Kevin McFarlandKevin McFarlandUniversity of RochesterUniversity of Rochester
Warwick University Physics Warwick University Physics Departmental ColloquiumDepartmental Colloquium
30 November 200530 November 2005
Neutrinos: Neutrinos: Worth the WaitWorth the Wait
Neutrinos: Neutrinos: Worth the WaitWorth the Wait
especially when snowed in…especially when snowed in…
Kevin McFarlandKevin McFarlandUniversity of RochesterUniversity of Rochester
Warwick University Physics Warwick University Physics Departmental ColloquiumDepartmental Colloquium
30 November 200530 November 2005
““snowed in”snowed in”
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 3
A Typical February View of the George Eastman Theater at
the University of Rochester
Neutrinos and Slowness…• Neutrino physics has historically
been a slowly developing field– due to the properties of the
neutrino, as we shall see
• But neutrino physics is heating up into a very active field– driven by experimental results– and by new technologies
• So first, some history and perspective…
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 4
The Birth of the Neutrino
Wolfgang Pauli
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 5
4th December 1930Dear Radioactive Ladies and Gentlemen,As the bearer of these lines, to whom I graciously ask you to listen, will explain to you in more detail, how because of the ”wrong” statistics of the N and 6Li nuclei and the continuous beta spectrum, I have hit upon a desperate remedy to save the ”exchange theorem” of statistics and the law of conservation of energy. Namely, the possibility that there could exist in the nuclei electrically neutral particles, that I wish to call neutrons, which have spin and obey the exclusion principle and which further differ from light quanta in that they do not travel with the velocity of light. The mass of the neutrons should be of the same order of magnitude as the electron mass (and in any event not larger than 0.01 proton masses). The continuous beta spectrum would then become understandable by the assumption that in beta decay a neutron is emitted in addition to the electron such that the sum of the energies of the neutron and the electron is constant...From now on, every solution to the issue must be discussed. Thus, dear radioactive people, look and judge. Unfortunately I will not be able to appear in Tübingen personally, because I am indispensable here due to a ball which will take place in Zürich during the night from December 6 to 7…. Your humble servant,W. Pauli
4th December 1930Dear Radioactive Ladies and Gentlemen,As the bearer of these lines, to whom I graciously ask you to listen, will explain to you in more detail, how because of the ”wrong” statistics of the N and 6Li nuclei and the continuous beta spectrum, I have hit upon a desperate remedy to save the ”exchange theorem” of statistics and the law of conservation of energy. Namely, the possibility that there could exist in the nuclei electrically neutral particles, that I wish to call neutrons, which have spin and obey the exclusion principle and which further differ from light quanta in that they do not travel with the velocity of light. The mass of the neutrons should be of the same order of magnitude as the electron mass (and in any event not larger than 0.01 proton masses). The continuous beta spectrum would then become understandable by the assumption that in beta decay a neutron is emitted in addition to the electron such that the sum of the energies of the neutron and the electron is constant...From now on, every solution to the issue must be discussed. Thus, dear radioactive people, look and judge.
Your humble servant,W. Pauli
4th December 1930Dear Radioactive Ladies and Gentlemen,As the bearer of these lines, to whom I graciously ask you to listen, will explain to you in more detail, how because of the ”wrong” statistics of the N and 6Li nuclei and the continuous beta spectrum, I have hit upon a desperate remedy to save the ”exchange theorem” of statistics and the law of conservation of energy. Namely, the possibility that there could exist in the nuclei electrically neutral particles, that I wish to call neutrons, which have spin and obey the exclusion principle and which further differ from light quanta in that they do not travel with the velocity of light. The mass of the neutrons should be of the same order of magnitude as the electron mass (and in any event not larger than 0.01 proton masses). The continuous beta spectrum would then become understandable by the assumption that in beta decay a neutron is emitted in addition to the electron such that the sum of the energies of the neutron and the electron is constant...From now on, every solution to the issue must be discussed. Thus, dear radioactive people, look and judge.
Your humble servant,W. Pauli
Translation, Please?
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 6
Translation, Please?• To save the law of conservation of energy?
• If the above picture is complete, conservation of energy says β has one energy, but we observe this instead– Pauli suggests “neutron” takes away energy!
