Don Lincoln

Fermilab

f

Neutrinos: Ghosts of the Universe

Beauty in the Universe

Much is explained by quarks and electrons.

But there remains the neutrino.....

~109 /proton!!

decay

neutronproton

e

22)( epn

ep

epn

epn

o

mmmp

pp

ppp

EEE

epn

Single Valu

ed Reality

Observed

decay

neutronproton

e

Dear radioactive ladies and gentlemen,

...I have hit upon a ‘desperate remedy’ to save...the law of conservation of energy. Namely the possibility that there exists in the nuclei electrically neutral particles, that I call neutrons...I agree that my remedy could seem incredible...but only the one who dare can win...

Unfortunately I cannot appear in person, since I am indispensable at a ball here in Zurich.

Your humble servantW. Pauli

December 4, 1930

Note: this was before thediscovery of the real neutron

Project Poltergeist

1956

Reines

Cowan

e+

H2O +CdCl2

Cd

neutrino

p+n

enpv o

(several)Cd on

2 ee

Signal 2, then several ~few s later

Experiment attempted at Hanford in 1953,too much background. Repeated at SavannahRiver in 1955. [Flux: 1013 neutrinos/(cm2 s)]

Neutrino Facts

Neutrino from Enrico Fermifor “Little neutral one”

flux on Earth from Sun

6.5×1014/(m2 s)

<E> ~ 0.3 MeV

Neutrino from sun will pass through 5 LY of solid lead, with 50% chance of interacting

Average number of solar neutrinos interacting in a person per year

30! 1 with ‘real

energy’

Neutrinos in Art

Seattle Rock Band

Neo-Swing

Cosmic Gall

Neutrinos, they are very small. They have no charge and have no mass

And do not interact at all.

The earth is just a silly ball To them, through which they simply pass,

Like dustmaids down a drafty hall Or photons through a sheet of glass.

They snub the most exquisite gas, Ignore the most substantial wall,

Cold-shoulder steel and sounding brass, Insult the stallion in his stall.

And, scorning barriers of class, Infiltrate you and me! Like tall

And painless guillotines, they fall Down through our heads into the grass.

At night, they enter at Nepal And pierce the lover and his lass

From underneath the bed—you call It wonderful; I call it crass.

John Updike Telephone Poles and Other Poems, 1963

More than one kind of neutrino?

Mel Schwartz

p+ ± ±

Tons of steel

Detector

Date: 1962Intent: Measure weak force at high energies

Expectation: Since neutrinosare created with muons and electrons, the neutrino beamshould create both electronsand muons in the detector.

Result: No electrons produced,only muons

Conclusion: There must be twokinds of neutrinos.

What Good are Neutrinos?

Neutrinos only feel the

weak force.u

d

u

Over simplified

Other probes of nucleon structure have tobeat their way through the mess that is areal proton.

Multiple interactions means messy interpretation.

Neutrinos interact at most once, so the collision is more easily understood.

Nucleon Structure

u

d

u

Z

u

d

u

W

18 m

28 m

Nucleon Structurenucleon

parton

p

px

)(xf parton

)( xfx parton

Fraction of momentumcarried by parton

Probability Distribution

“Expectation”

Structure of the proton can be determined by scattering neutrinos (or other probe particles) into hydrogen target

Typical Experiment

Need lots of mass to force a neutrino to interact.

Beam-based experiments typically have weight of ~1000 tons

At LEP

A Z can also decay into neutrino pairs. Thewidth of the mass distribution of the Z boson is sensitive to the total number of neutrino generations into which it can decay.

Neutrinos show number of generations

or or - eeqqZee

Obvious Conclusion: There are 3 generations

Cautious Conclusion: There are only three flavors of low-mass neutrinos into which

a Z can decay.

Star Trek

In the 1993 episode of Star Trek: Deep Space 9 called “Rivals” neutrinos were a plot twist.

• Quark was losing money.• Jadzia noticed that 98% of neutrinos were

spinning one way.

• She explains half should spin each way.• The crew locates ‘luck changing’

machines.Hah!

Neutrino Sources

Solar neutrinosp + p d + e+ + e

8B 8Be + e+ + e

Sun emits e

2×1038 s-1

A 5-10 GW reactor complex has a neutrinoflux of ~1020 s-1

Neutrinos fromcosmic rays~100 m-2 s-1

Uranium and Thorium in the Earth’s crust decay about 15 TW of energy.

Neutrino flux on Earth’s surface (from Earth)~ 5×1010 s-1 m-2

Homestake Gold Mine100,000 gallons of cleaning fluid C2Cl4

Expected 1.5 interactions per day Measured 0.5 interactions per day

Sensitive to 8B solar neutrinos only

e + 37Cl e- + 37Ar

Ray Davis

John Bahcall

1968!

Measured: 77 6 3 SNUPredicted: 123 + 9 -7 SNU

Soviet-American Gallium ExperimentSAGE

71Ga + 71 + Ge e- Sensitive to pp fusion in sun.

50 metric tons of GalliumThey extract a few tens of atomsof Germanium

Solar NeutrinoSummary

Different experiments are sensitive to different solar processes.

But all experiments show a marked deficit of electron neutrinos.

Could reflect ignorance of how the sun works.

Except.....

Accidental Evidence

oep

In the early 1980s, two experiments (IMB Irvine-Michigan-Brookhaven) and (Kamiokande) were built to look for proton decay.

None detected. Proton lifetime > 1033 years.

