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Solar Neutrino Experiments
A Review
The CAP'09 CongressMoncton, 7-10 June, 2009
Alain BelleriveOn behalf of the SNO CollaborationCarleton University, Ottawa, Canada
From Solving the Solar Neutrino Problem to Precision Physics
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Outline
Solar Neutrino Experiments A.Bellerive, ICHEP, July 2010
Introduction Solar Neutrino Flux (update)
First Generation of Solar Neutrino Experiments Chlorine – Gallium – Kamiokande
Second Generation of Solar Neutrino Experiment SuperK – Borexino – SNO
The new stuff for 2010 !!!
Constraints on Oscillation Parameters
Future Prospects
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Evidence for Neutrino Mixing
Earth
Underground e detector
Solarcore
Primary neutrino sourcep + p D + e+ + e
Sun
~10 8 kilometers
Cosmic-rayshower
0+
+
e
e+
Underground e,e,,
detector
Atmospheric neutrino source+ + +
e+ + e + – – +
e– + e +
~30 kilometers
30 meters
e detectorNeutrinos e, , and
Proton
beam
Pions
Copper beam stop
Muons and electrons
Watertarget
Solar Neutrinoslow energies
Atmospheric Neutrinoshigh energies
Beamstop Neutrinostunable energies
2 e
First evidence of neutrino oscillation
Today’s talk !!!
Parallel Session Talk by Dr. Yoshihisa Obayashi
Plenary Talk by Tsuyoshi Nakaya
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h
The First Piece
Solar Neutrino Flux
The Sun produces e in fusion nuclear reactions
Survival probability depends on the neutrino energy
Solar neutrino oscillation occurs inside the Sun
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±1%
±6%
BPS08
±6% ±1.1%
±11%
±16%
Borexino
Neutrino Production in the Sun
Earth
Underground e detector
Solarcore
Primary neutrino sourcep + p D + e+ + e
Sun
~10 8 kilometers
Light Element Fusion Reactions
p + p 2H + e+ + e
p + e- + p 2H + e
3He + p 4He + e+ + e
7Be + e- 7Li + e
99.75 %
0.25 %
15 %
~10-5 %
8B 8Be* + e+ + e 0.02 %
Neutrino Production Radius
BPS08: (Bahcall) Pena‐Garay C. & Serenelli A. 2008. arXiv:0811.2424
http://www.sns.ias.edu/~jnb/
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6
Sudbury Neutrino Observatory
FAAQ2006Alain Bellerive
e
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7
Solar Neutrino Mixing
quantity signed
21
22
212 mmm
mixingsolar 12
Survival Probability3 Parameters !
The state evolves with
time or distance
Pee ≡P(e→e)Pee = cos4()[1-sin2(2)
sin2()] Pee ≈ 1-sin2(2) sin2()
where =1.27m2 L / E
Main Solar Physics:m2 & sin(2)
Experiment:Distance (L) & Energy (E)
1212
1213
12
12
small 13 2-32
31 eV 10 2.3 m
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The Second Piece:
First Generation Experiments
Chlorine – Gallium - Kamiokande
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Solar Neutrino Problem (Pre SNO)
Experiment Medium Threshold (MeV)
Measured/SSM
Homestake Chlorine 0.814 0.34±0.03
SAGE+GALLEX/GNO Gallium 0.2332 0.52±0.03
SuperK H2O 7.0 0.406±0.013
Neutrino reactions
Source: arXiv:hep-ph/0406294
νe
~108 km
Measured PredictedPee
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Phys.Rev. D64 (2001) 093007
LMA
Allowed Regions
SMA
LOW
VAC
JustSo2
m2 (e
V2 )
tan2
Combination of theChlorine, Gallium, SK, and CHOOZ
restricted the mixingparameters
Pre SNO (~2001) 212
2 mm
12 013
TODAY
Mixing Parameters
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Arranging the Pieces:
Second Generation Experiments
SuperK – SNO - Borexino
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12
Super Kamiokande8B (and hep) neutrino(s)
detection x+ e- → x+ e-
Sensitive to e,,t
(,t + e- ) 0.15 × (e + e-)
• High statistics ~15 events/day• Real time measurement allow
studies on time variations• Studies energy spectrum• 50 ktons of pure water
•
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Timeline of Super-Kamiokande
11146 ID PMTs(40% coverage)