• The “exchange theorem of statistics”, by the way, refers to the fact that a spin½ neutron can’t decay to an spin½ proton + spin½ electron– he doesn’t call it the “Pauli exclusion principle”, to his credit…
β-decay
The Energy of the “β”
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 7
Fundamental Forces• Of the four fundamental forces, three are
important for the structure of matter around us
Gravity– holds planets,
galaxies, etc.together
Electromagnetism– holds atoms together– keeps matter from
collapsing under the force of gravity
Strong force– holds nucleus
together
– so strong that quarks are confined
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 8
Neutron Beta Decay Neutrino-Neutron“Quasi Elastic” Scattering
Theories of Forces• Modern force description is
quantum field theory…– often illustrated w/ its lowest order
perturbative expansion…
• First theory of weak interactions(Fermi theory of beta decay, 1933)– also names the “neutrino” to distinguish from
Chadwick’s neutron
Enrico Fermi
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 9
How to Hunt a Neutrino
• How do we see any fundamental particle?• Electromagnetic
interactions kickelectrons awayfrom atoms
• But neutrinos don’t haveelectric charge. They only interact weakly– so we only see by-products of their weak interactions
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 10
How Weak is Weak?
• Weak is, in fact, weak.• A 3 MeV neutrino produced
in fusion from the sun will travel
through water, on average, before interacting.– The 3 MeV positron (anti-matter electron) produced in
the same fusion process will travel 3 cm, on average.
• Moral: to find neutrinos, you need a lot of neutrinos and a lot of detector!
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 11
Discovery of the Neutrino• Reines and Cowan (1955)
– Nobel Prize 1995– 1 ton detector– Neutrinos from a nuclear
reactor p e n
Reines and Cowan at Savannah River
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 12
Solar Neutrino Hunting• Radiochemical Detector
Ray Davis (Nobel prize, 2002)
– ν+np+e- (stimulated β-decay)– Use this to produce an unstable
isotope, ν+37Cl37Ar+e- , whichhas 35 day half-life
– Put 615 tons ofPerchloroethylenein a mine
• expect one 37Ar atomevery 17 hours.
Ray Davis
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 13
Solar Neutrino Hunting
• Ran from 1969-1998• Confirmed that sun
shines from fusion• But found 1/3 of ν !
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 14
Modern Solar Neutrino Hunting
• Kamiokande andSuper-Kamiokande(Masatoshi Koshiba, Rochester PhD 1955, Nobel Laureate 2002)
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 15
Modern Neutrino Hunting• The Sun, imaged in neutrinos, by
Super-Kamiokande
The Sun, optical imageExistence of the sun confirmed by neutrinos!
sadly, not the same angular scale
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 16
Our Timescale So Far…• Pauli and Fermi (theory)
• to Reines and Cowan (discovery)
• to Davis (solar neutrinos)
• to Koshiba (supernova and oscillations)
– progress continues to accelerate into theexciting neutrino programs of today…
1930
1950
1970
1990
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 17
Next Steps: The Broadest Goals
• Understand mixing of neutrinos– a non-mixing? CP violation?
• Understand neutrino mass– absolute scale and hierarchy
• Understand interactions– new physics? new properties?
• Use neutrinos as probes– nucleon, earth, sun, supernovae
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 18
Qualitative Questions
• The questions facing us now are fundamental, and not simply a matter of “measuring oscillations better”
• Examples:– Are there more than three neutrinos?– What is the hierarchy of masses?– Can neutrinos contribute significantly to the
mass of the universe?– Is there CP violation in neutrino mixings?
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 19
The Broadest Goals
• Understand mixing of neutrinos– a non-mixing? CP violation?
• Understand neutrino mass– absolute scale and hierarchy
• Understand interactions– new physics? new properties?
• Use neutrinos as probes– nucleon, earth, etc.
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 20
What We Hope to Learn From Neutrino Oscillations
• Near future– validation of three generation picture
• confirm or disprove LSND oscillations (>3 neutrinos)
• precision tests of “atmospheric” mixing at accelerators
• Farther Future – neutrino mass hierarchy, CP violation?
• Precision at reactors• sub multi MegaWatt sources• 10 100 1000 kTon detectors
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 21
Minimal Oscillation Formalism• If neutrino mass eigenstates: 1, 2, 3, etc.
