Transcript file

LENS-CAL
I. Barabanov, V. Gurentsov, V. Kornoukhov
Institute for Nuclear Research, Moscow
and
R. S. Raghavan, Virginia Tech
LONU-LENS
Blacksburg, Oct 15, 2006
Nuclear Matrix Element for Indium Neutrino Capture Reaction
The Capture Cross Section is
σ = 1.632 x10-44 x [gA2 B(GT)] We pe F(ZW)]
gA2 = 1.58
We Prompt Electron energy in mc2 units
pe Electron momentum = √ (We2 – 1)
F(Z=50, We) Fermi function
B(GT) is reduced Gamow Teller Nuclear Matrix Element
B(GT) must be calculated/ measured in Laboratory
Theoretical Estimate made in RSR original PRL paper:
Using nuclear systematics and shell model parameters of the
The In (initial) and Sn (final) states:
B(GT) ~ 0.16
:
Measurement:
J. Rapaport et al, Phys.Rev.
Letters 54, 2325 (1985)
Performed via 115In(p,n) forward
scattering at Indiana U Cyclotron
In-Sn neutrino state
Neutrino state
σ (p,n) is proportional to B(GT)
Forward (0o) neutron emission with.
Ep= 120 MeV and 200 MeV
B calibrated against B(F)= 3 for
Analog state
Result:
B(GT) (neutrino state) = 0.17 (10%)
B(GT) ~0 to states upto 4 MeV
V. good agreement with rsr theory
Neutrino Source Calibration of B(GT)
In(p,n) reaction is strong interaction reaction which measures
B(GT) via strong interactions.
Desirable to have direct weak interaction measurement of B(GT)
Direct measurement using a megCuri neutrino source.
LENS-CAL
Source Technology & Expertise developed in Russia
(SAGE detector calibration with 51Cr and 37 Ar Sources)
LENS-CAL MegaCurie source made in Russia
+ Compact In loaded detector
Operated probably in Baksan
Table I: Characteristics of neutrino Sources for LENS-CAL
Source
DecayMode
/Produced by
t
En (keV)
Ee =
En-0.114 keV
Background
37Ar
EC/ (n, a)
50.5 d
814(100%)
700
Int. Bremms. 0-814;
~S5x10-4 hn/decay
EC/ (n,g)
40.1 d
751 (90%)
637
320g (10%)
Imp. g’s (MeV) %??
EC(b+)/ (n,g)
353 d
1350 (50%)
1236
1115 g (50%); 511 g (2%);
Imp. g’s.
Haxton
51Cr
RSR
Kuzmin
65Zn
Louis
Alvarez
Neutrino Energy typically 700 keV
Source Energy ~700
keV OK for LENS-CAL
First:
No other excited state
reached. LENS tag
ensures excitation of
specific state
in daughter Sn.
Usual problem in
radiochem expts such
Ga is not present here
Second:
Energy beyond In beta
Endpoint. So double
Coincidence enough
Simplified tag analysis
Design Concepts for LENS-Cal Detector
Indium Density
Consider a neutrino source in the center of a spherical detector
The event yield Y is:
Y= σ ε ρ { S /(4π r2 )} k 4π r2 dr = σ ε k ρ R(= radius of detector)
-k = the fraction of 4π enclosed by the detector array (k ≤1)
ε = the signal detection efficiency  In foil thickness
Y varies as ρ the Indium Density.
Need design with high Indium density
In LS typically In is 8% -15%
Can this be increased?
In foil –Plastic Sandwich Stack Detector
Basic Idea of Sandwich Stack
-Use thin Indium foil sandwiched
by thin plastic bar
Thicknesses:
Indium foil Signal electron
emerge with high efficiency
Plastic thickness > range of
electron
Optimized thicknesses: In foil
70-100 mg/cm2
Plastic: 300 mg/cm2
Good for Eν ~700 keV
In Sandwich Stack Expts
Bell Labs 1979
Original Intent –pp neutrinos !
very thin In foil <10mg/cm2
plastic 160mg/cm2 ρ~60g/l
Compared to Ar source:
In foil 100mg and Plastic 300 mg
ρ~330 g/l
Sandwich stack design offers
X2.2 higher Indium density
Modules with Stacks 20x20x200cm
Light attenuation OK
Recent INR Monte Carlos Verify
LENS-CAL: Conceptual Design based on Sandwich Stack In Loading
Side view
Plan view
60
37
37 Ar
Ar
Indium = 8 tons
Plastic 25 tons.
60
37Ar
Indium 100mg/cm2
Plastic 300mg/cm2
Indium Density ρ = 0.33 g/cm3.
Plastic Module 20x20x200 max
Light guides/PMT’s
360
Preliminary Simulation Results
51Cr source with activity - 5 mCq
Neutrino cross-section capture – 3.03x10-44 cm2
In thickness 0.1 g/cm2
Scintillator slab thickness 3 mm
Threshold for neutrino electron – 450 keV
Threshold of shower energy - 300 keV.
Total In mass – 5 t
Module cross section
5*5 cm2
cm2
Neutrino detection efficiency, %
31
Background (total) per day
1.5
Number of neutrino events per 100 d
1515
Good Event Rate and Low intrinsic In Bgd.
10*10 cm2
26
2.
1271
15*15
22
4.4
1075
New Physics from LENS Cal?
Look for Sterile Neutrino Oscillations in LENS-CAL
L. Mikaelyan et al, hep-ph/0310246; Jonathan Link
LSND Δm2 ~1eV2 ~104 x Δm12 2 of reactor νe ̃
sin2 2θ ~0.1to 0.001
Test at short baselines <10m available in LENS-CAL
Kamland 105 m x10-4 (0.7/3 MeV) ~ 2m in LENS-CAL
Look for event rate distribution vs. radius in LENS-CAL
detector !
Conclusions
Preliminary Analysis Shows Indium sandwich Stack Detectors with
Technically feasible 51Cr sources are viable
Further work for:
other sources
Source Strengths ….
Revisit In LS modules lower density but higher efficiency