Measuring the Low Energy Solar Neutrino SpectrumLENS-Sol

SNOLAB Workshop, Sudbury, Aug 15, 2005

R. S. RaghavanVirginia Tech

LENS-Sol / LENS-Cal Collaboration (US-Russia) (2004---)

Russia:Institute of Nuclear Research (INR Mosow)I. Barabanov, L. Bezrukov, V. Gurentsov, V. Kornoukhov, E. YanovichINR (Troitsk)V. Gavrin et al; A. Kopylov et al

U. S.BNLA.Garnov, R. L. Hahn, M. YehORNL J. Blackmon, C. Rascoe, A. Galindo-UrribariPrinceton:J. BenzigerU. North CarolinaA.ChampagneV. T. Z. Chang, C. Grieb, M. Pitt, RSR, R.B. Vogelaar

R.S.Raghavan/VT/June05

LENS-Sol GOAL: Experimental Measurement of the Neutrino Luminosity of the Sun (3-4%)

Measure the low energy neutrino spectrum (pp, Be, …) in real time & with precision

Exptal Tool: Tagged CC Nu Capture in Indium

νe + 115In e- + (delay) 2 γ + 115Sn

solar signal 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

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-Sol-- Low Energy Solar Nu Spectroscopy via Indium --Basics

CC Nu Capture in 115In to excited isomer in 115Sn

Tag: Delayed emission of 2 γ’s

Threshold: 114 keV pp Nu

115In abundance: ~96%

Basic Bgd Challenge:Natural β-radioactivity of In•In β-Spectrum overlaps pp signal (Be, CNO not affected• β max energy = tag energy

R.S.Raghavan/VT/June05

LENS-Sol Signal= [SSM(low CNO)+LMA] xDetection Efficiency:

pp ~40%; Be 85%; pep 90%Rate: pp 25 /y /t In

For pp ± 3%, need 2000 ev. / 5y

Signal Electron Energy (MeV)

Expected Result:

Nu- capture Signature: Isomeric Coincidence decay with τ =4.76 µsBgd measured concurrently with signal

S/N~1 AdequateFor Precision Flux

S/N=1

S/N=3

2000 pp events (0-10 µs) generated:Fit S=2044±62; (3.1%) S/N=1 (in 0-10µs)Fit S=2031±51; ( 2.5%) S/N=3

Random coinc bgd signal

pp 7Be

pepCNO

Detector ResolutionIncluded (800 pe/MeV)

~10 keV det. threshold

NEW SCIENCE—Discovery Potential of LENSSolar Nu spectrum <5 MeV Yet UNOBSERVED after 40 y of solar nu’s !!!

APS Nu Study 2004 Lo Energy Solar Nu Spectrum: one of 3 Priorities

R.S.Raghavan/VT/June05

In First two years of Data (No source Calib needed)• Proof of MSW LMA Physics from Pee of pp & Be nu --No proof yet! (no d/n effect, spectral shape a problem?)• Non-standard Fundamental Interactions?• CPT Invariance of nus ?• RSFP/ Nu magnetic moments—Time dependence?

In Five Years (with source Calib): pp Be fluxes measured to 3%First Exptal test of Neutrino Luminosity Photon Luminosity Ultimate test of Neutrino Physics and Solar Astrophysics Neutrino Physics: Precision Measurement of θ12 θ13

Sterile Neutrinos?Astrophysics: Is the Sun getting Hotter? Hidden new source of energy of Sun?

LENS: Studied world wide since 1976 !- Dramatic Progress in 2005-

2004 2005

Longitudinal modules + hybrid design

• In: 30 ton for 1900 pp’s /5y

• Total mass LS: 6000 ton

• PMTs: ~200,000

or

Cube lattice or non-hybrid longitudinal modular design

• In: ~14 ton for 1970 pp’s /5y

• Total mass In LS : ~175 ton

• PMTs: ~6,500 ( MPIK Talk at DPG 03/2004)

LENS Progress- - How?--

Major Advances in Scintillator Chemistry Absorption length ~ 1.5m @ 5% In > 10m @ 8% In Module size: ~ 1.5m ~ 6m Photoelectron yield:~ 230 pe/MeV ~ 900 pe/MeV + high energy resolution:

• Structure of internal 115In Bgd: partial study (1 component) complete study (5-6 comps.) only single- decay with BS multi- decays with or w/o BS considered 498keV from decay to 115Sn*

(single- decay not dominant!)

• New Insights in Analysis Strategy Old: pp-efficiency: ~ 20% New: ~ 45% Signal/Noise: ~ 1 ~ 3

• New Detector design: Design: Hybrid Hybrid design obsolete Longitudinal modules - Cube lattice - Event location analog- via PMT timing Event location digital

2004 2005

Components of Indium radioactive bgd

In115

Sn115

β0 , γ0 (BS) (Emax = 498 keV)

β1 (Emax< 2 keV)(1.2x10-6)*

498 keVBGD

0-300(e1)

116 (g2)

498(g3)

In SIGNAL

R.S.Raghavan/VT/June05

* Cattadori et al (2003) SnIn tag search volume around vertex of initial beta, occurrence ofa random event with minimum Nhit =3 1 beta decay: A1 = beta + BS gamma (Etot = 498 keV) A2 = 498 gamma 2 beta decays in random coinc: B = beta, BS or 498 in any

combination from each beta decay 3 beta decaysin random coinc : C = 3 betas mostly 4 beta decays in random coinc: DOnly A1 considered up to 2004 !