• … are not flavor eigenstates: e, , • … then one has, e.g.,
cos sin
sin cosi
j
take only two generations
for now!
cos sin4 4i j
sin cos4 4i j
time
different masses
alter time evolution
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 22
Oscillation Formalism (cont’d)• So, still for two generations…
• Oscillations require mass differences• Oscillation parameters are mass-squared differences, m2, and mixing angles, .
• One correction to this is matter… changes , L dep.
E
LmmP
4
)(sin2sin)(
21
2222
Wolfenstein, PRD (1978)
22
22
22
)2cos(2sin
)2cos(2sin
2sin2sin
xLL
x
M
M
nm
EnGx eF
2
22
e- density
appropriate units give the usual
numerical factor 1.27 GeV/km-eV2
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 23
Solar Neutrinos• There is a glorious history
of solar neutrino physics– original goals: demonstrate
fusion in the sun– first evidence of oscillations
SAGE - The Russian-AmericanGallium Experiment
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 24
Culmination: SNO• D2O target uniquely observes:
– charged-current– neutral-current
• The former is onlyobserved for e
(lepton mass)
• The latter for all types• Solar flux is consistent
with models– but not all e at earth
X Xd pn ed ppe
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 25
KAMLAND• Sources are
Japanesereactors– 150-200 km
for most offlux. Rate uncertainty ~6%
• 1 kTon scint. detector inold Kamiokande cavern– overwhelming confirmation
that neutrinos change flavorin the sun via mattereffects
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 26
Solar Observations vs. KAMLAND
+ KAMLAND =
• Solar neutrino observations are best measurement of the mixing angle
• KAMLAND does better on m212
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 27
Atmospheric Neutrinos
• Neutrino energy: few 100 MeV – few GeV• Flavor ratio robustly predicted• Distance in flight: ~20km (down) to 12700 km (up)
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 28
Super-Kamiokande
• Super-Kdetector hasexcellent e/separation
• Up / down difference!
old, but good data!
2004 Super-K analysis
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 29
K2K
• Experiment has completeddata-taking– confirms atmospheric
neutrino oscillation parameters with controlled beam
– constraint on m223 (limited statistics)
figures courtesy T. NakayaNeutrino Beam from KEK to Super-K
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 30
Enough For Three Generations
• Oscillations have told us the splittings in m2, but nothing about the hierarchy
• The electron neutrino potential (matter effects) can resolve this in oscillations, however.
figures courtesy B. Kayser
msol2 m12
2≈8x10-5eV2 matm2 m23
2≈2.5x10-3eV2
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 31
Three Generation Mixing
• Note the new mixing in middle, and the phase,
slide courtesy D. Harris
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 32
But CHOOZ…• Like KAMLAND, CHOOZ and
Palo Verde expt’s looked at anti-e from areactor– compare expected to observed
rate, ~4%
m223
• If electron neutrinos don’t disappear, they don’t transform to muon neutrinos
– limits ->e flavor transitions at and therefore |Ue3| is “small”
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 33
Optimism has been Rewarded
• By which he meant…had not
Eatm /Rearth < matm2 <Eatm /hatm
and had not solar density profileand msol
2 beenwell-matched…
• We might not be discussing oscillations!
“We live in the best of all possible worlds”– Alvaro deRujula, Neutrino 2000
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 34
Are Two Paths Open to Us?• If “CHOOZ” mixing, 13, is small, but not too
small, there is an interesting possibility
• At atmospheric L/E,
m232, 13
m122, 12
e
2 22 2 2 1( )
( ) sin 2 sin4e
m m LP
E
SMALLLARGE
SMALLLARGE
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 35
Implication of two paths• Two amplitudes
• If both small,but not too small,both can contribute ~ equally
• Relative phase, , between them can lead toCP violation (neutrinos and anti-neutrinos differ) in oscillations!
m232, 13
m122, 12
e
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 36
Leptonic CP Violation in Oscillations
• CP violation and matter effects lead to a complex mix…
• CP violation gives ellipsebut matter effects shiftthe ellipse in along-baseline acceleratorexperiment…
• Stakes are high:
– CP violation in leptons could, in fact, haveseeded Universe’smatter-antimatter asymmetry
Minakata & Nunokawa JHEP 2001
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 37
But LSND…• LSND anti-e excess
– 87.9±22.4±6.0 events– statistically overwhelming;
however…
figures courtesy S. Brice
LSND m2 ~ 0.1-1.0 eV2
Atmos. m2 ≈ 2.5x10-3 eV2
Solar m2 ≈ 8.0x10-5 eV2
cannot be accommodated with only three neutrinos
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 38
SignalMis-IDBeam
MiniBooNE
• A very challenging experiment!
