk by Henri PessardI shall not talk about the OPERA experiment: see next talk by Henri Pessard

Contents

A very brief history of the A very brief history of the neutrinosneutrinos

3

Pierre Becquerel (1886) discovers radioactivityErnest Rutherford (1897) identifies and radioactivityJ.J.Thomson and others (1897) discover electron

Pierre and Marie Curie (1902) show that -rays are electrons

40K 40Ca + e-

Lise Maitner and Otto Hahn and James Chadwick (1914) measure the -rays energy spectrum: incompatible with 2-body decay. Angular momentum is not conserved.

C.D. Ellis et W.A. Wooster (1927) and Lise Meitner and W. Orthman (1930) do a calorimetric measurement of the total energy released in the radium E (210Bi) decay: incompatible with 2-body decay and with 3-body decay involving a -ray

Niels Bohr and others contemplates the possibility that energy-momentum is not conserved in decays

From the discovery of radioactivity to the “energy crisis”

4

Letter from Pauli retained by a ball in Zurich to the “Gruppe der Radioaktiven” in meeting in Tübingen

“Invention” of the neutrino and the weak interaction formalism

Wolfgang Pauli “invents” the neutrino (1930): the Columbus egg-decay is a 3-body decay involving a “neutron”: light spin ½ neutral particle

Enrico Fermi (1933) names the “neutrino” and develops the -decay theory – the base of the electroweak theory in the Standard Model

James Chadwick had discovered the neutron in 1932

Local 4-fermions current-current interaction based on the 4-spinor Dirac description of Fermions

n p

e ee

FG

5

Enrico Fermi (1933) offers a case of champagne to whom will detect the first neutrino.

Hans Bethe and Rudolf Peierls (1934)

Mean free path of moderate energy in lead: tens to thousands ly

Fred Reines et Clyde Cowan (1953-56-58) detect the first neutrino interactions at Savannah River nuclear power plant

1010N eN

The experimental discovery of the neutrino

6

13

0.5

.8

prompt 2- coincidence from annhilation on

delayed 's from capture by "neutronphage" nuclei (Cadmium) - known

's detected by scintilators and P

ee

three

shEp e n E MeV

keV e e

n E

MeV

M tubes

0.511keV

100 200 s

Ray Davis et al. (1955-58) confirm the difference neutrino/antineutrino

37

37 37 50

4000

Radiochemical experiments days

Working principle suggested by Bruno Pontecorvo

tested with cosmic rays by Ray Davis

of carbon tetrachloride exposed to Brookhave

e ArCl Ar e

l

:No count above backgroun

n

d

reactor

n e p

Neutrino, antineutrino and neutrino families

-

Highest energy proton beam

sp N D X

X

13

0

3 10

'

-

Interaction-decay chain

or or se

N X

e

s

Bruno Pontecorvo (1959):electron and muon have different partners e and Leon Lederman, Melvin Schwartz, Jack Steinberger at al (1962) discover the

+BNL beam decays

e

N X

N e X

DONuT Collaboration (2001) observes the at Fermilab

7

Neutrino MixingNeutrino Mixing

8

Neutrinos exist in 3 different flavours (familes, types)

is produced in CC weak interaction of lepton

If neutrinos are massive and mass eigenstates are not degenerated

a pr

: , ,e

iori mixing between :

flavour eigenstates

mass eigenstates

(6) parameters 3mixing angles

Dirac (Majorana)

3

11,

2 3 23

1,

, ,

1, 3

4

1, ,

1

k

k kek

kk

e

k

U

U eU

(3)phases

Extension to 4 mass eigenstates straightforward

Additionnal light flavour eigenstates are sterile :

active neutrino with = from invisible width at LEP02 2.9841 0.0084ZN m M Z

Mixing matrix

9

PMNS parameterization of mixing matrixBruno Pontecorvo (1957) -

Ziro Maki, Masami Nakagawa, Shoichi Sakata (1962)

10

Neutrino nature:Neutrino nature:Dirac or Majorana particle?Dirac or Majorana particle?

