Results from the HARP Experiment

1. Results from the HARP Experiment Silvia Borghi Université de Gèneve On Behalf of the HARP Collaboration

2. Main goals • Inputs for prediction of neutrino fluxes for K2K () and MiniBooNE (,e) • , K yield for the design of proton driver and target system of Neutrino Factories and Superbeams • Inputs for precise calculation of atmospheric  fluxes • Input for MonteCarlo generators HARP Systematic study of hadrons produced by incident p and ± with pbeam from 1.5 to 15 GeV/c, more than 420 M pot • Large range of target materials, from H to Lead of different length; • Also measurements on specific targets of existing  beams: K2K and MiniBooNE Silvia Borghi

3. ECAL NDC NDC NDC Solenoid magnet RPC MWPC TOF A TOF B Beam TDS BCA BCB TPC BS HALO A HALO B FTP Dipole Magnet TOF target CKOV Large angle spectrometer Forward spectrometer Beam Detectors Experimental setup Silvia Borghi

4. Calculation of a cross section of positive pions number of protons on target Number of target nuclei and target thickness Correction matrix, i.e. unfolding of true ij variables from reconstructed i’j’’ reconstructed efficiency, acceptance, absorption, pion decay, tertiary production, PID efficiency and contamination… Unfold detector resolution (I=true, j=rec) Number of particles observed as ’ type in bins of reconstructed (pi’,j’), N(E) refers to data without target (correction for primary proton interactions out of target) Silvia Borghi

5. Top view NDC2 NDC5 NDC1 dipole x z beam target Reconstruction efficiency for positive x (rad) p (GeV/c) Total good tracks: 210,000 ForwardReconstruction • P is measured (downstream segment + upstream constraint) • PID detectors (TOF, CHE) Angular resolution Momentum resolution 0.5 GeV/c bins p< 4GeV/c and 1.5 GeV/c bins for 5-6.5 GeV/c; 30 mrad angular bins Silvia Borghi

6.   p p No CHE No TOFW CHE only No CHE No TOFW CAL 0.75 < p < 2.25 GeV/c 2.75 < p < 6.5 GeV/c To select pions To select pions Combined PID PID detectors 0 1 2 3 4 5 6 7 8 9 10 P (GeV/c) p/p TOF CERENKOV TOF p/k TOF CERENKOV CERENKOV p/e CERENKOV CALORIMETER Silvia Borghi

7. Evaluation of the measurement precision Systematic error evaluation on all the terms of the cross-section, to quantify errors on differential and integrated cross section. average error: diff=8.2% • Dominant error contributions to diff: • overall normalization • tertiary subtraction • momentum scale  for 0.75 < p< 6.5 GeV/c and 30<<210 mrad, error: int=5.8% • Dominant error contributions to int: • overall normalization • tertiary subtraction Silvia Borghi

8. Sanford-Wang parametrization Sanford-Wang results Sanford-Wang parametrization fit HARP results: p+Al++X cross-section pbeam=12.9 GeV/c Silvia Borghi

9. Measured By HARP Oscillation peak 2.0 1.5 2.5 0 0.5 1.0 R(En) Physics impact: Far and Near  fluxes at K2K • Similar E spectra arising from K2K default (pre-HARP) and HARP Sanford-Wang + parameterization • Errors shown: HARP + production uncertainties and K2K MonteCarlo • The error in R associated with the HARP measurement is of the order of 1%. Silvia Borghi

10. Beryllium target L =71 cm (1.7 ) The production cross section of pions in p-Be collisions Primary protons From Fermilab Booster Pp= 8.9 GeV/c Silvia Borghi

11. HARP results: p+Be++X pbeam=8.9 GeV/c Preliminary • primary protons: 7.3 M • pbeam=8.9 GeV/c • 5%  Be disc • quite similar Al data • analysis well covering • MiniBooNE phase space • 0.75 < p< 5 GeV/c • 30<  < 210 mrad Preliminary Sanford-Wang parametrization fit Silvia Borghi

