Transcript Slide 1

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?
•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
Two part Talk
I LENS overview- Properties relevant to
short baseline oscillations
II How to make a sensitive search for activesterile oscillations in LENS ?
LENS-Sol / LENS-Cal Collaboration
(Russia-US: 2004-)
Russia
INR (Moscow):
IPC (Moscow):
INR (Troitsk) I:
II:
I. Barabanov, L. Bezrukov, V. Gurentsov,
V. Kornoukhov, E. Yanovich
N. Danilov, G. Kostikova, Y. Krylov
J. Abdurashitov, V. Gavrin. et al.
V. Betukhov, A. Kopylov, I. Oriachov, E.Solomontin
U. S.:
BNL:
UNC:
ORNL:
Princeton U. :
SCSU:
Virginia Tech:
R. L. Hahn, M. Yeh
A. Champagne
J. Blackmon, C. Rasco, Qinlin Zeng, A. GalindoUribarri
J. Benziger
Z. Chang
C. Grieb, J. Link, M. Pitt, R.S. Raghavan,
R. B. Vogelaar,
Tagged ν –capture reaction in Indium
LENS is the only developed CC real time detector for solar neutrinos
 e 115In  e 115Sn*  2 115Sn
signal
The Indium Low Energy Neutrino Tag
e
7/2 + 1857
B(GT) ~0.01; Q  =1362
 = 231s
e1
115 In(p,n)
 = 4.76 s
B(GT) = 0.17; Q  = 114 (e/)2 115.6 (e/
 = 16 ps
++
9/29/2
115 In ( 95.7%)
 = 6.4x10 14 y
11/2 - 713.6
100.8 (e/  =5.7)
7/2+ 612.8
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 signal
Downside:
= 0.96 )
3/2 + 497.3
•
Bgd from 115In radioactivity to
( pp nu’s only) rate= 1011 x signal
Tools:
1/2 + 0
115 Sn
Unique:
• Specifies ν Energy
•
 3 497.3
 max = 498.8
delay Tag cascade
1. Time & Space coinc. Granularity
(106suppression)
2. Energy Resolution
In betas <500 keV; ∑Tag = 613 keV
3. Other analysis cuts
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
Major Progress --LENS
< Towards Hi Precision pp >
Hi Quality InLS Developed
Background Analysis Insights
New Detector Design Invented
Normalized Absorbance
•
•
•
0.05
Transparency
of InLS
0.04
10/06/05
01/23/06
03/22/06
0.03
05/31/06
0.02
8.6 m after 8
months
0.01
0
-0.01
350
Status
Design of Detector
Composition
PC based:
In content
Light attenutation L(1/e)
Signal Eff
Pe/MeV
NEW : LAB based- Similar as in
Cubic Lattice
Chamber
InLS
>8%
>10m
900
PC
Indium Mass(1900 pp/5y)
Total Mass
PMT’s
Neutrino detection eff.
S/N (β+γ (All In decay modes)
10 ton
125 ton
13,300
64% (pp)
>85% all other
~3 (pp)
>> 3 (ALL OTHER)
390
430
470
510
550
590
630
l (nm)
UV/Vis absorbance of zVt45 (pH 6.88) with time
670
Indium --Background Structure –
Space / Time coincidence
Signal
Signal Signature:
E() -114 keV
Prompt e- ( )followed by
low energy (e-/) ( )
and
Compton-scattered  ( )
->time/space coincidence
-> tag fixed energy 613keV
->compton scattered
shower
=4.76s
115In
e/
116 keV

497 keV
115Sn
115In
β1 (Emax< 2 keV)
(b = 1.2x10-6)*
β0 + n (BS)
(Emax = 499 keV)
*Cattadori et al: 2003
498 keV

115Sn
Background:
Random time and space coincidence
between 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 and Indium-Background Rates
pp
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
Technology
Indium Liquid Scintillator Chemistry Robust
LENS-Grade Properties Demonstrated in Lab Scale
Large Scale Production Next
Detector Design
Novel Scintillation Lattice Invented
Optical properties simulated and analyzed for optimal
Design
Prototypes in development
Indium Liquid Scintillator Status
Milestones unprecedented
in metal LS technology
BC505 Std
12000 h/MeV
8% InLS (PC:PBD/MSB)
10800 hν / MeV
10000
1000
LS technique relevant to
many other applications
100
In 8%-photo
10
Basic Bell Labs Patent,
Chandross & RSR. 2004
1
0
50
100
150
200
250
0.030
Norm. Absorbance in 10 cm
1. Indium concentration ~8%wt
(higher may be viable)
2. Scintillation signal efficiency
(working value): 9000 h/MeV
3. Transparency at 430 nm:
L(1/e) (working value): 10m
4. Chemical and Optical
Stability: at least 1 year
5. InLS Chemistry - Robust
Light Yield from Compton edges
of 137Cs -ray Spectra
L(1/e)(InLS 8%) ~ L(PC Neat) !
0.025
ZVT39: Abs/10cm ~0.001;
0.020
 L(1/e)(nominally) >>20 m
0.015
0.010
InLS
0.005
0.000
-0.005
PC Neat
350
390
430
470
510
550
590
630
l (nm)
670
Long Term Stability of L1/e of InLS
Sample
pH
In%
S%
zVt39
7.24
8.7
zVt40
7.22
zVt41



Abs@430nm at different time
Begin
1 Mon 3 Mon 5 Mon 8 Mon 9 Mon
64
0.001
0.002
0.003
0.009
0.012
0.013
8.4
63
0.001
0.003
0.005
0.006
0.010
--
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
--
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
New Detector Concept The Scintillation Lattice Chamber
Light propagation
in GEANT4
Concept
Test of transparent double foil
mirror in liq. @~2bar
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
Light loss by Multiple Fresnel Reflection
A small part of light crossing
a gap is reflected back and undergoes multiple reflections,
thus, suffers extra bulk absorption in the liquid
Photoelectron yield versus number of cells:
Upper limit ~1700pe/MeV (L=10m) reach via antireflective coating on films?
Adopt
1020 pe/MeV
7.5 cm cells
4x4x4m Cube
Absorption length = 10m
Real life issue--Foil Surface Roughness and
Impact on the Hit Definition
100 keV event in 4x4x4m cube, 12.5cm cells
Perfect 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
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
MINILENS
Final Test detector
for 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
LS Envelope
InLS
500 mm
Opt segmentation cage
Passive
Shield
Mirror
5” PMT
Table I: Characteristics of neutrino Sources for LENS-CAL
Source
DecayMode
/Produced by

E (keV)
Ee =
E0.114 keV
Background
37Ar
EC/ (n, a)
50.5 d
814(100%)
700
Int. Bremms. 0-814;
~S5x10-4 h/decay
EC/ (n,)
40.1 d
751 (90%)
637
320 (10%)
Imp. ’s (MeV) %??
EC(+)/ (n,)
353 d
1350 (50%)
1236
1115  (50%); 511  (2%);
Imp. ’s.
Haxton
51Cr
RSR
Kuzmin
65Zn
Louis
Alvarez
Neutrino Energy typically 700 keV
•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
LENS OFFERS
UNIQUE TEST
For Sterile Neutrinos
Already planned: LENS Cal
MCi Cr Source in LENS
Calibrate In X-section
Parasitic measurement
For sterile neutrinos
Active Sterile Osc of monoChromatic 753 keV
pure e-flavored neutrinos
Via
Spatial distribution of
Flavor Survival in ~5 m
Active-Sterile Oscillations
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
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
Statistical precision of oscillation parameter measurement in LENS
Gail Maclaughlin (Private Comm.)
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