Neutrino-less Neutrino-less -decay-decay

11

The Standard Model Weyl neutrino

• Tsung Dao Lee and Chen Nin Yang (1956) predict P violation in weak interactions

• Chien Shiung Wu et al. (1957) observe maximum P violation in -decay

• Maurice Goldhaber et al. (1958) measure the neutrino helicity

() are fully polarized: h = -1/2 (+1/2)

Massless neutrinos may not be overtaken by Lorentz transformation

The massless and differ by an invariant observable: h

12

and are also distinguished by a conserved quantum number:

Lepton nu

SM described by a chiral field

State ( ) an

mber

hilit

and, 1 , 1

l lL

l l

L l L v l

n p p n

p n n p

LH

ated (created) by field has -1/2 (+1/2)lL h

Charged leptons: conserved:

are conserved independently

6

12

10

, , 10e

L BR e

L L L BR e e e

State ( ) anhilitated (created) by field is linear sperposi

is no more invariant and c

tion of and

But state ( state) enters into su

annot distinguish and

per s

po it

-1 / 2 1/ 2

1/ 2 1/ 2

l l lL h

h

h

h h

Ap

io

pa

n wi

rent

th weigh

conservation of artefact of violation and sm

t

allness f ?

o

610m

n p p n

p n

m

E

n p

L P

Massive neutrinos: Dirac or Majorana ?

Dirac neutrinos: and distinguished by

described by Dirac spinors (almost) like other fermions

field is sterile: no coupling to bosons

Small mass implies very weak coupling

1( 1)

,

10

R

L

RH W Z

to boson13 H

Majorana neutrinos are their own antiparticle

See-Saw mechanisms to explain smallness of the mass

very heavy partners new physics at GUT scale,

leptogenesis to explain violation and

1510m GeV

CP

matter/antimatter asymmetry13

14

Dirac vs. Majorana? Neutrino-less -decay

© LHEP website

76 ,2 211/ 2

( , ) ( , 2) 2 2

(1.77 0.01 0.12) 10

2nd order SM weak interaction predicted M. Goeppert-Mayer (1935)

observed in a dozen nuclei:

e

Ge

A Z A Z e

T y

7633 As

7632Ge

2.04 Q MeV7634Se

, ) ( , 2) 2

2 forbidden for Dirac neutrinos

A Z A Z e

L

2

1 20 01 2

3 32 2

1, 1,

0 25 100% known to

e

e

k

e

ek k ekk

ik

k

mT M

m

m U m U m

M

e

Moscow-Heidelberg experiment at Gran Sasso: semi-conductor

Only - very disputed - claim of a discovery in 2001:

Cuoricino experiment at Gran Sasso: crystals bol

0 2.99 251/ 2 0.501.19 10 0.2 0.6

eT y m eV

ometers 130

0 241/ 2

130 2

3.0 10 0.19 0.68 @ 90% . .e

T Xe e

T y m eV C L

e

4 crystals

Direct mass measurementsDirect mass measurements

15

Very high energy resolution & counting rateVery low background

iif ~ of total counts131 2 10m eV

e effective mass - electron energy spectrum in Tritium -decay

16

220

0

2 2

1

0

32

0 ( )

0

0 0

( ) ( )

if

for

e

e

effe

e

e

e

eff

effek

ee e e

e

kk

E E

E Max E m

x

m

x

dN E E p E E E Ed

m

U m

E

m

offset 2

e

effm

0m

1m eV

e effective mass - status of Tritium experiments

Both experiments have reached their intrinsic limit of sensitivity

Troitsk gaseous T2-source Mainz frozen T2-source

at 2 2

2005 : 2.3 95%

0.6 2.2 2.1

e

e

eff

eff

m eV CL

m eV

at 2 2

1999 : 2.5 95%

1.9 3.4 2.3

e

e

eff

eff

m eV CL

m eV

Magnetic adiabatic electron collimation followed by an electrostatic filter

17

Neutrino oscillations Neutrino oscillations phenomenologyphenomenology

18

Neutrino propagation in vacuum: Neutrino oscillation

Assume created with momentum at in CC interaction of

Flavour eigenstates propagate as superposition of mass eigensates with different phases:

