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Hello folks, I have been trying to understand things a bit better myself, please apologize if I make mistakes. First, I am confused about the issue of the orders at which things are computed. It would be useful, also for posterity, that somebody, most likely Urs, writes down which are the formulas he points at that support our calculation. I will just start from Sven's posting http://babar-hn.slac.stanford.edu:5090/HyperNews/get/ISLDecays/222.html and assume lambda_bar = 0.48+/-0.09 (with error mutuated from PDG and the rescaling from Sven) lambda_1 =-0.30+/-0.14 I will also assume the correlation to be -0.8 ( Eckhard, where does the + come from? the correlation in all plots is always negative!!) I then assume that the relationships between mb,a and lambda_bar,lambda1 are lamda_bar = mB-mb+(3*lambda_2-(mB-mb)^2/(1+a))/2*mb lambda_1=-3 lambda_bar^2/(1+a) where I have neglected lambda_2/mb^2 terms in the third addendum of the first equation (actually I have also tried removing the third addendum overall with no real change). I then built the chi^2 chi^2=[(lambda_bar-0.48)/0.09]^2+[(lambda_1+0.3)/0.14]^2 and plotted it : a) in the case where no correlation is assumed http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/mba_nocorr.eps b) with a correlation of -80% http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/mba_90.eps c) blowing up the error to 150 MeV http://www.slac.stanford.edu/~rfaccini/phys/vub/theo/mba_150.eps My shapes are different from Eckhard's ones maybe because of the sign of the correlation or maybe because we are typing different formulas (I get a bit lost in maple code...), but the conclusions are similar: surprisingly the correlations increase the range in which each of the axes vary. On the contrary correlations should be taken into account, so I think we should make the systematics extracting lambdabar and lambda1 and then recomputing a and mb. The only problem is that we need to be sure of the equations and the values of the lamdas that should be used In summary I think that the next steps are: - write cleanly the relationships we use to convert cleo's or PDG results into our measurement (they might already be somewhere, but I could not find them) - implement the systematics in terms of lambda_1,lambda_bar and their correlation [this with the time scale of the conference, not of today...) let me know what you think of this ciao ric P.S. where is the 'code from Sven'? On Mon, 17 Feb 2003, Eckhard Elsen wrote: > I reevaluated the correlations of Friday. (They were in error since the > mean values of the parameters had not entered the MAPLE equations). > > The new version > http://www.slac.stanford.edu/~elsen/amb_new.pdf > > investigates the case of zero and 0.8 correlation between lambda_1 and > Lambda_bar. Consequently the assumed uncertainty of 0.09 (value of > draft) translates into a 0.09 GeV (0.15 GeV) uncertainty on m_b for > correlation=0 (or 0.8). > > The actual contour shape in the parameter a varies with the assumed > correlation. However, since the resulting uncertainty from a is smaller > it is probably not worth the effort to go into detailed simulations. > > The proposal is hence to increase the theoretical of m_b to 0.15 GeV, > such that it is by far the dominant error with ~20%... > > Eckhard > >