Experiments

1. and  observatories 2. Establishing oscillation & mixing 3. Present questions and experiments

Sofia Andringa, LIP July 2017 17th JINR-ISU Baikal Summer School on of Elementary Particles and Astrophysics What are neutrinos? 1, 2, 3 

Neutrino  sources detection

1. Neutrinos and  observatories Discovery of neutrino oscillations

the elementary particles

g .



W,Z Neutrino masses not to scale: == ZERO in the what are neutrinos? 1930: an “undetected particle” ensuring energy conservation in -decays (Pauli)

Dear Radioactive Ladies and Gentlemen,

(...) I have hit upon a desperate remedy to save (...) the law of energy conservation.

(...) emitted together with the electron, in such a way that the sum of the energies (...) is constant.

(...) electrically neutral particles (...) s

n (Z,A) –> (Z+1,A) +  mass not larger than 0.01 mass(...) o r t

c M(Z,A) = M(Z+1,A) + E

e (...) the question concerning experimental proof of l

e n –> p + e⁻ + v

such a neutron, if it has something like about 10 times n i

the penetrating capacity of a  -ray. y t i s n e t n I

Electron kinetic energy (MeV) “inverse beta decay” 1934: Fermi, “attempt at a theory of  rays”

weak interaction (GF~10⁻⁵ GeV ⁻ ²) cross-section ~ 10⁻⁴⁴ cm² for E ~ MeV

mean free path of 10¹⁹ m in water or 1 out of 10¹⁹ interact in 1m of water

need both a large number of neutrinos and a large number of targets (electron anti-)neutrinos detected 25 years after first proposal the Reines and Cowen experiment

delayed coincidences in liquid scintilator

Reines nobel lecture(1995) to detect neutrinos from nuclear reactors electron / muon / neutrino

 e

are all the neutrinos the same? 3 types of detectable neutrinos

Electron neutrino (1956)

Muon neutrino (1962) (by Lederman, Steinberg & Schwartz, at BNL)

following suggestion by B. Pontecorvo (1960)

Tau neutrino (2000) (by DONUT, at )

following the discovery of the (1975), the bottom quark (1977), and the top quark (1995) measuring 3 undetected neutrinos 3 neutrinos (m<45 GeV) @ LEP

x

Z x

all neutrinos are missing ET @ LHC neutral and charged interactions

Neutrino is not seen  but transfers energy to matter Lepton of the same family Z⁰  E > m=511 keV, e W 106 MeV,  1.78 GeV, 

ICARUS (Lar TPC) @ CNGS,

 with E=17 GeV interactions increase with energy

 

Z,W (Quasi)Elastic to Deep Inelastic N(p, n) p, n, , p / n, many , ...

K2K 1 GeV

interaction cross-section

sources of neutrinos ~ 30 orders of magnitude detected

Geo anti-neutrino 3 x 113 / cm³

observations Geo (Borexino)

SN1987A (Kamioka-II)

Astro (IceCube)

Sun (SuperK)

requirements

Large and uniform target for neutrino interaction

Sensitive detection medium for produced particles

Transparent for signal propagation (usually the signal is light) Baikal

Good efficiency and high coverage for (light) signal detection

+ Low background environment shielded from cosmic rays (and radioactivity at low E)

... water is one of the favorite media underground telescopes

1967 – start of construction

1977 – BUST (SN1987A )

Baksan Underground Telescope

11m x 280 m² 3180 detectors, 330 tons of liquid scint.

1987 – SAGE (Solar pp )

Soviet-American Gallium Experiment

50 tons of liquid Ga

2017 – being extended detecting Supernovae a Supernova explodes in the Large Magallean Cloud and SNEWS in February 23rd 1987 it is even visible with naked high

Neutrino observatories saw coincident events, three hours before!

Baksan Underground Scintillator Telescope KamiokaNDE 4-level building, 11m x 280 m² Nucleon Decay Experiment in Japan 3180 detectors, 330 tons of liquid scint. observing in 1 kton of water

monitoring the Sun with neutrinos SAGE: + Ga(31p,40n) --> Ge(32p,39n) main nuclear fusion process 50 tons of liquid Ga, 15 Ge atoms/month in the Sun is

2e⁻ + 4p -> ⁴He + 2  + 27 MeV

 

~60% of the expected rate!!

from measured luminosity: ~ 60 billion  / (cm² s)

[exercise: calculate Solar flux] something wrong with the Sun?

