DATA/MC COMPARISON AT THE Z0 PEAK

Using old preselections (including electrons from 4 GeV)

MC normalisation at hadronic selection

Real data

MC qq~

Normal. MC

Total

177350

66517

Hadronic

49950

65406

Presel.

6782

9170

6997

El. id.

205

396

302

Fair agreement in preselection, bad disagreement in el. id.

Data-MC comparison ( plots )reasonable

Look at electron energy for 2tight and 1tight1loose selected pairs: the disagreement is all in the low energy region, below 10 GeV. New preselections: require 2 electrons above 10 GeV

Real data

MC qq~

Presel.

440

368.6

El. id.

46

45.78

Unsatisfactory presel. agreement (but data-MC comparison plots not in bad shape). Conclusion: adopt new preselections and abandon the old 0.5 factor for 1tight-1loose pairs.