3

1

0

0

-0

k kk

kk k

p t

| ν U | ν

ν

iE t| ν t U e | ν

Mixings define

Oscillation termMaximum probability

as 23

1

2 21,3* * 2

*

0

/

2

[ ] [ ]( ( ) ( )) 4 sin 1.27

[ ]

2

kk k

k

kjj k j k

j k

j k

L

L E

m E p p m

E

m eV L kmP U U U U

E GeV

U U U

Null if CP conserved

Oscillation term

parameters:

mixing angles

CP phase

+

2 21,3*

2

2 2 2 2 2 221 32 31

/

6

[ ] [ ] 3sin 2.54

[ ] 1

2

kjj k

j k

kj k j

L E

m eV L kmU

E GeV

m

m m m m m m

not sensitive to diagonal Majorana CP violation phases

oscillation experiment cannot distinguish Dirac - Majorana

19

NC :

CC :

Collusion between and may lead to

mixing

Forward elastic scattering plane

angle in m

wave exp w

t

h

a

it

, ,

0

,

2

-

,

2

, , , ,

,

| 1 | 10

,

e

e e

e e

e

m

Vi px e iE

e u d e u dn n n

e e

tE

E

n n

m N

e

ter very different from in vacuum

in vacuum and at Sun centre are different mass eigenstates supe

= number

r

dens

positions

ity

2

2

22 2 2

sin 2tan 2 2

cos 2 2

cos 2 sin

m CC F e eCC

m CC

mV G N N e

m E V

m m E V m

22

Flavour transition caused by matter effects

20

If varies "slowly enough": MSW (Mikheyev, Smirnov, Wolfenstein) effect:

created at large is mass eigenstates superposition different from vacuum

propagate adiabatically from large

e

e m

i e

N

N

N

to vacuum superposition of mass eigenstates

remains unchanged during propagarion

superposition reaching vacuum is different from

Adiabaticity condition depends on 2, , , ,

i m

e em E N N

In vacuum:

Matter effects allow distinguishing between and or fix

2

2

sin 2

90 sgn

oscP

m

Neutrinos oscillation: what we know in 2010 ?

e

All results compatible with

- Compatible with full mixing

- Large mixings between and / in and

- Compatible with

_

2 2 5 221 2 1

2 2 3 231

2 2 231 32 21

1 2

7 10

2.5 10

30

sol

atm

m m eV m m

m m eV

m m m

e 3

- Absolute mass scale ?

from spectrum in

- Mass hierarchy?

strong

or inverte

n

d

or degenera

o

c

in

y ?

21

3 3

1 2 3

3 1,2

1, ,3

3

2

2.3

0, 8 , 50

0, 50

2

: sin 2 0.12

e

effee

m eV E H He e

m m meV m meV

m m meV

m eV

e- component in ? CP violation ?

- Dirac or Majorana neutrino?3

21

e

2 5 2 221 7 10 solm eV m

0

2m

2 0.3 0.35 0.35

3 ? 0.5 0.5

1 0.7 .15 .15

2 2 3 231 32

2

2.5 10| | | |

atm

m m eV

m

2 3 232

3 3 -

2.5 10

2.3 : e

m eV

eV H He e

Normal hierarchy

2 5 2 221 7 10 solm eV m

0

2 3 232

3 3 -

2.5 10

2.3 : e

m eV

eV H He e

2m

2

3 ? 0.5 0.5

0.3 0.35 0.35

1 0.7 .15 .152 2 3 231 32

2

2.5 10| | | |

atm

m m eV

m

Inverted hierarchy

2 5 2 221 7 10 solm eV m

0

2m

2 0.3 0.35 0.35

3 ? 0.5 0.5

1 0.7 .15 .15

2 2 3 231 32

2

2.5 10| | | |

atm

m m eV

m

2 eV2

Degeneracy

First evidences of neutrino First evidences of neutrino oscillations: a selectionoscillations: a selection

22

First evidences: atmospheric and solar neutrinos

First experimental indications of neutrino oscillations were incidental.

Experiments designed to study the interior of the Sun (Ray Davis at Homestake mine in 1968 …) and cosmic rays through interactions in the atmosphere (IMB at Morton mine in 1986 …) using neutrinos as messengers.

