Status Report of the HARP experiment

1
Status Report of the HARP experiment

• The HARP Experiment
• Physics goals and motivations
• Summary of the experimental programme
• Detector overview and performance
• TPC
• Calibration status
• The fist physics analysis pion yields for K2K
  target
• Goals
• Results
• Petar Temnikov
• INRNE Sofia, Bulgaria

2
Physics goals

• Precise (2-3 error) measurement of
• d2s/dpTdpL
• for secondary HAdRon Production by incident p
  and p with
• Beam momentum from 1.5 to 15 GeV/c
• Large range of target materials, from Hydrogen to
  Lead
• Acceptance over large solid angle
• Final state particle identification

3
Physics motivations
Input for prediction of neutrino fluxes for the
MiniBooNE and K2K experiments
Pion/Kaon yield for the design of the proton
driver and target system of Neutrino Factories
and SPL- based Super-Beams
Input for precise calculation of the atmospheric
neutrino flux (from yields of secondary p,K)
Input for Monte Carlo generators (GEANT4, e.g.
for LHC or space applications)
4
Data taking summary
HARP took data at the CERN PS T9 beam-line in
2001-2002 Total 420 M events, 300 settings
SOLID
CRYOGENIC
n EXP
5
The HARP experiment
Bari University ,  CERN ,  Dubna JINR , 
Dortmund University ,  Ferrara University , 
Geneve University , P.N. Lebedev Physical
Institute ,  Legnaro /INFN ,  Louvain-la-Neuve 
UCL ,  Milano University/INFN ,  Moscow INR , 
Napoli University/INFN ,  Oxford University , 
Padova University/INFN ,  Protvino IHEP,
Protvino ,  Paris VI-VII University ,  RAL
, Roma I University/INFN Roma Tre
University/INFN , Sheffield University , Sofia 
Academy of Sciences ,  Sofia  University , 
Trieste  University/INFN ,  Valencia University

124 physicists
24 institutes
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The HARP detector layout
TRACKING PARTICLE ID at Large angle and Forward
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Beam detectors
MWPCs
TOF-B
TOF-A
TDS
CKOV-A
CKOV-B
T9 beam
21.4 m

• Beam tracking with MWPCs
• 96 tracking efficiency (requiring 4 planes out
  of 4)
• gt99 efficiency using 3 planes out of 4
• Resolution lt100 mm

MiniBooNE target
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Beam particle selection

• Beam TOF
• separate p/K/p at low energy over 21m flight
  distance
• time resolution 170 ps after TDC and ADC
  equalization
• proton selection purity gt98.7
• Combined time resolution for time definition 70
  ps

p
3 GeV/c beam
p
d
K
12.9 GeV/c beam
p

• Beam Cherenkov (two counters)
• Identify electrons at low energy, p at high
  energy, K above 12 GeV
• 100 eff. in e-p tagging

K
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Large angle detectors

• TPC
• Full track reconstruction available
• Calibration campaign with TPC in T9 area in 2003
• Calibration with sources
• Calibration with cosmic rays
• Systematic study of corrections
• Basic calibrations revisited (time, charge,
  position)
• Cross-talk correction
• Distortion correction
• Ready for physics analysis
• RPCs
• Results later

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Raw Data
Track reconstruction
Equalisation
Clustering
Distortion Correction
Track finding
Track fit
Kalman filter
Momentum
dE/dx Algorithm
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Raw Data
Track reconstruction
Equalisation
Clustering
Distortion Correction
Track finding
Track fit
Kalman filter
Momentum
dE/dx Algorithm
12
Raw Data
Track reconstruction
Equalisation
Clustering
Distortion Correction
Track finding
Track fit
Kalman filter
Momentum
dE/dx Algorithm
13
Raw Data
Track reconstruction
Equalisation
Clustering
Distortion Correction
Track finding
Track fit
Kalman filter
Momentum
dE/dx Algorithm
14
Raw Data
Track reconstruction
Equalisation
Clustering
Distortion Correction
Track finding
Track fit
Kalman filter
Momentum
dE/dx Algorithm
15
Raw Data
Track reconstruction
Equalisation
Clustering
Distortion Correction
Track finding
Track fit
Kalman filter
Momentum
dE/dx Algorithm
16
TPC calibration campaign
High statistic cosmic ray calibration and
calibration with 55Fe and 83Kr sources
TPC re-installed in T9 Area
Trigger scintillator

• Cosmic data taking
• during 2003
• Trigger (scintillator
• of 2 cm thickness)
• inside inner field cage
• -345 mm lt z lt 255 mm

