Does CPS aid energy resolution of Z’s Part 3

1. Does CPS aid energy resolution of Z’sPart 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 Z’s and extract layer weights for 5 layers(EM1-4+FH) and 6 layers(+CPS) • Match electrons (reconstructed to MC) 0.02 in h f • c2 = S(a0*Ecps + a1*Eem1 + a2*Eem2 + a3*Eem3 + a4*Eem4 + a5*Efh –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->ee MC studies didn’t agree… • Generated single e MC at 50 GeV energy, at 4 fixed eta just like they did. (obviously not just like…)

5. Calo modern MC Calo+CPS modern MC 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. Smear all CPS Energy Smear layer Energy Smear strip Energy 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->ee 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.