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HARP measurements of pion yield for neutrino experiments

HARP measurements of pion yield for neutrino experiments. NuFact 04 @ Osaka. Issei Kato (Kyoto University) for the HARP collaboration. Contents: HARP experiment Physics motivations Detector status First physics analysis for K2K target Summary. Introduction - motivations -.

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HARP measurements of pion yield for neutrino experiments

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  1. HARP measurements of pion yieldfor neutrino experiments NuFact 04 @ Osaka Issei Kato (Kyoto University) for the HARP collaboration • Contents: • HARP experiment • Physics motivations • Detector status • First physics analysis for K2K target • Summary

  2. Introduction - motivations -

  3. Physics goal of HARP • Inputs for the prediction of neutrino fluxes for K2K and MiniBooNE experiments • Inputs for the precise calculation of atmospheric neutrino flux • Pion/Kaon yield for the design of proton driver and target system for neutrino factories and SPL-based super-beams • Inputs for Monte Carlo generators (GEANT4, e.g. for LHC or space applications) Systematic study of hadron production • Beam momentum: 1.5 – 15 GeV/c • Target materials: from hydrogen to lead

  4. Analysis for K2K: motivation m+ Horn Magnet nm Target p+ p 12GeV proton Decay pipe 250km Near detector Far detector pion monitor Spectrum @ KEK Spectrum @ SK Far/Near spectrum ratio ≠ 1 w/o oscillation ~0.6GeV measured by ND w/ oscillation >1GeV Confirmed by PIMON p momentum/angular distribution  neutrino enerugy spectrum (specially below 1 GeV)

  5. Region of Interest in K2K In K2K case: En : 0 ~ 5 GeV • Pp < 10 GeV/c • qp < 300 mrad Most important region (oscillation maximum: En ~ 0.6 GeV) • 1GeV/c < Pp < 2 GeV/c • qp < 250 mrad En Pp Oscillation max qp Pp vs qp Analysis forForward Region

  6. HARP Experiment

  7. HARP Collaboration 124 physicists 24 institutes

  8. HARP Detectors T9 beam Large angle tracks (inside solenoid) TPC: Tracking & PID RPC: PID Forward Particle ID TOF wall: PID for 0–4.5 GeV/c Cherenkov: PID for 3–15 GeV/c EM calorimeter: e/p separation Beam Detectors Beam Cherenkov: p/p/K separation Beam TOF: p/p/K separation MWPC: Beam direction Forward tracking NOMAD drift chambers: Dipole magnet: Tracking & Momentum analysis Used for Forward Analysis

  9. Detector Performances

  10. MWPCs TOF-B TOF-A CKOV-A CKOV-B T9 beam 21.4 m Beam Detectors • Beam tracking with MWPCs : • 96% tracking efficiencyusing 3 planes out of 4 • Resolution <100 mm MiniBooNE target

  11. Beam Particle Identifications p Beam TOF: separate p/K/p at low energy over 21m flight distance • time resolution 170 ps after TDC and ADC equalization • proton selection purity >98.7% p 3.0 GeV/c beam K d 12.9 GeV/c (K2K) Beam p/d p Beam Cherenkov: Identify electrons at low energy, p at high energy, K above 12 GeV • ~100% eff. in e-p tagging K Cherenkov ADC

  12. Forward Tracking: NDC NDC4 TOF-wall NDC1 NDC2 NDC5 Plane efficiencies Side modules • Reused NOMAD Drift Chambers • 12 planes per chamber (in total 60 planes) • wires at 0°,±5° w.r.t. vertical • Hit efficiency ~80% (limited by non-flammable gas mixture) • correctly reproduced in the simulation • Alignment with cosmics and beam muons • drift distance resolution~340mm TPC beam 0.8 0.6 Dipole Cherenkov reused from NOMAD EM calorimeter 0.4 NDC3 0.2 mod1 mod2 mod3 mod4 mod5 0 Plane number Resolution = 340 mm

  13. Forward tracking: resolution momentum resolution angular resolution MC MC data No vertex constraint included

  14. Forward PID: TOF Wall Separate p/p (K/p) at low momenta (0–4.5 GeV/c) • 42 slabs of fast scintillator read at both ends by PMTs TOF time resolution ~160 ps 3s separation:p/p up to 4.5 GeV/c K/p up to 2.4 GeV/c  7s separation of p/p at 3 GeV/c 3 GeV beam particles PMT data p Scintillator p

  15. Forward PID: Cherenkov Separate p/p at high momentum • filled with C4F10 (n=1.0014) • Light collection: mirrors+Winston cones  38 PMTs in 2 rows 3 GeV beam particles 5 GeV beam particles p data data p p+ e+ p+ Nphel Nphel

  16. Forward PID: Calorimeter Hadron/electron separation (Reused from CHORUS) • Pb/fibre: 4/1 (Spaghetti type) • EM1: 62 modules, 4 cm thick • EM2: 80 modules, 8 cm thick • Total 16 X0 • Energy resolution 3 GeV data Energy EM1/EM2 electrons pions EM Energy (a.u.)

