1. DVCS – Hall A Study of the Background Noise HUGS 2008 Florian ITARD

2. University Blaise Pascal Clermont-Ferrand Laboratory of Corpuscular Physics (LPC)

3. Deeply Virtual Compton Scattering The simplest experiment to access to the GPDs Small cross section ~ 10 -9 Barn Latest experiment ran in 2004 Next experiment will run in may 2009 Exclusive experiment

4. Spectrometer Up beam tube pipe Down beam tube pipe Scattering chamber Proton array Calorimeter Target

5. High luminosity ~ 2.5*10 37 cm 2.s Important background noise Production of a continuous signal in the photo-mutipliers which is going to inconvenience the measure Appeareance of a darkening in the cristal Systematic errors New calibration yelded light undervalued Curing?

6. Simulation Monte Carlo: GEANT 4 One aim: Reduce the background noise without change the place of the calorimeter in the last experiment New detector simulation toolkit written in C++ and developped by The CERN collaboration Enable to generate any particules and follow them in the geometry of the experiment 10 Millions electrons generated by run 9 hours calculation in a farm Window of 640 ns

7. Reference results Mean energy deposited by each electron reaching the target (KeV)

8. Cone beam pipe Rectangular beam pipe Tungsten shielding Polyethylen front shielding

9. Final results Mean energy deposited by each electron reaching the target (KeV)

10. Mean energy fonction on the depth of the block Curing ?

11. THE END