• Have ~0.6E21protons on tape
• First e
appearanceresults inearly 2006 (?)
figures courtesy S. Brice
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 39
Next Steps(Brazenly Assuming Three Neutrinos)
• MINOS and CNGS
• Reactors
• T2K and NOvA
• Mating Megatons and Superbeams
• Beta (e) beams andneutrino factories (e and )
graphical witcourtesy A. deRujula
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 40
Isn’t all of this overkill?• Disentangling the physics from the
measurements is complicated• Different measurements have different sensitivity to
matter effects, CP violation
– Matter effects amplified for long L, large E– CP violation cannot be seen in disappearance
(reactor) measurement ee Huber, Lindner, Rolinec,Schwetz, Winter
assumes sin2213 = 0.1
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 41
NuMI-Based Long Baseline Experiments
• 0.25 MWatt 0.4 MWatt proton source
• Two generations: – MINOS (running)– NOvA (future)
15mrad Off Axis
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 42
MINOS735km baseline5.4kton Far Det.1 kton Near Det.Running since early
2005
Goal: precise disappearancemeasurementGives m2
23
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 43
CNGSGoal: appearance• 0.15 MWatt source• high energy beam• 732 km baseline• handfuls of events/yr
e-, 9.5 GeV, pT=0.47 GeV/c
interaction, E=19 GeV
fiugres courtesy A. Bueno
3kton
Pb
Emulsion layers
1 mm
1.8kTon
figures courtesy D. Autiero
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 44
Back to Reactors• Recall that
KAMLANDsaw anti-e
disappearanceat solar L/E
• Have not seendisappearance atatmospheric L/E
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 45
Why Reactors?• CHOOZ (reactor) has left us without evidence of
anti-e disappearance indicating |Ue3|>0
– reactors are still the most sensitive probe!• CHOOZ used a single detector
– therefore, dead-reckoning used to estimate neutrino flux from the reactor
– could improve with a near/far technique
• KAMLAND has improved knowledge of how to reject backgrounds significantly
(remember, their reactors are ~200 km away!)
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 46
not an engineering
drawing
How Reactors?• To get from ~4% uncertainties to ~1% uncertainties,
need a near detector to monitor neutrino flux• For example, Double-CHOOZ proposes to add a second
near detector and compare rates– new detectors with 10 ton mass– total error budget on rate ~2%– low statistics 10t limit spectral
distortion, 1 km baseline likelyshorter than optimum
• Optimization beyond Double-CHOOZ…– ~100 ton detector mass
– optimize baseline for m223
– background reduction with active or passive shielding
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 47
Where Reactors?
• A series of proposals with different technical choices
• All challenging experiments to limit systematics
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 48
Megawatt Class Beams
• J-PARC– initially 0.7 MWatts 4 MWatts
• FNAL Main Injector– current goal 0.25 MWatts 0.4 MWatts– future proton driver upgrades?
• Others?
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 49
J-PARC Facility
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 50
• First Suggested by Brookhaven (BNL 889)• Take advantage of Lorentz Boost and 2-
body kinematics• Concentrate flux
at one energy• Backgrounds lower:
– NC or other feed-downfrom highlow energy
– e (3-body decays)
A Digression: Off-axis
figure courtesy D. Harris
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 51
T2K• Tunable off-axis beam from J-
PARC to Super-K detector– beam and backgrounds are kept
below 1% for e signal
– ~2200 events/yr (w/o osc.)
=0, no matter effects
figures courtesy T. Kobayashi
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 52
NuMI-Based Long Baseline Experiments
• 0.25 MWatt 0.4 MWatt proton source
• Two generations: – MINOS (running)– NOvA (future)
15mrad Off Axis
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 53
NOA• Use Existing NuMI
beamline• Build new 30kTon
Scintillator Detector • 820km baseline--
compromise between reach in 13 and matter effects
Assuming m2=2.5x10-3eV2
e+A→p + - e-
figure courtesy M. Messier
figures courtesy J. Cooper
Goal:eappearanceIn beam
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 54
Future Steps after T2K, NOvA
• Beam upgrades (2x – 5x)
• Megaton detectors (10x – 20x)
• BUT, it’s hard to make such steps without encountering significant
TECHNICAL DIFFICULTIES– hereafter “T.D.”
