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Solar Neutrino Observations at the Sudbury Neutrino Observatory (SNO). Alan Poon † Institute for Nuclear and Particle Astrophysics Lawrence Berkeley National Laboratory. † for the SNO Collaboration. Outline. Introduction — the Solar Neutrino Problem (SNP)

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Solar neutrino observations at the sudbury neutrino observatory sno

Solar Neutrino Observations at

the Sudbury Neutrino Observatory (SNO)

Alan Poon†

Institute for Nuclear and Particle Astrophysics

Lawrence Berkeley National Laboratory

†for the SNO Collaboration


Outline

Outline

Introduction — the Solar Neutrino Problem (SNP)

Results from the Sudbury Neutrino Observatory

Physics Implications

Summary


Solar neutrino problem

Solar Neutrino Problem

pp Chain:4p + 2e  4He +2ne+ 26.7MeV


Solar neutrino problem1

Solar Neutrino Problem

either

Solar models are incomplete/incorrect

or

Neutrinos undergo flavor-changing oscillation

In this talk, we will demonstrate that:

Solar model prediction of the active 8B n flux is consistent with experiments

AND

Neutrinos change flavors while in transit to the Earth


Neutrino oscillation

Neutrino Oscillation

2 n

Survival :

Prob.

Note: May also have resonant flavor conversion in matter —

Mikheyev-Smirnov-Wolfenstein (MSW) effect


Sudbury neutrino observatory

2 km to surface

Sudbury Neutrino Observatory

1006 tonnes

D2O

17.8m dia. PMT Support Structure

9456 20-cm dia. PMTs

56% coverage

12.01m dia. acrylic vessel

1700 tonnes of inner shielding H2O

Urylon

liner

5300 tonnes of outer shielding H2O

NIM A449, 127 (2000)


Detecting in sno

p

n

+

+

+

-

CC

d

p

e

e

n

+

+

+

n

NC

d

p

n

x

x

ES

-

-

+

+

n

e

n

e

x

x

Detecting  in SNO

  • Measurement ofneenergy spectrum

  • Weak directionality:

CC

  • Measure total 8Bnflux from the sun

  • s(ne)= s(nm)= s(nt)

NC

  • Low Statistics

  • Sf=f(ne)+0.154 f(nm+nt)

  • Strong directionality:

ES


Smoking guns for flavor changing oscillation

Smoking Guns for Flavor Changing Oscillation

Measure:

Oscillation to active flavor if:

THIS TALK


What else can nc tell us

What else can NC tell us?

nx+ d  n + p + nx

SNO NC

  • ne disappearance and nm/t appearance in one experiment:

    • Direct measurement of the total active 8B n flux

    • No ambiguity in combining results from experimentswith different systematics (e.g. energy resolution)

  • Lowest En threshold (2.2 MeV) for real time experiments

    [No energy spectral information]

SNO CC


Solar neutrino analysis nc cc es

June 2001

NC analysis

Radius (R/RAV)3

Solar Neutrino Analysis (NC+CC+ES)

  • NC and Day-Night Analysis in Pure D2O

  • Energy: Teff > 5 MeV

  • Fiducial vol.: R < 550 cm

E Threshold

Low E Background

T>5 MeV

T>5.5 MeV

T>6 MeV

Energy 

~8 PMT hits / MeV


Nc data analysis

NC Data Analysis

Data

(Similar to high E threshold CC analysis)

Instrumental Bkg Cut

+

Reconstruction inefficiency

+

Cherenkov “likelihood”

Low Energy Background Analysis

  • Energy response

  • Reconstruction

  • (vertex)

Energy Cut

+

Fiducial Volume Cut

  • Reconstruction

  • (vertex+directional)

Signal Decomposition:

CC, NC, ES

  • Neutron response


Data reduction

Data Reduction

Nov 2, 1999 to May 28, 2001

306.4 live days  Day=128.5 days, Night=177.9 days

[c.f. High energy CC paper: 240.9 live days, 1169 candidate events]