12. Magnet Rpc barrel 1.83 0.785 Radius 40 cm Momentum resolution Beam Tpc drift volume Rpc barrel Target position Magnet π+ and π- efficiency Drift length 1541 mm electrons positrons Large Angle Region Silvia Borghi

13. Preliminary HARP results: p+H2p+p (elastic scattering) pbeam=3 GeV/c • Elastic scattering: p (and π) on H2 target  1- or 2- prong final state • Cinematic selection, cuts on dE/dx (PID) • The missing mass plots show: • The missing mass value is corrected  the momentum scale is correct • The cross section is comparable with the PDG one  the efficiency and the systematic are under control Cross section = 6.1 mb Silvia Borghi

14. Nufact physics case: maximize p± production rate • Optimize: • target material and geometry • primary beam energy • collection scheme • Experimental data are poor (small acceptance, few materials) and old (Allaby et al.1970, Eichten et al. 1972) • Existing simulation packages show large discrepancies on pion yields and distributions Silvia Borghi

15. Preliminary Pion yields: in  bins π+π- Pion yields: 0.785<<1.57 rad Preliminary Preliminary Preliminary HARP results: p+Ta+Xpbeam=3 GeV/c • One beam particle identified as proton by MWPC and TOF beam counters • large angle interaction by ITC (≥99%) • Cuts on the event spill to reject events strongly affected by the dynamic distortions 0.785< <1.83 rad & 100 < pt < 700 MeV/c Silvia Borghi

16. Conclusion • Thin target analysis for Al (at 12.9 GeV/c, K2K) for + production: cross sections have been measured within 6 % uncertainty (8.2% point-to-point) in the forward region. Physics impact in K2K strong reduction of systematics of Far to Near neutrino flux ratio associated to secondary particle production • Thin target analysis for Be (at 8.9 GeV/c, MiniBooNE) for + production in forward direction is almost completed • On going analysis of thick and replica K2K and MiniBooNe targets, +/-, K/, A and energy dependence • Carbon results are expected to make a major contribution to the understanding of neutrino fluxes for accelerator neutrinos as well as atmospheric neutrino fluxes. • The analysis of  production for Ta at large angle already produced preliminary results. The goal is to give an experimental input to choose the proton driver energy of the Neutrino Factory Silvia Borghi

17. ECAL NDC NDC NDC Solenoid magnet RPC MWPC TOF A TOF B Beam TDS BCA BCB TPC BS HALO A HALO B FTP Dipole Magnet TOF target CKOV • Single track reconstructed in MWPC r<10mm, < 5 mrad • Proton identified by Cherenkov A, B and TOF A, B • No signal in BCA & BCB (selects proton) • T0interaction time within 70 ps using TOFA+TOB+TDS Beam Detectors Silvia Borghi

18. CAL TOF CERENKOV p p PID detectors 0 1 2 3 4 5 6 7 8 9 10 P (GeV/c) p/p TOF CERENKOV TOF p/k CERENKOV p/e CERENKOV CALORIMETER Silvia Borghi

19. PID performance and migration matrix Correction matrix, i.e. unfolding of true ij variables from reconstructed i’j’’ reconstructed efficiency, acceptance, abosorption, pion decay, tertiary production, PID efficiency and contamination pion efficiency pion purity pions protons PID corrections computed in bins of momentum and angle Silvia Borghi

20. Harp Sanford-Wang parameterization fit Old data p+Al++X: results versus previous data Silvia Borghi

21. Harp Sanford-Wang parameterization fit Old data p+Be++X : results versus previous data • Pbeam: 10÷15 GeV/c close to MiniBooNE •  < 200 mrad • HARP Sanford-Wang parameterization at 8.9 GeV rescaled to pbeamof old experiments Reasonable agreement, differences for >150 mrad Silvia Borghi

22. Harp Sanford-Wang parameterization fit Old data p+Be++X : results versus previous data Important variations w.r.t. Cho71 old data (Cho71 data are in disagrement also with BNL E910…) Silvia Borghi