Simulated Event

7:36 neutrinos observed9:30 amateur astronomer observes Tarantula

Nebula in LMC. Nothing unusual.10:30 LMC photographed, SN1987A observed.

~3 hours for shock wave to hit surface.

SN 1987A

Expected average ratio R = 1.

Background Becomes Signal

E x p e r i m e n t V a l u e

K a m i o k a n d e ( m u l t i - G e v ) 07.057.0 08.007.0

K a m i o k a n d e ( s u b - G e v ) 05.060.0 06.005.0

I M B 0 . 5 4 0 . 0 5 0 . 1 2S o u d a n 2 0 . 6 9 0 . 1 9 0 . 0 9

S

oep If proton decay goes as

Signal is ring in detector. Anything that can make a ring is background.

In cosmic rayshowers, expect 2

for each e

Knowledge of detector response problematic. Compensate by double ratio:

)events ()events (

)events ()events (

simulationesimulation

dataedata

NN

NNR

Hmmmm.....

Hmmmm.....

Quantum Cobwebs

Remember that information on a state is encoded in a wave function.

Remember that you can express the wave function in any orthogonal basis (coordinate system).

Under the electromagnetic force, the electrically-charged object (say an electron) is an eigenstate of mass and electrical charge.

Under the weak force, the weak-charged object (say an neutrino) is not both an eigenstate of mass and weak charge.

Weak charge = k1 (mass 1) + k2 (mass 2)

k21 + k2

2 = 1

Crucial insight

1

2

e

e

1

2

1

e

2

21

21

cos sin

sin cos

e

Massive Neutrinos Math

2

1

cossin

sincos

e

Massive Neutrinos Math

21 mm

Mass BasisWeak Charge Basis

Important!

)0(

)0(

0

0

),(

),(

2

1

2

1

2

1

tiE

tiExpi

e

ee

tx

tx

Massive Neutrinos Math

)0(

)0(

cossin

sincos

0

0

cossin

sincos

),(

),(2

1

e

tiE

tiExpie

e

ee

tx

tx

Substitute weak basis

Time dependentSchrodinger equation

Massive Neutrinos Math

Reasonable approximations

Initial conditions

]2

)([sin)2(sin),(

)(

12222 tEE

tx

P e

]4

[sin)2(sin)(2

22

E

LmP e

0),( and 1),( If txtxe

Evaluate

Massive Neutrinos Math

]4

[sin)2(sin)(2

22

E

LmP e

21 mm

Super Kamiokande

Super Kamiokande11 stories high1,000 meters underground50,000 tons of water22,500 tons fiducial volume11,200 photomultipliers0.5 meter photomultiplier diameterAbandoned zinc mine

Super Kamiokande DiscoveryAnnouncement June 5, 1998

Gist: “There are fewer upcoming muon neutrinos than expected from down-going neutrino flux. Data consistent with neutrino oscillations.”

SNO

•Cerenkov detector

•Heavy water (can do solar model independent measurements)

•6800 feet underground

•9600 PMTs

Sudbury Neutrino Observatory

In Sudbury, Ontario

SNO Physics

and Results

Charged interactions convert neutron to proton. Sensitive only to e.30 events/day

Neutral interactions disassociate deuteron into neutron and proton. Sensitive to e, , .30 events/day

Electron scattering mostly sensitive to e, with small contribution from , . 3 events/day

Comparison of SNO results with Super K indicates that the neutrino flux from the sun contains muon neutrinos, supporting neutrino oscillations.

Announcement:

June 18, 2001

So What Does It Mean?

]4

[sin)2(sin)(2

22

E

LmP e

• Data is consistent with neutrino oscillations. This can be accommodated, but not explained, by known physics.

• Data from solar and atmospheric neutrinos is consistent with m1 ~ m2 m3

• Solar electron neutrinos disappear and reappear into muon neutrinos

• Atmospheric muon neutrinos disappear and reappear into tau neutrinos

Cosmological Implications of Neutrinos

~ 330 /cm3 (from Big Bang)<E> ~ 0.0004 eV (from Big Bang)

Runiverse ~ 1010 lightyearsVuniverse ~ 4×1084 cm3

N ~ 1087

E(total) ~ 4×1083 eV

M(equivalent) ~ 7×1047 kg

Muniverse(visible) ~ 4×1052 kg

Electron < 2.2 eVMuon < 170 keVTau < 15.5 MeV

Neutrino Mass

If neutrinos were massive objects, theycould contribute significantly to the massof the universe.

Are Neutrinos Massless? 0.1% < M < 18%

Disaster Strikes!At 11:00, November 12, 2001,about 60% of the phototubesused in the Super-K detectorimploded within a few seconds.

$21,000,000 damage

We will rebuild the detector. There is no question.

- Yoji Totsuka Director, Super-K Observatory

Osama bin Laden on Super-K Disaster:Neutrinos are “...an abomination on the face of god...” and the search for neutrino mixing is: “...idolatry, which will be smashed beneath the fist of righteousness...”

Reports conversions of to e. Other experimentsdo not confirm.

Highly controversial result. If true, significant theoretical work needs doing.

Outstanding Questions

Fermila

b’s M

iniBoo

ne

to co

nfirm

or re

fute

Summer

2002

Liquid ScintillatorNeutrino DetectorLSND 1996

Neutrino Summary• They interact with ordinary matter

very weakly.

• Many experiments not mentioned here are ongoing to unravel this rich behavior.

• Their behavior is highly complex and will need new physics to explain it.

www-d0.fnal.gov/~lucifer/PowerPoint/Neutrinos.ppt