J. Goodman – January 03 The Solution to the Solar Problem Jordan A. Goodman University of Maryland...
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Transcript of J. Goodman – January 03 The Solution to the Solar Problem Jordan A. Goodman University of Maryland...
J. Goodman – January 03
The Solution to the Solar Problem
Jordan A. Goodman
University of Maryland
January 2003
• Solar Neutrinos• MSW Oscillations• Super-K Results• SNO Results• Kamland Results• Overall Results
J. Goodman – January 03
Our current view of underlying structure of matter
• P is uud
• N is udd
• is ud
• k is us
• and so on…
• P is uud
• N is udd
• is ud
• k is us
• and so on…
The Standard Model
The Standard Model
}Baryons }Baryons
}Mesons }Mesons
(nucleons)(nucleons)
J. Goodman – January 03
Facts about Neutrinos
• Neutrinos are only weakly interacting
• 40 billion neutrinos continuously hit every cm2 on earth from the Sun (24hrs/day)
• Interaction length is ~1 light-year of steel
• 1 out of 100 billion interact going through the Earth
• 1931 – Pauli predicts a neutral particle to explain energy and momentum non-conservation in Beta decay.
• 1934 - Enrico Fermi develops a comprehensive theory of radioactive decays, including Pauli's particle, Fermi calls it the neutrino (Italian: "little neutral one").
• 1959 - Discovery of the neutrino is announced by Clyde Cowan and Fred Reines
J. Goodman – January 03
Why do we care about neutrinos?
• Neutrinos – They only interact
weakly– If they have mass at all
– it is very small • They may be small, but there sure are a
lot of them!– 300 million per cubic meter left over from the
Big Bang– with even a small mass they could be
most of the mass in the Universe!
J. Goodman – January 03
Solar Neutrinos
J. Goodman – January 03
Solar Neutrino Spectrum
J. Goodman – January 03
Solar Neutrino Experiment History
• Homestake - Radiochemical– Huge tank of Cleaning Fluid
– e + 37Cl e- + 37Ar
– Mostly 8B neutrinos + some 7Be– 35 years at <0.5 ev/day– ~1/3 SSM– (Davis - 2002 Nobel Prize)
• Sage/Gallex - Radiochemical– “All” neutrinos
– e + 71Ga e- + 71Ge
– 4 years at ~0.75 ev /day– ~2/3 SSM
• Kamiokande-II and -III – 8B neutrinos only
– e Elastic Scattering
– 10 years at 0.44 ev /day– ~1/2 SSM– (Koshiba 2002 Nobel Prize)
J. Goodman – January 03
The Solar Neutrino Problem
J. Goodman – January 03
Disappearing Neutrinos?
• All of these experiments (except SNO) are
sensitive mostly to e
– The energies are too low to produce orso they can only see neutral current interactions from other flavors
• If neutrinos could transform from electron type to muon or tau type the data might be understood
• Neutrinos can only “oscillate” if they have different masses– This implies that they have mass!– This would have significant cosmological importance
• A neutrino mass of ~20ev would close the Universe– It would also imply violation of lepton flavor conservation
J. Goodman – January 03
Detecting Neutrino Mass
• If neutrinos of one type transform to another type they must have mass:
• The rate at which they oscillate will tell us the mass difference between the neutrinos and their mixing
GeV
kmeVxe E
LmLP
222 27.1
ins2sin;
J. Goodman – January 03
Neutrino Oscillations
1 21 2
=Electron =Electron
Electron
Electron
1 21 2
=Muon =Muon
Muon Muon
J. Goodman – January 03
Neutrino Oscillations
• Could Neutrino Oscillations solve the solar neutrino problem?– Simple oscillations would require a cosmic conspiracy– The earth/sun distance would have to be just right to
get rid of Be neutrinos
• Another solution was proposed – Resonant Matter Oscillations in the sun
(MSW- Mikheev, Smirnov, Wolfenstein)• Because electron neutrinos “feel” the effect of
electrons in matter they acquire a larger effective mass– This is like an index of refraction
J. Goodman – January 03
MSW Oscillations
Sin 2Spring =
e
Length = Mass
When length (i.e. effective mass) are equal the couplingis enhanced.