(Almost) all evidences based on disappearance: deficit in flux of a neutrino flavour measured at distant point the from its source.

Evidences first confirmed by several experiments using natural neutrinos sources. Astrophysical and instrumental explanations of the deficits progressively abandoned.

Undisputed interpretation as neutrino oscillation dates from about a decade:

• Atmospheric neutrinos (…Kamiokande, Super-Kamiokande-1998…)

• Solar neutrinos (Homestake,… Kamiokande, Super-Kamiokande, SNO-2002…)

23

Pioneers: Ray Davis: Homestake radiochemical experiment, first solar neutrino detectionMasatoshi Koshiba: first large water Cerenkov experiment Kamiokande – solar and atmospheric neutrinos

Atmospheric neutrinos : Super-Kamiokande 1996-2005

Events topology discrimination based on the shapes of the Cerenkov rings

Not obvious but -like -like separation100% /e

muon600 MeV

Sharp ring

electron500 MeV

Fuzzy ring

50 11 200

2700

ktons of highly purified water seen by PM tubes

Under of rocks in Mozumi mine, Kamioka, Japanmwe

24

N X

N X

e

e

N e X

N e X

p

e

20 km

13 000 km

p

e

,2

,e e

v v

v v

Super-Kamiokande results arXiv:hep-ex/0501064

25

e

Measured -like flux agrees with model expectations for every and

decouples for probed by

Measured -like flux is largely depleted and depletion oscillates in

larg

d

e - mix

omain2

/L

L

E

e E

m L E

ing for probed by domain2m L E

2 2

2

1

2 3 223

[ ] [ ]sin 1.27

[ ]

500

2.5 10

kjm eV L km

E GeV

Lkm GeV

E

m eV

data

MC no oscillation

Events observed/predicted

Best fit to

data

Numbers of events

like like

sin2 sin2

m2 32

(eV

2 )

m2 32

(eV

2 )Super-Kamiokande results arXiv:hep-ex/01002.3471

2

2e 3

2

Best fits:

sin full - mixing

sin no component in

sin at

23

2 3 2

13

13

0.50

2.1 10

0.

0.04 90% . .

m eV

C L

2 5 2 221 7 10 solm eV m

2m

2 0.3 0.35 0.35

3 ? 0.5 0.5

1 0.7 .15 .15

2 2 3 231 32

2

2.5 10| | | |

atm

m m eV

m

e

26

20 1

1

6 10 1 2%

3 1.8

e

known to

e

elec

e e

thresh

P GW

s

E MeV E MeV

p e n

0.511keV

5t17t9

0t

3 2 3 223

(8.5 ) 998 1114

3 10 2.5 10

(0.09%)

twin reactors @ and

5 tons -doped liquid scintillatior

GW L m

E MeVm eV

L m

Gd

spectrum measured

spectrum expectede

e

ER

E

E

2 2 3 213 31

1.010 0.028( ) 0.027 ( )

sin 2 0.13 90% . . 2.5 10

eNo disappearance

at for

R stat syst

C L m eV

CHOOZ reactor experiment: confirms that no e in 3

27

Detector : liquid scintillator vessel doped with high neutron capture cross-section

Solar neutrinos: measured event rates vs. SSM predictions (Bahcall and Pinsonneault)

0.34 / 0.59

e

e

Experim

flu

ents sensitive

x defici

to CC only

:

:

tmeas pred

N e X

e

No sensible astrophysical or

instrumental explanation to

disappearance except oscillation.

28

4

10 -2 -1

4 2 2 26.73 0.6

6.5 10

Sun fusion reactor Hans Bethe (1930's), William Fowler (1950's)

Solar flux at Earth level: ep e He MeV E E MeV

cm s

29

Solar neutrinos: SNO 2002 results

, , , ,

9500

6000 . . .

