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Hi Guglielmo, I am quite surprised that the events with a Kl have such a soft spectrum. The peakshould be around 2 GeVwhile it is below 1.5. Can you please check the events with a K+ and see if you are getting a harder spectrum? As far as the fact tht the Ks removed calculation is too soft, it would indicate that you need to estimte the average energy of the Kl and add it back to the event ciao ric On Wed, 13 Feb 2002, Guglielmo De Nardo wrote: > Hi, > > In order to estimate the low Mx shape of Vcb background with KL, I > produced the following plots: > http://www.slac.stanford.edu/~denardo/mxplots/klmasslepton.ps > http://www.slac.stanford.edu/~denardo/mxplots/kstruemasslep.ps > > They both are from true Vcb events. > The first plot is the MX distribution for events with at least a true KL. > The second plot is again the MX distribution after subtraction of a > reconstructed Ks. If more than one Ks is reco'ed, the one with the > smallest delta m is chosen. > > For both the distribution no selection cut is applied, apart requiring a > lepton in the fiducial acceptance. > > I naively expected to find similar distributions. Instead, the Ks looks > too much distorted towards small values of MX. > > Tomorrow I will change the code to add all the selected Ks (one by one) to > the distribution, but I expect that this will only add few more entries > but it will not change the shape. > Someone has any idea on why the MX ks-subtracted distribution should look > so different from KL events Mx one? (I can't exclude a bug in my code). > > Tomorrow I will investigate further. > > Guglielmo > > > > >