results from sudbury neutrino observatory
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Results from Sudbury Neutrino Observatory. Huaizhang Deng University of Pennsylvania. The SNO Collaboration. Canada. Carleton University Laurentian University Queen’s University TRIUMF University of British Columbia University of Guelph University of Oxford - PowerPoint PPT PresentationTRANSCRIPT
Results from Sudbury Neutrino Observatory
Huaizhang DengUniversity of Pennsylvania
The SNO Collaboration
Canada Carleton UniversityLaurentian UniversityQueen’s UniversityTRIUMFUniversity of British ColumbiaUniversity of Guelph
University of OxfordRutherford Laboratory/ University of Sussex
Brookhaven National LaboratoryLawrence Berkeley National LaboratoryLos Alamos National LaboratoryUniversity of PennsylvaniaUniversity of Texas at AustinUniversity of Washington
U.K.
U.S.A.
Outline
• Overview of SNO experiment
• Solar neutrino results from phase I and II
• Nucleon decay limit
• Antineutrino search
• Status of phase III
Solar neutrinos
Mev73.262He24 4 eep
The Sudbury Neutrino Observatory
• 2092 meters deep underground
• 1000 tons of ultrapure D2O in a 12 meter diameter acrylic vessel
• 7000 tons of ultrapure H2O as shield
• 9500 PMTs mounted on a 18 meter diameter frame
• 40 helium proportional counters with total length of 398 m
Goals of SNO
• Solar Neutrinos:– Measure mixing parameters, especially θ12.
– Search for direct signatures of neutrino oscillation. • Day – Night Asymmetry• Spectral Distortions.
– Rare solar neutrino searches.• Solar Antineutrinos
• Neutrinos from the hep reaction.
• Other Physics:– Atmospheric Neutrino– Proton Decay– Neutron – Antineutron Oscillations.– Supernovae.
Neutrino interaction in SNO
(CC) ppde e−
(ES) xx e e−
(NC) xx pd n
Only e ,Good measurement of E ,Weak angle correlation 1-1/3cos⊙
e + 0.154(μ +) ,Some energy informationStrong angle correlationLow statistics
e + μ + ,No angle and energy informationafter thermalization
D2O phase (November 1999 – May 2001)
0.0005b MeV,6.25 E: HH ,32 nn
EnergyDistribution
(MeV)
RadialDistribution(R3, RAV=1)
SolarDirection
Distribution
Model dependent
Salt phase (July 2001 – September 2003)
EnergyDistribution
(MeV)
RadialDistribution(R3, RAV=1)
SolarDirection
Distribution
IsotropyDistribution
All new dueto multiple ’s
NC Shifted tohigher energy
NC Changeddue to larger σ
Unchanged
bsn n 44 MeV,8.6 E: 'ClCl*Cl ,363635
Model dependent
Phase III (December 2003 – 2006)
b 5330 keV, 740 E: HHe 33 pn
PMTsNCDs3He
2H
p
n
p t
or , E > 2.2 MeV
• Neutrons can be detected besides through Čerenkov light events.
• Reduce the correlation between NC and CC measurements.
