Neutrino Physics: Experiments

Neutrino physics: experiments

The dark side of the Universe, ISAPP, MPIK Heidelberg, May 29/30, 2019 ν νe µ Christian Weinheimer Institut für Kernphysik, Westfälische Wilhelms-Universität Münster [email protected] ν τ A reminder: Neutrinos in the Standard Model of Particle Physics Prof. Dr. Takaaki Kajita Neutrino oscillations: experiments with atmospheric, solar, accelerator and reactor neutrinos

Neutrino masses: - cosmology and astrophysics - neutrinoless double β decay - direct neutrino mass experiments

Search for sterile neutrinos Coherent neutrino nucleus elastic scattering Prof. Dr. Arthur B. McDonald Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 1 Experimental proof n of neutrinos ν e p e+ 1956: Cowan and Reines: Poltergeist experiment

strong νe source: nuclear power reactor: 6 fission (from fission products), E 9 MeV νe  ν  energy gain / fission: 200 MeV 1 GW thermal power  2 1020 ν/s

+ Detection reaction: inverse β decay: νe + p  n + e (threshold: 1.8 MeV)

Signature:a) n: thermalisation by elastic scattering, capture on Cd  γ 's b) e+: annihilation  2 γ 's (511 keV)  spatial and time-delayed coincidence (nearly background free) measured cross section: (1.1 ± 0.3)  10-43 cm2 figure: Schmitz: Neutrinophysics, Teubner (in good agreement with Fermi`s theory for V-A)

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 2 ν's in the electroweak Standard Model: U(1)SU(2) 12 fundamental fermions 6 left-handed weak isospin dublets: pure weak isospin dublets

weak S. Glashow isospin dublets

9 right-handed weak isospin singulets: (no νR in SM)

massive leptons in charged S. Weinberg weak currents (CC): - lepton: For masseless particles (ν in SM): P(H = 1) = (1  -v/c))/2 P = -v/c  σ  Long c ΨL , ΨR have helicity H = -1  p - anti lepton: P(H = 1) = (1  v/c)/2  σ  P = v/c A. Salam c  p Long ΨR , ΨL have helicity H = +1 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 3 Lagrangian: Interaction part

l (d) ν (u) W + W -

ν (u) l (d) weak charged current (CC)

ν,l, u,d, .. Z 0

ν,l, u,d, .. weak neutral current (NC)

l, u,d, .. γ

l, u,d, .. em neutral current

coupling to electromagnetic current e.m. as in QED:g sin = e Jµ θW

o θW = 28.7  coupling of weak interaction  coupling of em. interaction, 2“ 2 but there is a term „mW (mZ ) in the denominator of the propagator, see later

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 4 Weakness of weak interaction

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 5 ν cross sections

σ  s

figure: Schmitz: Neutrinophysics, Teubner -fermion scattering cross sections: s = m 2 + 2E m s E ν σ  f ν f   ν Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 6 LEP: determination of number of neutrino generations

LEP: e- + e+  Z0 (γ)  e- + e+, µ- + µ+, τ-+ τ+, e l

u + u, b

i s i

d + d, v s + s, c + c, b + b,

νe + νe, e l

ν + ν , b µ µ i s i

+ , v ντ ντ n ???? i

figure: PDG Exp: full width: Γ = 2495(2) MeV

invisible width: Γinvisible = 499(2) MeV partial width = 167.1 MeV N = 2.99 ν Γν  ν Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 7 Angular distribution of neutrino-fermion scattering

Neutrino-fermion scattering:

no angular dependence:

y distribution is flat for νl scattering !