1 ktons of highly purified heavy water seen by PM tubes

Under of rocks in Creighton mine, Sudbury, Canada

Sensitive to NC: e e

m w e

d p n

SNO NC

0.35CC CCmeas e model e

NC NCmeas model e

v v

v v

Proof of the appearance of active-like neutrinos of flavour different from

However not identified as : ,,

e

CCthresh

v

v v E E v

n vacuum: assume

remember that and have same

In the Sun core:

large

I 12 13

2 212 1 12 2

1 2

, 1 2

2

12 2

2

tan 0.44 0

: cos sin

0.7 0.3

: 0.3 0.7

sin 2tan 2

cos 2 2 2

0 2 cos 2 tan 2

e

NC

m

F e

e CC

V V

m

m E G N

N E V m

created as

emerges from Sun in vacuum as

are created in the Sun core in nu

If adiabatic transi

clear f

tion

usi

satisfie

d:

2

2

2 22 12 , 12

,

0 2

( ) (0)exp / 0.1

: cos sin

0. 0.7 3

m m

e

e

e

e

e

eN x N x R

on reactions

A mixture of and propagates in the vacuum between Sun and Earth

Fraction of surviving varies with

,e

e E

Solar neutrinos results explained by matter effects

30

adiabatic

2 0.10 0.1012 0.07 0.06tan 0.44

Observation of neutrino Observation of neutrino oscillations at reactors and oscillations at reactors and accelerators: a selectionaccelerators: a selection

31

What about oscillation experiments at accelerators and nuclear reactors?

2 2m eV

2sin 2

410

10

Until late 1990’s• No theoretical prediction• Theoretical prejudice: small mixing c.f. quarks• Hot dark matter models: large m > 10 eV → large m2

Acceleratorexperiments

From ~2000: U and m2 known with reasonable precision:Design experiments for specific L/E & oscillation channel.

32

Probing atmospheric neutrinos solution: disappearance or its appearance into at accelerators

2 2 3 2

... :

10 10100

Beams: many or focus/defocus to choose or

multi Long Baseline experiments

Near detector: Beam flux, composition and energy spectru

several

p N

E GeVm eV

L km

m before oscillation takes place

Far detector: flux and energy spectrum and compare with no oscillation extrapolationCC

K2K : KEK to Kamioka LBL experiment (1999-2004) / 1.3 / 250 Far detector: Super-KamiokandeE L GeV km

Visible energy

-like events

No oscillation

Best fit

112

151

4.3

9

Small statistics:

- events observed

- events exp

No oscillation scena

ected if no oscillatio

rio excluded at

n

33

MINOS : the LBL experiment @ Fermilab NuMI beam (2005)Two similar detectors: segmented magnetized iron calorimeters:

- magnetized iron slabs

- planes of plastic scintillator strips read by WLS fibres and PM

Near detecto

tubes

r: at

Far det

0.98 1.04ktons L kmector: at in Soudan mine, Minnnesota

Beam spectrum centered on

5.4 733

2 5

ktons L km

GeV

Ratio of data to expected for no oscillations

E GeV

2 0.11 3 231 0.08

231

2.35 10

sin 2 0.91 90% . .

@

m eV

C L

P. Vahle, Neutrino 2010

34

35

Probing solar neutrinos solution:e disappearance at nuclear reactors

2 4 5 210 1010

1- 2

0

%

e

Long Baseline experiments

Flux and energy spectrum at source known at level

Detector a la CHOOZ: doped liquid scintillator vessel

3

-

E MeVm eV

L km

p e n

liquid scintillator

PM tubes

1000

2100

tons

KamLAND LBL experiment at Kamioka 13 m diameter balloon

0 180 is the flux weighted average

distances to reactors

L kmKamLAND results

Expect 2179±89 events from reactors

+ 276±23 backgrounds

Observe 1609 events.

Oscillation pattern observed

36

2 0.21 5 221 0.21

2 0.0612 0.05

7.59 10

tan 0.47

KamLAND + Solar best fit assuming CPT: e e

m eV

arXiv:hep-ex/0801.4589

Common fit to KamLAND and solar neutrinos results

Near future (current decade) Near future (current decade) as conclusionsas conclusions

37

We know with good precision the few we knew

e

@ full mixing

large mixing

2 0.21 5 221 0.21

2 2 0.11 3 232 31 0.08

231

2 0.0612 0.05

7.59 10

2.35 10

sin 2 0.91 90% . .

tan 0.47 /

m eV

m m eV

C L

38

e

Absolute mass scale ?

