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Subject: RE: UED simulation %BR%
From: Greg Landsberg <landsberg@hep.brown.edu> %BR%
Date: Fri, 14 Jul 2006 11:24:16 -0400 %BR%
To: mercadan@fnal.gov %BR%
CC: 'Sergio Lietti' <lietti@fnal.gov>, "'Eduardo M. Gregores'" <gregores@fnal.gov>, 'Sergio Novaes' <novaes@fnal.gov>
 
Hi Pedro,
 
Thanks - this is quite revealing. It looks like the same-sign lepton
branching fraction is about 2% (can you provide us with the precise number
and also break it into ee, mu-mu, and e-mu categories) and we will have
sensitivity up to 1/R ~ 300 !GeV (100 fb) in this channel. This looks very
promising, especially if we require some missing ET or presence of jets to
decrease the backgrounds. The background itself should be fairly small and
likely dominated by heavy flavor production with subsequent decays into
muons and charge misidentification, which is small for low-pT leptons.
 
It would be nice to know what price we would have to pay if we require an
extra (third) lepton of any sign. 5 !GeV pT cut on the second-leading lepton
is probably too soft for muons (and definitely too soft for electrons). I'd
suggest using 10 !GeV as a default (factor of ~1.7 down in cross section
judging by Fig. 13) for muons and perhaps 15 !GeV for electrons (what's the
corresponding acceptance loss?). One thing that I find surprising is that
the ratio of cross sections with 5 and 10 !GeV cut seems to be constant in
the entire range of 1/R between 200 and 400 !GeV. This is somewhat
counterintuitive, but perhaps implies that the mass splitting between the
states doesn't depend much on the overall scale. However, one should have
much larger jet activity for higher 1/R.
 
Greg
Topic revision: r1 - 2006-11-16 - SergioLietti
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