Overview of the TEXONO Research Program in Low Energy Neutrino Physics

1
Overview of the TEXONO Research Program in Low
Energy Neutrino Physics
Venktesh Singh(On behalf of the TEXONO
Collaboration)Academia Sinica, Taiwan

• Introduction
• KS Neutrino Lab. Hardware Updates
• DAQ Status in P-- III
• TEXONO Physics program
• Summary

_at_ The Sixth Particle Physics Phenomenology
Workshop (PPP6)
2
Introduction
W.C. Chang, K.C. Cheng, M.H. Chou, H.C. Hsu, C.H.
Iong, G.C.Jon, F.S. Lee, S.C.Lee, H.B. Li, V.
Singh, D.S. Su, P.K.Teng, H.T.K.Wong,  S.C. Wu
Academia Sinica, Taipei, Taiwan W.P. Lai Chung
Kuo Institute of Technology, Taipei, Taiwan C.H.
Hu, W.S. Kuo, T.R. Yeh Institute of Nuclear
Energy Research, Lungtan, Taiwan H.Y. Liao, S.T.
Lin, M.Z. Wang National Taiwan University,
Taipei, Taiwan F.K. Lin National Tsing Hua
University, Hsinchu, Taiwan Z.M. Fang, R.F.
Su Nuclear Power Station II, Kuosheng, Taiwan J.
Bao, K.J. Dong, S. Jiang, L. Hou, Y.H. Liu, H.Q.
Tang, B. Xin, Z.Y. Zhou Institute of Atomic
Energy, Beijing, China J.Li, Y. Liu, J. Nie,
Z.P.Mao, J.F.Qiu, H.Y.Sheng, P.L.Wang, X.W.
Wang, D.X.Zhao, P.P.Zhao, B.A.Zhuang Institute
of High Energy Physics, Beijing, China J.Q. Lu,
T.Y. Chen Nanjing University, Nanjing, China Y.
An, D.Z. Liu, Q. Yue, Y.F. Zhu Tsing Hua
University, Beijing, China C.Y. Chang, G.C.C.
Chang University of Maryland, Maryland, U.S.A. M.
Deniz, M. Zeyrek Middle East Technical
University, Turkey Co-Prinicipal Investigators
Ph.D. Students

• HISTORY
• Initiate Chang Chung-Yung 1996
• First Collab. Meeting/Official Start October
  1997
• First Paper October 1998
• KS Reactor Experiment Installation June 2000
• First Ph.D. Liu Yan , July 2000
• First Physics Data Taking June 2001.
• First Physics Results Dec 2002.

3
KS Neutrino Lab.
KS NPS -II 2 cores ? 2.9 GW
KS n Lab 28m from core1
4
Hardware Update
5
Reactor Neutrino Interaction Cross-Sections
P2 SM (ne) gt 3 MeV
P1 MM (ne) 1-100 keV
P3 Coh. (nN) lt 1 keV
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TEXONO Physics Program

• HPGe 1 kg
• mn Gn x2 more data from PRL
• improved background analysis
• study ne flux from reactor
• study possible nuclear transitions
• e.g. 73Ge decays by 2gs separated by
  t1/24.6 ms
• Possible reactor axion search
• Trace Radio Purity with AMS
• CsI(Tl) 186 kg
• attempt measurement of Standard Model s(nee-)
• ? sin2qw at MeV range
• Prototype ULE-HPGe 5 g see H.B. Lis talk
  on 02/01
• threshold lt 300 eV ? 100 eV
• explore potentials on nN coherent scattering
  CDM

V.Singh
7
Production of ne from Reactor
Submitted (2005)
8
Production of ne from Reactor
MCNP neutron transport simulation
Mostly rich in neutrons
? Decay back to ? stable valley
Anti-neutrino Emisson
9
MC Simulation of reactor ne Geometry description
Reactor Core Fuel elements, Cooling water,
Control rods structure Construction
materials Adopted Homogeneous distribution of
these materials Exact dimensions and material
compositions were derived according to KS Power
Plant in Taiwan Adopted Std. Watt fission
neutron spectrum parameterization as input.

