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Hi Masahiro, On Wed, 21 Jun 2006, Masahiro Morii wrote: > I thought I'd write down the question BobK asked this morning before > I forget. > > Heiko explained to me that there is still a difficulty with mES fit. > My understanding is that it is difficult, in mES fits on small > samples, to separate the signal and the peaking background reliably. > Bob's questions boil down to the following: > > 1) Why is it not possible to fix the peaking background using MC > prediction, and assign systematic error on this by varying inputs to > the MC? Does it lead to excessive systematic errors? If so, We are working on this but have not the answer ready how large the systematic error could be. In any case, we see in some instances quite large variations for the ratio peaking BG/comb. BG as a function of the kinematical variables whic is not a real surprise: e.g. for large mX we have a larger multiplicity in the recoil and as a consequence a larger comb. BG. The variations in signal/peaking BG are smaller but still substantial. We are currently checking how the data compares with MC when looking into the depleted sample which would serve than as our control sample when fixing such a ratio. Currently, we can not say more. > 2) Does it make sense to tighten the purity cut of the Breco tags to > reduce the background, and thus the systematics? You lose > statistics, of course, but isn't it possible to find an optimum that > is tighter than what you use now? This is something we have not considered yet. Cheers, Heiko > Masahiro > -- > Masahiro Morii <[log in to unmask]> > Harvard University, Department of Physics > 17 Oxford Street, Cambridge, MA 02421, USA > > >