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E07-007 & E08-025 s tatus report

E07-007 & E08-025 s tatus report. Maxime DEFURNE CEA-Saclay/ Irfu / SPhN. Goals. Measure DVCS and p 0 electroproduction cross sections at different Q² off proton and neutron . Two beam energies: - Separate DVCS.BH and |DVCS|² terms. - Separate σ L / σ T of p 0 cross sections.

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E07-007 & E08-025 s tatus report

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  1. E07-007 & E08-025 status report Maxime DEFURNECEA-Saclay/Irfu/SPhN

  2. Goals • Measure DVCS and p0 electroproductioncross sections atdifferent Q² off proton and neutron. • Two beam energies:- Separate DVCS.BH and |DVCS|² terms.- Separate σL/σT of p0 cross sections. g, p0 g* GPD Q2 p p’ t=(p-p’)²

  3. Experimental Setup • Data taken from October to December 2010. Calorimeter208 PbF2 blocks

  4. 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

  5. G4 Simulation package G3 counts G4 counts G4/G3 counts R. Paremuzyan G3-G4 in relatively good agreement

  6. 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->ep0 X and invariant mass of the two photons in the calorimeter (GeV²)

  7. Calorimeter calibration * Before calibration * After calibration C. Desnault Missing and invariant mass much more stable after calibration!!

  8. Normalization • Normalization studies through Deep Inelastic Scattering cross section extraction.-> Quality control, run-by-run-> Quality of the normalization (corrections, charge calculation,…) Downstream BCM Upstream BCM 2%

  9. Multitrackevents in HRS Pion rejectorspectrum of single and multitrackevents Multitrackevents contribution Energy (GeV)

  10. Multitrackevents 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) ≥ 2tracks E>2 GeV in 2 tracks: Electrons E<2GeV: Only pions 2 tracks 3tracks 4 tracks 5tracks

  11. HRS acceptance • First kinematics was run without collimator. • 5 other kinematics were run with the collimator. R-function> 0.005 ……. Monte Carlo ……. Experimental data Collimator at the wrong position ? IN PROGRESS…

  12. M. Defurne IN PROGRESS… CerenkovThreshold BCM problem

  13. BCM problem 1 week

  14. 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.

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