Subject: RE: Update on UED
From: Greg Landsberg <landsberg@hep.brown.edu>
Date: Sun, 12 Nov 2006 11:20:56 -0500
To: mercadan@fnal.gov
CC: 'Sergio Lietti' <lietti@fnal.gov>, "'Sergio F. Novaes'" <novaes@fnal.gov>, "'Eduardo M. Gregores'" <gregores@fnal.gov>

Hi Pedro,

Great - the new plots make perfect sense! The longer MET tail for the 4-muon channel is due to the fact that muon momentum at high pT is reconstructed with large uncertainty. Moreover, the effect is Gaussian in 1/pT, so it results in a very long upper tail in pT (i.e., the higher the pT of the muon is, the more uncertainty it has).

One way to aid the muon momentum resolution is to fit the muon track to the primary vertex position (beam spot x,y, or even 0,0 point). There is a standard package to do this in CAFÉ, and it would reduce the tails and make the distribution a bit sharper. However, the electron channel will still be better, since the calorimeter is more precise device than the muon system and tracker.

By the way, is there any reason you are not looking at the 4e channel, but just at ee-mumu and 4 mu?

Greg