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Although we have frozen our selection I was curious to check a couple more distributions between electrons and muons. I did the data-MC comparison on the B0 sample for pnu (missing momentum) http://www.slac.stanford.edu/~rfaccini/phys/vub/mm2_min/comparisonnorm7pnuallcuts.ps (electrons) http://www.slac.stanford.edu/~rfaccini/phys/vub/mm2_min/comparisonnorm7pnuallcuts-mu.ps (muons) pznu (projection along Z of missing momentum) http://www.slac.stanford.edu/~rfaccini/phys/vub/mm2_min/comparisonnorm7pznuallcuts.ps (electrons) http://www.slac.stanford.edu/~rfaccini/phys/vub/mm2_min/comparisonnorm7pznuallcuts-mu.ps (muons) ctnu=pznu/pnu (missing momentum collinearity with the beam) http://www.slac.stanford.edu/~rfaccini/phys/vub/mm2_min/comparisonnorm7ctnuallcuts.ps (electrons) http://www.slac.stanford.edu/~rfaccini/phys/vub/mm2_min/comparisonnorm7ctuallcuts-mu.ps (muons) comments: - there is a clear indication of low missing momentum, high beam collinearity events in the muon sample. They should be due to misidentified muons, i.e. other background, peaking far from the signal region in Mx - the electrons seem to be reasonably reproduced , a part from a peak at 0 in the pznu distribution which is completely absent in MC. These events don't have 0 momentum, so they seem to be events with missing momentum pointing in the vertical direction. The effect is no that significant and it does not seem to be related to high mm2 events which are instead at high pznu (>2 GeV) nothing conclusive, but suggestions are welcome ciao ric