A neutrino candidate event

A neutrino candidate event

Event Reconstruction:

Vertex, Direction,

Energy, Light Isotropy

PMT Information:

Positions,

Charges, Times


Data reduction cuts

Data Reduction Cuts

  • Removeinstrumental background using:

  • PMT time & charge distribution

  • Event time correlation

  • Veto PMT tag

  • Reconstruction information

  • Light isotropy & arrival timing

Light isotropy measure

Light arrival timing

nsignal loss:

< 3 events (95% CL)

Residual instrumental bkg. contamination:


Nc data analysis1

NC Data Analysis

Data

(Similar to high E threshold CC analysis)

Instrumental Bkg Cut

+

Reconstruction inefficiency

+

Cherenkov “likelihood”

Low Energy Background Analysis

  • Energy response

  • Reconstruction

  • (vertex)

Energy Cut

+

Fiducial Volume Cut

  • Reconstruction

  • (vertex+directional)

Signal Decomposition:

CC, NC, ES

  • Neutron response


Energy response

Energy Response

  • Calibration:

  • PMT & Optics

  • Normalized to16N [Eg=6.13 MeV]

  • Check with

    • 8Li [13 MeV b]

    • 252Cf[d(n,g), Eg=6.25 MeV]

    • 3H(p,g) [19.8 MeV g]

DE/E = ± 1.21%

Ds/s = + 4.5%

Linearity = ±0.23%@ Ee=19.1 MeV


Event reconstruction

Event Reconstruction

Example: Angular Resolution

(16N far from source)

Given:

Hit PMTs’ positions & timing

Determine event’s: (x,y,z) & (q,f)

Fiducial

volume

determination

(Ntarget=?)

Separation

of n signals from background

Tools: Triggered g and b sources


Nc data analysis2

NC Data Analysis

Data

(Similar to high E threshold CC analysis)

Instrumental Bkg Cut

+

Reconstruction inefficiency

+

Cherenkov “likelihood”

Low Energy Background Analysis

  • Energy response

  • Reconstruction

  • (vertex)

Energy Cut

+

Fiducial Volume Cut

  • Reconstruction

  • (vertex+directional)

Signal Decomposition:

CC, NC, ES

  • Neutron response


Neutron detection efficiency

Neutron Detection Efficiency

Response vs 252Cf source position

  • Calibrate using 252Cf fission source (~3.8 n per fission)

  • Capture Efficiency

  • Total:29.90 ± 1.10 %

  • With energy14.38 ± 0.53 %

  • threshold &

  • fiducial volume

  • selections

  • (T>5 MeV, R<550 cm)


Nc data analysis3

NC Data Analysis

Data

(Similar to high E threshold CC analysis)

Instrumental Bkg Cut

+

Reconstruction inefficiency

+

Cherenkov “likelihood”

Low Energy Background Analysis

  • Energy response

  • Reconstruction

  • (vertex)

Energy Cut

+

Fiducial Volume Cut

  • Reconstruction

  • (vertex+directional)

Signal Decomposition:

CC, NC, ES

  • Neutron response


Low energy background overview

Low Energy Background (Overview)

Daughters in U or Th chain

  • b decays

  • bg decays

“Photodisintegration” (pd)

g+ d  n + p

Indistinguishable from NC !