Counting at low energy with inverse ⁺ decay

⁷¹Ga -> ⁷ ¹Ge (E>0.2 MeV): => 60% of expected fluxes ³⁷ Cl -> ³ ⁷ Ar (E>0.8 MeV) => 30% of expected fluxes

Seeing with “-e scattering”

=> 50% of expected fluxes

SN1987A detection && the solar neutrino problem lead to new experiments the new water Cherenkov detectors

the Super Kamiokande 1000 m underground in Japan 50,000 ton of pure water

+ 2 000 in OD) ｍ 11,000 PMT 50 cm ( ２ ４

３９ｍ

the Sudbury Neutrino Observatory 2000 m underground in Canada 1,000 ton of (salted) heavy water

9,000 PMT 50 cm (+ 90 in OD) 20 ｍ the new water Cherenkov detectors

the Super Kamiokande 1000 m underground in Japan 50,000 ton of pure water

11,000 PMT 50 cm (+ 2 000 in OD) the Super Kamiokande detector

Cherenkov detectors

Cherenkov effect PMTs velocity higher than ...

SKI 1996-2001 SKII 2002-2005 (50% PMTs) SKIII 2006-2008 (100% PMTs) SKIV 2009-now (new electronics)

KamiokaNDE II saw SN1987A, now discussing HiperKamiokande

solar neutrinos in water

500 days and nights of exposure to Sun

Flux is one half of what is expected from the Standard Solar Model Constant along years and seasons, equal during day and night (*)

the new water Cherenkov detectors the Sudbury Neutrino Observatory 2000 m underground in Canada 1,000 ton of (salted) heavy water

9,000 PMT 50 cm (+ 90 in OD)

Three different phases with different neutron capture efficiency: I – capture in D2O; II – in Salt (Cl*);

III – in dedicated counters 20 ｍ the Sudbury Neutrino Obsevatory located 2000 m underground In a still active nickel mine

lots of heavy water in Canada

solar neutrinos in (salted) heavy water

1) Electron scattering (as in H2O)  + e ->  + e (only 0.50 x SSM)

instead of mixing neutrino types SNO can count them separately!

[exercise: Feynman diagrams]

2) Charged Current, only e 3) Neutral Current, all x

separating counts in SNO

radius Very low background in inner volume

ES pointing to the Sun, confirms SK

CC (one ring) vs NC (more rings)

Normalization of the 4 components

direction

isotropy

solution of the solar neutrino problem NC (all neutrinos) = 1.00 x Solar Model CC (e) / NC (x) = 0.35 the Sun is well! neutrinos change between production in the Sun and detection at Earth

neutrinos must have mass

1 SNU = 10⁻ ³ ⁶ captures / atom /second

 from Nature @ Super Kamiokande 500 days + nights exposure

Flux lower than Solar e Solar e @ MeV

Atmospheric e e  

@ GeV

higher energy but lower flux

e ~ 2 in all directions GeV events at Super Kamiokande

l l = e,  

p, n, ,...



e

identifying electrons and muons l = e,  l kinematics of e/ give  energy and direction

no charge measurement

muon neutrino disappearence

e e

 / e ~ 2

Fluxes confirmed bye

10 km cos =1

10 000 km cos =-1 first measurement of  oscillations

expected from cosmic ray fluxes confirmed by electron measurements fit with 1 - sin²2 sin²(1.27 m² L/E)

@GeV

1 10 100 1000 km

first measurement of  oscillations

 new 1 - sin²2 sin²(1.27 m² L/E) results maximal amplitude at L ~ 500 km / E ~ 1 GeV m² ~ 10⁻ ³ eV² No time to change Fast  change @GeV

1 10 100 1000 km

two neutrino oscillations

Amplitude Frequency

|V> cos sin |V1>

[ |V >]=[ -sin cos ][|V >]    2

|V(0)> = |V> = cos |V1> + sin |V2> |V(t )> = cos exp[-i (E1 t – p1 x)] |V1>

+ sinexp[-i (E2 t – p2 x)] |V2>

2 2 2 2 2 P=||² with L = ct Ei = p + mi ~ (p + mi /2E)

oscillations and mass

 (E, M) E²=P²+M²  = (Mx²-My²)/E

For propagation, only energy and mass are relevant L = c.Time For interaction, only the energy and flavor are relevant

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

VeVV Mx and My at production and detection

L = c.Time (interaction in dense matter can be seen as inducing an effective mass)