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HARP

HARP. K2K. Anselmo Cervera Villanueva. University of Geneva (Switzerland). Neutrino CH Meeting Neuch â tel, June 21-22, 2004. Overview. HARP K2K HARP contribution to K2K Geometrical acceptance Tracking efficiency Particle identification Pion yields. HARP.

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HARP

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  1. HARP K2K Anselmo Cervera Villanueva University of Geneva (Switzerland) Neutrino CH Meeting Neuchâtel, June 21-22, 2004

  2. Overview • HARP • K2K • HARP contribution to K2K • Geometrical acceptance • Tracking efficiency • Particle identification • Pion yields

  3. HARP

  4. The HARP experiment (CERN) 124 people 24 institutes

  5. Physics goals • Systematic study of HAdRonProduction: • Beam momenta:1.5-15 GeV/c • Target:from hydrogen to lead • Motivation: • Pion/kaon yield for the design of the proton driver ofneutrino factories and SPL-based super-beams • Input for precise calculation ofatmospheric neutrino flux • Input for prediction of neutrino fluxes for theMiniBooNEandK2Kexperiments • Input forMonte Carlogenerators (GEANT4, e.g. for LHC, space applications)

  6. K2k

  7. K2K Experiment (Japan) • First long base line neutrino experiment (250 km) • To confirm with beam neutrinos the Super-K results 250 km m-like event at Super-K • <En> = 1.3 GeV • almost pure nm: ~98%

  8. Beam MC predicted measured no oscillation confirmed by pimon oscillation Far/Near spectrum ratio ≠ 1 Overview of K2K pion monitor (cerenkov) muon monitor near detectors 12.9 GeV proton beam Super-K nm decay pipe nm p+ p m+ 1Kt Target + Horn 100m 200m 250km

  9. HARP contribution to K2K

  10. 2.0 1.5 2.5 0 0.5 1.0 Motivation of this analysis One of the largest systematic errors on the neutrinooscillation parametersmeasured by the K2K experiment comes from the uncertainty on thefar/near ratio pions producing neutrinos in the oscillation peak To be measured by HARP oscillation peak K2K far/near ratio K2K interest En(GeV) Beam MC, confirmed by Pion Monitor Beam MC

  11. Forward Acceptance y z x MC NDC2 NDC1 dipole B x z top view

  12. The ingredients pion purity (background) bin migration matrix (p,q) acceptance absolute normalization pion id efficiency pion yield total efficiency To measure all this one needs: • p and q measurement (at the interaction vertex) • connect tracks with particle identification (PID) measurements tracking • Identify pions • Reject protons, kaons and electrons PID • We have reproduced in HARP the exact K2K conditions: • 12.9 GeV/c proton beam • An exact replica of the K2K target (2l aluminium) data

  13. B x z Forward Tracking NDC4 • We distinguish 3 track types depending on the nature of the matching object upstream the dipole • 3D-3D • 3D-2D • 3D-Target/vertex (independent of NDC1) • The idea is to recover as much efficiency as possible to avoid hadron model dependencies. Top view NDC2 NDC1 dipole magnet NDC5 3 target 1 beam 2D segment 2 NDC3 solutions problems • Saturation of NDC1 in the beam spot region • High density of hits in NDC1 provokes correlation between particles hadron model dependencies systematic error

  14. Momentum and angular resolutions The momentum and angular resolutions are well inside the K2K requirements angular resolution momentum resolution MC type MC 1 No vertex constraint included data

  15. Tracking efficiency • It can be computed with the DATA as a function of x2 and qx2 • We use the MC to perform the conversion: • once demonstrated that DATA and MC agree in their x2 and qx2 distributions Top view NDC2 NDC1 NDC5 dipole magnet 3 target 1 beam B 2D segment 2 x z extrapolation to this plane

  16. data Module efficiency NDC4 • The efficiency of NDC2 and NDC5 is flat within ~5%. • The efficiency of the lateral modules (3 and 4) is flat within 10% • The combined efficiency is not sensible to these variations. NDC5 NDC2 dipole NDC3 NDC 2 NDC 4 NDC 3 NDC 5

  17. Downstream efficiency NDC4 NDC5 NDC2 dipole NDC3 MC

  18. Up-down matching efficiency NDC4 Top view • Is the probability of matching a downstream track with the other side of the dipole NDC2 NDC1 NDC5 dipole magnet 3 target 1 beam B 2D segment 2 NDC3 x z We tune to the DATA the absolute scale of each track type MC and data agree within ~3% in their shapes MC data +

  19. MC data + Total tracking efficiency • The MC reproduces the up-down matching efficiency in terms of x2 and qx2 within ~3% • The downstream efficiency is flat We can use the MC to compute the total efficiency as a function of p and q

  20. Particle identification 0 1 2 3 4 5 6 7 8 9 10 P (GeV) p/p TOF CERENKOV CAL TOF ? p/k CERENKOV TOF CERENKOV p/e CERENKOV CALORIMETER data 3 GeV/c beam particles CALORIMETER TOF p CERENKOV h+ p+ p inefficiency e+ p+ p e+ number of photoelectrons

  21. data Pion ID efficiency and purity Using the Bayes theorem: momentum distribution tof calorimeter cerenkov we use the beam detectors to establish the “true” nature of the particle 1.5 GeV 3 GeV 5 GeV 1.5 GeV 3 GeV 5 GeV

  22. Pion yield • To be decoupled from absorption and reinteraction effects we have used a thin target 5% l Al target 200% l Al target K2K replica target data p-e/p misidentification background

  23. data

  24. Conclusions • The tracking efficiency is known at the level of ~5% • The pion ID correction factor is fully computed with data (except kaon contamination below 3GeV) Small systematic error • However, a detailed study of the PID systematic error is still missing Next • Increase tracking efficiency reduce systematic (<5%) • Use the MC to compute the systematic error on the pion ID correction factor • Larger MC and data statistics (p,q) 2D distribution • Detailed study of migration effects • Replica target z dependence

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