Minutes of the EW Group held on 15-jan-97
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   Present:   A. Venturi (AV), A. Lucotte (AL), B. Pietrzyk (BP) 
              B. Bloch (BB), M.N. Minard (MNM), M. Pepe-Altarelli (MP) 

   Main Topics:  /Treatment of the errors in the fits / Paper writing/


   ELECTRONS: MP reports for Lee Thompson that Lee seemed to have  
              understood the discrepancy between ALISTAR and TOPAZ0 
              for the t-channel subtraction. Lee will report on this
              during the Aleph week.     

   MUONS:     AV talked about the sagitta correction he applied for the 
              tracking. Using these corrections imply, all years 
              combined, a change of 3+-3 10^-5 in the number of selected
              events. AV need some MC at off-peak points for 90 and 91 
              analysis: a sample of 4*50 K events will be produced at 
              P+-1 and P+-3 energies with present MC. 

   HADRONS:   After some discussion about the way of improving 2-gamma 
              background, AL will try to evaluate such background from
              on wider integrated energy range.   
              A Year-to year Correlation matrix has been computed in 
              the same format as for the luminosity matrix used in 
              MIZA, assuming in a first approach, a full correlation 
              within each data taking period.  

   LUMINOSITY:BB will add in her the SiCAL note a part dealing with
              the influence of the change of Ecm on the luminosity. 
              She pointed out that no reference on energy value was 
              available. In fact, final corrected LEP energy files 
              are still expected for Moriond.  

   FIT OF THE RESONANCE: 
              BP reported on his work concerning the treatment of the 
              uncertainties in MIZA.
              - he found a "trap" present in the code, which increased 
                the correlation between 2-gamma background estimation 
                in the hadronic cross-section. The effect of correcting 
                for this is to decrease the error on G_z by 0.2 MeV 
                (from 4.66 to 4.46 MeV). 
              - BP refitted the data assuming that 2-photons in the 
                hadrons selection, are fully correlated between year 
                (93,94 and 95).
                For an error of 11 pb in 2-photons:  delta(G_z)=4.52 MeV
                  "  "   "   "   5 pb "   "       :  delta(G_z)=4.42 MeV 
                (L3 quote an error of 3 pb, but with an acceptance 
                very different from Aleph)
              A discussion arose on the way to implement correlations
              in the fitting programm MIZA. Two ways are possible:
                - a 27X27 correlation matrix per analysis, taking into 
                  account year-to-year AND point-to-point correlations
                - the same but as a function, each group having to 
                  provide the corresponding subroutine to the fitters.
              BP prefers the second option but will contact Manel to 
              have his opinion. 

   EW PAPER:  MP reports about the organization of the writing of the 
              EW paper:
                - The structure of the paper is put on the Web, with 
                  designed author(s) for each part. 
                - AL will care about the compilation of individual 
                  parts and put the ps file accessible in an .html 
                  format on the Web ("paper in preparation").
               MP encouraged people to start as soon as possible.

  Next meeting: monday 03 February at 2.00 pm. Room still to be fixed.

  Submitted by A. Lucotte