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Translation from Near to Far at K2K

July 4, 2002 n Fact02 @Imperial College London. Translation from Near to Far at K2K. T.Kobayashi IPNS, KEK for K2K beam monitor group (K.Nishikawa, T.Hasegawa, T.Inagaki, T.Maruyama, T.Nakaya, ....)

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Translation from Near to Far at K2K

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  1. July 4, 2002 nFact02 @Imperial College London Translation from Near to Far at K2K 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/analysis

  2. Strategy of K2K nm p+ m+ ＳＫ Target+Horn 100m ~250km 200m decay pipe MUMON FD Pion monitor (PIMON) Extrapolate by multiplying ratio(≠0) nm spectrum@production nmspectrum @SK （ＭＣ） （ＭＣ） arb. unit w/o osc. arb. unit w/ osc? （ＭＣ） measure w/ FD measured by PIMON

  3. What’s 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

  4. 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-

  5. 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.

  6. Enrec spectrum shape term for FC 1Rm Total 29 events for Nov99~ data P: reconstructed En distribution for 1Rm (gen’ed by using MC) Detector response from MC

  7. 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) sn11:overall norm. err. for Nov99~ (=5.34%) sEsk: SK Enery scale error (3%)

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

  9. A tool:Pion 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 <2GeV (En<1GeV) PMT array

  10. 1GeV MC 0 (2x2) 1GeV PIMON 0 (4x4) 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 >1GeV • Error matrix MC part: Fit previous pion production data below ~2GeV/c move paraemters within error  get error matrix No correlation w/ PIMON part

  11. qp : : ….. w2 w1 w4 w3 pp : : Pion Monitor Results

  12. p+ q beam axis Pion Monitor Result(relative weight)

  13. En 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(i=1~50) 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)

  14. Other systematic errros treated in matrix form as described • move syst. parameter within error • Check correlation btw energy bins Rj Ri

  15. nm spectra from Pion Monitor Measurement Agree with MC very well.

  16. PIMON result for F/N ratio Good Agreement!

  17. 0-0.5 2-2.5 0.5-1 1-1.5 1.5-2 2.5- Far/Near Error Matrix “sqrt” of error matrix (%) PIMON Beam MC

  18. Summary of systematic errors on total # of events w/o osc.

  19. Summary • K2K uses pion distribution measured in-situ(>1GeV) and beam MC(<1GeV) 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

  20. Typical OA beam(80mDV) 295km 280m 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

  21. POT 4.81019 POT for Analysis 200kA 250kA PIMON meas.

  22. Stability of m-Energy Spectrum Every months Muon Energy in KT on ’01, ‘00 Muon Energy of MRD events

  23. Exp’ed Enrec spectrum for 1Rm estimated by FD measurements

  24. PIMON in target station

  25. K2K osc. analysis overview nm spectrum @ 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)

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