  17. Forward Analysis- for K2K target -

  18. B x z Forward Tracking NDC4 • Categorize into 3 track types depending on the nature of the matching object upstream the dipole • Track(3D)-Track(3D) • Track(3D)-Plane segment(2D) • Track(3D)-Target/vertex constraint • To recover as much efficiency as possible • To avoid dependencies on track density in 1st NDC module (hadron model dependent) Top view NDC2 NDC1 dipole magnet NDC5 3 target 1 beam Plane segment (2D) 2 Track (3D) NDC3

  19. Forward Analysis - cross section - i = bin of true (p,) j = bin of recosntructed (p,) migration matrix (not computed yet) pion yield (raw data) Acceptance (MC) pion efficiency (Data) tracking efficiency (Data+MC) pion purity (Data)

  20. Forward acceptance 1 0.8 acceptance 0.6 K2K interest 0.4 MC 0.2 0 2 4 6 8 P(GeV/c) 1 NDC1 NDC2 dipole MC 0.8 x acceptance 0.6 z B 0.4 K2K interest If a particle reaches the NDC module 2, the particle is accepted. 0.2 -200 0 q(mrad) 200

  21. Tracking efficiency Downstream tracking efficiency ~98% Up-downstream matching efficiency ~75% Total Tracking Efficiency 1.0 1.0 0.8 0.8 Green: type 1 Blue: type 2 Red: type 3 Total tracking efficiency Total tracking efficiency 0.6 0.6 0.4 0.4 Black: sum of normalized efficiency for each type 0.2 0.2 2 6 8 10 -200 -100 0 100 200 0 4 P (GeV/c) qx (mrad) etrack is known at the level of 5%

  22. exclude |qx| < 25 mrad, this time 1.0 0.8 0.6 0.4 0.2 -200 -100 0 100 200 qx (mrad) Dependence of tracking efficiencyon hadron production models • Total tracking efficiency as a function of p(left) and qx (right) • computed using MC with 2 hadron generators properly • Both hadron models compatible (except for |qx| < 25 mrad) • Need more study for this region. 1.0 0.8 Total tracking efficiency Total tracking efficiency 0.6 0.4 0.2 0 2 4 6 8 10 P (GeV/c)

  23. 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 TOF CERENKOV CALORIMETER p h+ p+ p inefficiency e+ p+ p e+ number of photoelectrons

  24. Forward PID: p efficiency and purity momentum distribution Using the Bayes theorem: tof cerenkov calorimeter Iteration: dependence ontheprior removed after few iterations data 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 1 1 pion purity pion efficiency 0.8 0.8 0.6 0.6 0.4 0.4 Type1 Type3 Type1 Type3 Type1 Type3 Type1 Type3 Type1 Type3 Type1 Type3 Type2 Type2 Type2 Type2 Type2 Type2 0.2 0.2 0 0

  25. Pion yield: K2K thin target 5%l Al target (20mm) Use K2K thin target (5%l) • To study primary p-Al interaction • To avoid absorption / secondary interactions K2K replica (650mm) p > 0.2 GeV/c |y | < 50 mrad 25 < |x| < 200 mrad Raw data 2 4 6 8 10 -200 -100 0 100 200 0 qx(mrad) P(GeV/c) p-e/p misidentification background

  26. Pion yield After all correction 5% l Al target p > 0.2 GeV/c |y | < 50 mrad 25 < |x| < 200 mrad 6 10 2 4 0 8 -200 -100 0 100 200 P(GeV/c) qx(mrad) • Systematics are still to be evaluated: • tracking efficiency knownat 5% level • expect small effect from PID

  27. Summary • HARP experiment has collected data for hadron production • With wide range of beam momentum and targets • Analysis for Forward region • Improvement in tracking efficiency ~75% • Downstream the dipole magnet: tracking efficiency ~98% • Matching through the magnet: ~75% (MC behaves well, only scale factor by data) • Little dependence on hadron production models • PID performance is also robust • HARP first results for K2K thin target are available

  28. Outlook & To do • K2K thin target for primary interaction • Compute deconvolution and migration matrix • Evaluate systematic uncertainties • Investigate super-forward region (|qx|<25 mrad) • Empty target study for background subtraction • Normalization for absolute cross section (using minimum biased trigger) • Analysis of K2K replica target for far/near ratio calculation • Similar analysis for MiniBooNE target • These are just two out of a number of measurements relevant for neutrino physics, those will be provided by HARP in the near future

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