T2KK sensitivity as a function of L and Dm2

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T2KK sensitivity as a function of L and Dm2

• Kimihiro Okumura (ICRR Univ. of Tokyo)

2nd International Workshop on a Far detector in
Korea for the J-Parc Neutrino Beam
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Introduction

• Merit of Korea detector
• larger CP phase effect by a factor of 3
• large energy dependence of P(nm?ne) vs P(nm?ne)

Distance from the target (km)
SK/HK 295km
Korea 1000km
JPARC
2.5deg.off-axis beam _at_Kamioka
K. Hagiwara Nucl. Phys. Proc. Suppl. 137 84 (2004)
Off-axis angle
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Expected physics for T2KK
Ishitsuka et al. PRD72 033003 (2005)
CP violation
Mass hierarchy
4MW 2.5deg OA beam 4yr for n 4yr for n
Kamioka only 0.54Mton
KamKorea 0.270.27Mton

• Mass hierarchy can be determined for
  sin22q13gt0.055 (3s) for any d
• Sensitivity for CP violation is kept or enhanced
  for sin22q13gt0.01

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T2KK sensitivity study

• We have investigated optimized conditions for
  mass hierarchy and CP violation sensitivities
• Previous studies
• detector mass ratio of Kamioka and Korea
  detectors ? 11
• neutrino anti-neutrino running time ?
  4yr 4yr
• uncertainties due to matter density, detector
  systematic error, sin2q23
• Updates for this conference
• baseline length (L)
• uncertainty due to Dm232
• beam off-axis angle

? this talk
? Fannys talk
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Improvement of analysis method

• Analysis method is based on that used in
  previous analysis, but some improvements has been
  added
• detector energy response (Eture ? Erecon) using
  matrix method
• flux spectrum shape for Korea detector
• energy-dependence in ne CC non-QE interaction

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Calculation of P(nm?ne) signal spectrum
CC QE
CC non-QE
f(En) neutrino beam spectrum s(En) cross
section e(En) event selection efficiency S(En,
Enrecon) detector response function
Analytical calculation is adopted with
consideration of selection efficiency and energy
response of SK
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Energy response function
ne CCQE
ne CCnQE
Reconstructed Neutrino Energy
True neutrino Energy (GeV)
True neutrino Energy (GeV)
Energy response of detector is precisely
introduced using matrix method for CCQE and CC
non-QE respectively
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Procedure of making signal spectrum
nm ? ne oscillation probability
X efficiency X neutrino flux X cross section
event spectrum w/o smearing
detector response
CC QE
event spectrum w/ smearing
CC non-QE
binning
analysis histogram
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c2 calculation

• nm CC and NC background events are considered
• five energy binning for spectral analysis
• 400-500, 500-600, 600-700, 800-900, 900-1200MeV
• systematic error
• 5 signalBG normalization, 5 energy spectrum

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Sensitivity as a function of baseline length
Tested points
L 10001250 km 50km interval 6 points
beam off-axis angle is fixed to 2.5 degree for
both Kamioka and Korea
Dm1228.0x10-5eV2 Dm2322.5x10-3eV2 sin2q120.31 s
in2q230.5
4MW, 4yr for n 4yr for n 0.27 0.27 Mton
fiducal
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baseline dependence of mass hierarchy and CP
violation
3s contour
CP violation
mass hierarchy
Preliminary
normal
truenormal
Kamioka only
Inverted
trueinverted
baseline length dependence of mass hierarchy is
small for large fraction of d
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Preliminary
baseline dependence of mass hierarchy and CP
violation
Inverted
normal
mass hierarchy
normal
Inverted
CP violation
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spectrum _at_ Korea 4MW 4year 0.27Mton 2.5deg OA
beam neutrino run normal hierarchy
sin22q130.02 d0
sin22q130.02 dp
Oscillation Probability
signal spectrum (w/o detector response)
signal spectrum (w/ detector response)
Neutrino energy (MeV)
Neutrino energy (MeV)
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Sensitivity as a function of Dm2
Dm2
Tested points
6 points in 2.03.0 ?10-3 eV2
3.0?10-3 eV2
2.0?10-3 eV2
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Dm2 dependence of mass hierarchy and CP violation
Preliminary
CP violation
mass hierarchy
3s contour
normal
normal
Inverted
Inverted
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Dm2 dependence of mass and CP violation sensitivit
y
normal
Inverted

• mass hierarchy sensitivity at Dm22.0?10-3eV2
  is best. difference is within factor of 3
• CP violation little dependence

normal
Inverted
Preliminary
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Korea 4MW 4year 0.27Mton 2.5deg OA beam neutrino
run
Dm2322.5x10-3eV2 sin22q130.02 dp
Oscillation Probability
signal spectrum (w/o detector response)
signal spectrum (w/ detector response)
Neutrino energy (MeV)
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Summary

• Mass hierarchy and CP violation sensitivities in
  T2KK were investigated as a function of baseline
  length and Dm2 parameter
• Dependence in baseline length is small for math
  hierarchy sensitivity for large fraction of d.
• Difference of sensitivity due to Dm2 is within
  factor of 3 for 2.03.0?10-3 eV2.
• For CP violation sensitivity, there is little
  dependence of Dm2 and baseline length.