Neutrino Physics - Lecture 4
Steve Elliott
LANL Staff Member
UNM Adjunct Professor
505-665-0068, [email protected]
Spring 2007 Steve Elliott, UNM Seminar Series
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Lecture 4 Outline
• Neutrinos from the SunThe neutrinos
Past experiments
What we know and what we want to learn
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Cl Results
2.56 ± 0.16 ± 0.16 SNU
Expect7.5 SNU
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SAGE and Gallex (GNO)
• 71Ga(e,e)71Ge
• 71Ge has 11.4 day half life.
• Expose Ga to neutrinos
• Extract Ge and count via its decay
• Decays of 71Ge are by electron capture: the signature is the 1.2 or 10.4 keV x rays, Auger electrons
Spring 2007 Steve Elliott, UNM Seminar Series
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SAGE Operations
1. Add carrier to Ga.2. After about 3-4 weeks, extract
Ge carrier and solar neutrino induced Ge.
3. Synthesize counter gas and fill proportional counter.
4. Count sample for about 6 months.
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Map to SAGE
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Baksan Valley, UG Laboratory
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Source Calibration
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
92.4% enriched in 50Cr512.7 g of CrIrradiated for ~3 mnths517 kCi activity
Spring 2007 Steve Elliott, UNM Seminar Series
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Reactor Layout
10 reactorsEach can hold 8 tons of GaKept warm so Ga is liquid
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Proportional Counters
• R: recombination• IC: ionization
chamber• PC: proportional
chamber• GC: Geiger counter• D: continuous
discharge
R
IC
PC
GC
D
Voltage
Co
llec
ted
Io
ns
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Proportional Counter Spectrum
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Results - Solar Rate
€
66.9−3.8, −3.2+3.9, +3.6 SNU
Expect128 SNU
Each run saw about 6 signalEvents.
Spring 2007 Steve Elliott, UNM Seminar Series
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Gran Sasso
Italy:Not too far from Rome
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GNO Layout
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GALLEX Results
Expected128 SNU
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Kamiokande & SuperK
• Elastic scattering of e-
in a large water detector
• Mostly sensitive to e because CC cross section is about 6x higher than NC
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Cherenkov Radiation
“Electrons in the atoms of the medium will be displaced and polarized by the passing EM field of a charged particle. Photons are emitted as an insulator's electrons restore themselves to equalibrium after the disruption has passed. (In a conductor, the EM disruption can be restored without emitting a photon.) In normal circumstances, these photons destructively interfere with each other and no radiation is detected. However, when the disruption travels faster than the photons themselves travel, the photons constructively interfere and intensify the observed radiation.”
Wikipedia
€
cosθ =1nβ
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Photomultiplier Tubes
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SuperKamiokande Characteristics
• 50,000 t water
• 11,146 20” pmt
• 1,885 8” pmt
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SuperK Data
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SNO
• ES, CC, and NC
• CC: d(e, pp)e-
– Sensitive only to e
• NC: d(x, np)x
– Sensitive to all x
• NC/CC ratio
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SNO’s Location
< 100 /day102
103
104
105
106
107
Muon flux (m
-2 y
-1)
8000600040002000Depth Underground (ft)
IMB
Soudan
Kamioka
Gran Sasso
Frejus, Baksan, Homestake Mont Blanc
Sudbury
Kolar
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The SNO Detector
9438 inward & 91 outwardWith concentrators = 54% coverage
Control room
Vectransupportropes
Urylon liner
5300 tonneslight water
1000 tonnesheavy water 1700 tonnes
light water
2039 m to surface1011 m to Sun
12 m diameteracrylic vessel
Support structure for 9500 PMTs,concentrators
Norite rock
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SNO Calibration
Electronics CalibrationsBuilt-in programmable pulsers
Optical CalibrationsLaser ball: attenuation, scattering, reflectivity
Energy Calibrations16N source: 16O(n,p)16N*
-tagged 6.1-MeV source8Li Source: e- spectrum similar to 8B252Cf source: fission neutron source
Encapsulated U/Th source (low-E ’s)3H(p, )4He: 19.8-MeV Triggered U: Th sources (low-E ’s)
Michel electrons
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An example Event: atmospheric neutrino
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SNO data
Radius of event vertex Angle with Sun
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Event Energy
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NC vs. CC