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 8 Angular distribution of antineutrino-fermion scattering

Antineutrino-fermion scattering (neglect NC):

angular dependence:

distribution y distribution is not flat for νl scattering ! Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 9 Deep inelastic (anti)neutrino-nucleon scattering

Average: e g d expect: and i r b m Experiment: a C

, s c but i s y h P

y g r e

From helicity arguements we deduce n E

h g for the y distribution and for σtot: i H

o t

ν q = ν q and ν q = ν q n o i t c u d o r t n I

: s n i k r e P

with : s e

with r u g i f  Sea quark fraction q(x) in nucleon is about 15% Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 10 Neutrino sources and energy spectra

figure: Schmitz: Neutrinophysics, Teubner Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 11 Summary of neutrinos in the Standard Model of particle physics

● ν's are left-handed, charged fermions in CC reactions (W exchange) are also left-handed charged fermion coupling to the Z0 is more complicated (since the Z0 is a superposition of the „hypercharge photon B“ and the W3)

● ν's are massless, since there is no right-handed neutrino to construct a „Dirac mass term“

= - m ΨL ΨR – m ΨR ΨL L

● ν's have very small cross section (due to the large masses of W and Z)

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 12 Neutrino physics: experiments

Neutrino masses: - cosmology and astrophysics - neutrinoless double β decay - direct neutrino mass experiments

Search for sterile neutrinos Coherent neutrino nucleus elastic scattering Prof. Dr. Arthur B. McDonald Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 13 Atmospheric neutrino anomaly: too few muon neutrinos

Interaction of cosmic rays (p,α, ..) in outer atmosphere: π, K,... + + + π  µ νµ +  e + νµ + νe - - + π  µ νµ e- + +  νµ νe + / 2  νµ νµ νe  νe  n o i t a t c e ν e

p  x

e e

ν /

t /

n µ e ν

+ m

i µ r ν e p x e

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 14 Kamioka Nucleon Decay Experiment: KamiokaNDE (II)

3000 t water Cherenov detector to search for proton decay (→ GUT) 16m high, 16m diameter 1000 38cm PMTs at the surface If a charged particle moves faster than speed of light in the medium, polarisation does not follow: → Emission of Cherenkov-light into a cone: cosθ = 1/βn o (→ 42 for H20 assuming β=v/c → 1)

→ ring structure at wall covered by PMTs Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 15 Atmospheric neutrinos in a water Cherenkov detector

Cherenkov cone gives: ● energy ● direction (-) ν ● electron/muon differentiation: muons: sharp ring

l+/-

electrons: washed-out ring (multiple scattering, em shower)

(Super-)Kamiokande

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 16 Physics results of KamiokaNDE II

No observation of proton decay → main mission failed but KamiokaNDE II performed extremely well, e.g.

- Discovery (together with IMB) of neutrinos from SN1987a → Nobel prize 2002 to Masatoshi Koshiba

- confirmation of nuclear burning in the sun by observing solar neutrinos

- atmospheric neutrino anomaly: wrong muon neutrinos/electron neutrino ratio & wrong angular distribution Y. Fukuda et al., Phys. Lett. B 335 (1994) 237 → decision to build Super-Kamiokande Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 17 Super-Kamiokande: Start of data taking in April 1996

water Cherenkov detector

H20: 50 000 t 40 m high, 40 m 

11146 PMTs a 50 cm 

1 km overburden in Kamioka Mine, Japan

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 18 Super-Kamiokande's first result at Int. Conf. Neutrino 1998 at Takayama

Nobel prize 2015 to Takaaki Kajita

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 19 Angular distribution of and at SK νe νµ

θ ν p, α, .. L

Expectation no neutrino oscillation

Fit νµ → ντ Oszillation

R. Wendell – Neutrino 2014 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 20 Angular distribution of and at SK νe νµ

 Clear deficit of muon neutrinos coming from below, θ (i.e. muon neutrino which travelled a long distance) ν p, α, .. Measurement is compatible to neutrino oscillation: L (detector is nearly blind for ν ) νµ  ντ τ „Neutrino oscillation“ with parameters (Δm2  2 ×10-3 eV2. sin2(2θ)  1)

Expectation no neutrino oscillation

Fit νµ → ντ Oszillation

R. Wendell – Neutrino 2014 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 21 Angular distribution of and at SK νe νµ

All data sets and analyses (FC, PC, up-going θ µ, NC enhanced): ν compatible with p, α, .. ν  ν oscillation L µ τ (Δm2  2 ×10-3 eV2. sin2(2θ)  1)

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 22 Angular distribution of and at SK νe νµ

θ Question to think about: ν What is the connection of the expected multi-GeV p, α, .. angular distributions of atmospheric neutrinos L with the red sky at sun rise or sun set ?