Technique:Radiochemical assay

Light isotropy

“Cherenkov Tail”

Cause: Tail of resolution, or

 Mis-reconstruction

Technique: U/Th calib. source

 Monte Carlo

Must know U and Th concentration in D2O


Measuring the u and th concentration in water

Measuring the U and Th Concentration in “Water”

I.Ex-situ (Radiochemical Assays)

  • Count daughter product decays: 224Ra, 226Ra, 222Rn

    II.In-situ (Low energy physics data)

  • Statistical separation of 208Tl and 214Bi using light isotropy


Le background summary

LE Background Summary

For Te 5 MeV, R<550cm

[c.f.: 2928 n candidates]

12% of the number of observed NC neutrons assuming standard solar model n flux


Nc data analysis4

NC Data Analysis

Data

(Similar to high E threshold CC analysis)

Instrumental Bkg Cut

+

Reconstruction inefficiency

+

Cherenkov “likelihood”

Low Energy Background Analysis

  • Energy response

  • Reconstruction

  • (vertex)

Energy Cut

+

Fiducial Volume Cut

  • Reconstruction

  • (vertex+directional)

Signal Decomposition:

CC, NC, ES

  • Neutron response


Extracting the n signals

OR

+

Df

Extracting the n Signals

Max. Likelihood Fit

  • PDFs:

  • kinetic energyT, event location R3,

  • and solar angle correlation cosq


Signal extraction results

Signal Extraction Results

Assume standard 8B n spectrum

Null hypothesis:

no neutrino flavor mixing

+61.9

-60.9

CC1967.7events

NC576.5events

ES263.6events

+49.5

-48.9

+26.4

-25.6


Flux uncertainties shape constrained

Flux Uncertainties (Shape constrained)

%

fCC

fNC

fmt


Solar n flux summary

NCSNO(2002)

ESSNO (2001)

ESSNO (2002)

CCSNO(2001)

CCSNO (2002)

Solar n Flux Summary

8B from CCSNO+ESSK (2001)

Constrained

CC shape

5.3s

Unconstrained

CC shape

Null hypothesis rejected at 5.3s

F(ne+nm+nt)

F(ne)

F(ne)+0.15F(nm+nt)

STRONG Evidence for

ne nm and/or nt


Disappearance and reappearance

Note:

Disappearance and Reappearance

Solar Model predictions

are verified: [in 106 cm-2 s-1]


Day flux vs night flux

Day Flux vs Night Flux

Day

Night

  • Day: cos qzenith>0 (128.5 days)

  • Night: cos qzenith<0 (177.9 days)

  • 8B shape constrained extraction

NC

ES

CC

 in units of x106 cm-2 s-1


Day night uncertainties

Day-Night Uncertainties

%

The day-night analysis is currently statistics limited


Global solar n analysis

Global Solar n Analysis

  • Inputs:• 37Cl, latest Gallex/GNO, new SAGE, SK 1258-day day & night spectra

    • SNO day spectrum (total: CC+NC+ES+background)

    • SNO night spectrum (total: CC+NC+ES+background)

    • 8B floats free in fit, hep n at 1 SSM

m2>m1

m1>m2

Global

SNO Day and Night spectra


Global n analysis fit results

Global n Analysis Fit Results

  • SNO CC/NC measurement directly constrains the survival probability at high energy

    • forces LOW solution to confront the Ga experimental results:

[Experimental results: SK=2.32x106 cm-2 s-1, Ga=72.0±4.5 SNU, Cl=2.56±0.23 SNU]


Neutrino mixing what do we know now

Neutrino Mixing: What do we know now?

Atmospheric n

Uai =

CHOOZ

Solar n LMA

Present situation:

Solar nemix with


Ckm vs mnsp

CKM vs MNSP

Contrast between VCKM (quark) and UMNSP (lepton)

[B  Big s=small ]


Present status future of sno

Present Status & Future of SNO

The Salt Phase

Neutral Current Detectors

3He proportional counters

n3He  p  t

  • 2 tonnes of NaCl added to D2O

  • Higher n-capture efficiency

  • Higher event light output

  • Light isotropy differs from e-

  • Running since June 2001

  • To be deployed in early 2003

  • Event-by-event separation of n


Sno summary

SNO Summary

  • Newest SNO results :

  • • nenm or nt appearance at 5.3 s

  • • Total 8B n flux measured for En>2.2 MeV

  • SSM prediction for total active 8B n flux verified

  • Day-Night results consistent with MSW hypothesis

  • Global fit including the newest SNO results :

