Future solar neutrino projects

Value for neutrino oscillations Value for astrophysics Current status of future solar neutrino projects Conclusions

Neutrino Champagne, Oct.19, 2009

M.NakahataKamioka observatory, ICRR, Univ. of Tokyo

Thanks to M.Chen, D.McKinsey, G.Ranucci, R.Raghavan, G.Ranucci, T.Lasserre, K.Inoue, H.Ejiri, S.Petcov, A.Kopylov, R.E.Lanou, M.Smy, Y.Takeuchi, B.Yang, M.Ikeda, Y.Koshio for information and discussion

Solar global and KamLAND reactor

Solar global

KamLAND

Do we fully understand solar neutrino oscillation?What future solar neutrino experiments can improve (or find something new) in solar neutrino oscillation?

SNO collaboration: arXiv:0910.2984

Energy dependence of the survival probability

P(

e

e)

Vacuum osc. dominant

matter osc.

(MeV)SSM spectrumpp

7Bepep

8B

P=1 - 0.5 ・ sin22

P=sin2

13N15O

17F

Current status of 8B spectrum measurement

m2=6.3x10-5eV2, tan2=0.55m2=7.2x10-5eV2, tan2=0.38

systematic errorSK-I

SNO CC (LETA)

4.5 9.5Ekin(MeV)

unoscillated MC

Oscillated MC

246 days100tons

Borexino

Dat

a/S

SM

2=21.52/15d.o.f. for flat = 22.56/15d.o.f. for LMA

Nonstandard models to predict flat spectrum

Holanda and Smirnov, Phys.Rev.D69(2004)113002.(hep-ph/0307266)

Barger, Huber and Marfatia, Phys.Rev.Lett.95:211802,2005(hep-ph/0502196)

Miranda, Tortola and Valle, JHEP 0610:008,2006.(hep-ph/0406280)

Friedland, Lunardini, Pena-GarayPLB594(2004)347(hep-ph/0402266)

Gonzalez-Garcia,Holanda,Zukanovich ,Funchal, JCAP 0806:019,2008. (hep-ph/0803.1180)

Sterile neutrino

Non standard Interaction

MaVaN

Unparticle

8B day/night asymmetry

Summary of ADN(D-N) / 0.5(D+N)

ES CC

Solar global(95%CL)

Solar+KamLAND

This is for Electron Scattering (ES). Expected Day/Night of CC is about 1.5 x ES

Day/night asymmetry is 1~5% level for the solar global solution.

~1.5% for the solar+KamLAND solution.

Current statusExpected D/N asymmetry

Sensitivity of Megaton Water Cherenkov detector8B spectrum distortion

Hep neutrino measurementEe (MeV)

Dat

a/SS

M

5 Mton·years

Correlated sys. error of SK

(energy scale error : 0.64%)

5 Mton·years

Integral spectrum

1/2 of SK

Day/Night Asymmetry

ADN= -1.5% ±0.3%(stat.) ± ??(sys.) with 5 Mton·years (sin2=0.31, m2 =7.6×10-5 eV2)

Assuming ±0.4%(sys.), error of m2 is ±~17%(1).

sin2=0.28, m2 =8.3×10-5 eV2

Estimated based on SK signal/noise ratio

Expected energy spectrum of -e scattering

With oscillation

Event rate: (/5years/10tonXe, 8.3tonNe, 7.2ton liq. Scint.)

pp: 11646 7Be: 6257 pep: 352 CNO: 651 8B: 66 (assuming 50keV threshold, BPS08(GS), tan2=0.467, m2 =7.59×10-5 eV2)

(Above 7Be energy: pep: 158 CNO: 119 )

Sensitivity of mixing angle by pp experiments

Value of13 is needed for precise determination of 12.