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 55
TD: More Beam Power, Cap’nExample: Fermilab Proton Driver
~ 700m Active Length8 GeV Linac
8 GeVneutrino
MainInjector@2 MW
SY-120Fixed-Target
Neutrino“Super- Beams”
NUMI
Off- Axis
Parallel Physics and Machine Studies …main justificationIs to serve as source for new Long baseline neutrino experimentsfigure courtesy G.W. Foster
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 56
TDs: Beamlines• Handling Many MWatts of proton power and
turning it into neutrinos is not trivial!
NuMI downstream absorber. Note elaborate cooling. “Cost more than NuTeV beamline…” – R. Bernstein
NuMI Horn 2. Note conductors and alignment fixtures
NuMI tunnel boring machine. 3.5yr civil construction
NuMI Target
shielding. More mass
than far detector!
pictures courtesy D. Harris
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 57
TDs: Detector Volume• Scaling detector volume is not
so trivial
• At 30kt NOvA is about the same mass as BaBar, CDF, Dzero, CMS and ATLAS combined…– want monolithic, manufacturabile structures– seek scaling as surface rather than volume if possible
figure courtesy G. Rameika
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 58
For Perspective…• Consider the Temple of the
Olympian Zeus…• 17m tall, just like NOvA!
– a bit over ½ the length
• It took 700 years to complete– delayed for lack of funding
for a few hundred years
• Fortunately construction technology has improved– has the funding situation?
17m
your speaker
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 59
TDs: Detector Volume (cont’d)• For megatons, housing a detector is difficult!
• Sensor R&D: focus on reducing cost
– in case of UNO,large photocathode PMTs
– goal: automated production,1.5k$/unit
figures courtesy C.-K. Jung
10% photocathode
60m60m
40% photocathode
UNO. ~1Mton. (20x Super-K)
Dep
th (
bel
ow
su
rfac
e)
Span
UNO: 60m span1500m depth
Field Map, Burle 20” PMT
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 60
TDs: Neutrino Interactions• At 1-few GeV neutrino energy (of interest for osc. expt’s)
– Experimental errors on total cross-sections are large• almost no data on A-dependence
– Understanding of backgrounds needsdifferential cross-sections on target
– Theoretically, this region is a mess…transition from elastic to DIS
n–p0
nn+
figures courtesy D. Casper, G. Zeller
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 61
Futuristic Accelerator Beams
• Great experimental benefits to new beam technology, but beams are very challenging! And costly…
Detector Needsfigures courtesy D. Harris• Conventional Beam
• Beta Beam
• Neutrino Factory
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 62
The Broadest Goals
• Understand mixing of neutrinos– a non-mixing? CP violation?
• Understand neutrino mass– absolute scale and hierarchy
• Understand interactions– new physics? new properties?
• Use neutrinos as probes– nucleon, earth, etc.
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 63
Neutrinoless Double-Beta Decay
• Double beta decay
is a rare, butobserved process
• “Neutrinoless” implies that the neutrino is its own anti-particle (Majorana particle)
• The prize:
Z Z+2 2 2AA
e
graphics courtesy Symmetry magazine
0 2 phase space nucl. matrix elems.m
calculable evaluable w/ largish uncertainties
2ii
ei ii
m U m e (i is a “Majorana phase”. Please look it up because
I’m not going there…)
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 64
Experimental Challenges• Observables: electron energy,
final state nucleus (EXO)
– Electron energyrequires excellentresolution and lownon backgrounds
– Tagging the finalstate nucleus is “findinga needle in a haystack”
• Must have significant quantities of isotopes– not necessarily easy to purify. good detector material?– nuclear physics guidance limited on “best” isotopes
sum electron energy / Q
2
0
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 65
Current Results to Date• Results• To notice:
– 76Ge, 130Te havelarge quantities,best limits so far
– There is a claimedobservation
• controversial• significant non-
backgrounds(hard-to-predict Bi lines)
figure and table from APS report: direct mass group
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 66
Future
• If the Heidelberg-Moscow 76Ge result is correct, should be confirmed “easily”
• If not, want to push sensitivities to m2 to
at least level of m223 (maybe m2
12)
– approximately two (maybe four) orders of magnitude lower than present situation
• Experiments are very difficult want confirming signals in multiple isotopes– many exciting ideas for future experiments
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 67
Approaches: CUORE• Calorimetric (thermal) detector which
is the source (TeO2)– ~keV resolution at endpoint (2528 keV)– Currently running “Cuoricino”, 40 kg– Full CUORE expects to have 750 kg,
reduced background levelsTeO2 crystal
heat bath
Thermal sensor
e-
e-
figures courtesy E.Fiorini
Cuoricino (Hall A)
CUORE R&D (Hall C)
CUORE (Hall A)
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 68
Other Approaches• COBRA: Semi-conductor CdZnTe detector
– multiple isotopes!