5182 ID PMTs(19% coverage)
11129 ID PMTs(40% coverage)
Energy ThresholdTotal energy
Kinetic energy
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
SK-I SK-II SK-III SK-IV
Acrylic (front)+ FRP (back)
Electronics Upgrade
SK-I SK-II SK-III SK-IV
5.0 MeV~4.5 MeV
7.0 MeV~6.5 MeV
5.0 MeV~4.5 MeV
Target< 4.0 MeV<~3.5 MeV
Current~4.5 MeV~4.0 MeV
41.4
m
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Solar neutrino data of SK (period I)May 31,1996 – July 13,2001 (1496 days)
Ee = 5.0 - 20 MeV
22404226(stat) solar events
8B flux: 2.35 0.02(stat) 0.08(syst) [x 106 /cm2/sec] Data
SSM≈ 0.41
Phys. Rev. D 73, 112001 (2006)
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Daily Variation of SK Rate (Period I)
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Borexino7Be and 8B neutrinos
detection x+ e- → x+ e-
Sensitive to e,,t
(,t + e- ) 0.2 × (e + e-)
• Challenge: Control of Low Energy Background
• Energy window: [0.16 – 2.0] MeV for 7Be
> 3.0 MeV for 8B
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Work on installation continuesNeeds to resolve “political situation”
Borexino Detector
18m
Scintillator detector with an active mass of 278 tons of pseudocumene
PC buffer and water for shielding to rarioactivity
Scintillation light is detected via 2212 inward looking PMTs
Energy resolution 5% (at 1 MeV) and position resolution 10‐15 cm
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7Be Analysis Borexino (192 live‐days)
Signature for the monoenergetic 0.862 MeV 7Be neutrinosis the Compton-like edge of the recoil electrons at 665 keV
85Kr Cosmogenic 11C 210Bi + CNO neutrinos
After statistical subtraction of 210Po alphas
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Result of Borexino’s 7Be AnalysisRate(7Be) = 49 ± 3 (stat) ± 4 (syst) cpd/100tons
Φ(7Be) = (5.18 ± 0.51) × 109 cm‐2 s‐1
Pee = 0.56 ± 0:10 at 0.862 MeV
Under the assumption of SSM flux
Detail by Sandra Savatarelli in parallel session talkSolar neutrino and terrestrial antineutrino fluxes measured with Borexino at LNGS
Phys. Rev. Letts. 101, 09132 (2008)
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20
1700 tonnes InnerShield H2O
1000 tonnes D2O
5300 tonnes Outer Shield H2O
12 m Diameter Acrylic Vessel
Support Structure for 9500 PMTs, 60% coverage
Image courtesy National Geographic
Sudbury Neutrino
Observatory
6000 mwe overburden
17.8 m
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Key signatures for mixing with SNO
21
t
e
e
NC
CC
)(154.0 t
e
e
ES
CC
Flavor change ? Pee(E) ≠ 1 !CC
ES
NC
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Timeline of SNO
Commissioning D2O + Salt D2O D2O + 3He counters
3He countersInstallCommission
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
D2O
Phase I Phase II Phase III
306days 391days 396days
PRL 87, 071301, 2001PRL 89, 011301, 2002PRL 89, 011302, 2002PRC 75, 045502, 2007
PRL 92, 181301, 2004PRC 72, 055502, 2005
Total of ~1100 live-days
PRL101, 111301, 2008
PRC, 055504, 2010
Upcoming… Phase I-II-III combined analysis
Combined Phase I-IILow Energy Threshold Analysis
DataAnalysis
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SNO NCD’s Phase III
191573
pt
n
Ni wall
3He:CF4 gas
Cu wire
573
191
191
keV
573
keV
764
keV
PRL101, 111301, 2008
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SNO Phases I+II Major Improvements Tune up the Monte Carlo on calibration data based on 5 years of
operational experience - Reduction of systematic uncertainties Improve optics (especially at large radii) with late light and new
energy estimator (improve energy resolution by 6%)
Energy ThresholdD2O phaseTeff = 5 → 3.5 MeVSalt phaseTeff = 5.5 → 3.5 MeV
Improve statistics CC by ~40% NC by ~70%
Allow to fit the background wall
Night
Day
Pee typical LMA
E
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No distortion, no D/N:2 = 1.94 / 4 d.o.f.LMA-prediction:
2 = 3.90 / 4 d.o.f.