10 ton (Xe) detector

e scattering experiment

5 years data

Statistical error(~1%) + SSM flux error (1%)

Current error size (68% C.L.)From the SNO LETA paper

68% CL

95% CL

68% CL

95% CL

Future: with reactor 13 experiments

1 error (assuming m

23=2.3x10-3 eV2)

Double CHOOZ value from T.Lasserre

Sensitivity of mixing angle by pp experiments

Value of future solar neutrino experiments for astrophysics

Solar neutrino spectrum from standard solar model

Spectroscopic measurement byKamiokande, Super-K, SNO, Borexino

Measured by Borexino

8B is only 0.01% of all solar neutrinos.Be is 8% of all solar neutrinos.Majority of solar neutrinos, especially pp , are not measured yet.Measurement of various neutrinos, especially CNO , is important for astrophysics.

Why do solar neutrino experiments below 1-MeV?J.N.BahcallProceedings of LOWNU 2000, 172-176, e-Print: hep-ex/0106086

C. Pena-Garay and A.M.Serenelli, arXiv:0811.2424

Difference

+1.2%

+2.8%

+4.1%

-10%

-21%

-34%

-31%

-44%

In units of 1010(pp), 109(7Be), 108(pep, 13N, 15O), 106(8B, 17F), 103 hep cm-2s-1

Two solar abundances: GS98 vs AGS05Z/X = 0.0229 0.0165 Especially, C,N,O,Ne,Mg are 30~50% reduced in AGS05

BPS08: Neutrino fluxes and uncertainties

A problem in standard solar model

AGS05:Inconsistent with helioseismology…

Surface helium mass fraction

Sound speed Density

Boundary of convection zone

R/Rsun R/Rsun

c/c

Revised Solar modelAGSS09

6.03

1.44

8.18

4.64

4.85

2.07

1.47

3.48

AGSS09vs. GS98

+1.0%

+2.1%

+3.5%

-8.5%

-18%

-28%

-32%

-40%

AGSS09

0.724

0.231

Sound speed

Density

R/Rsun

c/c

AGS05

AGSS09

GS98

AGS05

AGSS09

GS98

(Serenelli et al.,astro-ph/0909.2668 ) Released on Oct.7, 2009

AGSS09 slightly improved the disagreement.But, still it does not yet reproduce heliosismology, RCZ and YS.

What is Standard Solar model• Solve evolution from zero age along the main sequence

– Using equations of hydrostatic equilibrium, mass continuity, energy

conservation, energy transformation (either by convection or radiation), and equation of state

– Input parameters of nuclear fusion cross section (S factor) and etc.

• Boundary conditions– Current mass, radius, luminosity, age of the sun

• Assumptions– Sun was chemically homogeneous at Time=0.– Initial abundances of heavy element ｓ (i.e. other than H and He) are

same as current surface abundance or meteorite.Are the assumptions correct?For example, Haxton proposed that metal depletion during planet formation. It might have lowered metal content in the solar photosphere, but keeping higher metal content in the core.(arXiv:0809.3342 [astro-ph] )

It is important to look at solar core using solar neutrinos.

8B – 7Be flux correlation

8B flux

7B

e flu

x

C.Pena-Garay, PHYSSUN workshop at Gran Sasso Oct.16-17, 2008

GS98 abundance

AGS05 abundance

With SNO LETA

M. Chen, SNOLAB workshop, Aug.2009

Preliminary

Measure CNO flux (to ±10%) and compare with solar models to differentiate high-Z / low-Z core metallicity

N13 flux vs. 8B (made by M.Chen et al.)

Currentexperiment reaction detector

SAGE e71Ga→e- 71Ge 50 ton gallium radiochemical (pp, 7Be)

Super-K e-→e- 32,000 ton water Cherenkov (8B)

BOREXINO e-→e- 100 ton Liquid scintillator (7Be, 8B, CNO)

KAMLAND e-→e- 1000 ton Liquid scintillator (7Be, 8B, CNO)

SNO+ e-→e- 1000 ton Liquid scintillator (pep, CNO)

XMASS e-→e- 10 ton Liquid Xe (pp, 7Be)

CLEAN e-→e- 50 ton Liquid Ne (pp, 7Be)

