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Hi all, I've updated the web page that now has a large section dedicated to the q2 cut investigation. http://www.slac.stanford.edu/~asarti/recoil/talks/130503.html There are still some problems and things to understand but the information provided has been cross-checked and I think that it's ready to be read from all. Please read carefully the webpage: I've tried to be as clear as possible. Let me know if something looks odd to you. My comments are: 1) Two different executables (the stand-alone reweighting machinery and the fit) agree on one thing: the relative error on the efficiency of q2,mx cut due to the model (mb,a) drops while cutting harder and harder in q2. The drop is ~ a factor of 2 (10-11% --> 5-6%) 2) The net effect on the efficiency of our selection (eps_u AND eps_mx,q2) is reduced. The effect has been evaluated looking ONLY at the fit results. Correlation of analysis cuts variables can be the origin of that. 3) While looking directly at BRBR results the power of q2 cut on reducing model sys error (estmated looking at fit results and not efficiency from fit) is nearly gone. The deep understanding of that effect is ongoing. I'm currently investigating possible differences btw resonant and non-resonant effects of q2 cut in order to understand some of the results presented in the web-page. I'll keep everybody updated as soon as the study proceeds. Alessio ______________________________________________________ Alessio Sarti Universita' & I.N.F.N. Ferrara >>>I'm in Ferrara<<< tel +39-0532-974328 Ferrara roma +39-06-49914338 SLAC +001-650-926-2972 "... e a un Dio 'fatti il culo' non credere mai..." (F. De Andre') "He was turning over in his mind an intresting new concept in Thau-dimensional physics which unified time, space, magnetism, gravity and, for some reason, broccoli". (T. Pratchett: "Pyramids")