DAY
NIGHTADN
(8B) = 5.046in units of 106 cm−2 s−1
SNO Phases I+IIDirect joint-phase fit of Pee
PRC, 055504, 2010
+0.159 +0.107 -0.152 -0.123
Previous global best-fit LMA point tan212=0.468 m2=7.59x10-5 eV2
12
Previous global best-fit LMA point tan212=0.468 m2=7.59x10-5 eV2
12
Previous global best-fit LMA point tan212=0.468 m2=7.59x10-5 eV2
12
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Global View
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Data Sets Solar Oscillation Analysis Radiochemical : Cl, Ga
– Ga rate: 66.1 ±3.1 SNU SAGE+GNO/GALLEX [PRC80, 015807(2009)]– Cl rate: 2.56 ±0.23 [Astrophys. J. 496 (1998) 505]
SK– SK-I 1496 days, zenith spectrum E ≥ 5.0 MeV– SK-II 791 days, spectrum + D/N E ≥ 7.5 MeV
Borexino– 7Be rate: 49 ± 5 cpd/100tons [PRL101, 091302(2008)]
SNO– Phase I + II (PMT Low Energy threshold E ≥ 4.0 MeV)– Phase III (NCD and PMT E ≥ 6.5MeV)
KamLAND reactor experiment: 2008 [PRL100, 221803 (2008)]
8B spectrum: W. T. Winter et al., PRC 73, 025503 (2006). Plenary Talk by Fabrice Piquemal
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Oscillation Analyses: Global Solar
Best-fit LMA point: tan212 = 0.457 (+0.038 -0.041)
m2 = 5.89x10-5 eV2 (+2.13 -2.16)
(8B) = 5.104in units of 106 cm−2 s−1
-2.95Δ8B = +3.90 %
12
2 model
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2 model
Solar + KamLAND 2-flavor Overlay
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Best-fit LMA point:
tan212 = 0.457
12=34.06 deg
m2 = 7.59 x10-5 eV2
Solar + KamLAND 2-flavor2
model
-0.029
+0.040
+0.20
-0.21
+1.16
-0.84
-2.95Δ8B = +2.37 %
(8B) = 5.013in units of 106 cm−2 s−1
12
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3 model
Solar + KamLAND 3-flavor
Best-fit: sin213=2.00 +2.09
-1.63 x10-2
sin213 < 0.057 (95% C.L.)
Best-fit LMA point:
tan212 = 0.468
m2 = 7.59 x10-5 eV2
-0.023
+0.042
+0.21
-0.2112
Remark: SNO and SK global oscillation analyses consistent
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32
Sudbury Neutrino Observatory
FAAQ2006Alain Bellerive
Newest stuff for summer 2010 !!!
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Vertex distributions in SK-IIIData sample before fiducial volume cut
33
Tight fiducial volume cut is applied in Etotal<5.5MeV to
remove the background events. (Rn g-rays from detector wall).
5.0-5.5MeV (13.3kt)4.5-5.0MeV (12.3kt) 5.5-20MeV (22.5kt)
Fiducial volume in SK-III
Z
RSK detector
Neutrino 2010
Rat
e/bi
n
See poster: Solar neutrino results from SuperK by Hiroyuki Sekiya
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Systematic uncertainties on total flux (SK-III) SK-III SK-I (PRD73,112001)
Energy scale +/-1.4 +/-1.6Energy resolution +/-0.28B spectrum shape +/-0.2 +1.1/-1.0Trigger efficiency +/-0.5 +0.4/-0.3Vertex shift +/-0.54 +/-1.3Reduction +/-0.65 +2.1/-1.6Small cluster hits cut +/-0.5 Spallation cut +/-0.2 +/-0.2External event cut +/-0.25 +/-0.5Background shape +/-0.1 +/-0.1Angular resolution +/-0.67 +/-1.2Signal extraction method +/-0.7Cross section +/-0.5 +/-0.5Live time calculation +/-0.1 +/-0.1Total +/-2.1 +3.5/-3.2%
The systematic error on total flux of SK-III is reduced by precise
calibrations and software improvements
Neutrino 2010
Energy region: Etotal=5.0-20.0MeV
Preliminary
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Neutrino 2010
Total live time: 548 days, Etotal ≥ 6.5 MeV 289 days, Etotal < 6.5 MeV
Energy region: Etotal=5.0-20.0MeV
8B Flux: 2.32±0.04(stat.)±0.05(syst.) (x106/cm2/s)
)syst.(013.0)stat.(031.0056.02/)(
)(
NightDay
NightDayDNA
SK-III solar neutrino results Preliminary
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8B Analysis Borexino (487.7 live-days)
arXiv:0808.2868v3 [astro‐ph] accepted by Rev. Phys. D
Rate(8B) = 0.22 ± 0.04(stat) ± 0.01(syst) cpd/100tonsΦ(8B) = (2.4 ± 0.4 ± 0.1) × 106 cm‐2 s‐1
(oscillated)
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7Be flux: 2.35 0.02(stat) 0.08(syst) [x 106 /cm2/sec]
Impact of Borexino 7Be & 8B Analyses
7Be
8B (>5 MeV)
8B (>3 MeV)
Pee Δm2=7.69×10−5 eV2 and tan2θ=0.45
BX: Under the assumption of SSM flux SNO: Directly measure Pee
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Preliminary
7Be Day spectrum: 387.46 days7Be Night spectrum: 401.57 days
Statistical error: 2.3 cpd/100tThe 7Be flux is obtained from separate full fits of day and night spectra
