EM resolutions from low to high energy

1
EM resolutions from low to high energy

• Jan Stark, LPSC Grenoble

CAT Force meeting, May 13th, 2003
2
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 10th, 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
J/? ? e e- using road method

• Use all available p13.06.01 data.
• J/? selection criteria
• pairs of road electron candidates with opposite
  charge,
• ? lt 1.1 and pT gt 4 GeV for each electron
  candidate
• (as said on previous
  slide, we cut at pT gt 3 GeV for b-ID),
• pT asymmetry
• where pT,1 and pT,2 are the transverse
  momenta of the two electron candidates,
• pT gt 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
J/? yields in p13.06 data
one tight one loose electron
two tight electrons
candidates in peak n2 347 30
candidates in peak n1 440 63
Estimate efficiency to tag loose electron as
tight
MC prediction ? 92 (somewhat old sample,
with lower J/? transverse momentum). Revised
cardfiles for MC production, generating more
appropriate MC samples
at CCIN2P3.
5
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.