  • • LMA highly favored (Dm2 ~ 5.0 x 10-5 eV2)

  • • No “dark side” and not maximal mixing (m1>m2, tan2(q)<1)

  • • Predictions for Borexino & KamLAND

The NC and Day-Night papers (in July 1 issue of PRL), along with a HOWTO guide on using the SNO results are available at the official SNO website:

http://sno.phy.queensu.ca


The sno collaboration

The SNO Collaboration

G. Milton, B. Sur

Atomic Energy of Canada Ltd., Chalk River Laboratories

S. Gil, J. Heise, R.J. Komar, T. Kutter, C.W. Nally, H.S. Ng,

Y.I. Tserkovnyak, C.E. Waltham

University of British Columbia

J. Boger, R.L Hahn, J.K. Rowley, M. Yeh

Brookhaven National Laboratory

R.C. Allen, G. Bühler,H.H.Chen*

University of California, Irvine

I. Blevis, F. Dalnoki-Veress, D.R. Grant, C.K. Hargrove,

I. Levine, K. McFarlane, C. Mifflin, V.M. Novikov, M. O'Neill,

M. Shatkay, D. Sinclair, N. Starinsky

Carleton University

T.C. Anderson, P. Jagam, J. Law, I.T. Lawson, R.W. Ollerhead,

J.J. Simpson, N. Tagg, J.-X. Wang

University of Guelph

J. Bigu, J.H.M. Cowan, J. Farine, E.D. Hallman, R.U. Haq,

J. Hewett, J.G. Hykawy, G. Jonkmans, S. Luoma, A. Roberge,

E. Saettler, M.H. Schwendener, H. Seifert, R. Tafirout,

C.J. Virtue

Laurentian University

Y.D. Chan, X. Chen, M.C.P. Isaac, K.T. Lesko, A.D. Marino,

E.B. Norman, C.E. Okada, A.W.P. Poon, S.S.E Rosendahl,

A. Schülke, A.R. Smith, R.G. Stokstad

Lawrence Berkeley National Laboratory

M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky,

M.M. Fowler, A.S. Hamer, A. Hime, G.G. Miller,

R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters

Los Alamos National Laboratory

J.D. Anglin, M. Bercovitch, W.F. Davidson, R.S. Storey*

National Research Council of Canada

J.C. Barton, S. Biller, R.A. Black, R.J. Boardman, M.G. Bowler,

J. Cameron, B.T. Cleveland, X. Dai, G. Doucas, J.A. Dunmore,

A.P. Ferarris, H. Fergani, K. Frame, N. Gagnon, H. Heron, N.A. Jelley, A.B. Knox, M. Lay, W. Locke, J. Lyon, S. Majerus, G. McGregor,

M. Moorhead, M. Omori, C.J. Sims, N.W. Tanner, R.K. Taplin,

M.Thorman, P.M. Thornewell, P.T. Trent, N. West, J.R. Wilson

University of Oxford

E.W. Beier, D.F. Cowen, M. Dunford, E.D. Frank, W. Frati,

W.J. Heintzelman, P.T. Keener, J.R. Klein, C.C.M. Kyba, N. McCauley, D.S. McDonald, M.S. Neubauer, F.M. Newcomer, S.M. Oser, V.L Rusu,