Mechanical Analogy for Neutrino Oscillations
In theSun
In theVacuum
Resonance
(Mikheev, Smirnov, Wolfenstein)
J. Goodman – January 03
Oscillation Parameter Space
LMA
LOW
VAC
SMA
J. Goodman – January 03
Solar Neutrinos in Super-K
• The ratio of NC/CC cross section is ~1/6.5
J. Goodman – January 03
Cherenkov Radiation
Aircraft moves throughair faster than speed ofsound.
Sonic boom
J. Goodman – January 03
Cherenkov Radiation
When a charged particle moves throughtransparent media fasterthan speed of light in thatmedia.
Cherenkov radiation
Cone oflight
J. Goodman – January 03
Super-K
J. Goodman – January 03
Super-Kamiokande
J. Goodman – January 03
Detecting neutrinos
Electron or
muon track
Electron or
muon track
Cherenkov ring on the
wall
Cherenkov ring on the
wall
The pattern tells us the energy and type of particle
We can easily tell muons from electrons
The pattern tells us the energy and type of particle
We can easily tell muons from electrons
J. Goodman – January 03
A muon going through the detector
J. Goodman – January 03
A muon going through the detector
J. Goodman – January 03
A muon going through the detector
J. Goodman – January 03
A muon going through the detector
J. Goodman – January 03
A muon going through the detector
J. Goodman – January 03
A muon going through the detector
J. Goodman – January 03
Stopping Muon
J. Goodman – January 03
Stopping Muon – Decay Electron
J. Goodman – January 03
Low Energy Electron in SK
J. Goodman – January 03
Solar Neutrinos in Super-K
• 1496 day sample (22.5 kiloton fiducial volume)• Super-K measures:
– The flux of 8B solar neutrinos– Energy spectrum and direction of recoil electron
• Energy spectrum is flat from 0 to Tmax
– The zenith angle distribution– Day / Night rates– Seasonal variations
J. Goodman – January 03
Solar Neutrinos
)s cm 10 x (syst)0.03(stat) (2.32
ssm) (syst) %0.5%(stat) (45.1%
1-2-608.00.07
1.61.4 -
e
J. Goodman – January 03
Energy Spectrum
J. Goodman – January 03
Seasonal/Sunspot Variation
J. Goodman – January 03
Day / Night - BP2000+New 8B SpectrumPreliminary
(syst)(stat)0.0200.021N)(D
21
DN 0.0130.012-
J. Goodman – January 03
Combined Results e to
SK+Gallium+Cholrine - flux only allowed 95% C.L.
95% excluded by SK flux-independent zenith angle energy spectrum
95% C.L allowed. - SK flux constrained w/ zenith angle energy spectrum
J. Goodman – January 03
Combined Results e to sterile
SK+Gallium+Cholrine - flux only allowed 95% C.L.
95% excluded by SK flux-independent zenith angle energy spectrum
95% C.L allowed. - SK flux constrained w/ zenith angle energy spectrum
(Like SK)
J. Goodman – January 03
SNO CC Results
e= (35 ± 3 )% ssm
J. Goodman – January 03
Combining SK and SNO
• SNO measures e= (35 ± 3 )% ssm
• SK Measures es= (47 ± .5 ± 1.6)% ssm
• No Oscillation to active neutrinos:– ~3 difference
• If Oscillation to active neutrinos:– SNO Measures just e
• This implies that ssm (~2/3 have oscillated)
– SK measures es =(e + ( /6.5)
• Assuming osc. SNO predicts that SK will see es ~ (35%+ 65%/6.5) ssm = 45% ± 3% ssm
J. Goodman – January 03
SNO Results (NC)
J. Goodman – January 03
SNO Results (NC/CC)
• SNO Results
J. Goodman – January 03
SNO Results
J. Goodman – January 03
Combined Results
J. Goodman – January 03
Kamland – Terrestrial Neutrinos
J. Goodman – January 03
Reactors Contributing to Kamland
J. Goodman – January 03
Kamland Results (Dec. 2002)
J. Goodman – January 03
Kamland
J. Goodman – January 03
Kamland
J. Goodman – January 03
All Experiments Combined with Kamland
J. Goodman – January 03
• It looks like the Solar Neutrino problem has been solved!– All Data (except LSND) is now consistent
with the large angle MSW solution– We have ruled out SMA and Low solutions– Disfavor Sterile Neutrino solutions
• Neutrinos have mass!– This confirms the atmospheric neutrino results– Neutrinos contribute approximately as much
mass as all of the visible stars
• Future Experiments – – MiniBoone – LSND effect
Solar Neutrino Conclusions