LENS e115In→e-

115Sn,e,10 ton In loaded scintillator

HERON e-→e- 10 ton super-fluid He (pp, 7Be)

MOON e100Mo→e-

100Tc()3.3 ton 100Mo foil + plastic scintillator

Lithium e7Li→e- 7Be Radiochemical, 10 ton lithium

Future/Proposed solar experiments

800kg detector(FV 100kg)

Dark matter

~20 ton detector(FV 10ton)pp, 7Be solar neutrinosDark matterDouble beta decay

Prototype detector (FV 3kg) R&D

~2.5m~1m~30cm

Confirmation of feasibility of the ~1ton detector

Under construction

finished

XMASS

神岡坑内

Water tank for cosmic ray veto,Shield gamma and neutrons ２０ｍ

１５ｍ

XMASS 800kg detector

Hall C at Kamioka

800 kg liquid XeViewed by 640 2-inch PMTs

10mx10mh water tankDistillation tower(remove Kr with 6kgXe/hour)

700L liquid Xe reservoir

Gas Xe reservoir

Hall C at Kamioka

Hmamatsu/XMASS product

Low background PMT　Ｕ : ～１．４ｍＢｑ／ＰＭＴ　Ｔｈ : ～１．９ｍＢｑ／ＰＭＴMass production of all PMTs was finished.

PMT support structure under construction. (ready by middle of November)

Preparation for XMASS 800kg detector

Construction by the end of 2009.Data taking will start early next year.

CLEAN

Schedule:

2010-2012: engineering of CLEAN2012-2015: Detector construction2015-2019: Liquid argon operation2020-2024: Liquid neon operation

Science:WIMP dark matterpp solar neutrinosSupernova neutrinos (coherent)

R&D progress:

Charcoal work well to remove impurities in neon

Neon light yield is ~30,000 ptohons/MeV (comparable to other noble liquids. ~6 p.e./keV in the full size CLEAN)

Compton edge of 511 keV gamma(measured by 3.14 liter MicroCLEAN)from D.McKinsey

from D.McKinsey

SNO+

Schedule:

2009-2010: Construction of hold-down net2009-2010: Scintillator process and purification install.Early 2011: Ready for filling liquid scintillator.2011: Commissioning and data taking

Science:

Double beta decay using Ndpep and CNO solar neutrinosGeo neutrinosReactor neutrinosSupernova neutrinosSupernova neutrinos (coherent)

Information from M.Chen

SNO+ Budget approved in June 2009.

1000 ton liquid scintillator at 6000 m.w.e. underground

SNO+ pep and CNO Solar Neutrino Signals

3600 pep events/(kton·year), for electron recoils >0.8 MeV

CNO extracted with±6% uncertainty (assuming target background levels 210Bi and 210Po, U, Th, 40K achieved) in three years

from M.Chenpep neutrino measurement uncertainty ~ 4.5%

Cylindrical cut Around muon-track

Spherical cut around 2.2 gamma to reject 11C event

Neutron production

Muon track

+12C-->11C+n+

11B+e++e

n capture (2.2 MeV)

Borexino Coll.:Phys.Rev.C74,045805(2006)

Best estimate for cosmogenic 11C is 25 cpd/100 tons (1.1 m-2h-1, <E>325 GeV) CNO:≈ 5 cpd/100 tons pep:≈ 2 cpd/100 tons Expected from SSM with oscil.

Borexino for CNO and pep

Necessity of both ES and CC experiments

Charged Current(CC) experiment: e flux measuremente scattering(ES) experiment: e + flux measurement

=0.30 for pp neutrino=0.21 for 7Be neutrino

SSM prediction

e

e

CC exp.

e

ES exp.

Total flux (exp.)

e

compare

Both of ES and CC experiments are necessary, if we want to measure total flux without relying on oscillation parameters obtained by other experiments.

