Solar Neutrino Experiments A Review

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

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

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

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

±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/

6

Sudbury Neutrino Observatory

FAAQ2006Alain Bellerive

e

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

The Second Piece:

First Generation Experiments

Chlorine – Gallium - Kamiokande

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

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

Arranging the Pieces:

Second Generation Experiments

SuperK – SNO - Borexino

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

•

Timeline of Super-Kamiokande

11146 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

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)

Daily Variation of SK Rate (Period I)

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

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

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

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)

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

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

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

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

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

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


12


12

Global View

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

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

2 model

Solar + KamLAND 2-flavor Overlay

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

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

32

Sudbury Neutrino Observatory

FAAQ2006Alain Bellerive

Newest stuff for summer 2010 !!!

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

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

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

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)

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

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

SNO hep neutrino sensitivity (3phase)

SSM

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

All phases combined D2O+Salt+NCD8B Pee(E) fit

SNO Full 3-Phase Expected improvement

Δχ2

Δχ2

Pee

day

ADN

Conclusion & Future


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%

Merci !

Thank you!


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

SNOSurvival

ProbabilityDAY

NIGHT

Fit to spike energy spectrum allowing energy scale to float: shift is 0±0.6%

Test of PDF shapes (distributed Rn spike)

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

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

Solar Neutrinos

53

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

54

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

Solar Neutrino Experiments A Review

Documents

Transcript of Solar Neutrino Experiments A Review