Backgrounds
• Instrumental backgrounds
• Low energy ’s and ’s from U and Th decay chain
misrecontruction energy resolution
• Neutrons photodisintegration of deutrons by ’s cosmic ray muons Atmospheric neurtinos (,n) processes natural fission anti-neutrinos
• ’s (proportional counter only)
Measuring low energy background
The low energy backgroundAdd Rn in D2O (unmixed)Add Rn in D2O (mixed)Fit to the low energy events with Rn in D2O
energy
Isotropyradius
direction
Signal extraction in salt phase
Neutrino flux results
)sys()stat(21.2Φ 10.010.0-
+0.310.26-ES
+=
)sys()stat(76.1Φ 09.009.0-
+0.060.05-CC
+=
)sys()stat(39.2Φ 12.012.0-
+0.240.23-ES
+=
)sys()stat(09.5Φ 46.043.0-
+0.440.43-NC
+=
)sys()stat(59.1Φ 06.008.0-
+0.080.07-CC
+=
)sys()stat(21.5Φ 38.038.0-
+0.270.27-NC
+=
D2O phase salt phase(unit 106/cm2/s)
SSM8
meas8 )(0.23(th))exp)(04.088.0()( BB
Oscillation parameters
• Maximal mixing is excluded by 5.4σ• LMA I only at >99%
Nucleon decay limit
The invisible (N3) nucleon decay in 16O produce the de-excitation ’s
• For vanishing neutron, BR(E=6.18MeV)=44% and BR(E=7.03MeV)=2%• For vanishing proton, BR(E=6.32MeV)=41% and BR(E=7.0 MeV)=4%
For neutron modes : inv > 1.9 × 1029 yearFor proton modes : inv > 2.1 × 1029 year
n
n
nf
Rf
n
n
R
RNC
R R
RNC
R and RNC didn’t change while other parameters changedfrom D2O phase to salt phase
n
nnn
nn
nn
ff
RR
R
(Phys. Rev. Lett. 92, 102004, 2004)
Electron antineutrino search
MeV03.4 nnede
93.045.0
2
68.1 of background expectedecoincidenc tripleone
ecoincidenc double oneO)(D days 305.9 timelive
Differential limit
Integral limit at 90% CL:
Ф < 3.4 × 104 cm-2s-1
experiment Energy (MeV) Limit (%)
KamLAND 8.3-14.8 0.028
SNO 4.0-14.8 0.81
SK 8.0-20.0 0.8
LSD 8.8-18.8 1.95
Kamiokande 12.0-13.0 5.07 E (MeV)
F
lux
(cm-
1s-1
MeV
-1)
5 cm
Cu anode wire(50 m)
3He-CF4 gas mix
Fused silicainsulator
CVD nickel counterbody (0.36 mm thick)
Delay linetermination
Vectran braid
Acrylic ROV ball
Acrylic anchor ball
Length
of N
CD
Strin
gs: 9
11
m
I4 I2
J3 K3 K2 J2
J4 L4 M3 M2 L1 J1
I3 K4 M4 N2 N1 M1 K1 I1
I5 K5 M5 N3 N4 M8 K8 I7
J5 L3 M6 M7 L2 J8
J6 K6 K7 J7
I6 I8
From phase II to phase III
8/28/2003 end of salt phase start salt removal
10/3/2003 end of salt removal start 2nd D2O phase
10/27/2003 end of 2nd D2O phase old optics restored
12/3/2003 first counter deployed
2/12/2004 last counter deployed
start deployment of proportional counters
4/23/2004 removal of deployment equipment, start phase III
commissioning
10/??/2004 start of production data taking of phase III
3He 4He
Data from proportional counters
3He
2H
p
n
p t
or , E > 2.2 MeV
1.5
1.0
0.5
0.0
-0.5
86420
neutron with p-t track wire
curr
en
t
Time (μs)
20
15
10
5
0
5 4 3 2 10
track wire
curr
en
t
Time (μs)
80
60
40
20
0
10 8 6 4 20
Microdischarge
curr
en
t
Time (μs)
• p and t have total energy 764 keV
• neutron produces two particles while background has only one particle
• backgrounds come from wall
• 4He string provides pure background
Conclusions
• Measure the 8B solar flux without assumption about energy dependence of neutrino survival probability
• Restrict the mixing parameters, and exclude maximal mixing in solar sector
• New limit on invisible nucleon decay
• Commissioning helium proportional counter system
• Will run for 2.5 years with helium proportional counters.
Solar neutrino oscillation
3
2
1
1313
1313
2323
23231212
1212
0
010
0
0
0
001
100
0
0
ces
esc
cs
sccs
sc
i
ie
Flavor eigenstates are not mass eigenstates :
In vacuum
In matter
03.0sin ,24 13
2223
E
Lm s
E
LmP s
ees 4sinsin1)(
2122
122
x x
e
Z
e
e
ee
W +
e
e
mm
mm
m
m
cossin
sincos
2
1
Solar neutrino problem