Does CPS aid energy resolution of Z

1
Does CPS aid energy resolution of ZsPart 3

• Drew Alton
• University of Michigan
• See http//d0server1.fnal.gov/Users/
• dalton/CPS_d0note_v1.doc

2
CPS purpose

• Recover EM energy resolution lost by solenoid and
  other tracking materials
• Improve EM identification
• Better spatial match then Cal. for track
  matching. And other separation of electrons from
  fakes.
• Separation of p0 and g.
• Soft electron tag for b jet id.
• CPS is ready for all of these.
• What about EM energy resolution

3
Plan

• Take MC Zs and extract layer weights for 5
  layers(EM1-4FH) and 6 layers(CPS)
• Match electrons (reconstructed to MC) 0.02 in h f
• c2 S(a0Ecps a1Eem1 a2Eem2 a3Eem3
  a4Eem4 a5Efh Emc)
• Minumize wrt as gives 6 equations and 6 unknowns.
• Solve the linear algebra and get as
• Apply and see how much better the resolution is.
• Now look at saturation effects.
• Smearing effects.
• Comparison to D0 note 3535

4
D0 Note 3535

• This note looked at including CPS Energy in layer
  weights.
• Used single 50 GeV electrons at fixed eta and
  phi.
• Phi hit center of module
• No clustering for Cal or CPS, all geant energy
  used.
• Determined CPS needed 10 calibration.
• My Z-gtee MC studies didnt agree
• Generated single e MC at 50 GeV energy, at 4
  fixed eta just like they did. (obviously not
  just like)

5
MC vs MC

• Energy Resolution vs eta
• Note differences
• Fixed phi/eta vs whole dist
• Clustered Cal and CPS
• Saturated CPS (60 MeV)
• Anything else?

6
More MC vs MC

• Energy Resolution vs smearing

7
Saturation

• MC saturation at 60 MeV.
• Less then 10 of electrons have saturated strip
• Almost 30 have floorE(0)0.
• Apply other saturations
• CPS cluster
• 3 layers
• Each layer 5 or less strips
• Only have strip energy for center 3

Cal only Raw from MC
Cal only New MC weights
Electron energy resolution in Z-gtee
Saturation of CPS in GeV
8
Saturation and smearing
Cal only Raw from MC

• Smear for 2 saturations.
• Smear each available channel by gaussian
• Gaussian centered on MC value, with sigma a
  fraction of that value.

Saturation of 0.02 GeV
Cal only New MC weights
Saturation of 0.06 GeV
9
Conclusions/Plans

• Saturation is worse than mis-calibration.
• Gain set to saturate at 60 MeV is reasonably good
  for electrons from Z and W.
• No one cares about CPS for higher pt electrons
  right?
• Refocus our efforts to
• Set the gain in this fashion
• Extrapolate for the 10 which saturate
• Calibration will be left with the 30
  uncertainty.
• Make MC and Data agree as well as we can.

10
What went wrong

• Turns out the pipeline of the svx saturates at
  about 20 above how we are operating the detector
  now.
• The only fix would involve removing all CPS
  boards and changing capacitors.
• Other options
• Counting strips
• Achieves 2/3 the improvements of perfectly
  calibrated cps
• predicting the energy lost due to saturation
• Simple predictions based on the MC give an
  effective smearing of 10. Should be smaller
  than but about the same as smearing from
  calibration.