Expectation no neutrino oscillation

Fit νµ → ντ Oszillation

R. Wendell – Neutrino 2014 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 23 Neutrino (vacuum) oscillations

1) non-trivial unitary ν mixing matrix U between neutrino flavour states ( ) and mass states ( ): νe νµ ντ ν1 ν2 ν3 d d g s mixin d 3 state

2) a flavour state propagates as a coherent sum of mass states m(νi)

if the m(νi) differ  neutrino oscillation ν U 1 U * - + µ1 τ1 ντ τ nt + µ ν perime W U 2 U * slit ex µ2 τ2 Triple ν ν + µ U 3 U * W µ3 τ3 creation of a detection of a νµ propagation as coherent ντ via weak interaction superposition of mass states via weak interaction Formula is correct, P but correct derivation (να  νβ) needs wave packages or QFT (see E. Akhmedov) Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 24 Neutrino (vacuum) oscillations

2 Flavor case: Probability for an oscillation sin2(2 ) from to (and back) for Θ να νβ an amplitude value of average E/L 2 sin (2θ) = 0.2 in units of the

y oscillation length L . t

i osc l i

b 2 a for sin (2Θ) = 0.2

b The colored curves take o r into account that we don't P

have sharp values for

average E/L E and L, but that these

are smeared out over a sin2(2Θ) certain distribution.

3 Flavor mixing: General oscillation formula

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 25 Atmospheric neutrinos: really neutrino oscillation ?

here black here blue

Y. Ashie et al. (Super Kamiokande) Phys.Rev.Lett.93:101801,2004 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 26 Neutrinos from the sun

Nuclear fusion in sun core: Radial dependence 4 + (+ 26.7 MeV) 4 p  He + 2e + 2νe more correct:

νe νe

νe

νe on earth surface: 2 65 billion of neutrinos per s and cm Neutrino energy [MeV]

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 27 The Homestake experiment by Ray Davis

380 000 l perchloro-ethylene in the Homestake Mine

37 37 - νe + Cl  Ar + e

Bubbling out of the 37Ar (0.5 atoms/d) 002 ard 2 and radiochemical detection el aw Nob

Result is only 30% of expectation

● Is the experiment wrong ?

● Is the theory of the sun wrong ?

● Do the neutrino behave differenctly ?

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 28 GALLEX and other gallium experiments

● GALLEX (later GNO), SAGE):

o 71

s Inverse β decay of solar νe on Gallium ( Ga) (110 t) s to X

a e ensitiv

E s S 71 71 - s ino L ν + Ga  Ge + e neutr n e p

L p a A r 71 G G

radiochemical detection of Ge:

m 71 i 1) Chemical separation of Ge νe 2) Detection of decay back to 71Ga Detection efficiency  90 % (checked with ν source)

+9 SSM(BP) 128 -7 SNU +4.3 GALLEX 77.5 ± 6.2 -4.7 SNU GNO 62.9 ± 5.4 ± 2.5 SNU GALLEX GNO SAGE 69.1 +4.3 SNU -4.2 65 solar runs 58 solar runs Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 29 Solar neutrinos at Super-Kamiokande

Different to atmospheric neutrinos: - - (elastic e- scattering) νe + e  e + νe νe

Detection of neutrinos: - νe creates an e νe v(e-) > c/n Cherenkov cone:  direction and energy e-

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 30 Determination of signal: angular distribution

2-dim intensity distribution

Picture of the sun in neutrinos taken from 1km underground

Y. Koshio – Neutrino 2014

 νe are really coming from the sun (first direct proof of nuclear fusion in the core of the sun by Kamiokande in 1990)

(0.34 considering NC: but there are too few: #ν / #ν = 0.45 - - measured expected ν + e → ν + e ) µτ µτ Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 31 Solar neutrino puzzle

Solar neutrino deficit:

4 + Expectation from nuclear fusion: 4 p  He + 2e + 2νe (+ 26.7 MeV)

 know νe rate from solar luminosity n o i t a t c e p x e / t n e m i r e p x e

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 32 Neutrino vacuum oscillation and solar neutrino problem

Strong reduction observed at chlorine experiment (1/3 < 1/2) distance sun-earth = 1.44 1011 m , with E 10 MeV    λosc ν   Δm2 = 10-10 eV2 ( fine-tuning problem)

Solution: matter enhanced oscillation/ matter-enhanced flavor transitions (MSW effect, Mirkheyev-Smirnov-Wolfenstein) Coherent forward scattering of ν on e-

Different refraction index for and  νe νµ  Different phase difference during propagation  Neutrino oscillation Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 33 Matter-enhanced neutrino oscillation: MSW effect

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 34 Matter-enhanced neutrino oscillation: MSW effect

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 35 Matter-enhanced neutrino oscillation: MSW effect

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 36 Matter-enhanced neutrino oscillation: MSW effect

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 37 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 38 MSW effect and vacuum oscillation solutions for solar neutrinos

Large Mixing Angle Small Mixing solution (LMA) Angle solution (SMA)

LOW solution (LOW)

Vacuum Oscillation solution (VO)

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 39 Solar neutrino experiments of 3rd generation

Requirements: ● real time (day/night asymmetry, length variation) Borexino ● spectral information SNO

● flavour information, proof: νe  νx

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 40 The Sudbury Neutrino Observatory SNO

Creighton Mine: 2 km deep underground in Sudbury, Ontario, Canada

1000 t D2O

support structure for 9500 light detectors (photomultipliers)

12 m diameter acrylic vessel

1700 t inner

shielding, H2O 5300 t outer

shielding, H2O

Urylon sealing

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 41 Solar ν fluxes from the Sudbury Neutrino Observatory SNO

Cherenkov 1 0

sensitive to 3 1

- - 1

ES ν + e ν + e ν (ν , ν ) 0 x  x e µ τ )

- 2 CC νe + d  p + p + e νe 0 0 2 (

, , NC νx + d  p + n + νx νe νµ ντ 9 8

Clear finding: NC > ES > CC R P

excistence of O  νµ  ντ N S  ν oscillation & m(νi)  0 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 42 Solar ν fluxes from the Sudbury Neutrino Observatory SNO

Question to think about: The lightest nucleus, deuterium, consisting of one proton and one neutron has spin 1 Why do the SNO measurements confirm S(d) = 1 ?

Cherenkov 1 0

sensitive to 3 1

- - 1

ES ν + e ν + e ν (ν , ν ) 0 x  x e µ τ )

- 2 CC νe + d  p + p + e νe 0 0 2 (

, , NC νx + d  p + n + νx νe νµ ντ 9 8

Clear finding: NC > ES > CC R P

excistence of O  νµ  ντ N S  ν oscillation & m(νi)  0 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 43 Reactor νe experiments

Inverse β decay:

sum of β spectra of the various fission products

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 44 Use all japanise and corean nuclear reactors for KamLAND

Japanese and Korean reactors

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 45 Long baseline reactor neutrinos: KamLAND at Kamioka mine: = 180 km Δ

1 kt liq. scint. 3000m³ ) 80% iso-paraffine 8 steel 0 20% pseudocum. 0 sphere 2 (

9 8 5 4 .

L/E plot shows oscillation 1 L/E plot shows oscillation 0 8

& agreement with solar neutrinos 0 1200m³ .

& agreement with solar neutrinos v Nylon i no other neutrino flavour conversion possible X  no other neutrino flavour conversion possible r ball  a

, → really neutrino oscillation l

→ really neutrino oscillation a

t e

e 1280 PMTs Water Cherenkov some tension in mixing angle: Θ  0 ? b 13 A

some tension in mixing angle: Θ  0 ? 17-inch anti-counter 13 . S Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 46 Solar ν fluxes from the Sudbury Neutrino Observatory SNO

Nobel prize 2015 to Arthur B. McDonald

(and because of solar 8B / = 1/3 νe νx Nobel prize 2002 to R. Davis)

