active-sterile neutrino oscillations in lens c. grieb, j. link and r. s. raghavan virginia tech
DESCRIPTION
Active-Sterile Neutrino Oscillations in LENS C. Grieb, J. Link and R. S. Raghavan Virginia Tech XII Neutrino Telescopes Venice, March 8 2007. LENS is a high-resolution, real time spectrometer for low energy solar neutrinos such as pp, Be etc Why LENS for active-sterile oscillations? - PowerPoint PPT PresentationTRANSCRIPT
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Active-Sterile Neutrino Oscillations in LENS
C. Grieb, J. Link and R. S. RaghavanVirginia Tech
XII Neutrino TelescopesVenice, March 8 2007
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LENS is a high-resolution, real time spectrometer for low energy solar neutrinos such as pp, Be etc
Why LENS for active-sterile oscillations?
•Novel Technology brings unique tools in play for short baseline disappearance experiments using monoenergetic e-flavor neutrinos from a radioactive source
•Parasitic measurement to solar neutrino program—sterile neutrinos are free!
•Sensitivity highest, well beyond Miniboone projected - new physics and astrophysics irrespective of LSND and Miniboone result
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Two part Talk
I LENS overview- Properties relevant to short baseline oscillations
II How to make a sensitive search for active-sterile oscillations in LENS ?
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Russia INR (Moscow): I. Barabanov, L. Bezrukov, V. Gurentsov,
V. Kornoukhov, E. YanovichIPC (Moscow): N. Danilov, G. Kostikova, Y. Krylov INR (Troitsk) I: J. Abdurashitov, V. Gavrin. et al. II: V. Betukhov, A. Kopylov, I. Oriachov, E.Solomontin
U. S.:BNL: R. L. Hahn, M. YehUNC: A. ChampagneORNL: J. Blackmon, C. Rasco, Qinlin Zeng, A. Galindo- UribarriPrinceton U. : J. BenzigerSCSU: Z. ChangVirginia Tech: C. Grieb, J. Link, M. Pitt, R.S. Raghavan, R. B. Vogelaar,
LENS-Sol / LENS-Cal Collaboration(Russia-US: 2004-)
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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
SnSneIne115*115115 2
Tagged ν –capture reaction in IndiumLENS is the only developed CC real time detector for solar neutrinos
Unique:• Specifies ν Energy
Eν = Ee + Q Complete LE nu spectrum• Lowest Q known 114 keV access to 95.5% pp nu’s• Target isotopic abundance
~96%• Powerful delayed coinc. Tag Can suppress bgd =1011 x
signalDownside:• Bgd from 115In radioactivity to ( pp nu’s only) rate= 1011 x
signalTools:1. Time & Space coinc.
Granularity (106suppression)2. Energy Resolution In betas <500 keV; ∑Tag =
613 keV3. Other analysis cuts
signal delay Tag cascade
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Expected Result from LENS
• Background precisely and concurrently measured
• Well resolved low energy solar nu spectrum –
pp, 7Be, pep, CNO with 99+% of solar nu flux
Solar luminosity in nu’s pp spectral shape
accessible for first time
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Status
Design of Detector Cubic Lattice Chamber
Composition InLS
PC based: In contentLight attenutation L(1/e)
Signal Eff Pe/MeV NEW : LAB based- Similar as in PC
>8% >10m900
Indium Mass(1900 pp/5y) 10 ton
Total Mass 125 ton
PMT’s 13,300
Neutrino detection eff. 64% (pp)>85% all other
S/N (β+γ (All In decay modes) ~3 (pp)>> 3 (ALL OTHER)
Major Progress --LENS < Towards Hi Precision pp >• Hi Quality InLS Developed• Background Analysis Insights• New Detector Design Invented
UV/Vis absorbance of zVt45 (pH 6.88) with time
-0.01
0
0.01
0.02
0.03
0.04
0.05
350 390 430 470 510 550 590 630 670l (nm)
Nor
mal
ized
Abs
orb
ance
10/06/05
01/23/06
03/22/06
05/31/06
8.6 m after 8 months
Transparency of InLS
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Indium --Background Structure – Space / Time coincidence
Signal
E() -114 keV
116 keV
497 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 ( )->time/space coincidence-> tag fixed energy 613keV->compton scattered shower
115In
β0 + n (BS) (Emax = 499 keV)
498 keV
*Cattadori et al: 2003
β1 (Emax< 2 keV)(b = 1.2x10-6)*
115Sn
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Signal and Indium-Background Ratespp Signal
/y /t In
Bgd tot
/y /t In
Bgd A1
/y /t In
Bgd A2
/y /t In
Bgd B
/y /t In
Bgd C
/y /t In
RAW 62.5 79 x 1011
Valid tag (Energy, Branching, Shower) in Space/Time delayed coinc. with prompt event in vertex
55 2.76 x 105 8.3 x 104 2.8 x 103 1.9 x 105 43.9
+ ≥3 Hits in tag shower 49.5 6.23 x 104 5.81 x 104 2.76 x 103 1.4 x 103 43.7
+Tag Energy = 613 keV 44.4 458 0.48 5.2 445 8.0
+Shower Radius 43.9 270 0.48 5.1 264 0.73
+Hit Separation 40.2 13.3 ±0.6 0.48 4.7 8.1 0.004
Signal / Background ~3 with pp- event detection efficiency 64%Remember: only pp- events affected by Indium Background, 7Be, pep and CNO Background-free
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Technology
Indium Liquid Scintillator Chemistry RobustLENS-Grade Properties Demonstrated in Lab ScaleLarge Scale Production Next
Detector DesignNovel Scintillation Lattice InventedOptical properties simulated and analyzed for optimal DesignPrototypes in development
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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,Chandross & RSR. 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 670l (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
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Sample pH In% S%Abs@430nm at different time
Begin 1 Mon 3 Mon 5 Mon 8 Mon 9 Mon
zVt39 7.24 8.7 64 0.001 0.002 0.003 0.009 0.012 0.013
zVt40 7.22 8.4 63 0.001 0.003 0.005 0.006 0.010 --
zVt41 7.09 8.4 59 0.003 -- -- 0.008 0.009 --
zVt46 6.98 8.5 58 0.002 -- -- 0.007 0.008 --
zVt38 6.94 8.3 61 0.002 0.003 0.005 0.005 0.006 0.007
zVt47 6.92 8.0 59 0.0025 -- 0.005 -- 0.006 --
zVt45 6.88 8.2 56 0.003 0.004 0.005 0.005 0.005 --
zVt44 6.86 8.6 56 0.003 0.004 0.004 0.004 0.005 --
Long Term Stability of L1/e of InLS
The S values of the samples were found not to change with time. The L1/e of the samples synthesized at pH 6.88 were found to stabilize
in 3 months, and their L1/e have stayed > 8 m for 8 months.