Mapping of gain Mapping of dead pads First dE/dx
evaluation Evaluation of the performance of
correction for cross-talk effect and distortions
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Charge calibration data with sources
55Fe ? E 3.0 keV 5.9 keV
83Kr E 32.2 kev 41.6 kev
5.9 keV
41.6 keV
32.2 keV
3.0 keV
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Momentum and dE/dx response

• dE/dx over full track

Protons (few )
protons
Muons and pions
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Elastic scattering
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

Missing mass mx2 ( pbeam ptarget pTPC )2

• Target liquid H2 (cryogenic target)
• Target length 18 cm
• Beam of p and ? of 3 GeV/c

20
Missing mass distributions
p p -gt p p
? p -gt ? p
Red using dE/dx for PID

• missing mass for p p?p p and ?p ? ? p
• Select p and ? in the beam by ToF
• BLUE Simple selection
• Only 1 pos. track in the TPC coming from the
  target
• RED Additional cut on dE/dx in TPC (select
  proton)

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Forward spectrometer

• Analysis for pion yields in K2K

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Analysis for K2K motivations
near/far ratio R For point-like
source (without oscillation), R1/r2
If the near detector does not see a
point-like source -gt R depends on En
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Analysis for K2K interesting region
Dip from neutrino oscillations in K2K

• K2K needs measurement of pions with
• Egt1 GeV
• Elt4.5 GeV
• qlt300 mrad
• Forward region
• Main tracking detectors drift chambers
• PID detectors TOF, Cherenkov, calorimeter

they come from decay of these pions
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Forward acceptance
K2K interest
p GeV/c
NDC2
NDC1
dipole
x
z
B
K2K interest
A particle is accepted if it reaches the second
module of the drift chambers
P gt 1 GeV
q mrad
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Forward tracking
Downstream
Upstream

• 3 track types depending upstream information
• Track-Track
• Track-Plane segment
• Track-Target/vertex
• recover efficiency and avoid dependencies on
  track density in 1st NDC module (model
  dependence)
• Calculate efficiency separating downstream system
  first

Downstream tracking efficiency 99
Up-downstream matching efficiency 75
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Tracking efficiency
MC
data

• Computed with DATA and MC
• DATA detector inefficiencies and finite
  resolution
• MC Geometrical effects
• Known now to 5

Green type 1 Blue type 2 Red type 3
Black sum of normalized efficiency for each type
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Particle identification
0 1 2 3 4 5 6
7 8 9 10
P (GeV)
p/p
TOF
CERENKOV
CAL
TOF
p/k
CERENKOV
TOF
CERENKOV
p/e
CERENKOV
CALORIMETER
data
3 GeV/c beam particles
CALORIMETER
TOF
p
CERENKOV
h
p
p inefficiency
e
p
p
e
number of photoelectrons
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Combined PID correction factor
The yield of each type of track must be corrected
by pion efficiency and purity computed using
beam particles (clean particle selection from
beam detectors)
Pion purity ?j?-(t) Nj?-true-obs / Nj?-obs
Pion efficiency ?j?-(t) Nj?-true-obs /
Nj?-true
Pion yield Nj?-true-obs Nj?-obs - Njbkg
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Pion yields
p gt 0.2 GeV/c ?y lt 50 mrad 25 lt ?x lt 200
mrad
Raw data
p e-
After PID correction
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Preliminary results

• To do
• Correction for resolutions
• Absolute normalisation
• Empty target subtraction
• q0 region, full statistics

p gt 0.2 GeV/c ?y lt 50 mrad 25 lt ?x lt 200
mrad
After efficiency and acceptance correction
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Summary

• The HARP Experiment has collected data for hadron
  production measurements with a wide range of beam
  energies and targets
• Status of detector
• Forward region good tracking and PID
• Large angle much recent progress
• First physics results are available K2K target
  replica
• Using forward region of the detector
• Next MiniBooNE analysis and first large angle
  analysis
• TPC calibration nearly complete, physics can
  start now

Measurements that will be provided by HARP in the
near future are important for neutrino physics
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Forward Tracking
NDC4
Top view
NDC2
NDC1
dipole magnet
NDC5
3
target
1
beam
Plane segment (2D)
2
Track (3D)
NDC3

• Categorize into 3 track types depending on the
  nature of the matching object upstream the dipole
• Track(3D)-Track(3D)
• Track(3D)-Plane segment(2D)
• Track(3D)-Target/vertex constraint
• To recover as much efficiency as possible
• To avoid dependencies on track density in 1st NDC
  module (hadron model dependent)

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The cross section

• The 3 types of tracks must be treated separately
  because of the different momentum resolution

i bin of true (p,?) j bin of recosntructed
(p,?)
depend on momentum resolution
migration matrix (not computed yet)
pion yield
acceptance
pion efficiency
tracking efficiency
pion purity