Results from HARP. Malcolm Ellis On behalf of the HARP collaboration DPF Meeting Riverside, August 2004

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1 Results from HARP Malcolm Ellis On behalf of the HARP collaboration DPF Meeting Riverside, August 2004

2 The HAdRon Production Experiment 124 physicists 24 institutes2

3 Physics Goals Input for precise calculation of atmospheric neutrino flux Input for prediction of neutrino fluxes for the MiniBooNE and K2K experiments Systematic study of HAdRon Production: Beam energy: 2-15 GeV Target: from hydrogen to lead. Pion/kaon yield for the design of the proton driver of neutrino factories and SPL-based super-beams Input for Monte Carlo generators (GEANT4, e.g. for LHC, space applications) 3

4 Data Taking Summary HARP took data at the CERN PS T9 beam-line in Total: 420 M events, ~300 settings SOLID: CRYOGENIC: ν EXP: K2K: Al 5% 50% 100% Replica GeV/c MiniBoone: Be 5% 50% 100% Replica +8.9 GeV/c LSND: H 2 O 10% 100% +1.5 GeV/c

5 TPC Large Angle Full track reconstruction available Calibration campaign in 2003: Calibration with sources ( 55 Fe, 83 Kr) Calibration with cosmic rays. Systematic study of corrections: Basic calibrations revisited (time, charge, position) Cross-talk correction Distortion corrections 5

6 TPC Cross talk parent Full simulation exists cross-talk model capacitive couplings + preamplifier transfer functions data model oscilloscope DAQ daughter cross-talk measurements Individual pulse injection in all pads 50% of pads affected by x-talk x-talk only relates neighbouring pads residuals capacitive couplings # daughters Introduced in MC rms~3mm 6

7 Momentum & de/dx Compare single arm with de/dx over full track Protons (few %) 1 A 2 β protons full track p t = abs(ρ 1 +ρ 2 ) p t 2( ρ tot ) ρ charge 1/p t Muons and pions 7

8 Elastic Scattering p p -> p p Red: using de/dx for PID π p -> π p missing mass for p p p p and πp πp o Select p and π in the beam by ToF o BLUE: Simple selection o Only 1 pos. track in the TPC coming from the target o RED: Additional cut on de/dx in TPC (select proton) 8

9 Forward Analysis NDC 1 NDC 2 NDC 5 p π > 1GeV/c θ π < 250 mrad Main tracking detector: NOMAD drift chambers Forward PID detectors 9

10 Beam Instrumentation MWPCs Beam composition and direction T9 beam CKOV-A TOF-A CKOV-B TOF-B 21.4 m MWPCs Beam Cherenkov K-π separation at high energy 12.9 GeV K π Beam Tof k/π/p separation at low T0 π k p 3 GeV d MiniBooNE target 10

11 NOMAD Drift Chambers Cosmic rays Alignment Iter 1 Iter 2 Courtesy of NOMAD Hit reconstruction efficiency ~ 80 % Resolution Module eff Iter 10 σ=340 µm 95 % in NOMAD Harp: Not flammable gas (safety regulations) Lateral modules 11

12 π/p using TOF GeV m 2 TOF TDS 2 2 tw t0 = p 1 L Tof ~160 ps 7σ 3 GeV Beam ~70 ps entries 3 GeV beam particles 5 GeV beam particles Beam TOF t a t b t c π + p m 2 (GeV 2 ) target t 0 data π + L k 12 t w Tof Wall

13 data entries 3 GeV beam particles p π + π/p using Cherenkov Cherenkov π inefficiency e N phe entries π / p p> 3 GeV π / k 3 <P< 9 GeV 5 GeV beam particles p π inefficiency π N phe number of photoelectrons N phel 2.6 GeV Threshold pions 3-15 GeV e + π GeV Threshold kaons P (GeV) 2 ( 1+ ( m ) ) 1 N phel α N0 1 / p 2 n 13 N phel N phel

14 e/π using calorimeters Spaghetti type Courtesy of the CHORUS experiment 2 planes (EM1, EM2) Resolution 3 GeV σ E = E 23% E( GeV ) --- Chorus electrons pions 14

15 NDC Tracking Efficiency x NDC1 dipole NDC2 NDC5 beam z (q, p, θ x, θ y ) 0 B (x, y, θ x, θ y ) 2 2 Multi-track events (hit efficiency, hit density, pattern recognition) tracks type 1 (3-d segment in NDC1) migrate to type 2 tracks (2-d segment in NDC1) and type 3 tracks (hits in NDC1) Tracks type 2 & 3 + vertex constrain measure (p,θ,q). Size of migration hadronic model dependent Total efficiency hadronic model independent

16 Cross section σ π ij = F norm M kl ij ε 1 π kl ( π bkg N N ) kl kl (p,θ) absolute normalization Migration matrix Total efficiency Pion Yield Background 16

17 Cross section revisited track types Tracking Pion efficiency purity Runs on bins of (p,θ) acceptance Migration matrix Pion efficiency Measured pion yield 17

18 Number of primary particles with P measured Tracking efficiency Number of primary particles accepted Number of primary particles accepted with a reconstructed track segment downstream the dipole Downstream tracking efficiency up-down matching efficiency 18

19 Module acceptance and efficiency Acceptance of modules 3,4 & 5 normalized to acceptance in module 2 as a function of p and θ x (MC) Tracking efficiency of modules downstream the dipole as a function of x 2 and θ x2 (DATA) 19

20 Downstream tracking efficiency E down ~ cte(p,θ) = 98 % 20

21 Total tracking efficiency Total tracking efficiency as a function of p(left) and θ x (right) computed using MC properly scaled by data 21

22 PID probabilities P( p, λ π ) P( p, N phe π ) P( p, E1, E2 π ) tof cherenkov ecal λ=m 2 /p Nphe E 1 vs E 2 /p 2 2 entries entries electrons m 2 (GeV 2 ) N phe pions 22

23 Pion correction factor The yield of each track type must be corrected by pion efficiency & purity Compute using beam particles (clean particle selection from beam detectors) 23

24 K2K target Pion yield raw efficiency PID acceptance 24

25 Summary and Outlook HARP first results using the K2K replica target are now available. Measurement needed to improve the calculation of the far/near ratio in K2K will come soon. A similar analysis is proceeding on the MiniBooNE replica target (see talk by L.Coney) Further measurements of interest to the neutrino physics community will be provided by HARP in the near future... 25