Alexandre Camsonne Jefferson Laboratory Hall A Collaboration meeting June 21 st 2007

Complete Separation of Deeply Virtual Photon and 0

Electroproduction Observables on Unpolarized ProtonsE07-007

Alexandre Camsonne

Jefferson Laboratory

Hall A Collaboration meeting

June 21st 2007

http://hallaweb.jlab.org/experiment/DVCS

Hall A Collaboration meetingApril 19, 2023

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Overview

• New DVCS experiment

– What we learnt from E00-110 and E03-106

– DVCS2

– 0 production

• Detector upgrade

– Calorimeter

• Radiation hardness test

• Calorimeter upgrade

– Electronics upgrade

• Sampling system upgrade

• Calorimeter trigger upgrade

• Man power

• Timeline

• Conclusion


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E00-110 and E03-106

• First dedicated experiment proposed for the study of the Deeply Virtual Compton Scattering ( E00-110 )

• 4 years of developments, ran in 2004

• A unique approach from what was done previously and now

– High resolution on a limited kinematic range

• Study of scaling with fixed xbj and variation in Q2

– High resolution calorimeter

– Focus on cross section measurement

– Ensure exclusivity

– High luminosity1037 cm-2.s-1


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Experimental setup


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What we learnt from E00-110 and E03-106

• The good– Experiment is possible– New dedicated electronics worked ( elastic cross section )– Resolution is sufficient to work in double arm

• The “less” good– Triple coincidence cross sections are difficult ( on going effort to

understand efficiency of proton array )– Radiation damage very random– Calibration of the calorimeter is very important because of

radiation damages– 0 were cut by threshold on calorimeter trigger– Dead time can be large with high spectrometer rates– Better study of background effects needed to be taken into account

in simulation ( more random runs )


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What we learnt about physics

• Early scaling

• Contribution of the DVCS2 amplitude is not negligible at JLab kinematics

• 0 production very interesting to study

• Calibration is possible using 0 and -


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E07-007 motivations

• Improvements compared to previous experiment

– Use of 2 beam energies

• Study 0 production with a LT separation

• Study of the importance of the DVCS2

– Calorimeter work

• Increase size for larger acceptance

• Blocks selection

• Curing of radiation damage

– Improvement in 0 detection

• Better kinematical range ( lower threshold cut)

• Improved 0 subtraction


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E07-007 motivations

At this day (Jun 21 2007):

3% HRS+PbF2 acceptance +luminosity + target

3% H(e,e’)X p0 background

2% Inclusive H(e,e’)Np

2% Radiative Corrections only on the cross section difference

2% Beam polarization measurement

Total (quadratic sum)= 5.1% (5.6%)

1% X

1% X

2% X

For the future experiments

3.6 - 3.7 %

Expected errors :


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New experimental setup• Double arm experiment : proton array not needed

• Calorimeter

– Increased size of the calorimeter from 132 to 208 blocks for larger acceptance in t

• Electronics

– Improved trigger for optimal pi0 detection

– Speed improvement to accommodate lower threshold


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Experimental setup

New beamline design


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E07-007 new issues

• No proton array means higher luminosity but also higher irradiation damages

• 0 detection imply lower thresholds

– New trigger scheme

– Improve rate capability of system


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Calorimeter curing

• Systematic irradiation of blocks to reject the bad ones

• Ohio State University – Test transmission

summer student Sylvain Gregoire

– FEL block irradiation test: recreate dose from experiment

– Blue light curing process similar to process used at Mainz on PVA4


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Data acquisition

• Redesign for new calorimeter geometry

• New trigger

– Triggering on total sum

• Digital

• Analog sum

– Multiple level trigger

Effectively reduce threshold on many clusters event to detect 0


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Data acquisition

• Sampling system– Different alternative

• Simple one increase bandwidth by using larger number of crates

• Upgrade ARS motherboard to new technologies using same form factor

– VME64 ( 80 Mbytes/s )– 2eVME ( 160 Mbytes/s )– VME320SST ( 320 Mbytes/s)

• Switch serial VXS ( 1 Gbyte/s)• Technical choice to be decided soon since we have 2 years to

develop • Depends on man power available


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Man power

• Ohio

• Clermont Ferrand

• ODU

• Jefferson Laboratory

– More collaborators welcomed !

• Calorimeter design

• Mechanical design

• electronics

• Analysis

• Collaboration meeting in September


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Timeline

•MRI submitted for financing calorimeter upgrade by ODU/OU

•Result by the end of June

•Procurement of PMTs and PbF2 blocks

•Electronics

•FEL irradiation tests

•Fall 2007

•Start fiscal year 2008 : mechanical design

•might be scheduled as soon as second half of 2009


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Conclusion

• Capitalizing on what was learnt from the previous experiments by improving the method

– LT separation for the 0

– Evaluation of the importance of the DVCS amplitude

– 6 GeV experiment in could run in 2009

• Research and development on PbF2 calorimeter curing

• Development of new trigger scheme and investigating electronics speed improvement.

Documents

Alexandre Camsonne Jefferson Laboratory Hall A Collaboration meeting June 21 st 2007