• 50Cr in RC , SS Zr-alloy
• 54Fe in RC , SS Zr-alloy
• 58Ni in RC , SS Zr-alloy
• 112Sn in Zr-alloy

On average 2.5 neutrons per fission
generated !!
Absorbed by (n, fission) with fuel elements (n,
g) with core materials
Nuclear fuel material UO2 Enrichment of 235U
3 Height of the fuel rod 400cm Radius of
the fuel rod 0.45cm
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MC Simulation-source of reactor ne
Fission products
ne
Structure material
The ne-source and their yields Yn, Yn (both in
10-4) at the reactor core
The variation of the Effective multiplication
factor (Keff) parameter and ne yields Yn from
51Cr as function of control rod fraction x.
Total ne-fluxes at a 2.9 GW reactor 51Cr
7.5x1016 s-1 55Fe 2.7x1016 s-1ne/anti-ne
1.6x10-4
Isotopic abundance (IA)
Keff is define as the fraction of neutrons that
remain after every possible process in a nuclear
reactor.
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Data Analysis ne magnetic moment
No excess of events !
mn(ne) lt 1.3x10-8 mB tnm3n gt5.7x1014 eV3s
_at_90 CL
Reactor NOFF1445 hrs
Series of comparisons were made with
industry-standard calculations and actual reactor
operation data a) x0.08 at Keff1 b) the
relative fission ratio of the four fissile
elements c) the simulated neutron-spectra,
having a total flux1.8x1014 cm-2s-1 d) Yn0.59
for 238U(n,g)239U
Reactor NON 3458 hrs
NON- NOFF
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Physics Potential To enhance the ne flux
e Create radiation safety problems e
Technically feasible ready e Costs much less
than the Accelerator-based n-factory projects
The amount of necessary inserted materials as a
fraction of the fuel-element mass.
The optimal scenario is with 50Cr(pure), where
Yn0.31ne/fission, providing ne-flux of
3.3x1012cm-2s-1 at 10m from a 4.5 GW core.
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Physics Potential Detection of Elow Solar n
Flavor-specific charged-current interactions
(neNCC) would be IDEAL!
e 1 statistical accuracy with a ton-year data on
115In target e Mono-energetic ne-source To
study mixing angle q13 with better systematic
control e Optimal L0340m at Dm20.002 eV2 for
51Cr source
For sin22qW a 1 sensitivity level in 5 years
using 100 ton target i.e., comparable to the
other reactor-and accelerator based projects
!!!
10 of the 239Pu production rate leads to a 4
of the ne-flux!
_at_ 3s level at a 4.5 GW power reactor with a
maximally-loaded 51Cr-source by a 10-ton Indium
detector at 10m in 21 days !!
Simulated correlations between the fractional
changes of ne-yield (DYn) from a reactor
51Cr-source versus those for the 238U(n,g)239U
reaction (DYng)
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g
g


g
For (ne-e), both NC CC and their interference
term contribute
15
Period-2 CsI(Tl) Array 186 kg, 93 crystals
Period II Jan.28, 2003 Jan.08 2004 ( 50
days OFF 130 days ON)
Single Crystal QL Vs QR (Raw Data)
Z 0 cm
Z 40 cm
208Tl
40K
137Cs
Region of Interest for SM s(ne)
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Data Analysis Techniques
No Cut Energy Spectrum
Defining Cuts 1 General Cuts a) No Cut energy
spectrumb) Single Event Hit Single
Crystal Hit c) Cosmic ray Cut d) Rough
Z-pos. cut
SEH, SCH
SEH, SCH
SEH, SCH, Cosmic
SEH, SCH, Cosmic-ray, Z-pos
SEH, SCH
SEH, SCH
SEH, SCH
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Data Analysis Techniques
Defining Cuts2 Special Cuts a) Alpha Event
Cut (having fast decay time) Check-Alphas
are located around 2 MeV Select-event having
Time average less than 40 Nucl. Instrum.
Methods A 523, 116 (2004)
Normal Event Pulse
Alpha Event Pulse
A .
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Data Analysis Techniques
Defining Cuts3 Special Cuts a) Double Event
Cut (Left side double pulse) b a pulse !

