GPD program COMPASS

1
GPD program _at_ COMPASS
COMPASS unique for its range in Q2 and x
1- First experiment in 2011 dedicated to the GPD
H ?, ?- beam of 100 GeV RPD
ECAL1,2 and 0 all COMPASS equipments
d?/dt ? impact parameter
2- Second experiment in 2013 dedicated to the
GPD E with ? and transverse target
recoil ECAL1,2 and 0 all COMPASS
equipments

2

• Detector, targets, beam condition
  required
• 1- for 1rst exp (H)
• 4m long Recoil Proton Detector
  (Saclay-Freiburg-Bonn-Mainz-Warsaw)
• a long 2.5m long H2 (CERN? Saclay?)
• 2- for 2nd experiment (E) ? 2 possibilities
  to study
• or the 4m long Recoil Proton Detector
• a new transversely polarized NH3
  target inserted inside the RPD
• RD (W. Meyer)
• or the present transversely polarized NH3
  COMPASS
• a tricky Recoil Detector placed
  inside the target (SciFi?) RD (who?)
• 3- Calorimetry angular and energy domain
• ECAL12 studied in the Calorimeter
  sub-group
• ECAL0 to be build role, design, preliminary
  study (Dubna)

3
(DVCS, DY,Transv)

• DVCS at large Q2 gt 1 GeV2 at E?100 GeV
• ? many scattered muons end up in the first
  spectrometer
• Solution with 2 hodoscopes one at z2.2m and
  another at z16m
• 2007 installation efficiency close to 50
• for future
• used of HCAL1 but still lower threshold and
  higher rate
• used af a flexible electronics (with FPGA)
• for a higher granularity
• for a better vetoing (for only
  corresponding veto channel)

4
E?160 GeV
E?100 GeV
5
Status of simulations of DVCS

• Fast simulations
• Etienne VGG generator experimental
  resolution PYTHIA background
• Andrzej FFS generator experimental
  resolution
• ?
  background to be introduced
• Alexander VGG generator experimental
  resolution PYTHIA background
• ?
  for ECAL0 design
• ? it is URGENT to have convergence with all
  these simulations
• next week Etienne and Andrzej at CERN

• Complete simulations
• Marcin started the work
• Andrzej Sebastian are introducing the RPD
• Franck with the Calorimeter group ? to produce
  a realistic simulation of ECAL
• ? it is URGENT to get more support for
  this important task

6
List of Figures to produce
0- selection of DVCS events with missing mass,
angular cuts above the background resolution
in t, ? 1- for H2 target - d?/dt as a
function of t at different values of x, Q2
statistics and systematics to extract the
impact parameter - 2- for Transverse
target - no prediction yet
Not only the BCSA
7
2008 DVCS feasibility study in the
COMPASS environment
µ p ? µ ? p
in the RPD
in ECAL12
2008 Request to the collaboration for
switch-over from pion beam to muon beam
for 5 days Goal 1 a better knowledge of the ?
and ?- beams beam size (Si),momentum
(BMS), beam halo (forward spectro, RPD) Goal 2
a better knowledge of the RPD and its
extrapolation to a larger size comparison
hadrons (5?107 ? / 10s (5 MHz)) muons (2?5 108
? / 5s (50 MHz)) - rates in PMT, multipl.,
waveforms using Rand., Incl., RPD
triggers 1000 exclusive rho events in 5 days
- efficiency, purity of the RPD -
kinematical fit, azimuthal correlation -
comparison t from recoil proton detector
or from COMPASS spectro t
(p - p)2 (q? - q?)2
8

• Goal 3 a better knowledge of the Calorimetry
• ? detection
• as a function of E? and the E? threshold
  energy
• in ECAL2 (x_Bj 0.05 and E? DVCS gt 10 GeV)
• in ECAL1 (x_Bj 0.1 and E? DVCS gt 5 GeV)
• thresholds of 1 GeV in ECAL1 and 2 GeV in ECAL2
• should be necessary for a good ?/? separation
• low noise level and pile up rejection (with the
  SADC)
• study as a function of the beam
  intensit
• necessity to measure with random
  trigger without/with beam
• selection of all ? produced with a scattered
  muon and a recoil proton
• (we have only 125 DVCS
• which could be hardly observed above the
  background)

9
One day workshop on the COMPASS physics
case When 14 November 2008 starting at 900
or 17 November ?? or in
2009 Where Freiburg Invited speakers
Markus Diehl physics case for COMPASS proposal
Matthias Burckart spin bugdet of the proton
they have already accepted Dieter
Mueller Models Maxime Polyakov Marc
Vanderhaeghen Pierre Guichon Andreas
Schaeffer Lattice projection in the next years
Next GPD meeting before the next analysis
meeting Wednesday 15
October 1700