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