Low Energy Neutrinos Neutrino Luminosity of the Sun & LENS Neutrino Oscillation Workshop

Low Energy Neutrinos

Neutrino Luminosity of the Sun

& LENS

Neutrino Oscillation WorkshopConca Specchiulla, September 11, 2006

Christian GriebVirginia Tech

Luminosity and LENS Christian Grieb, Virginia Tech, September 2006

LENS-Sol Signal =

SSM(low CNO) + LMAx

Detection Efficiency

Rate: pp 40 pp ev. /y /t In 2000 pp ev./ 5y/10t In ±2.5% Design Specification: S/N ≥ 3

LENS Expected Result: Low Energy Solar -Spectrum

Access to pp spectral shape for

the first time

Signal (= 4.76 µs)

>98% Flux <2MeV

pp: = 64% 7Be: = 85% pep: = 90%


Test of Solar Models

Solar models predict relative intensities in the pp-chain

Reaction rates depend on temperature profile and abundances

Cross check with measured fluxes (using neutrino oscillation physics)

Data taken from John N. Bahcall, M.H. Pinsonneault, Phys.Rev.Lett.92, 121301 (2004)

Solar Neutrino fluxes at the earth according to SSM


Neutrino Inferred Solar Luminosity

Nuclear fusionreactions in the

solar core

pp-chain+ CNO cycle

H.A. Bethe Phys.Rev.55, 434 (1939)

No solar modelneeded

inferredL

J. N. Bahcall and R. Ulrich, Rev. Mod. Phys. 60, No. 2, p. 297 (1988)

Nuclear reactions in the pp-chain:


Solar Luminosity: Neutrino vs. photon

Will be met under these conditions:1. Fusion reactions are the sole source of energy production in the sun2. The sun is in a quasi-steady state (change in 40,000 years is negligible)3. The neutrino oscillation model is correct & no other physics involved;

From a single detector:

Test of astrophysics, solar model (absolute fluxes);Test of neutrino physics (LMA-MSW at low E, NSI, mass-varying s, CPT invariance, 13, …) (relative fluxes)

Measured neutrino fluxes at earth + oscillation physics

nuclear reaction rates energy release in the sun

Solar luminosityas measured by photon flux

=?

inferredL hL

Energy Balance:


Main contributions: pp 0.917Be 0.074(CNO 0.014)

8B 0.00009

Neutrino inferred Luminosity of the Sun - Experimental Status

Measured neutrino fluxes at the earth:8B (SK, SNO) known very well7Be + 8B (Cl) sensitive mostly to 8Bpp + 7Be + 8B (Ga)7Be (Borexino, Kamland – in the future)

in principle can deduce pp- fluxProblem: disentangling fluxes from individual neutrino

sources

Predicted relative neutrino fluxes at the sun (SSM):

Experimental status – No useful constraint!

37.06.01

2.03.0(inferred) 4.1/ hLL 2.02.1/(inferred) hLL

R.G.H.Robertson, Prog. Part. Nucl. Phys. 57, 90 (2006)J.N.Bahcall and C.Peña-Garay, JHEP 0311, 4 (2003)


Temperature in the Solar Core impacts Neutrino Spectra, not just relative fluxes

Neutrino Production Temperature Profile




hep:

Relative kinetic particle energies add to the Q-value of capture and fusion reactions.Not all energies contribute evenly:

32

150 91.5 TkeVE

Temperature in the Solar Core impacts Neutrino Energies, not just relative fluxes

C. Grieb and R.S. Raghavan, hep-ph/0609030 (2006)

E0

pep

pp

pp- and pep neutrino production temperatureand related Gamow peak energy:

7Be electron capture: maxwellian energy distribution shifts mean energy of 7Be line by <E> ~ 1.29 keV

32

)105.1/(73.10 70 KTkeVE

pp-fusion:Gamow Peak at

pp endpoint shifted up by ~5.2keV

Maxwellianenergydistribution XTunnelingprobability

J.N. Bahcall, Phys. Rev. D 44(6), 1644(1991)

32

)105.1/(91.5 70 KTkeVE

J.N. Bahcall, Phys. Rev. D 44(6), 1644(1991)

pep: combination, delta <E> ~ 6.6 keV

J.N. Bahcall, Phys. Rev. D 49(8), 3923 (1994)


Measurement of the Gamow Energy of pp-fusion in the sun with (improved) LENS

C. Grieb and R.S. Raghavan, hep-ph/0609030 (2006)

Top:pp- spectrum with/without Gamow shift

Bottom: Signal spectrum in LENSwith/without Gamow shift12t Indium - 6years - E/E=6% at 300keV

Measured Gamow shift in improved LENS:10000 simulations with ~3000 pp events each=1.62keV

Conclusion: Slightly improved LENS can detect the predicted Gamowshift in the pp- endpoint E=5.2keV with 95% confidence.


Background Challenge:• Indium-target is radioactive! (t = 6x1014 y)• 115In β-spectrum overlaps pp- signal Basic background discriminator: Time/space coincidence tag Tag energy: E-tag = Eβmax +116 keV Requires good spacial resolution

7Be, CNO & LENS-Cal signalsnot affected by Indium-Bgd!

