1. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/1 The HARP experiment at CERN PS Neutrino Oscillation Workshop Conca Specchiulla, Otranto, September 11-18 2004 M.Bonesini INFN, Sezione di Milano, Italy Dipartimento di Fisica G. Occhialini, Universita’ di Milano-Bicocca On behalf of the HARP collaboration

2. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/2 Talk overview The HARP Experiment –Physics goals and motivations –Data taking summary –Experimental setup and program –Detector overview and performance First physics analysis: pion yields for K2K target –Motivations –Results Conclusions and overlook

3. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/3 Physics goals of HARP Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments Pion/Kaon yield for the design of the proton driver of neutrino factories and SPL- based super-beams Input for precise calculation of the atmospheric neutrino flux Input 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: from hydrogen to lead Acceptance over full solid angle Final state particle identification 2000 – 2001 Installation 2001- 2002 Data taking

4. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/4 factory design factory design maximize  + (  - ) production yield as a function of: proton energy target material geometry collection efficiency (p L,p T ) but different simulations show large discrepancies for  production distributions, both in shape and normalization. Experimental knowledge is rather poor (large errors: poor acceptance, few materials studied)  aim: measure p T distribution with high precision ( < 5%) for high Z targets

5. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/5 beams flux prediction beams flux prediction Energy, composition, geometry of a neutrino beam is determined by the development of the hadron interaction and cascade  needs to know  spectra, K/  ratios Beam MC Beam MC confirmed by Pion Monitor 0.5 1.0 1.5 2.0 2.5 0 Oscill. MAX E (GeV) K2K : Al target, 12.9 GeV/c Al targets 5%, 50%, 100% (all p beam ), K2K target replica (12.9 GeV/c)  special program with K2K replica target aiming at  (Far/Near)/(Far/Near) < 3% MiniBooNE:Be target 8.9 GeV/c Be targets: 5%, 50%, 100%, MiniBoone target replica Precise p T and p L spectra for extrapolation to far detectors and comparison between near and far detectors

6. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/6 Atmospheric flux Primary flux is now considered to be known to better than 10% Most of the uncertainty comes from the lack of data to construct and calibrate a reliable hadron interaction model. Model-dependent extrapolations from the limited set of data lead to about 30% uncertainty in atmospheric fluxes.  need measurements on cryogenic targets (N 2, O 2 ) covering the full kinematic range in a single experiment

7. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/7 Barton et. al. Atherton et. al. NA56/SPY Serpukov Allaby et. al. Abbott et. al. Eichten et. al. Cho et. al. 1 GeV101001 TeV Parent energy 10 Population of hadron- production phase-space for pA → πX interactions. ν μ flux (represented by boxes) as a function of the parent and daughter energies. Measurements. 1-2 p T points 3-5 p T points >5 p T points 1 GeV 10 100 1 TeV 10 Daughter energy Hadron production experiments HARP

8. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/8 An example from G.Battistoni, NOW 2000 Tuning of Montecarlo generators General problem: little exp. data and large uncertainties in calculations In particular for high Z materials and low primary energy  Thin and thick targets, scan the periodic system and momenta

9. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/9 Data taking summary K2K: AlMiniBoone: BeLSND: H 2 O 5% 50% 100% Replica 5% 50% 100% Replica 10% 100% +12.9 GeV/c+8.9 GeV/c+1.5 GeV/c SOLID targets: CRYOGENIC targets: EXP replica target: HARP took data at the CERN PS T9 beamline in 2001-2002 Total: 420 M events, ~300 settings

10. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/10 The HARP detector layout TRACKING + PARTICLE ID at Large angle and Forward

11. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/11 Detector Performances 1.Beam detectors 2.Large angle detector 3.Forward spectrometer

12. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/12 1. Beam instrumentation Beam Tof  K Beam cherenkov MBoone target Beam tracking with MWPCs : –96% tracking efficiency using 3 planes out of 4 –Resolution <100 mm 12.9 GeV MWPCs Beam TOF: –separate  /K/p at low energy over 21m flight distance –time resolution 70 ps –proton selection purity >98.7% Beam Cherenkov: –Identify electrons at low energy,  at high energy, K above 12 GeV –~100% eff. in e-  tagging  k p d Corrected TOF (ps) 3 GeV Beam composition and direction TOF-A CKOV-A CKOV-B TOF-B 21.4 m T9 beam MWPCs

13. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/13 2. Large angle detector: status of TPC  p T /p T dE/dx p  and  Relativistic rise

14. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/14 Elastic scattering Measure elastic cross-section To normalise the data (elastic cross section is well known) To evaluate the acceptance + efficiency in TPC To check momentum scale Calibration tool for merging forward and large angle analysis oTarget: liquid H 2 (cryogenic target) oTarget length: 18 cm o3 GeV/c beam 1 GeV/c Pa 3GeV/c PcPc PdPd Missing mass: m x 2 = ( p beam + p target – p TPC ) 2

15. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/15 p p -> p p  p ->  p Red: using dE/dx for PID missing mass for p p  p p and  p   p oSelect p and  by beam TOF oBLUE: Simple selection oOnly 1 pos. track in the TPC coming from the target oRED: Additional cut on dE/dx in TPC (select proton) Missing mass distributions

16. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/16 3. Forward spectrometer: NDC tracking 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, it was 95 % in NOMAD) –correctly reproduced in the simulation Alignment with cosmics and beam muons: drift distance resolution ~340  m Plane efficiencies Side modules Plane number 0.2 0.4 0.6 0.8 0 Resolution = 340  m TPC NDC1NDC2NDC5 NDC4 NDC3 Dipole Cherenkov TOF-wall EM calorimeter beam reused from NOMAD

17. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/17 The momentum and angular resolutions are well within the K2K requirements MC data 1 type No vertex constraintincluded MC momentum resolution angular resolution Forward tracking: resolution

18. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/18 Forward particle identification e+e+ ++ p number of photoelectrons  inefficiency e+e+ h+h+ 0 1 2 3 4 5 6 7 8 9 10  p P (GeV)  e  k TOF CERENKOV CALORIMETER 3 GeV/c beam particles TOF CERENKOV TOF CERENKOV CALORIMETER TOF CERENKOV CAL ++ p data

19. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/19 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 Calibration / equalization –Cosmic ray runs (every 2-3 months) –Laser (continuous: monitor stability) PMT Scintillator

20. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/20 TOF Wall calibration  A good and redundant system is needed for good TOFW timing measurements 1.Cosmic ray calibration ( every 2-3 months ): –Measure the relative time-offset between photomultipliers 2.Laser calibration ( many times a day ): –TOF wall stability check –Good agreement with cosmic ray calibration laser cosmics 70 ps

21. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/21 Forward PID: Cherenkov Separate  /p at large momenta 31 m 3 filled with C 4 F 10 (n=1.0014) Light collection: mirrors+Winston cones → 38 PMTs in 2 rows LED flashing system for calibration  mass is a free parameter nominal threshold N pe → 21 p (GeV/c) Number of photoelectrons e+e+ ++ 3 GeV beam particles p p ++ 5 GeV beam particles N phel data

22. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/22 Forward PID: Calorimeter Separate  /e Pb/fibre: 4/1 –EM1: 62 modules, 4 cm thick –EM2: 80 modules, 8 cm thick Total 16 X 0 Reused from CHORUS Calibration with cosmic rays: –Measurement of attenuation length in fibers –Module equalization Energy resolution 23%/sqrt(E) intrinsic resolution 15%/sqrt(E) convoluted with beam spread at detector entrance electrons pions 3 GeV data

23. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/23 oscillation peak 0.5 1.0 1.5 2.0 2.5 0 Forward Analysis for K2K target Focuses on the needs of K2K experiment Exploits the forward part of the spectrometer (NDCs, TOFW, CKOV) beam 250 km  (E ) SK = R(E ).  (E ) ND Range of interest: 1 GeV/c < p  < 8 GeV/c  < 250 mrad Beam MC Beam MC confirmed by pion monitor 0.5 < E < 0.75 GeV

24. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/24 Analysis for K2K: motivations

25. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/25 pion efficiency (data) pion purity (data) pion yield (raw data) tracking efficiency (data+MC) migration matrix (not computed yet) Acceptance (MC) depend on momentum resolution i = bin of true (p,  ) j = bin of recosntructed (p,  ) The forward unnormalized cross section

26. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/26 P > 1 GeV K2K interest K2K interest Forward acceptance dipole NDC1 NDC2 B x z A particle is accepted if it reaches the second module of the drift chambers

27. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/27 Forward tracking dipole magnet NDC1 NDC2 B x z NDC5 beam target Top view 1 2 NDC3 NDC4 Plane segment 3 3 track types depending on the nature of the matching object upstream the dipole  Track-Track  Track-Plane segment  Track-Target/vertex Aim: recover as much efficiency as possible and avoid dependencies on track density in 1st NDC module (hadron model dependent)

28. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/28 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 0 2 4 6810 0.2 0.4 0.6 0.8 1.0 0.2 0.4 0.6 0.8 1.0 -200-1000200100 P (GeV/c)  x (mrad) Total tracking efficiency

29. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/29 tof cerenkov calorimeter momentum distribution Using the Bayes theorem: 1.5 GeV 3 GeV 5 GeV data we use the beam detectors to establish the “true” nature of the particle Forward PID:  efficiency and purity Iterative approach: dependence on the prior removed after few iterations  j  -(t) = N j  -true-obs / N j  -true  j  -(t) = N j  -true-obs / N j  -obs  j  -(t) /  j  -(t)

30. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/30 To be decoupled from absorption and reinteraction effects we have used a thin target p-e/  misidentification background 5% Al target Raw data (20% of stat) p > 0.2 GeV/c |  y | < 50 mrad 25 < |  x | < 200 mrad Pion yield: K2K thin target

31. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/31 Pion yield After all corrections 5% Al target p > 0.2 GeV/c |  y | < 50 mrad 25 < |  x | < 200 mrad To do: Correction for resolutions, absolute normalisation, empty target subtraction full statistics

32. NOW 04 Otranto, September 11-18 2004 M. Bonesini - The HARP expt at CERN PS/32 Conclusions and overlook Status of HARP detector –Forward region: good tracking and solid PID –Large angle: much recent progress (TPC calibration campaign in 2003) First preliminary results are available: thin (5% ) K2K target (mainly as an example of the many HARP analysis capabilities) –Using forward region of the detector We plan to have a detector paper (incorporating performances of all subdetectors, that are now well understood) and a first physics paper on thin K2K target on a 2 month timescale. A first large-angle analysis (H/Tn targets for -factory study) will be shown at the Villars SPSC meeting