HARP measurements of pion yield for neutrino experiments Issei Kato (Kyoto University) for the HARP collaboration Contents: 1.HARP experiment Physics motivations Detector status 2.First physics analysis for K2K target 3.Summary NuFact Osaka

Introduction - motivations -

Physics goal of HARP Systematic study of hadron production –Beam momentum: 1.5 – 15 GeV/c –Target materials: from hydrogen to lead 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)

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

Region of Interest in K2K In K2K case: E : 0 ~ 5 GeV P  < 10 GeV/c  < 300 mrad Most important region (oscillation maximum: E ~ 0.6 GeV) E ~ 0.6 GeV) 1GeV/c < P  < 2 GeV/c 1GeV/c < P  < 2 GeV/c  < 250 mrad  < 250 mrad E PP  P  vs  Analysis for Forward Region Oscillation max

HARP Experiment

HARP Collaboration 124 physicists24 institutes

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

Detector Performances

Beam Detectors TOF-A CKOV-A CKOV-B TOF-B 21.4 m T9 beam MWPCs Beam tracking with MWPCs :Beam tracking with MWPCs : –96% tracking efficiency using 3 planes out of 4 –Resolution <100  m MiniBooNE target

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

Forward Tracking: NDC 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 ~340  m Plane efficiencies Side modules Plane number mod1mod2mod3mod4mod5 Resolution = 340  m TPC NDC1NDC2NDC5 NDC4 NDC3 Dipole Cherenkov TOF-wall EM calorimeter beam reused from NOMAD

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

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

Forward PID: Cherenkov Separate  /p at high momentum filled with C 4 F 10 (n=1.0014) Light collection: mirrors+Winston cones  38 PMTs in 2 rows e+e+ ++ p p ++ N phel data 3 GeV beam particles 5 GeV beam particles data

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 X 0 Energy resolution electrons pions 3 GeV data EM Energy (a.u.) Energy EM1/EM2

Forward Analysis - for K2K target -

Forward Tracking dipole magnet NDC1 NDC2 B x z NDC5 beam target Top view 1 2 NDC3 NDC4 Plane segment (2D) 3 Categorize into 3 track types depending on the nature of the matching object upstream the dipole 1.Track(3D)-Track(3D) 2.Track(3D)-Plane segment(2D) 3.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) Track (3D)

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

K2K interest Forward acceptance dipole NDC1 NDC2 B x z If a particle reaches the NDC module 2, the particle is accepted P(GeV/c) acceptance acceptance  (mrad) K2K interest MC MC

Downstream tracking efficiency ~98% Up-downstream matching efficiency ~75% Tracking efficiency  track is known at the level of 5% Green: type 1 Blue: type 2 Red: type 3 Black: sum of normalized efficiency for each type Total Tracking Efficiency P (GeV/c)  x (mrad) Total tracking efficiency

Total tracking efficiency as a function of p(left) and  x (right) computed using MC with 2 hadron generators properly  Both hadron models compatible (except for |  x | < 25 mrad) Need more study for this region. Dependence of tracking efficiency on hadron production models P (GeV/c)  x (mrad) exclude |  x | < 25 mrad, this time Total tracking efficiency

Particle identification e+e+ ++ p number of photoelectrons  inefficiency e+e+ h+h  p P (GeV)  e  k TOF CERENKOVCALORIMETER 3 GeV/c beam particles TOF CERENKOV TOF ? CERENKOV CALORIMETER TOF CERENKOV CAL ++ p data

tofcerenkovcalorimeter momentum distribution Using the Bayes theorem: 1.5 GeV 3 GeV 5 GeV data Forward PID:  efficiency and purity 1.5 GeV 3 GeV 5 GeV Type1 Type2 Type3Type1 Type2 Type3Type1 Type2 Type3Type1 Type2 Type3Type1 Type2 Type3Type1 Type2 Type pion efficiency pion purity Iteration: dependence on the prior removed after few iterations we use the beam detectors to establish the “true” nature of the particle

Use K2K thin target (5% ) To study primary p-Al interaction To avoid absorption / secondary interactions 5% Al target (20mm) Raw data p > 0.2 GeV/c |  y | < 50 mrad 25 < |  x | < 200 mrad Pion yield: K2K thin target K2K replica (650mm) P(GeV/c)  x (mrad) p-e/  misidentification background

Pion yield After all correction 5% Al target p > 0.2 GeV/c |  y | < 50 mrad 25 < |  x | < 200 mrad Systematics are still to be evaluated: tracking efficiency known at 5% level expect small effect from PID P(GeV/c)  x (mrad)

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

Outlook & To do K2K thin target for primary interaction –Compute deconvolution and migration matrix –Evaluate systematic uncertainties –Investigate super-forward region (|  x |<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