- Sign of Mass hierarchy?

normal

or inverted

- at

component in ?

- ? violation ?

231

1 2 3

3 1,2

213

3

2.3

0, 8 , 50

0, 50

sin 2 0.13 90% . .

e

eff

CP

m eV

m

m m meV m meV

m m meV

C L

CP

- Dirac or Majorana neutrino ?

2 5 2 221 7 10 solm eV m

0

2m

2 0.3 0.35 0.35

3 ? 0.5 0.5

1 0.7 .15.15

2 2 3 231 32

2

2.5 10| | | |

atm

m m eV

m

2 3 232

3 3 -

2.5 10

2.3 : e

m eV

eV H He e

e

Observations made with natural neutrinos sources confirmed with manmade neutrinos sources and measurements improved

A lot that we do not know 10 years later

Oscillation: Why will it be difficult and maybe very difficult ?

13

231

1%

: sin

sgn :

e

e

13

Oscillation at accelerators: appearance in beam in LBL experiments

irreducible contamination in beam

: It all depends how small it is

violation

understandi

CPiCP e

m

231, ,sgn13

ng matter effects in Earth in LBL experiment

Correlations and intrinsic ambiguities between CP m

232

20 -100

,23

First generation of Super-beams:

factor on neutrinos flux

Principle: Near / Far detectors

Considerable improvement on m

sin 2 213 =0.25

sin 2 213 =0.09

sin 2 213 =0.17

2 800

E L

GeV km

○ CP=0▼ CP= ● CP=▲ CP=3/2

231 0m 231 0m

39

T2K (Tokai to Kamioka) experiment

First event in Super-K on 24 February 2010

Sensitivity after 5 years

0.6 295E L GeV km

Oscillation experiments at accelerators Strong correlation13 CP

2.4×

10-3

0.004 – 0.02

NOA experiment at Fermi Lab

far and near detector:

Liquid scintillator tracker/calorimeter

Take profit that and have different

matter effects to explore

Sensitivity after 6 years (3 +

231

2 810

15 220

sgn

E L GeV km

kton kton

m

3 )

Full lines for realistic fluxes

2 -3 231 2.4 10m eV

Strong correlation13 CP

0.005 – 0.013

More? Ask

40

Search for disappearance with detectors "a la CHOOZ"

Near and far detectors to overcome precision on flux knowledge

Limitation: systematic after 4 - 5 years data taking

1- 2%e

Oscillation experiments at reactors

East Reactor

West Reactor

351 m465 m

1115 m998 m

Double-CHOOZ

Twin reactors:

far detector: 2010

near detector: 2011-2012

Sensitivity in 2014:2

13si

8.5

1

1

n 2 0.03@ 90% . .

thG

C L

W

Daya Bay, China

twin reactors of

far detectors: 2011

near detector: 2010-2011

Sensitivity in 2014:2

13sin 2

3 2.9

4

2

0.01@ 9 . .

2

0%

th

C L

GW

41

Direct mass and 0-decay : why will it be very difficult ?

Katrin Tritium experiment - Karlsruhe

Sensitivity: factor improvement factor on

Measure at if

20.2 : 10 100

0 5 0.35

e e

e e

eff eff

eff eff

m eV m

m m eV

Degen

erat

e m

asse

s

2910 y

2510 y0-decay experiments

Inverted hierarchy: resolution

Factor improvement on best resolutions

Normal hierarchy: resolution

Beyond current reach of kn

A dozen projects in years 2011-2020

EXO -

own tech

niques

136

10

20 - 50

1

meV

me

Xe

V

Xenon TPC - aims at resolution10 50 meV

More? Ask

42

Ten years of collaboration with

Before doing physics with the OPERA detector from 2008, we built together the OPERA Target Tracker between 2000 and 2007

Scientific knowledgeWisdomKindnessPerpetual smile

In particular with

43

Scientific knowledgeWisdomKindnessPerpetual smile

Thank you, U

rs

44