Cherenkov 1 0

sensitive to 3 1

- - 1

ES ν + e ν + e ν (ν , ν ) 0 x  x e µ τ )

- 2 CC νe + d  p + p + e νe 0 0 2 (

, , NC νx + d  p + n + νx νe νµ ντ 9 8

Clear finding: NC > ES > CC R P

excistence of O  νµ  ντ N S  ν oscillation & m(νi)  0 Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 47 BOREXINO

ultraclean liquid scintillator (300t) looked at by 2212 photomultipliers in a water shield

looking for „ν Compton“ scattering

located in Gran Sasso underground lab

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 48 Borexino looks for the „Compton-edge“ of the monoenergetic 7Be neutrinos

Neutrino energy [MeV]

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 49 BOREXINO results

expectation for „no oscillation“: 74  5 cpd/100 t measured (arXiv:1104.1816): +1.6 46  1.5 -1.5 cpd/100 t very low background & understanding it → even pp neutrinos by understanding Super-Kamiokande, SNO 14 Borexino C spectrum and its pile-up Homestaake (37Cl) 71 Gallex, Sage ( Ga) 2 0 7 3 1

) 4 1 0 2 (

2 1 5

e r u t a

Neutrino energy [MeV] N

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 50 Full neutrino spectrum of pp-chain by real-time experiment BOREXEINO

2 1 - ½ sin (2 ) 2 Θ12 sin Θ12

vacuum osc. matter enh. osc.

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 51 Typical accelerator neutrino beam

neutrino energy [GeV] Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 52 Confirmation of disappearance by oscillation: νµ  νµ long baseline experiments: MINOS 8 1 0 2

o n i r t u e N

, o n a s i r u A

. A

m o r f

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 53 T2K: J-PARC to Super Kamiokande, 232 km off-axis beam → monoenergetic k r a W

e v a D

m o r f

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 54 Confirmation by accelerator experiments: MINOS, T2K, OPERA

A. Sousa – Neutrino 2014

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 55 3 flavor mixing, θ13  0 → CP-violation in lepton sector possible

3 flavor oscillation (without matter effects):

Reactor neutrino disappearance:

θ  0

13 , 2 2 2 2 2 m m x Δm 13  Δm atm  Δm 23 Δ 12  Δ solar u

 CP violation o c i

in lepton sector R - a o

possible 8 h 1 c 0 O 2

o o r n d i r e t u P

e . J N

m o r f

y l t r a p

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 56 DAYA BAY, Double Chooz, (RENO): + p → n + e+ νe near+far detectors to minize systematics DAYA BAY

Double Chooz DAYA BAY DAYA BAY

Similar detector concept first by Double Chooz Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 57 DAYA BAY results: precise determination of Θ13 8 1 0 2

o n i r t u Q13 e N

, x u o c i R - a o h c O

o r d e P

. J

m o r f

Θ13 = 8.5°

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 58 DAYA BAY oscillation curve & neutrino flux 8 1 0 2

o n i r t u e N

, x u o c i R - a o h c O

o r d e P

. J

m o r f

Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 59 Positive results from ν oscillation experiments

atmospheric neutrinos  non-trivial ν-mixing (Kamiokande, Super-Kamiokande, IceCube, ANTARES)

accelerator neutrinos

(K2K, T2K, MINOS, OPERA, MiniBoone)

2 0.37 < sin (θ23) < 0.63 maximal! solar neutrinos 2 0.26 < sin (θ12) < 0.36 large ! (Homestake, Gallex, 2 Sage, Super-Kamiokande, 0.018 < sin (θ13) < 0.030 8.5° ) SNO, Borexino) s (MSW -5 2 2 -5 2 ffect 7.0 10 eV < Δm12 < 8.2 10 eV atter e M -3 2 2 -3 2 2.2 10 eV < | Δm13 | < 2.6 10 eV m( ) 0, but unknown reactor neutrinos  νj  (KamLAND, CHOOZ, Daya Bay, additional sterile neutrinos ? Double CHOOZ, RENO, ...) Christian Weinheimer ISAPP Heidelberg May 29/30, 2019 60