Results from HARP Malcolm Ellis On behalf of the HARP collaboration DPF Meeting Riverside, August 2004
The HAdRon Production Experiment 124 physicists 24 institutes2
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
Data Taking Summary HARP took data at the CERN PS T9 beam-line in 2001-2002 Total: 420 M events, ~300 settings SOLID: CRYOGENIC: ν EXP: K2K: Al 5% 50% 100% Replica +12.9 GeV/c MiniBoone: Be 5% 50% 100% Replica +8.9 GeV/c LSND: H 2 O 10% 100% +1.5 GeV/c
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
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
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
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
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
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
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
π/p using TOF 0-4.5 GeV m 2 TOF TDS 2 2 tw t0 = p 1 L Tof ~160 ps 7σ π/p @ 3 GeV Beam ~70 ps entries 3 GeV beam particles 5 GeV beam particles 350 300 250 200 150 100 50 0 Beam TOF t a t b t c π + p -1-0.5 0 0.5 1 1.5 2 m 2 (GeV 2 ) target t 0 data π + L k 12 t w Tof Wall
data entries 3 GeV beam particles 1400 1200 1000 800 600 400 200 0 p π + π/p using Cherenkov Cherenkov π inefficiency e + 0 5 10 15 20 25 30 35 40 45 50 N phe entries π / p p> 3 GeV π / k 3 <P< 9 GeV 5 GeV beam particles 1200 1000 800 600 400 200 0 p π inefficiency π + 0 5 10 15 20 25 30 35 N phe number of photoelectrons N phel 2.6 GeV Threshold pions 3-15 GeV e + π + 9.2 GeV Threshold kaons P (GeV) 2 ( 1+ ( m ) ) 1 N phel α N0 1 / p 2 n 13 N phel N phel
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
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 1 3 15
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
Cross section revisited track types Tracking Pion efficiency purity Runs on bins of (p,θ) acceptance Migration matrix Pion efficiency Measured pion yield 17
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
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
Downstream tracking efficiency E down ~ cte(p,θ) = 98 % 20
Total tracking efficiency Total tracking efficiency as a function of p(left) and θ x (right) computed using MC properly scaled by data 21
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 350 300 250 entries 1400 1200 1000 200 150 800 600 electrons 100 50 0-1 -0.5 0 0.5 1 1.5 2 m 2 (GeV 2 ) 400 200 0 0 5 10 15 20 25 30 35 40 45 50 N phe pions 22
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
K2K target Pion yield raw efficiency PID acceptance 24
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