• 232Th series
• 212Bi(ß-, 60.6min, 64) ? 212Po(a, 304ns) ? 208Pb

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Cut Summary
Cut Type All energy Above 3 MeV Efficiency (
Suppression) (Suppression) 1 Raw
data 1.00 1.00 1.002 Cosmic
ray 0.11 0.88 0.933 anti-Compton 0.70 0.86
0.994 Single Trigger 0.01 0.02 0.995
Alpha 0.10 0.83 0.956 Wrong
Trigger 0.98 6 Double Pulse 0.11 0.38 0
.99 (Left side Right side) Z-position
cut is not applied !!
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232Th Decay chain

• a- a events Selection
• Simply choose a events and inspect the time
  interval between two adjacent ones
• CutsCosmic ray veto,
• Single hit, delay timelt1s
• 220Rn --(55.6 s Ea6.405MeV)-gt
• 216Po --(0.145 s Ea6.907MeV-gt
• 212Pb

• Results

• Delaytime
• T1/20.153 sec.
• Energy
• 6.405MeV 3424.1KeV
• QF 1.87
• 6.907MeV 3775.2KeV
• QF 1.83

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Background Understanding

• From tagging event by event
• beta-alpha rate 0.43 /day/kg
• alpha-alpha rate 0.71 /day/kg
• Results
• Above 3 MeV
• 0.0043 /day/kg
• Above 3.5 MeV
• 0.0042 /day/kg

?-? delayed coincidence
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Period-II CsI(Tl) Array Results (Prilim.)
ON/OFF DATA
Energy Spectrum of recoil electron
137Cs (661 keV)
137Cs (661 keV)
Days 3.99
Days 48.35
OFF-Spectrum
40K (1461 keV)
40K (1461 keV)
ON-Spectrum
208Tl (2615 keV)
208Tl (2615 keV)
ON-OFF 0.004277 above 3.5 MeV ON-OFF
0.004305 (SM) above 3.5 MeV
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Period-II CsI(Tl) Array New way of getting
signals !!
a-event
Amplitude
g-Reference Pulse
b-event
a-Reference Pulse
Time bin
c2a gtc2g ? a-event and c2g gt c2a ? g- event
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Axion production Detection at Reactor

• Axions can be emitted through magnetic nuclear
  transitions.
• By thermal neutron capture (10B n ? 7Li a)
  in the cooling water, 7Li(1/2-) is produced.
• The decay 7Li(1/2-) ? 7Li(3/2-) ?(a) is one
  possible axion source in the reactor.

As indicated by a similar experiment, we will
use HP-Ge detector for I. Primakoff production
off the Ge nuclei II. Axion Compton production
off the electrons in detector F. T. Avignone
et al., Phys. Rev. D 37, 618 (1988).
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Axion Exclusion Plot (Estimated)
The nearer triangular part is the estimated
exclusion region in axions parameter space. Here
we only consider the Primakoff conversion of
axion from 7Li decay to photon in the HPGe
detector. And some nuclear dependent parameters
are presumed.
gaN coupling constant of axion-nucleon
(isoscalar isovector) ga? coupling constant of
axion-photon ma axion mass
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Study of possible nuclear transitions

• Event-by-Event background-free tag with PSD
• To do Reactor ON/OFF analysis on the system 1
  s before the transition
• To look for possible n-induced nuclear
  transitions

We know 70 events Origins !

Selection on ON-data
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Trace Radio-purity with AMS

• Based at AMS facilities _at_CIAE with 13 MV Tandem
• Potential Merits
• ? small samples, quick
• ? versatile on sample choice
• ? sensitive to a/b emitters
• ? sensitive to stable isotope extrapolate
  (e.g. 39K)
• ? gt103 improvements over ICP-MS
• .. once prescriptions are
  known.
• Status ? demonstrate 129I/127I lt 10-13
  g/g Preliminary
• ? Current measurement
  40K12.3x10-15 g/g in liquid scintillator
• Future ? Goal 40K 10-17 g/g
• ? 87Rb 238U / 232Th
  series after Tandem upgrade

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Summary Outlook

• TEXONO Collaboration ? Built-Up Growing
• Kuo-Sheng Neutrino Lab.
• ? Established Operational ? Modular
  Flexible Design
• ? Physics Data Taking since June 01
• ? Unique HPGe Low Energy Data
• ? Bkg Level Underground CDM Expt.
• Results published on mn (Gn)
• ? Other DAQ analyses under way
• Diversified RD Program in parallel
• ? Current Research Focus at mn (Gn) s(n-e )
  scoh(nN)
• SonoLum. CDM AMS AXION
• Reaching Out
• ?Y2L _at_ Korea/Daya Bay Project (?)/Regional
  Framework (?)
• TEXONO is (a modest) part of world neutrino
  physics community

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Thanking You !!
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