Discovery of neutrino oscillations Super Kamiokande atmospheric data

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Discovery of neutrino oscillations- Super
Kamiokande atmospheric data

• Neutrinos produced in Earth atmosphere
• Comparison with expectation from calculations
  using cosmic ray fluxes and cross sections
• Comparison of ?e??and?????
• Neutrinos entering detector from
• above (short distance)
• or below (long distance)

From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Super-K I results contained events
Higher energy
Low energy
Data
MC 1ring e-like 772
707.8 ?-like 664
968.2
Data
MC 1ring e-like 3266 3081.0
?-like 3181 4703.9

Double ratio
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Double ratios in various experiments
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Super-K zenith angle for multi-GeV events
Contained events, multi-GeV only (Evisgt1.33 GeV)
M.C. simulations (without oscillations)
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Zenith angle distributions all samples
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Oscillations of muon neutrinos
Looks like ?? oscillation..
What is the ?
Lets look at the oscillation length
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Definition of ?2 for oscillation analysis
A fit is performed i.e. a minimum of ?2 is found.
The corresponding
are the best fit oscillation parameters
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Oscillation parameters from different experiments
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Atmospheric neutrinos - summary
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Solar neutrinos other place where?? are missing
Solar neutrinos other place where ? are missing
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Energy Production in the Sun
Solar model
Tiny fraction
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Solar Neutrino Spectrumthresholds for different
thechniques

• radiochemical
• low threshold
• only event rates counted
• no time information
• no direction
• scintillation
• time information
• Cherenkov detectors
• time and direction

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Solar neutrino experiments

• Radio-Chemical (CC)
• Homestake (Chlorine), Gallex (Gallium),
• SAGE (Gallium), GNO (Gallium)
• Electron Elastic Scattering (CCNC)
• Kamiokande (Water-Cherenkov),
• Super-Kamiokande (Water-Cherenkov),
• Borexino (liquid scintillator in future)
• Cherenkov (CC) SNO (Deuterium)
• Cherenkov (NC) SNO (Deuterium)

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Solar models prediction of fluxes in energy
ranges
Definition of SNU (Solar Neutrino Unit) -
10-31 atom-1 s-1
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Idea of the experiment using Davis-Pontecorvo
reaction

• Argon atoms have to be extracted and counted

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Reaction with Cl producing radioactive argon and
electron

• Reaction has a threshold at 0.81 MeV
• The produced Ar isotope has half-life time for
  electron capture of 35 days
• To measure neutrino flux one has to count the
  number of produced
• 37Ar atoms

• First measurements at Brookhaven, 1955
• with 3 900 liters of CCl4
• Gives limits on cross section per atom
• 2x10-42 cm2
• Possibility of signal from the Sun considered
• New 100 times bigger experiment proposed based on
  these results and Bahcalls calculation of
  neutrino flux from the Sun
• Nobel prize in 2002 !!!

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Solar neutrino chlorium experiment
(radiochemical measurement)

• Tank contained 615 tons of C2Cl4 (agent used for
  dry cleaning)
• Localization in Homestake Gold Mine in South
  Dacota at 1 500 m depth
• Started data taking in 1967
• Running almost continuously until 1994
• Extraction of 37Ar by helium done once every two
  month (to match life time)
• Extracted atoms were counted in proportional
  counters (using additional information on the
  signal rise time to reduce background)

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Schematic view of Davis argon recovery system
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Results
Rate and flux from single extractions

• Rate 0.48 0.16(stat) 0.03(syst) argon
  atoms/day
• Flux 2.56 0.16 0.16 SNU

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Solar neutrinos comparison of observed and
expected ??fluxes for Cl experimentsratio
observed/expected
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
21
Experimental thresholds
Lowest ? energies gallium
detectors
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Gallex/GNO and Sage
two detectors using reaction
Threshold at 233 keV, dominant p-p reaction SAGE
in Caucasus, experiment started with 30ton tons
of Gallium next upgraded to 57 tons Gallium
kept in liquid form (melting point 29.8 oC)
extraction destillation callibrated on
added 700 ?gr of natural Ge (efficiency 80)
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Gallium experiments (cont.)
71Ge decays with half-life of 11.4 days by
electron capture to the ground state of
Ga detection low-energy mono-energetic Auger
electron and x-rays Gallex in Italy, Gran Sasso
underground laboratory, 30 tons of Gallium
dissolved in HCl continued as GNO (Gallium
Neutrino Observatory) extraction efficiency
tested with strong radioactive source (51Cr)
both experiments use presently more than half
of world supplies of Gallium
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SAGE experiment results from extraction
seen

of expected neutrino flux
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Pronciple of extraction (GNO)
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Gallex and GNO

• conts as a function of time
• additional test with izotope
• life time
• background estimate
• calibration of the method with
• introduction of known number
• atoms and counting them
• from this measurement estimate
• of efficiency of the method

From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Gallex
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Gallex - GNO
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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Solar neutrinos in SuperKamiokande
Kamiokande - underground Cherenkov detector
build to search for proton decay gives the
neutrino image of the sun
Energy threshold around 5 MeV, good energy
resolution
Light emitted gives direction of particle, for
processes with one track - easy reconstruction,
from reconstructed tracks - neutrino direction
(approximatly)
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Super-K solar neutrino rate
other active flavors
e-type neutrino
1496 Day Final Sample
Expect
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SuperKamiokande rate
reminder angular distribution for ? scattering
on atomic electrons (this allows extraction of ?
from the Sun)
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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and how well Sun is seen at different energies
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Solar peak gt 5 MeV
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Day/Night asymmetry
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From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
36
The electron recoil spectrum in Super-Kamiokande
?2(flat)20.2/20 (44.3 C.L.)
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not possible to find SM version consistent with
the data (even only fluxes)
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Neutrino oscillation search for
parametersDefinition of ?2 for oscillation
analysisreminder (used for atmospheric neutrino
fits)
using rates, day/night asymmetry, sesonal
variation, energy spectrum A fit is performed
i.e. a minimum of ?2 is found.
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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fitting oscillation parameters to all these data
from Solar ???few allowed solutionsLMASMALow
Vac

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Distortions of the Solar Neutrino Spectrum
Different oscillation parameters imply different
distortion of the observed energy spectrum
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Solar Neutrino Observatory
From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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SNO (Sudbury Neutrino Observatory)

• Water detector with a difference
• 2 km underground
• 1000 tonnes D2O
• 104 - 8 PMTs
• 6500 tons H2O

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From neutrinos to cosmic sources, D.
Kielczewska and E. Rondio
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SNO results data
Integrated over energy assuming standard B8
shape and ?e cross sections
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Solar ? oscillation from SNO and Super-K
?CC ?e ?ES ?e 0.154 ??,?
SNO ?CC 1.76?0.11 SK ?ES 2.32?0.09
x106/cm2/s
??,? 3.45?0.65 ?X 5.21?0.66 (total
active 8B neutrino flux)
(?SSM 5.051.01/-0.81)
SK
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Solar ?s