Neutrino Oscillations and the Sudbury Neutrino Observatory
Transcript of Neutrino Oscillations and the Sudbury Neutrino Observatory
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ν Oscillations in the `Solar Sector’ and the Sudbury Neutrino Observatory
Aspen Winter 2005: The Highest Energy Physicsvelocity
Joshua R. KleinUniversity of Texas at Austin
Testing the New Neutrino ModelUpcoming ResultsFuture PhysicsSNO Phase III Status
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After Six Solar ν Experiments
• 3 Gallium (Radiochemical)• 1 Chlorine (Radiochemical)• Kamiokande + Super-Kamiokande (Water Cerenkov)
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ν Reactions in SNONC
xx νν ++⇒+ npdCC -eppd ++⇒+ν e•Good measurement of νe energy spectrum•Weak directional sensitivity ∝ 1-1/3cos(θ)
•Measure total 8B ν flux from the sun.•Equal cross section for all ν types
ES -- +⇒+ eνeν xx
•Mainly sensitive to νe,, some sensitivity to νµ and ντ•Strong directional sensitivity
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The Three Phases
• Phase I: Pure D2O• Simple detector configuration, clean measurement• Low neutron sensitivity• Poor discrimination between neutrons and electrons
• Phase II: D2O + NaCl• Very good neutron sensitivity• Better neutron electron separation
• Phase III: D2O + 3He Proportional Counters• Good neutron sensitivity• Great neutron/electron separation
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Phase I + First Phase II ResultsSNO Compared to Other Solar Expts.
But the new neutrino model makes other predictions besides fluxes…
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Matter (MSW) Effects
σ(νµ,τ) = 0.155σ(νe)
Day/Night νe Asymmetry
Rise in Survival Probability at low Eν
Generally speaking, neutrino oscillations in matter provide a resonant interferometer to detect very small effects.
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Spectral Shape/Earth RegenerationSuper-Kamiokande
Day/Night Asymmetry: Recoil (ES) electron spectrum:
Super-Kamiokande Collaboration, Phys. Rev. Lett. 86(2001)5651-5655
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SNOSpectral Shape/Earth Regeneration
Day/Night Asymmetry? (ACC or ANC)?
ACC=
ANC Unconstrained:
AE=ANC =0:
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SNOSpectral Shape/Earth Regeneration
CC reaction has good energy response
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Solar Sector (1,2) Mixing Parameters
SNO alone, no Solar Model Fluxes
All Solar Experiments+Model Constraints
Maximal mixing ruled out at ~ 3 σ
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Notes On `Solar Sector’Parameters (∆m2
12,sin22θ12)
Parameters measured by solar experiments require matter (MSW) effect:
but specific signatures of MSW effect areas yet unobserved (`unlucky’ parameters).
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Testing the New Neutrino ModelIs our model of neutrino mixing and oscillation complete, or are there other mechanisms at work?
Given KamLAND measurements, model predicts solar parameters
Reactor Solar
E 2-10 MeV 0.1-15 MeV
L 150 km 1.5 x 108 km
MSW No Yes
ν Anti-νe νe
KamLAND Collaboration, hep-ex/0406035, 11/1/2004
Only(?) Standard Model predicts these 2 experimentalregimes see the same effect
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All Solar Results+KamLAND
KamLAND Collaboration, hep-ex/0406035, 11/1/2004
Maximal mixing ruled out at 5.4 σ
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Testing the New Neutrino Model
Resonant neutrino `inteferometry’ allows us to look for even very small new interactions, which will look like an `MSW’-like effect
Miranda, Tortola, and Valle, hep-ph/0406280v2
Friedland, Lunardini, and Peña-Garay,Phys. Lett.B594:347,2004
Sterile neutrinos will disappear from νe spectrum but not reappear in NC rate
So how do we do further tests?
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SNO Phase I: Extracting SignalsCan use derived observables (R3, cosθsun, and E)
to produce pdfs.
Max. Likelihood fit for relative signal amplitudes
EnergyDistribution
RadialDistribution(R3, RAV=1)
SolarDirection
Distribution
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SNO Phase I Signal FitsUndistorted 8B spectral shape assumed, except for bin-by-bin
extraction above 7.25 MeV
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SNO Phase II (Salt Phase)Advantages of NaCl: Event Isotropy
14β0 0.2 0.4 0.6 0.8
0
0.01
0.02
0.03
0.04
0.05
0.06 ElectronsNeutrons
Legendre Terms (β14)
γ multiplicity means PMT hit pattern for neutron events moreisotropic than for single Cerenkov electrons
~2−4 gammastotalling 8.6 MeV
γ
γγ
Cl36
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SNO Phase II (Salt Phase)Advantages of NaCl: Signal Extraction
EnergyDistribution
RadialDistribution(R3, RAV=1)
SolarDirection
Distribution
IsotropyDistribution
CC ES NC
All New
NC Shifted
NC Changed
Unchanged
Covariances between Isotropy and Energy actually require 2D PDFs
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SNO Phase II Signal FitsSolar Direction Isotropy
Now entire analysis can be done bin-by-bin. Radius (R3)
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First Phase II ResultsFlux Measurements (units 106 cm-2 s-1)
Still not really a spectrum
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Upcoming Phase II Results
• Roughly 50% more data (391 live-days)
• First spectrum with all differential sys. uncertainties
• New Day/Night asymmetry result
• `Full’ details (~40 pp)
• (`Long’ paper detailing Phase I results starting internal editing and review process ~70 pp)
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Work underway to push threshold on Phase I+II data to T > 4 MeV
SNO Low Threshold Analysis
Predictions for SNO response for various MSW solns:
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Detection Principle2H + νx → p + n + νx -2.22 MeV (NC)
3He + n → p + 3H
νx
n
Array of 3He counters40 Strings on 1-m grid
440 m total active length
NCD
PMT
SNO Phase III (NCD Phase)3He Proportional Counters
Production data taking began Dec 2004
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SNO Phase III (NCD Phase)Physics Motivation---Energy Spectrum
• CC and NC separation in pure D2O had big covariances(>90% correlations)
• Salt phase broke covariance with isotropy, but additional neutrons dilute CC signal
• Third phase has best of both worlds• 3He (`NCD’) counters absorb neutrons• Independently constrain remainder• And can be applied retroactively
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Conclusions
• Starting to look at `precision’ tests of the new neutrino model• KamLAND + SNO + Super-K + BOREXINO +???
• Upcoming SNO results will contain first `precision’ SNO spectrum and new Day/Night asymmetry results
• Further work to lower SNO energy threshold, test model further
• SNO Phase III likely to highest precision low threshold 8B measurement
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