– room temperature, so no cryogenics(advantages for growing detector size,keeping contaminated materials away)
• NEMO– Tracking/calorimetric detector
external to source foils(10kg of isotopes in prototype)
– Geiger mode wire chambers, B=25G
– Scint/Low Rad. PMT calorimeter
• Field is being driven by a multiplicity of prototypes
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 69
decay kinematics: microcalorimeters magnetically adiabatic collimating electrostatic spectrometers
3H
187Re
Other Mass Determinations?
powerful, but very indirect
cosmology &structure formation
D.N. Spergel et al: m < 0.69 eV (95%CL)
figures courtesy K. Eitel
potential for ~few eV sensitivity
astrophysics:SN ToF measurements
direct, but precision requires detailed knowledge of SN
direct, but very challenging experiments
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 70
10 eV
KATRINphase space determines energy spectrumE0 = Ee + E (+ recoil corrections)
theoretical spectrum near endpoint
dN/dE (E0-Ee) × [ (E0-Ee)2 – m2 ]1/2
retarding (variable) E-field allows only E>Eret. to pass
energy resolution:: E/E=Bmin/Bmax
Bmax = 6 TBmin = 3×10-4 Tso E~1 eV
MAC-E spectrometers(Mainz, Troitsk) m<2.2eV(95%CL)
(sensitivity limit)
KATRIN sensitivity m<0.2eV(90%CL)commissioning in 2008
3 3H He
figures courtesy K. Eitel
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 71
The Broadest Goals
• Understand mixing of neutrinos– a non-mixing? CP violation?
• Understand neutrino mass– absolute scale and hierarchy
• Understand interactions– new physics? new properties?
• Use neutrinos as probes– nucleon, earth, etc.
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 72
Neutrino Interactions
• So broad a subject… so little time
• Precision EWK
• Neutrino magnetic moments
• Non-standard neutrino interactions
• Parity-violating probe
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 73
Neutral Currents in Neutrinos• Neutrino neutral current?
– LEP invisible width, only 2– NuTeV may be
very largeisospin violation
• Future reactors? Conrad, Link, Shaevitz
– if reactor experiments have precision for 13, may also be able to measure neutral currents
– opportunity for a purely leptonic probe
e ee e
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 74
MINERvA, for Oscillations• Noted that neutrino interactions are poorly known…• Backgrounds or signal rate uncertainties for next
accelerator oscillation experiments could limit precision• Enter MINERvA at NuMI beamline
– newly approved cross-sectionexperiment in NuMI near hall
– construction start in late 2006;taking data by 2008
νµp→νµpπ0
Photon tracks!
For example,MINERvA helpsMINOS knowrelationshipbetween visibleand true energyfigures courtesy B. Ziemer, D. Harris, R. Flight
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 75
The Broadest Goals
• Understand mixing of neutrinos– a non-mixing? CP violation?
• Understand neutrino mass– absolute scale and hierarchy
• Understand interactions– new physics? new properties?
• Use neutrinos as probes– nucleon, earth, etc.