LENS-Indium: FoundationsCC -capture in 115In to excited isomeric level in 115Sn

SneeIne115

s)4.76( tagdelayedsignalsolar

115 )/(

Tag: Delayed emission of (e/)+ Threshold: 114 keV pp-’s115In abundance: ~ 96%


1. Indium concentration ~8%wt (higher may be viable)2. Scintillation signal efficiency (working value): 9000 h/MeV3. Transparency at 430 nm: L(1/e) (working value): 10m4. Chemical and Optical Stability: at least 1 year5. InLS Chemistry - Robust

Basic Bell Labs Patent,filed 2001, awarded 2004

1

10

100

1000

10000

0 50 100 150 200 250

8% InLS (PC:PBD/MSB) 10800 hν / MeV

BC505 Std12000 h/MeV

In 8%-photo

Light Yield from Compton edgesof 137Cs -ray Spectra

-0.005

0.000

0.005

0.010

0.015

0.020

0.025

0.030

350 390 430 470 510 550 590 630 670 (nm)

Nor

m.

Abs

orba

nce

in 1

0 cm

L(1/e)(InLS 8%) ~ L(PC Neat) !

ZVT39: Abs/10cm ~0.001;

L(1/e)(nominally) >>20 m

InLS

PC Neat

Indium Liquid Scintillator Status

Milestones unprecedented in metal LS technology

LS technique relevant to many other applications


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 -The Scintillation Lattice Chamber

Light propagationin GEANT4

Concept


Indium --Background Topology – Space / Time coincidence

BackgroundSignal

E() -114 keV

116 keV

498 keV

115In

115Sn

e/

=4.76s

Background:

Random time and space coincidencebetween two -decays ( );Extended shower ( ) can be created by:a) 498 keV from decay to excited

state;b) Bremsstrahlungs -rays created by ;c) Random coincidence (~10 ns) of

more -decays;Or any combination of a), b) and c).

Signal Signature:

Prompt e- ( )followed bylow energy (e-/) ( )and Compton-scattered ( )

115In

β0 + n (BS) (Emax = 499 keV)

498 keV

*Cattadori et al: 2003

β1 (Emax< 2 keV)(b = 1.2x10-6)*

115Sn


Results of GEANT4 Monte Carlo simulation (cell size = 7.5cm, S/N=3)

Signal (pp) y-1 t In)-1

Bgd (In)

y-1 (t In)-1

RAW rate 62.5 79 x 1011

A. Tag in Space/Time delayed coincidence

with prompt event in vertex50 2.76 x 105

B. + ≥3 Hits in tag shower 46 2.96 x 104

C. +Tag Energy = 614 keV 44 306

D. +Tag topology 40 13 ± 0.6

Background rejection steps:

A. Time/space coincidence in the same cell required for trigger;

B. Tag requires at least three ‘hits’;C. Narrow energy cut;D. A tag topology: multi- vs. Compton shower;

Classification of events according to hit multiplicity; Cut parameters optimized for each event class improved efficiency;

Reduction by ~3.107 through

time/space coincidence

Indium --Background Discrimination


Test all the concepts and the technology developed so far & demonstrate Indium solar signal detection:MINI-LENS - 130 liter InLS scintillation lattice detector

Summary

● Indium liquid scintillator synthesis● New detector technology (Scintillation Lattice Chamber)● GEANT4 Simulation of Indium - background

Basic feasibility of In-LENS-Sol secure (10t In, 125t In-LS)

Major breakthroughs in LENS:

Science in LENS:

Measure solar -spectrum below 2MeV

Luminosity of the sun Gamow shift of pp- spectrum probes the T profile Test of Astrophysics & physics in one experiment

Next Step:


Russia: INR (Moscow): I. Barabanov, L. Bezrukov, V. Gurentsov,V. Kornoukhov, E. Yanovich;

INR (Troitsk): V. Gavrin et al., A. Kopylov et al.;

U. S.: BNL: R. L. Hahn, M. Yeh;

U. N. Carolina: A. Champagne;

ORNL: J. Blackmon, C. Rascoe, A. Galindo-Uribarri,

Q. Zeng;

Princeton U. : J. Benziger;

Virginia Tech: Z. Chang, C. Grieb, M. Pitt, R.S. Raghavan, D. Rountree, R.B.

Vogelaar;

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

New collaborators cordially invited!


Additional Slides


Signal Reconstruction• Event localization relies on

PMT hit pattern (NOT on signal timing)

• Algorithm finds best solution for event pattern to match PMT signal pattern

• System is overdetermined, hardly affected by unchannelled light

• Timing information + position shower structure


Data: Main Simulation of Indium Events with GEANT4• ~ 4x106 In decays in one cell centered in ~3m3 volume (2-3 days PC time)• Analysis trials with choice of pe/MeV and cut parameters (5’ /trial)

Indium Background Simulations and Analysis

Analysis Strategy• Primary selection - tag candidate shower events with Nhit ≥ 3• Classify all eligible events (Nhit ≥ 3) according to Nhit• Optimize cut conditions individually for each Nhit class

Main Cuts• Total energy: g2+g3• Tag topology: Distance of lone from shower


5” PMTPassiveShield Mirror 5” PMTPassiveShield Mirror

Opt segmentation cage

InLS500 mm

InLS

LS Envelope

500 mm

• InLS : 128 L

• PC Envelope : 200 L

• 12.5cm pmt’s : 108

MINILENS

Final Test detectorfor LENS


MINILENS: Global test of LENS R&D

• Test detector technology Large Scale InLS Design and construction

• Test background suppression of In radiations by 10-11

• Demonstrate In solar signal detection in the presence of high background

Direct blue print for full scale LENS


Proxy pp nu events in MINILENS from cosmogenic 115In(p,n)115Sn isomers

• Pretagged via , p tracks• Post tagged via n and 230 s delay

Gold plated 100 keV events (proxy pp), Tagged by same cascade as In- events

Demonstrate In- Signal detection even in MINILENS

Proxy pp- events in MINILENS

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Low Energy Neutrinos Neutrino Luminosity of the Sun & LENS Neutrino Oscillation Workshop

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