Evaluation of Run 9 BTOW Calibration for W analysis

Motivation:

A 2x2 cluster of barrel towers is used in the W analysis to measure of the electron energy.  The absolute scale of the current BTOW calibration uses relatively low energy electrons.  The extrapolation of this calibration to higher energies should be confirmed, in order to use it for high Et electrons from W decay.

Ideas:

1) Electrons

    a)  Low Et   ->  Matt set absolute scale of calibration from low Et electrons in pp200 link

    b)  High Et  ->  W -> e + nu candidates provide a ~clean sample of electrons where an E/p analysis could be done preliminary study. 

    c)  Mid Et    ->  A similar procedure to what Matt did at low Et could be done at some Et ~ 15 to try and get another point for linearity. 

                         ->  Could use looser cuts to increase statistics (eg. use 2x2 cluster instead of single tower with dR cut).

2)  Reconstruct Invariant Mass

    a)  Pions -> photon separation might be too small at high Et

    b)  Etas   -> at high Et photon separation is similar to low Et pions, but this is big job

    c)  Zs       -> provide calibration point at the desired energy scale, but only ~15-20 in Run 9

3)  What else?

Other things to check:

• Longitudinal Shower Leakage
• Transvers Shower Leakage
• Energy loss from material
• What else?