PPT - SNOLAB 2005 Workshop

Measuring the Low Energy Solar Neutrino
Spectrum
LENS-Sol
SNOLAB Workshop,
Sudbury, Aug 15, 2005
R. S. Raghavan
Virginia 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. Yanovich
INR (Troitsk)
V. Gavrin et al; A. Kopylov et al
U. S.
BNL
A.Garnov, R. L. Hahn, M. Yeh
ORNL
J. Blackmon, C. Rascoe, A. Galindo-Urribari
Princeton:
J. Benziger
U. North Carolina
A.Champagne
V. 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 +
solar signal
tag
115Sn
LENS-Sol-- Low Energy Solar Nu Spectroscopy via Indium
--Basics
The Indium Low Energy Neutrino Tag
e
7/2 + 1857
Tag: Delayed emission of 2 γ’s
B(GT) ~0.01; Q  =1362
 = 231s
e1
115 In(p,n)
 = 4.76 s
115In ( 95.7%)
 = 6.4x10 14 y
11/2 - 713.6
100.8 (e/  =5.7)
B(GT) = 0.17; Q  =114 (e/)2 115.6 (e/ = 0.96)
 = 16 ps
++
9/29/2
CC Nu Capture in 115In to
excited isomer in 115Sn
7/2+ 612.8
3/2 + 497.3
3 497.3
max = 498.8
1/2 + 0
115Sn
R.S.Raghavan/VT/June05
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
Expected Result:
LENS-Sol Signal=
[SSM(low CNO)+LMA] x
Detection Efficiency:
~10 keV det
. threshold
pp
pp ~40%; Be 85%; pep 90%
Rate: pp 25 /y /t In
Detector Resolution
Included (800 pe/MeV)
7Be
CNO
pep
For pp ± 3%, need
2000 ev. / 5y
Signal Electron Energy (MeV)
Nu- capture Signature:
Isomeric Coincidence
decay with τ =4.76 µs
Bgd measured
concurrently with signal
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
S/N=1
S/N~1 Adequate
For Precision Flux
signal
Random coinc bgd
S/N=3
NEW SCIENCE—Discovery Potential of LENS
Solar 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
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:
Astrophysics:
Precision Measurement of θ12 θ13
Sterile Neutrinos?
Is the Sun getting Hotter?
Hidden new source of energy of Sun?
R.S.Raghavan/VT/June05
LENS: Studied world wide since 1976 !
- Dramatic Progress in 20052004
 2005
or
Longitudinal modules + hybrid design
Cube lattice
longitudinal
or
non-hybrid
modular design
• In: 30 ton for 1900 pp’s /5y • In: ~14 ton for 1970 pp’s /5y
• Total mass LS: 6000 ton
• Total mass In LS : ~175 ton
• PMTs: ~200,000
• PMTs: ~6,500
( MPIK Talk at DPG 03/2004)
LENS Progress- - How?-2004

