Translation from Near to Far at K2K

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Translation from Near to Far at K2K
July 4, 2002 nFact02 _at_Imperial College London

• T.Kobayashi
• IPNS, KEK
• for K2K beam monitor group
• (K.Nishikawa, T.Hasegawa, T.Inagaki, T.Maruyama,
  T.Nakaya, ....)
• Especially for T.Maruyama(KEK?Chicago) who played
  major role in PIMON construction/measurement/analy
  sis

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Strategy of K2K
nm
p
m
SK
TargetHorn
100m
250km
200m decay pipe
MUMON
FD
Pion monitor (PIMON)
Extrapolate by multiplying ratio(?0)
nm spectrum_at_production
nmspectrum _at_SK
(MC)
(MC)
w/o osc.
arb. unit
arb. unit
w/ osc?
(MC)
measure w/ FD
measured by PIMON
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Whats new in the treatment of far/near
extrapolation

• Before
• Observable for osc. analysis
• total of events
• added syst. error from each energy bins linearly
  ( 100 positive correlation) to be safe.
• New
• Observables for osc. analysis
• total of events,
• Enrec spec. shape for 1-ring m-like events
• Correlation for far/near ratio btw energy bins
  are taken into account

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Far/Near ratio in oscillation analysis (method1)
Maximum Likelihood Method
systematics parameters
spec
nQE/QE
Far/near
eSK(efficiency)
SK Enegry scale
Overall Norm Error For Jun99 and Nov99-
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Normalization term
i energy bin index j processes (QE, nQE)
Spectrum meas. in FD(fFi) cancels first order but
far/near ratio fF/N does not.
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Enrec spectrum shape term for FC 1Rm
Total 29 events for Nov99 data
P reconstructed En distribution for 1Rm (gened
by using MC)
Detector response from MC
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Systematic constraint term
Far/near ratio
MFD, Mp, MSK error matrix of syst. errors. sn6
overall norm. err. for Jun99 (0.80-0.68
evts) sn11overall norm. err. for Nov99
(5.34) sEsk SK Enery scale error (3)
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Qeustions

• Central values of far/near ratio (relative to MC
  prediction)
• fF/Ni
• Correlation of far/near ratio btw. energy bins
  (error matrix)
• Mp

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A toolPion Monitor (PIMON)
N(pp, qp) ? Neutrino flux F(En) at any
distance using only decay kinematics
R(En)FSK(En)/FFD(En)
as a result of pion monitor
Gas Cherenkov detector
to avoid signal from 12GeV protons ? insensitive
to pp lt2GeV (Enlt1GeV)
PMT array
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Strategy to obtain fF/N, error matrix

• Above 1GeV ? PIMON
• Below 1GeV ? Beam MC(Sanford-Wang
  parameterization fitted to previous data)
  validated by PIMON measurement at gt1GeV
• Error matrix

MC part Fit previous pion production data
below 2GeV/c move paraemters within error
? get error matrix
No correlation w/ PIMON part
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Pion Monitor Results
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Pion Monitor Result(relative weight)
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Pion distribution to far/near ratio (incl. error
matrix)
Contribution to n flux from each p-q bin (by MC.
To 1st order, depend only on decay kinematics
geometry
From PIMON fitting
Relative weight Wi(i150)
FD,SK flux
Ratio as func. of weights
Dependence of R on W (50x4 matrix)
50x50 error matrix on weight
Error matrix transformation from p weight ?
far/near ratio
(4x4) (4x50) (50x50) (50x4)
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Other systematic errros
treated in matrix form as described

• move syst. parameter within error
• Check correlation btw energy bins

Rj
Ri
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nm spectra from Pion Monitor Measurement
Agree with MC very well.
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PIMON result for F/N ratio
Good Agreement!
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Far/Near Error Matrix
sqrt of error matrix ()
PIMON
Beam MC
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Summary of systematic errors on total of events
w/o osc.
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Summary

• K2K uses pion distribution measured
  in-situ(gt1GeV) and beam MC(lt1GeV) for spectrum
  extrapolation
• The beam MC is validated by the PIMON
  measurements
• Correlation of far/near ratio btw energy bins is
  taken into account (instead of linear sum 100
  positive correlation
• Still far/near ratio is major source of
  systematic error
• Expect precise data from HARP (measurement in
  Aug.26). Many many thanks to HARP collaborators

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Syst. error far/near spectrum diff.
K2K case (MC)
FD(300m) (xLSK2/LFD2)
SK
Large(x2) effect around peak!!
Important not only for nm disappearance, but also
for sig/BG estimation for ne search
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POT
4.8?1019 POT for Analysis
200kA
250kA
PIMON meas.
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Stability of m-Energy Spectrum
Every months
Muon Energy in KT on 01, 00
Muon Energy of MRD events
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Exped Enrec spectrum for 1Rm estimated by FD
measurements
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PIMON in target station
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(No Transcript)
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K2K osc. analysis overview
nm spectrum _at_ production
Far
Near
PIMON pp-qp dist
near/far extrapolation
oscillation probability
Want to know this!!
neutrino interaction in water
detector responce(1kt, scifi)
detector responce(SK)

• FD observation
• 1KT
• Scifi

• SK observation
• total of events
• Enrec spectrum shape(1ring m-like events)

(1Rm)