* Cattadori et al: 2003

451.610.632+Tag topology

290623x10253.5+Tag Energy

1.4x103

1.9x105

B

3x103

3.3x103

A2

2.6x104

8.5x104

A1

3x10458+ Min 3 Hits

2.8x105

75x1011

(Singles)

In Bgd

/ton In/y

62.5Vertex Del.Coinc. (Granularity: 35g/ton)

62.5

(singles)

RAW

Signal

/ton In/y

Bgd Suppressed by a factor ~1011

Signal Loss Factor ~2

Task of Design and Analysis is to suppress bgd by only 3x105--- NOT ~1011 Generate 4x106 events for analysis

Role of Experimental Tools in Bgd Suppression in LENS-Sol

Basic Design Vectors

•Detection Technology: In loaded liq. Scintillator (InLS) (E resln)Advances in Scint. Chemistry

•DetectorArchitecture: Segmented /Granularity ~1kg/100 tonNew Design

•Bgd Suppression at high Det. EfficiencyNew Analysis Strategy

1

10

100

1000

10000

0 50 100 150 200 250

InLS (PC:PBD/MSB): 10800 hν / MeV

BC505 Std12000 hν/MeV

In 8%-photo

Light Yield from Compton edges of 137Cs γ-ray Spectra

PCNEAT

ZVT27; Abs/10cm=0.004; L(1/e)=10.8 m

ZVT28,32: Abs/10cm=0.002; L(1/e)~20m

In LS Status (July ‘05) – Summary1 Indium conc. ~8 wt% (higher may be viable)2.Scintillation signal eff (typical): 9000 hν/MeV3.Transparency at 430 nm: L(1/e) (typical): 10 m4.Chemical and Optical Stabililty: ~ 2 years5. InLS Chemistry Robust (>1000 syntheses )

•Milestones unprecedented in metal LS technology•LS technique relevant to wide science experiments•Basic Bell Labs patentApplied 2001; awarded: 2004 R.S.Raghavan/VT/Aug 05

Detector Design:---Segmented

Objective: Moderate Granularity (~1kg/100 T)

Two Approaches for close packed architecture: •Longitudinal Modules (1-D) (“classical”)•Scintillation Lattice “chamber” (3-D) (new)

Both Designs under studyScintillation Lattice Design Detailsin this talk

R.S.Raghavan/VT/June05

GEANT

NEW DETECTOR CONCEPT—SCINTILLATION LATTICE (RSR ’93)

Concept Simulation: ideal optics

•Light output 75% (6PMT) vs 50% (2PMT) in long. modules•Precise 3D Digital Event Localization ~10cm v. 60 cm (±2σ) in longitudinal modules•Event localization independent of event energy •Particle tracks, γ-ray shower structure directly seen

•reconstructed hit times reduced randoms

Perfect optical surfaces Ideal optics: 20 pe

rough optical surfaces:20% of light with non-ideal optics:12 pe in vertex + 4pe in “halo”

1211

1

10.750.75

0.75

0.75

11.75 1 0.751211

1

10.750.75

0.75

0.75

11.75 1 0.75

Vertex definition in non-smooth optical channels

12.5 cm cells in 4x4x4m cube

100 keV event /9000 hν/MeV

Total signal 6x16=96 pe

7.5cm cells 700 pe/MeV

12.5cm cells 950 pe/MeV

18cm cells—1100 pe/MeV

5x5x5m Cube

Analysis

Basic Constraining Tools: (key for (A1, A2)

1. Total Shower Energy of tag candidate (g2 energy in vertex wide open)

2. No. of hits in tag candidate shower

(key for B, C, D…) 3. Shower sphere radius 4. Maximum inter-hit distance 5. e1-g2 coincidence window 10µs

R.S.Raghavan/VT/June05

nu events

g2+g3

Total Tag Energy

BS>450 kev

498

Before Cuts

Nu

Bgd

After Cuts

Nu

Bgd

Surviving bgd different fordifferent Nhit showersNew Analysis Paradigm (VT)Apply progressively less tight cuts for larger NhitIncreased detection Efficiency and lower bgd

R.S.Raghavan/VT/June05

Analysis Strategies:

Basic selection: Events with given NhitEvery hit in candidate event is a possible vertex with a previous beta in that cell to mimic nu event

NEW ANALYSIS STRATEGYClassify events according to NHitOptimize cut conditions separately for each class

19.3

15.3

10

Mass for

2000 ev/5y

(pp flux3%)

T (In)

22

9

13

Bgd

Rate /T In/y

20.7

26

40

Nu Rate /T In/y

33.1

41.8

64

Det Eff

%

1801000

p/MeV

6x6x6

125950pe/MeV

5x5x5

751000p

e/MeV4x

4x4

Cell

Size (mm x mm x

mm)

2401

1902.9

1253

S/N

T (InLS)

Typical LENS-Sol: DESIGN FIGS. OF MERIT (Lattice Design)4mx4mx4m supermodules: InLS: 8% In; L(1/e) =1000cm; Y= 9000hν/MeV;

R.S.Raghavan/VT/June05

g2

g2+g3

Shower Rad.

R.S.Raghavan/VT/June05

Summary•Major breakthroughs in• In LS technoloy• Detector Design• Analysis and Background Simulations Conceptual feasibility of In-based LENS secure

Simple Small ( < 10 t In /125 ton InLS) LENS in view

•Next Steps—Work in Progress

•Chemical Technology of large scale InLS production•Detector construction technology•

R.S.Raghavan/VT/June05

VT-NRL Low Bgd Laboratory @ Kimballton Mine VA