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J/Psi kinematics (200/500 GeV in FMS)

Updated on Thu, 2016-06-23 09:28. Originally created by oleg on 2016-06-03 14:00.
Kinematics of J/Psi->e+e in the FMS acceptance from PYTHIA simulation.

pythia6->SetMSUB( 86, 1 ); // g+g->J/Psi+g
pythia6->SetMSUB( 87, 1 ); // chi_c0+g
pythia6->SetMSUB( 88, 1 ); // chi_c1+g
pythia6->SetMSUB( 89, 1 ); // chi_c2+g
pythia6->SetMSUB( 106, 1 ); // g+g->J/Psi+gamma
pythia6->SetMSUB( 107, 1 );
200 GeV

(scaled to 40 pb-1 integrated luminosity = recorded in run 15)

The colored ranges under the top left plot refer to the colors in the stack plot below.

 
500 GeV

(scaled to 40 pb-1 as above)

The colors in the stack plot (bottom left) are the same energy ranges as for 200 GeV.

There are about an order of magnitude more J/Psis at 500 GeV.
Energy and transverse momentum distributions are a little wider, but not too different.




Minimum bias (QCD) pythia, 500 GeV 

100M events
Selection of photon pairs in the FMS acceptance only
(no hadronic toy modeling, vertex smearing, or energy resolution)

Invariant mass distribution for Epair>50 GeV



Example from run 15 (day 66)
Minimal cuts:
- cluster energy > 2.0 GeV
- energy asymmetry < 0.5

Bottom plot:
- comparison of suppression for preshower response
- both hits need a match in first two preshower layers (remove photons)
- including layer 3 for electrons has no mass dependence either


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