1. EM resolutions from low to high energy Jan Stark, LPSC Grenoble CAT Force meeting, May 13 th, 2003

2. Jan StarkCATF, May 13th, 20032 Goal Goal: Compare mass resolutions (i.e. electron energy resolutions) predicted by MC and determined in data for resonances that decay to e + e -. Use different resonances that cover a wide energy range (i.e. J/ , , Z). Studies of J/  and  e + e - are difficult as we do not have a trigger for these events (yet). Extremely difficult to trigger on because of high low-energy di-EM rates. Made easier by the additional information that is now provided by the CTT. J. Stark, “Di-EM triggers using CTT”, Trigger Board workshop, April 10 th, 2003. New trigger currently under implementation (work done with V. Büscher et al.) While we are waiting for data taken with the new trigger: run over all events we write to tape an look for J/  and . Over the last few days I went through the painful process of running over all available p13.06.01 data to make a road di-EM skim.

3. Jan StarkCATF, May 13th, 20033 J/   e + e - using road method Use all available p13.06.01 data. J/  selection criteria: pairs of road electron candidates with opposite charge, |  | 4 GeV for each electron candidate (as said on previous slide, we cut at p T > 3 GeV for b-ID), p T asymmetry where p T,1 and p T,2 are the transverse momenta of the two electron candidates, p T > 12 GeV for J/  candidate. Remark:Ultimately, we want the energy resolution for EM clusters, not for road tracks. The road study is just a first step to get some signal (think of it as an alternative form of track-matching). It also allows us to test if the calorimeter response in the road is well modelled in MC.

4. Jan StarkCATF, May 13th, 20034 J/  yields in p13.06 data Estimate efficiency to tag loose electron as tight: one tight + one loose electron two tight electrons candidates in peak: n 1 = 440 ± 63 candidates in peak: n 2 = 347 ± 30 MC prediction:  92 % (somewhat old sample, with lower J/  transverse momentum). Revised cardfiles for MC production, generating more appropriate MC samples at CCIN2P3.

5. Jan StarkCATF, May 13th, 20035 Next steps Have J/ , get corresponding clusters. Determine mass resolution using EM information rather than track parameters. Optimise  selection. Look at the latest Monte Carlo (also for Z) Make inventory of resolutions. Looking forward to presentation of numbers in the next meetings.