From Raghavan

LENS Signal [SSM(low CNO) + LMAxDetection Efficiency

pp: =64%;7Be ^others: >85% Rate: pp 40 /y /t In 2000 pp ev. / 5y ±2.5% Design Goal: S/N ≥ 3

Access to pp spectral Shape for the first time

Signal electron energy (= Eν – Q) (MeV)

Coincidence delay time μs

Tag Delayed coincidenceTime Spectrum

Signal area

BgdS/N = 1

S/N = 3

Fitted Solar Nu Spectrum(Signal+Bgd) /5 yr/10 t In

Indium Bgd

S/N=3pp

7Be

pepCNO

7Be*;;;

115In ( 95.7%) = 6.4x1014 y

115Sn

B(GT) = 0.17; Q=114

e1

(e/)2 115.6 (e/ = 0.96)

3 497.3

115 In(p,n)100.8 (e/ =5.7)

= 4.76 s

max = 498.8

= 16 ps

= 231s

9/2+

1/2+

3/2+

7/2+

11/2-

0

497.3

612.8

713.6

7/2+ 1857

B(GT) ~0.01; Q =1362

e

115In ( 95.7%) = 6.4x1014 y

115Sn

B(GT) = 0.17; Q=114

e1

(e/)2 115.6 (e/ = 0.96)

3 497.3

115 In(p,n)100.8 (e/ =5.7)

= 4.76 s

max = 498.8

= 16 ps

= 231s

9/2+

1/2+

3/2+

7/2+

11/2-

0

497.3

612.8

713.6

7/2+ 1857

B(GT) ~0.01; Q =1362

e

The Indium Low Energy Neutrino Tag

115In ( 95.7%) = 6.4x1014 y

115Sn

B(GT) = 0.17; Q=114

e1

(e/)2 115.6 (e/ = 0.96)

3 497.3

115 In(p,n)100.8 (e/ =5.7)

= 4.76 s

max = 498.8

= 16 ps

= 231s

9/2+

1/2+

3/2+

7/2+

11/2-

0

497.3

612.8

713.6

7/2+ 1857

B(GT) ~0.01; Q =1362

e

115In ( 95.7%) = 6.4x1014 y

115Sn

B(GT) = 0.17; Q=114

e1

(e/)2 115.6 (e/ = 0.96)

3 497.3

115 In(p,n)100.8 (e/ =5.7)

= 4.76 s

max = 498.8

= 16 ps

= 231s

9/2+

1/2+

3/2+

7/2+

11/2-

0

497.3

612.8

713.6

7/2+ 1857

B(GT) ~0.01; Q =1362

e

The Indium Low Energy Neutrino Tag

LENS

3D Digital Localizability of Hit within one cube ~75mm precision vs. 600 mm (±2σ) by TOF in longitudinal modules x8 less vertex vol. x8 less random coinc. Big effect on Background Hit localizability independent of event energy

Test of double foilmirror in liq. @~2bar

New Detector Technology –hi event position localization

The Scintillation Lattice Chamber

Light channeling in 3-d totally Internally reflecting cubic Lattice GEANT4 sim. of concept.

Demonstration Acrylic Model

From R.Raghavan

MINILENSFinal Test detectorfor LENS-Under Construction in KURF

Goals for MINILENS 8kg In; 400 liter InLS-9x9x9 cellIn scintillation lattice

• Test detector technology Medium Scale InLS production Design and construction

• Test background suppression of In radiations by 10-11

Expect ~ 5 kHz In -decay singles rate; adequate to test trigger design, DAQ, and background suppression schemes

• Demonstrate In solar signal detection in the presence of high background (via “proxy”)

Direct blueprint for full scale LENS

Conclusions• We should make more efforts to improve our understanding

of solar neutrino oscillations, especially, matter effect.• So far, spectroscopic measurement was done only for 8B and

7Be neutrinos. Measurement of other solar neutrinos(especially, pp ) are important for astrophysics.

• SSM with improved metal abundance does not agree with helioseismology.

• Neutrino flux measurements of CNO, 7Be and 8B are important to investigate metal abundance in the core.

• Status and R&D of the future solar neutrino experiments were presented.