1962 Lederman,Schwartz,Steinberger Brookhaven National Laboratory

using a as a source of antineutrinos

and a 44-foot thick stack of steel (from a dismantled warship hull) to shield everything but the ’s

found 29 instances of

+ p + + n

but none of

+ p e+ + n

1988 Nobel Prize in Physics

"for the neutrino beam method and the demonstration of the doublet structure of the leptons through the discovery of the muon neutrino"

Bep

The Nuclear pp cycle producing energy in the sun

6 protons 4He + 6+ 2e + 2p 26.7 MeV

Begins with the reaction

eedpp

0.26 MeV neutrinos

1967 •built at Brookhaven labs•615 tons of tetrachloroethylene•Neutrino interaction 37Cl37Ar(radioactive isotope, ½ = 35 days)Chemically extracting the 37Ar, its radioactivity gives the number of neutrino interactions in the vat(thus the solar neutrino flux). Results: Collected data 1969-1993 (24 years!!) gives a mean of 2.5±0.2 SNU while theory predicts 8 SNU (1 SNU = 1 neutrino interaction per second for 10E+36 target atoms). This is a neutrino deficit of 69%.

Homestake MineExperiment

The energy spectrum of solar neutrinos predicted by the BP04 solar model. For continuum sources, the neutrino fluxes are given in number of neutrinos cm-2s-1 MeV-1

at the Earth's surface. For line sources, the units are number of neutrinos cm-2s-1. Total theoretical uncertainties are shown for each source.

The difficulttodetect CNO neutrino fluxes have been omitted in this plot.

Solar models predict the spectrum and flux of solar neutrinos reaching the earth

The Solar Neutrino ProblemThe rate of detection of solar e’s from

ee

ArCl 3737is 3 smaller than expected!

Is the sun’s core cooler than we thought? 6%

Is it a different age than we had assumed?

New and extraordinarily precise measurements of “solar sound speeds”

1998

• small oscillations in spectral line strengths• studied by solar seismologists• due to pressure waves traversing the solar volume

confirm the predictions of internal temperature and pressure bystandard solar models to with 0.1%

Atmospheric Neutrino Detection

all showers start

e

(all Ks decaying rapidly into s)with s and Kaons

e

e

e

e

e

→ +

Each pion decays by

→ e + e +

and each muon decays by

Note: at sea level

N

Ne

= 2

MCee

DataeeR)/()(

)/()(

One detector measures this significantly more accurately than any otherSuperKamiokande

They find

Rsub-GeV = 0.63 0.06

Rmulti-GeV = 0.65 0.09

Given the time dilation of muon lifetimes (and the probabilisticnature of their decays) we can still calculate/simulate the ratiowe expect to observe at the ground, and compare:

The observed handedness of neutrinos is consistent with being massless

p

but in a framemoving faster than

the neutrino p

In quantum-field theoretical terms: overtaking a particle corresponds to the Lagrangian term:

)(LRRL

g

=g

=g

=g

=g g

initial R final L

a Dirac mass term!

† †

† †

† †

†

][ 00

LLRRPP

])()[( 00 LRRL

PPPP ][ 00

LRRLPP

)]([ 0

LR

We know the strong “mass” eigenstates of the quarksmix into the weak eigenstates.

dc = dcos + ssinDo the lepton families also mix?

What really distinguishes from ?

Both appear massless, chargeless…

Could ee

? Like the neutral kaons?

Could

e ? Like the Cabibbo mixed quark families?

If e state produced along with e in weak interactions

state produced along with in weak interactions

but these “weak-interaction” states e , , are actually

super-positions (linear combinations) of the

“mass” eigenstates1 ,2 ,3

For a (simple) example of 2-d mixing

2

1

cossin

sincos

e

Giving the states PRODUCED(initial state) by a weak decay

while the propagation through space-time is quantum mechanically determined by

/222

/111

)0()(

)0()(tiE

tiE

et

et

/222

/111

)0()(

)0()(tiE

tiE

et

et

Since these components of the weaklyproduced states must initially be

spacially coherent (have the same momentum)

Then, using for mi << Ei (but not zero)

p

m

iipE 2

2

22422 cpcmE

2

222 1p

mppmE

pmppp

m 2/)1( 222

2

And writing

21sincos

observed weakly interacting state

“mass” or vacuum states

)0(sin)0(cos)(21

21

tiEtiEeet

If, for example, we started with -type neutrinos at t = 0

then the probability of remaining a :

P ( )2

22 21 sincostiEtiE

ee

)()0( t

)0(|)(

t= | |2

and if the |i are orthogonal states 021

1ii

P ( ) tiEtiEtiEtiE

eeee 2121 2222 sincossincos

tEEitEEiee

)()(2244 2121cossinsincos

using eix=cosx + isinx

}cos{cossin2sincos21

2244 tEE

P ( ) }cos{cossin2sincos

21

2244 tEE

using 2244 cossin21sincos

along with the approximation pmpE 22

P ( )

t

pm2

222 cos1cossin21

and finally with 2sincossin21

2sin22cos1

P ( )

t

p

m

4sin2sin1

222

and of course, then

P ( )e

1 P ( )

=

The photon is masslessand has no antiparticle(is its own antiparticle)

But all the fundamental particles of matter do have antiparticles:

e+e

ee+ +

p p n n

du du The quark content of pions show

while other mesons are their own antiparticle

uu dd

1965 Gellmann & Paisnoted a 2nd order (~rare) weak interaction could induce the strangeness-violating transition of K

o K o

a particle becoming

its own antiparticle!

u u

s

d s

d

Ko

Ko

W

u

u

s

d s

d

Ko

Ko

W W

sd

sdK

The neutral kaon however is not its own antiparticle:

K

u

d

e

e

_uu

dd

eepn

W

enpe

e+

e

_

ud u

dd u

epne

but have never observed:

have observed:

Cowan & Reines: Savannah River

In many even-even nuclei, -decay is energetically forbidden.

This leaves -decay as the allowed decay mode.

76As33

76Ge32

76Se34

EndpointEnergy

2

0+

0+

2+

0+

Atomic mass (u)

76Ge32 75.92140276As33 75.92239376Se34 75.919913

ee

34

76

4232

76

44SeGe is observed!

If were its own antiparticle (or could oscillate into )

there could be a chance to observe neutrino-less double-beta decay events.

ee

34

76

4232

76

44SeGe the observed process

34

76

4232

76

44SeGe being searched for!

neutrino-less

Energy Spectrum for the double-beta decay

Summed Energy for the 2 Electrons (MeV)

Neutrinoless double beta decay• A single claimed observation has been made…but is very controversial ! It

needs to be independently verified! • Major US efforts

– MAJORANA expt- 500 kg Ge76 (86%)– EXO - 1-ton LXe TPC

• Deeper site for later versions of GS experiments? – e.g, CUORE - 760 kg TeO2