R. Van Berg, P. Wittich

University of Pennsylvania

R. Kouzes

Princeton University

E. Bonvin, M. Chen, E.T.H. Clifford, F.A. Duncan, E.D. Earle,

H.C. Evans, G.T. Ewan, R.J. Ford, K. Graham, A.L. Hallin,

W.B. Handler, P.J. Harvey, J.D. Hepburn, C. Jillings, H.W. Lee,

J.R. Leslie, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat,

T.J. Radcliffe, B.C. Robertson, P. Skensved

Queen’s University

D.L. Wark

Rutherford Appleton Laboratory, University of Sussex

R.L. Helmer, A.J. Noble

TRIUMF

Q.R. Ahmad, M.C. Browne, T.V. Bullard, G.A. Cox, P.J. Doe,

C.A. Duba, S.R. Elliott, J.A. Formaggio, J.V. Germani,

A.A. Hamian, R. Hazama, K.M. Heeger, K. Kazkaz, J. Manor,

R. Meijer Drees, J.L. Orrell, R.G.H. Robertson, K.K. Schaffer,

M.W.E. Smith, T.D. Steiger, L.C. Stonehill, J.F. Wilkerson

University of Washington


Solar neutrino observations at the sudbury neutrino observatory sno

Supplementary slides from this point on


How to solve the solar neutrino problem

How to solve the Solar Neutrino Problem?

PRL 55, 1534 (1985)


Recap t e 6 75 mev

Recap [Te > 6.75 MeV]

Result 1: nenm,t

SK ES (1s)

Excludes:

pure nensterile at 3.1 s

1.6 s

3.3 s

Result 2:

Solar model predictions

are verified


Bifurcated analysis

Bifurcated Analysis

Bifurcated analysis

  • Use a subset of the Pass 0 cuts and the HLC as two independent cuts

  • Number of residual instrumental background event = K = y1y2fB

  • K < 3 events (95% CL)

Pass Cut 1: a+c = a1fn + y1fB

Pass Cut 2: a+b = a2fn + y2fB

Pass Cuts 1&2:a = a1a2fn + y1y2fB

Total Data: S= fn + fB

ai=neutrino acceptance for cut i

yi=leakage of background for cut I

fn=number of neutrino events

fB=number of background events


Understanding the detector response

  • Charge Pulsers

  • Pulsed Laser

  • 16N

  • 3H(p,g)4He

  • 8Li

  • 252Cf

  • U/Th Background

Electronic

337nm to 620 nm

6.13 MeV g’s

19.8 MeV g’s

<13.0 MeV b’s

neutrons

214Bi & 208Tl b-g’s

Understanding the Detector Response

Monte Carlo

  • Cherenkov production (e-, g)

  • Photon propagation and detection

  • Neutron transport and capture

  • Event Reconstruction

Calibration


Energy calibration uncertainties

Energy Calibration Uncertainties

Absolute Energy Calibration Uncertainties

Energy Response

functions


Solar neutrino observations at the sudbury neutrino observatory sno

Neutron Capture Efficiency

252Cf source data

Measured:

n capture on d (uniform source)

29.9 ± 1.1 %


Pd background from d 2 o av h 2 o radioactivity

pd background from D2O, AV, H2O radioactivity

[c.f. SSM ~ 2 detected n d-1]

The photodisintegration background is small compared to the SSM expectation


U and th in on the acrylic vessel

U and Th in/on the Acrylic Vessel

  • Original Target (2 ppt): 60 mg Th or U

  • Bulk acrylic assayed (NAA)

  • Dust concentration on inner and outer surfaces measured prior to filling

  • Hot spot (“Berkeley Blob”) found in Cherenkov data

Z vs X projection

[c.f. SSM ~ 2 detected n d-1]


Cherenkov tail d 2 o

Cherenkov Tail — D2O

  • Monte Carlo of detector response well calibrated in the D2O region

  • Determine Cherenkov tail background due to D2O radioactivity by Monte Carlo, using the U and Th concentration obtained above.

  • MC predictions cross checked with a Th calibration source

T>5 MeV, R<550cm:


Cherenkov tail

Cherenkov Tail

  • Determined from U/Th source calibration and Monte Carlo

  • Consistent with expectation based on measured U and Th concentration

For Te 5 MeV, R<550cm

[c.f.: 2928 n candidates]


A e vs a total

Using:

Ae vs Atotal

  • Signal Extraction in fCC, fNC, fES :

  • Signal Extraction in fe, fTotal :

    • [fTotal = fe +fm+ft]

  • Signal Extraction in fe, fTotal +Atotal=0:


Does the sun shine brighter at night

Does the sun shine “brighter” at night?

