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

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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 3

Transcript of E07-007 & E08-025 status report Maxime DEFURNE CEA-Saclay/Irfu/SPhN 1.

Page 1: E07-007 & E08-025 status report Maxime DEFURNE CEA-Saclay/Irfu/SPhN 1.

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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.