)stat.(073.0007.02/)(
)(
NightDay
DayNightDNA
PS: Mass varying neutrino models of P.C. de Holanda rejected at 3σ level
7Be Day/Night Asymmetry Borexino
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SNO hep neutrino sensitivity (3phase)
SSM
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SNO Improvement – NCD (3-phase) Pulse shape discrimination to separate neutron(signal) from alpha (background)
Distinguish neutron and alpha pulses Neutron pulses are created with two particles (a proton and a triton), and alpha pulses are created by a single particle Timing and Ionization tracks are fundamentally different After discrimination perform a fit of energy spectrumProjected
Uncertainty on theNumber of NC Neutrons
Without+ 77-76
With
±56
Signal-to-Background ratio: 0.33 (before cut) → 11.7 (after cut)
alpha
neutron
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All phases combined D2O+Salt+NCD8B Pee(E) fit
SNO Full 3-Phase Expected improvement
Δχ2
Δχ2
Pee
day
ADN
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Conclusion & Future
Solar Neutrino Experiments A.Bellerive, ICHEP, July 2010
Great physics out of solar neutrino experiments From solving SNP to precision physics Direct evidence of solar neutrino oscillation by SNO Global solar solution favors LMA (Cl+Ga+SK+BX+SNO)
Upcoming new SK I+II+III publications (3-flavor analysis) SK-IV is capable of a lower energy threshold More precise 7Be from Borexino with more live-days soon
Δ7Be 10%→5%
Expect further improvement with SNO 3-phase analysis The only model-independent fit of solar survival probability Δ8B 4%→3.5%
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Merci !
Thank you!
Solar Neutrino Experiments A.Bellerive, ICHEP, July 2010
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Solar + KamLAND 3-flavor Overlay
Best-fit: sin213=2.00 +2.09
-1.63 x10-2
sin213 < 0.057 (95% C.L.)
Best-fit LMA point:
tan212 = 0.468
m2 = 7.59 x10-5 eV2
-0.023
+0.042
+0.21
-0.2112
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SNOSurvival
ProbabilityDAY
NIGHT
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SNOSurvival
ProbabilityDAY
NIGHT
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SNOSurvival
ProbabilityDAY
NIGHT
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SNOSurvival
ProbabilityDAY
NIGHT
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Fit to spike energy spectrum allowing energy scale to float: shift is 0±0.6%
Test of PDF shapes (distributed Rn spike)
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ijijijij
i
sc
cs
sc
iδecssccs
scU
sinand,coswhere
0010
0
00010001
00
001
10000
1313
1313
2323
23231212
1212
As in the quark sector one defines a neutrino
mixing matrix which relates the mass and
weak eigenstates
e
t
U e1 U e2 U e3
U1 U2 U 3
Ut1 Ut 2 Ut 3
1
2
3
Mixing Matrix
solar atmospheric CP violation short-baseline
6/12 4/23 20/13 Neutrino:
14/12 76/23 870/13 Quark: yes
???
Neutrino Mixing
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Active solar neutrino oscillation: 4 parameters
θ12 & θ13 mixing strength between flavor & mass eigenstates
Δm2 and Δm2
where Δm2 = m2 – m2
Δm2 ∼ Δm2
θ23 & CP phase irrelevant
Mass hierarchy with m2 > 0 is assumed! Note the small e component in 3 from atmospheric results P(→)!!!
It implies neutrinos have masses which leads to physics beyond the Minimal Standard Model
Neutrino Mass
12
21
31
j i
31
32
ij
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Solar Neutrinos
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Matter-Enhanced Neutrino Oscillations
Neutrinos produced in weak state e
Þ High density of electrons in the Sun
Þ Superposition of mass states 1, 2, 3 changes through
the MSW resonance effectÞ Solar neutrino flux detected
on Earth consists of e
+ ,t
Pee
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Phase I (D2O) Phase II (Salt+D2O) Phase III (3He+D2O)Nov. 99 - May 01 July 01 - Sep. 03 Nov. 04 - Nov. 06
γγγ
35Cl 36Cl
36Cl*
n
γ
2H 3H
3H*
n
n captures on Deuterium 2H(n,γ)3H
σ = 0.0005b 6.25 MeV single γ PMT array readout
2 tons of NaCl added n captures on Chlorine
35Cl(n,γ’s)36Cl σ = 44b
8.6 MeV multiple γs PMT array readout
n captures on 3He 3He(n,p)3H σ = 5330b
0.764 MeV(p,3H)NCD readout
n + 3He p + 3H
p3H
5 cm
n
3He
Three methods to detect neutrons
νx + d→ νx+ P + n