1. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 1 HARP STATUS REPORT A. De Min for the HARP Collaboration SPSC Open Session 26 March 2002

2. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 2 Outline Introduction Summary of data taken in 2001 Status of hardware: –Problems encountered –Update on some subdetecors Some preliminary analysis results –Large angle analysis Programme for 2002: –Hardware –Data taking campaign Summary and conclusions

3. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 3 Introduction HARP (Hadron Production Experiment at the PS) –designed to measure with few % accuracy cross sections for hadron production of protons (3 to 15 GeV/c) on various elements –necessary to calibrate Monte Carlo simulations for: HARP was designed, built and assembled in 17 months! the design of a nu-factory the mastering of existing nu-beams the interpretation of atmospheric nu-oscillation experiments

4. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 4 HARP collaboration

5. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 5 HARP schematic layout TPC Tof with RPC Ckov ToF e-id Ckov Tof beam Forward spectrometer MWPC HARP consists of a barrel spectrometer (TPC) and of a forward spectrometer (NDC) to cover the full solid angle, complemented by particle-id detectors Target

6. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 6 Summary of data taken in 2001 Data taking period: August to November 2001 targetZThin (cm) Thick (cm) Be40.81 C60.7638 Al130.79 Cu290.3015 Sn500.45 Ta730.2211.14 Pb820.34 K2K target~60 cm Al MiniBooNE target~65 cm Be Target tube Target holder => 1/3 of solid targets programme completed Candidate physics events collected: 2001 targets:

7. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 7 Status of hardware: trigger (I) Trigger selectivity: Soft particles accompanying the beam particle can trigger the FTP (in 5% of cases) beam Non-interacting beam particle Forward trigger plane (FTP) Inner Trigger Cilinder (ITC) Consequence: 1/2 to 2/3 of our thin-target data are non-interacting beam particles (used to align the forward spectrometer) A detailed GEANT4 simulation could reveal the origin of these FTP triggers  

8. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 8 Status of hardware: trigger (II) To count the number of incoming beam particle, a beam trigger is downscaled (factor 256) for thin targets This provides total normalization for cross-section measurements Data analysis showed it was unstable in 2001 (accidental feature of the trigger design) and correlated with beam intensity However: –It is measured in the data (a special bit is set) –It is measured independently by scalers Consequence: Small additional statistical uncertainty in the total normalization (1-2%)

9. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 9 Status of hardware: TPC cross-talk Evidence of cross-talk has been found in the TPC electronics Produced in various stages, but mainly due to the design of the motherboard connections (asymmetric input-output coupling of the preamplifiers) No hope to cure it in the hardware An accurate mapping is being produced which should allow software recovery Cross-talk is limiting energy and space resolution in TPC pads: it will be hard to achieve better than 1mm resolution in R  A to B: BAD B to A: OK

10. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 10 Status of hardware: an update All other components work as expected Cherenkov fully efficientElectron identifier: 3 GeV/c beam particles Non interacting beam particles: Nominal beam momentum Pion mass is a free parameter Nominal threshold Electrons tagged by the beam Cherenkov e+ ++ ++ Nominal beam momentum Em1/Em2 Em energy

11. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 11 Status of hardware: an update Nomad Drift Chambers behave as expected. Two difficulties: –Efficiency limited by (non-flamable) gas (  ~ 90% per plane) –Vertical coordinate reconstruction requires extremely accurate alignment (in progress) Momentum reconstruction is in the horizontal plane!

12. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 12 Preliminary Data Analysis Demonstrates HARP capability to do good physics Limited manpower imposed a choice: 1.Concentrate effort in forward spectrometer (small-angle region) 2.Focus analysis in TPC acceptance (large-angle region) Second option finally chosen. Motivations: –Wider angular acceptance => More interesting! –Apparatus completely new => More challenging! –Quantitative analysis in the forward region requires very accurate NDC alignment, not yet available Involves information from: Beam Dets, ITC, TPC, RPC

13. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 13 Large Angle Analysis Reference data sample: –3 GeV/c protons on 73 Ta –Three target settings: Thin (2% ), Thick (1 ), No target First step: establish data quality and reject bad runs Second step: proton selection in the beam Third step: large angle (TPC) analysis: –pad calibration (Cosmic tracks, 83m Kr) –cluster reconstruction –pattern recognition –track fitting –track extrapolation to target (impact parameter) and RPC

14. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 14 Beam particle selection Beam particles are traced by 4 MWPC ’s (accuracy <1 mm) Particle identification performed by: – Cherenkov, Tof (21 m), Mu-identifier (6.5 ) Proton selection in the 3 GeV/c beam: Proton selection purity > 98.7% Provides beam momentum calibration For measurements of total cross section

15. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 15 TPC pad calibration Pads response will be calibrated with 83m Kr Radioactive 83m Kr is mixed with the Ar/CH 4 gas and data are collected with random trigger Equalization precision is at the % level Energy resolution affected by cross-talk Independent cross-check with cosmics: 9KeV 12KeV 32KeV 40KeV 83 Kr cosmics

16. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 16 Track impact parameter RPC are fully efficient and noise-free RPC timing removes off-time tracks 2 mm stesalite wall Target (fixed to the magnet) (fixed to the TPC)

17. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 17 Programme for 2002: hardware Increase data acquisition speed by 2.5 –A source of noise has been found and removed in TPC –Expect to readout 500 trigger/spill (presently 200/spill) Improve trigger selectivity by >2 –Non-interacting beam particles (FTP problem) will be reduced by increasing thin targets thickness to 5% (from 2%) –Additional improvements are being studied to further reduce FTP unwanted triggers: Build a veto on non-interacting beam particles Skip TPC readout in case of FTP-only triggers (Choice still to be taken) Expect good event rate to improve by >5 for thin targets

18. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 18 Programme for 2002: data taking elementH2H2 D2D2 N2N2 O2O2 boiling temp. 20.4  K23.6  K77.4  K99.2  K # 0.84 %2.13 %5.52 %7.52 % 1.Complete solid target programme 2.Complete K2K and MiniBooNE measurements 3.Exploit use of cryogenic targets : All targets produced (6 cm, 2 cm  ) Two distinct setups: (H 2 /D 2, N 2 /O 2 ) Filling: 4-6 hour. Emptying: 1 hour H 2, N 2 and O 2 targets tested

19. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 19 Programme for 2002: targets List of targets for 2002: NEW

20. SPSC, 26 March 2002 A. De Min, HARP STATUS REPORT 20 Summary and conclusions HARP has operated successfully for its first year A first (partial) inspection of data has shown that: –The general data quality is good –Particle reconstruction in the TPC region is extremely solid During the 2002 data taking campaign HARP will: –Improve considerably trigger selectivity and data-taking speed –Complete the collection of data with solid targets –Exploit the use of cryogenic targets for gaseous materials No evidence has been found of any problem which might: – affect HARP capability to complete its programme within the allocated time and with the expected precision