Optimum value for the extraction pH ~6.88
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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 transparent double foilmirror in liq. @~2bar
New Detector Concept -The Scintillation Lattice Chamber
Light propagationin GEANT4
Concept
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Light loss by Multiple Fresnel ReflectionA small part of light crossing
a gap is reflected back and undergoes multiple reflections, thus, suffers extra bulk absorption in the liquid
Upper limit ~1700pe/MeV (L=10m) - reach via antireflective coating on films?
Adopt1020 pe/MeV7.5 cm cells
Photoelectron yield versus number of cells:
4x4x4m CubeAbsorption length = 10m
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100 keV event in 4x4x4m cube, 12.5cm cellsPerfect optical surfaces : 20 pe (per channel)Rough optical surfaces : 20% chance of non- ideal optics at every reflection 12 pe in vertex + ~8 pe in “halo”
Conclusion - Effect of non-smooth segmentation foils:• No light loss - (All photons in hit and halo counted)• Hit localization accuracy virtually unaffected
Real life issue--Foil Surface Roughness andImpact on the Hit Definition
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Can we get away with a single foil optical structure-? “Hard Lattice”
No trapped air
Easier construction
More robust
Most photons still “channeled” crit~60
Still Good event localization
Less trapping
Greater light output
Solid Teflon Segmentation
Challenges:
How to deal with “spray”?
Background rate
Trigger logic
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5” PMTPassiveShield Mirror 5” PMTPassiveShield Mirror
Opt segmentation cage
InLS500 mm
InLS
LS Envelope
500 mm
MINILENSFinal Test detectorfor LENS
Goals for MINILENS
• 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 blue print for full scale LENS
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Source DecayMode /Produced by
EkeV) Ee=
E0.114 keV
Background
37Ar Haxton
EC/ (n, 50.5 d 814(100%) 700 Int. Bremms. 0-814;~5x10-4 h/decay
51Cr RSRKuzmin
EC/ (n,) 40.1 d 751 (90%) 637 320 (10%) Imp. ’s (MeV) %??
65Zn Louis Alvarez
EC(+)/ (n,) 353 d 1350 (50%) 1236 1115 511 (2%); Imp. ’s.
Table I: Characteristics of neutrino Sources for LENS-CAL
Neutrino Energy typically 700 keV
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•Sterile neutrino tests in LENS•Unique advantages
•Put strong articial Neutrino Source into LENS•Pure, e-flavor, monochromatic neutrino line•Measure Pee as function of Distance—Disappearance Measurement•3-D location allows measurement of RADIAL dependence of Pee•All systematic, normalization and spectral peeling errors endemic in broad beam reactor spectra drop out•Measure Pee (r) with100,000 detectors, not just 2 or 3
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Already planned: LENS CalMCi Cr Source in LENSCalibrate In X-section
Parasitic measurementFor sterile neutrinos
Active Sterile Osc of mono-Chromatic 753 keVpure e-flavored neutrinos
ViaSpatial distribution ofFlavor Survival in ~5 m
Active-Sterile Oscillations
LENS OFFERSUNIQUE TESTFor Sterile Neutrinos
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Sterile Neutrinos—( Neutrinos of the wrong helicity)Physics well beyond the Standard Model
--Fourth (Fifh) mass state with high mass splitting triggered by LSND
Appearance of e flavor from μ beams at short base lines ~30m!Implies Δm2 ~ 1 eV2
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Pee = 1 − s2 (e4) s2 (41) – s2 (e5) s2( 51)
where cross terms such as s2 (e4)s2 (e5) are neglected. In (2) the mixing terms
s2( en) = sin2 2θen = [4U2 (en) (1-U2(en)]
and the frequencies s2 n1 = sin2 [(1.27Δm(n1)2 eV2 ) x L(m)/Eν(MeV)). The values of s(en) and Δm2 are from
Ref 4 (Table 1). With Δm2 = 1 eV2 and Eν ~0.753
MeV (from 51Cr), (2) full flavor recovery occurs in ~2m, directly observable in a lab-scale detector
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Statistical precision of oscillation parameter measurement in LENS
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Gail Maclaughlin (Private Comm.)
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Conclusions
•LENS offers a new and sensitive tool for searching for active-sterile nu oscillations
•The advanced sensitivity allows the search in its own right towards new physics and astrophysics
•Independent of LSND or Miniboone results
•Parasitic measurement—No extra resources needed