neutrinos: ghosts of the universe
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Neutrinos: Ghosts of the Universe. Don Lincoln Fermilab f. Beauty in the Universe. Much is explained by quarks and electrons. But there remains the neutrino..... ~10 9 n /proton!!. neutron. proton. e. Single Valued. Reality. b decay. Observed. proton. neutron. e. n. - PowerPoint PPT PresentationTRANSCRIPT
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