T>5 MeV

R<550 cm

  • Data divided into two sets

  • (to test statistical bias)

  • Sub-divide data into two zenith angle bins:

    • Day: cos qz>0 (128.5 days)

    • Night: cos qz<0 (177.9 days)

  • Extract fCC, fNC, and fES in these 2 bins

  • (8B shape constrained fit)

Night-Day

Day: 9.23±0.27 events d-1

Night: 9.79±0.24 events d-1

*Signal and background included


Systematic uncertainties d n

Systematic Uncertainties (D-N )

Shape constrained

The D-N analysis is currently statistics limited


Cosmological implications

Cosmological Implications

1. SNO + CHOOZ: | m12-m22 | < 10-3 eV2

  • 2. Super-Kamiokande: | m22-m32 | ~ 2.510-3 eV2

  • 3. 3H b decay (Mainz exp.): |Ue1|2m12+ |Ue2|2m22 < (2.2)2 eV2

Sum of neutrino masses mn: 0.05 <  mn < 6.6 eV

Limit on closure density  0.001 <  < 0.14


Salt phase

Salt Phase

Detector is in GOOD shape

Injection

Ended

Salt Injected on

May 28, 2001

24Na Background

Injection

began

t1/2=15 hrs

Counts

The NaCl brine in the underground buffer tank was activated

by neutrons from the rock wall. We observed the decay of 24Na after the brine is injected in the SNO detector.

-200

-100

0

100

200

Time Since Salt Injection (hrs)


N in the standard electroweak model i

n in the Standard Electroweak Model (I)

Quark Sector

Lepton Sector


N after april 2002

n After April 2002

Accelerator n

MiniBoone

Atmospheric n

MINOS

Off-axis expt.

Solar n

SNO

KamLAND

Borexino

Outstanding Issues

• Precision determination of parameters, 3 family mixing

• Absolute n mass scale

• Sterile neutrinos?

• Modifications to Standard Model

• Origins of n mass

H. Murayama

Hitoshi Murayama


Prediction for kamland

Prediction for KamLAND

Global fit:

LMADm2=5x10-5 eV2


Lma solution

LMA Solution?

  • LARGE MIXING SCENARIO?

  • KamLAND (Kamioka, Japan)

    reactor n @ “right” baseline for probing the currently favored LMA region

1 kt liquid scintillator as target

2x coincidence

Alan Poon, SLAC Summer Institute Topical Conference (2002)


Reactor n physics at kamland

Reactor n physics at KamLAND

  • No oscillation scenario, expect:

  • ~150 events in 3 months

  • If LMA, expect:

  • ~110 events in 3 months

  • ~ 3s statistical significance in 3 months

Data taking began on

Jan. 22, 2002

Alan Poon, SLAC Summer Institute Topical Conference (2002)


Low solution

  • LOW: large D-N asymmetry in 7Be flux

  • Borexino (Gran Sasso, Italy)

LOW solution?

Bahcall et al. hep-ph/0204314

300t liquid scintillator as target. Measure the 7Be n flux by elastic scattering:

n + e n + e

Very stringent radioactive background requirements

Data-taking will begin in 2003

Borexino prototype (“Counting Test Facility”)

Alan Poon, SLAC Summer Institute Topical Conference (2002)


Low e solar n experiment

Low E solar n experiment

  • Goals:

  • Precision measurement of q12, test unitarity of MNSP matrix

  • Constrain on active-sterile n mixing

  • Test of solar models

Alan Poon, SLAC Summer Institute Topical Conference (2002)


Future solar n experiments

Future solar n experiments

Nakahata, LowNu2002

Alan Poon, SLAC Summer Institute Topical Conference (2002)


Future experiments

Future Experiments

Alan Poon, SLAC Summer Institute Topical Conference (2002)


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