2005
Major Advances in Scintillator Chemistry
Absorption length ~ 1.5m @ 5% In
Module size:
~ 1.5m
Photoelectron yield:~ 230 pe/MeV
• Structure of internal
partial study (1 component)
only single- decay with BS
considered
> 10m @ 8% In
~ 6m
~ 900 pe/MeV
+ high energy resolution:
115In Bgd:
complete study (5-6 comps.)
multi- decays with or w/o BS
498keV  from decay to 115Sn*
(single- decay not dominant!)
• New Insights in Analysis Strategy
Old: pp-efficiency: ~ 20%
Signal/Noise:
~1
• New Detector
Design:
Hybrid
Longitudinal modules Event location analog- via PMT timing
New: ~ 45%
~3
design:
Hybrid design obsolete
Cube lattice Event location digital
Components of Indium radioactive bgd
In115
BGD
β0 , γ0 (BS)
(Emax
= 498 keV)
β1 (Emax< 2 keV)
(1.2x10-6)*
498 keV
0-300(e1)
In
Sn115
116 (g2)
SIGNAL
498(g3)
* Cattadori et al: 2003
In tag search
volume
around vertex of initial beta, occurrence of
* Cattadori
et al (2003)
Sn
a 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:
D
Only A1 considered up to 2004 !
R.S.Raghavan/VT/June05
Role of Experimental Tools
in Bgd Suppression in LENS-Sol
Signal
/ton In/y
62.5
(singles)
RAW
In Bgd
/ton In/y
A1
A2
B
75x1011
Vertex Del.Coinc.
(Granularity: 35g/ton)
+ Min 3 Hits
62.5
(Singles)
2.8x105
8.5x104 3.3x103 1.9x105
58
3x104
2.6x104 3x103
1.4x103
+Tag Energy
53.5
3x102
2
6
290
+Tag topology
32
10.6
1.6
5
4
Task of Design and Analysis is to suppress bgd by only
3x105--- NOT ~1011  Generate 4x106 events for analysis
Bgd Suppressed by a factor
Signal Loss Factor
~1011
~2
Basic Design Vectors
•Detection Technology:
In loaded liq. Scintillator (InLS) (E resln)
Advances in Scint. Chemistry
•DetectorArchitecture:
Segmented /Granularity ~1kg/100 ton
New Design
•Bgd Suppression at high Det. Efficiency
New Analysis Strategy
In LS Status (July10000
‘05) – Summary 1000
1 Indium conc. ~8 wt%
(higher may be viable) 100
2.Scintillation signal eff
(typical): 9000 hν/MeV 10
3.Transparency at 430 nm:1
L(1/e) (typical): 10 m
0
4.Chemical and Optical
Stabililty: ~ 2 years
5. InLS Chemistry Robust
(>1000 syntheses )
•Milestones unprecedented
in metal LS technology
•LS technique relevant to
wide science experiments
BC505 Std
12000 hν/MeV
InLS (PC:PBD/MSB):
10800 hν / MeV
In 8%-photo
Light Yield from Compton edges
of 137Cs γ-ray Spectra
50
100
150
200
250
ZVT27;
Abs/10cm=0.004;
L(1/e)=10.8 m
ZVT28,32: Abs/10cm=0.002;
L(1/e)~20m
PC
NEAT
•Basic Bell Labs patent
Applied 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 study
Scintillation Lattice Design Details
in this talk
R.S.Raghavan/VT/June05
NEW DETECTOR CONCEPT—
SCINTILLATION LATTICE (RSR ’93)
GEANT
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”
0.75
Vertex definition in
non-smooth optical
channels
1
0.75
1
11.75
12
1
12.5 cm cells in 4x4x4m cube
0.75
100 keV event /9000 hν/MeV
Total signal 6x16=96 pe
1
0.75
1
0.75
5x5x5m Cube
18cm cells—1100 pe/MeV
12.5cm cells 950 pe/MeV
7.5cm cells 700 pe/MeV
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
Before Cuts
BS
>450 kev
After Cuts
Bgd
Nu
Nu
Bgd
g2+g3
nu events
498
Total Tag Energy
Surviving bgd different for
different Nhit showers
New Analysis Paradigm (VT)
Apply progressively less
tight cuts for larger Nhit
Increased detection Efficiency
and lower bgd
R.S.Raghavan/VT/June05
Analysis Strategies:
Basic selection:
Events with given Nhit
Every hit in candidate event is a possible vertex with a
previous beta in that cell to mimic nu event
NEW ANALYSIS STRATEGY
Classify events according to NHit
Optimize cut conditions separately for each class
Typical LENS-Sol: DESIGN FIGS. OF MERIT (Lattice Design)
4mx4mx4m supermodules: InLS: 8% In; L(1/e) =1000cm; Y= 9000hν/MeV;
Cell
Size
(mm
x
mm x
Det
Eff
%
mm)
75
1000p
e/MeV
4x4x4
125
Nu
Bgd
Rate Rate
/T
/T In/y
In/y
64 40
13
S/N
3
Mass for
2000
ev/5y
(pp
flux3%)
T (In)
10
g2
T (InLS)
125
g2+g3
41.8
26
9
2.9
15.3
190
22
1
19.3
240
950pe/
MeV
5x5x5
180
1000
p/MeV
6x6x6
33.1 20.7
Shower Rad.
R.S.Raghavan/VT/June05
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

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