e07-007 & e08-025 status report maxime defurne cea-saclay/irfu/sphn 1
DESCRIPTION
Experimental Setup Data taken from October to December Calorimeter 208 PbF 2 blocks 3TRANSCRIPT
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E07-007 & E08-025 status report
Maxime DEFURNECEA-Saclay/Irfu/SPhN
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Goals
• Measure DVCS and p0 electroproduction cross sections at different Q² off proton and neutron.
• Two beam energies:- Separate DVCS.BH and |DVCS|² terms.- Separate σL/σT of p0 cross sections.
t=(p-p’)²
GPD
g* g, p0Q2
pp’
xB Q² (GeV²) Energie faisceau(GeV)
0.36 1.5 (3.355 ; 5.55)
0.36 1.75 (4.455 ; 5.55)
0.36 2 (4.455 ; 5.55)
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Experimental Setup
• Data taken from October to December 2010.
Calorimeter
208 PbF2 blocks
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Data analysis• Beam line
- Polarimetry (Compton + Moller) data (FINISHED), E. Fuchey- Beam charge monitors (BCM) calibration (FINISHED), J. Roche
• HRS- Optics and mispointing checks (FINISHED), P. Bertin- Drift chambers time offsets (FINISHED), C. Munoz- Trigger/ detectors efficiency (FINISHED), M. Defurne, C. Hyde, M. Mazouz- Normalization : DIS cross section (IN PROGRESS), M. Defurne
• Calorimeter-Calibrations (FINISHED), A. Marti, C. Desnault, M. Ben Ali- Waveform analysis of PMT pulses (FINISHED), A. Marti- Timing corrections (FINISHED), M. Mazouz
• MC simulation- GEANT4 written from scratch based on previous GEANT3 and their comparison, (FINISHED) R. Paremuzyan, M. Defurne
• Physics analysis (IN PROGRESS)- DVCS off proton, A. Marti- DVCS off neutron, C. Desnault , M. Ben Ali- p0 electroproduction cross section, M. Defurne
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G3 counts
G4 counts
G4/G3 counts
R. Paremuzyan G3-G4 in relatively good agreement
G4 Simulation package
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Calorimeter calibration
• First step: block calibration coefficients are determined using elastic runs (proton in HRS, electron in the calo). (A. Marti)
• Second step: gain variations can be monitored and corrected day-by-day using e N -> e N p0 (C. Desnault – M. Ben Ali)
Missing mass eN->e p0 X and invariant mass of the two photons in the calorimeter (GeV²)
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C. Desnault
* Before calibration
* After calibration
Calorimeter calibration
Missing and invariant mass much more stable after calibration!!
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Normalization
• Normalization studies through Deep Inelastic Scattering cross section extraction.
-> Quality control, run-by-run
-> Quality of the normalization (corrections, charge calculation,…)
Upstream BCM Downstream BCM
2%
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Pion rejector spectrum of single and multitrack events
Energy (GeV)
Multitrack events in HRS
Multitrack eventscontribution
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Multitrack events in HRS• Between 5 and 10% of multitrack events
Failure of the tracking -> remove them and apply a correction
• BUT they are not all electron events: down to a 3% correction (max)
E<2GeV: Only pions
≥ 2 tracks
2 tracks3 tracks4 tracks5 tracks
E>2 GeV in 2 tracks: Electrons
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HRS acceptance
• First kinematics was run without collimator.
• 5 other kinematics were run with the collimator.
Collimator at the wrong position ?
R-function> 0.005
……. Monte Carlo
……. Experimental data
IN PROGRESS…
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M. Defurne
BCM problemCerenkov Threshold
IN PROGRESS…
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1 week
BCM problem
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Next …
• Adapt the R-function and/or find a suitable set of cuts to compute the HRS acceptance.
• Compare DIS results with theoretical value (F2 parametrization).
• First DVCS cross sections off proton for late Fall 2013.(A. Marti)
First DVCS off neutron (C. Desnault – M. Ben Ali) and p0
electroproduction cross sections (M. Defurne) for 2014.