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 76
MINERvA, Axial Form Factors• An experiment like MINERvA
can add to knowledge ofnucleon structure!– Jefferson Lab for
neutrinos
• Example: axialstructure of protonat high Q2.– of interest because
of puzzling behaviorof vector form factors
figures courtesy H. Budd, R. Flight
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 77
Journey to the Center of the (Spherical) Earth: Geoneutrinos
• Another use of neutrinos as a probe• The journey in brief:
– earth radiates 30-45 TWatts in heat– the hypothesis: this is due to
radioactivity of the earth– this radioactivity emits low energy
anti-neutrinos from U and Thdecays detectable via
– one complication: much ofU/Th is in crust
1.8p e n MeV
figures courtesy G. Fiorentini
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 78
Geoneutrinos (cont’d)• Crust distribution is location
dependent, but can be determinedby geochemical surveys
• Subtraction of the variable (local)part leaves the “global” U/Th
• At right, expected local andmaximum “global” signal for U– “TNU” unit is 10-32 ev/prot-yr
Kamiokafigures courtesy G. Fiorentini
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 79
Geoneutrinos (cont’d)• First measurement from KamLAND!
– very challenging backgrounds!
figures courtesy Nature
• Rate of U+Th anti-neutrino reactions of (28±14)x10-
32/proton/yr– heat limit of <60 TW at 95% confidence
2.0 3.0Neutrino Energy (MeV)
reactors
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 80
Breathless Conclusions• There is a lot going on in neutrino physics!• Nature has been kind to us
so far, and answers tofundamental questionsmay be ripe for the picking
• But, new experiments aregetting more difficult…– Still, we’ve been historically patient in neutrino
physics (e.g., 30 years from Pauli to Reines and Cowan)
– And it’s been worth the wait!
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 81
Acknowledgements
input or source material supplied by (with or without their knowledge):A. deRujula, B. Kayser, D. Harris (also editorial help! thank you!), T. Nakaya,S. Parke, S. Brice, D. Autiero, T.. Kobayashi, M. Messier, J. Cooper, G.W. Foster, G. Rameika, C.-K. Jung, M. Bishai, H. Gallagher, B. Ziemer, H. Budd, E. Fiorini, G. Gratta, X. Sarazin, K. Eitel, R. Flight, D. Casper,H. Minakata, G. Zeller, G. Fiorentini, Nature, The Particle Adventure, Star Trek and Symmetry magazine
Supplementary Slides
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 83
More to learn from the sky?• Sign-separated atmospheric neutrinos
– MINOS detector is first with this capability– determine charge
from bend
• Why study neutrino vs. anti-neutrino oscillations? – possibility to test CPT violation scenarios if suggested by MiniBooNE and
LSND results
Time vs Y
Time vs Z
Y vs X
Y vs Z
yx
z
Strip vs Plane
~1 yr MINOSfigures courtesy M. Bishai, H. Gallagher
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 84
Observing Matter Effected Oscillations
• We apparently have seen matter effects in the sun… can we verify it in the earth?
• Best resultsfrom Super-K
• Expect ~2%effect– Not there yet
• Interestingfor futuresolar experiments…
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 85
Who Cares About β-Decay?• Weak Nuclear Force
– its exciting role is to, well, make β-decays– that sounds awfully anticlimactic… who cares?
• actually,you do. A lot.
– Fusion in the sun requires that a protonturn into a neutron. Inverse of β-decay!
– Without β-decay, we are stuck where the sun don’t shine…
Slides for my Amusement
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 87
Is there an easier way?• Why, yes! Leave it to Star Trek to point the way!• Apparently, according to several
episodes, Lt. Jordy LaForge’s VISORcan actually detect “neutrino fieldemissions”– and what do we do in science except
emulate Star Trek?
• Sadly, this technology is the sole purview of the Pentagon for use in spotting neutrino emissions from their political opponents… so we need other tools.
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 88
Is there no escape from Neutrinos?
Cosmic GallNeutrinos, 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
30 November 2005 K. McFarland, Neutrinos: Worth the Wait 89
Solar Neutrino Hunting• Radiochemical Detector
Ray Davis (Nobel prize, 2002)
– ν+np+e- (stimulated β-decay)– Use this to produce an unstable
isotope, ν+37Cl37Ar+e- , whichhas 35 day half-life
– Put 615 tons ofPerchloroethylenein a mine
• expect one 37Ar atomevery 17 hours.
Physicist Ray Davis
not to be confused with Ray “Stingray”
Davis, bass vocalist for Parliament Funkadelic,
seen below “Tearing the Roof Off the Sucka” in a rare Homestake Mine
Concert appearance