Joachim Meyer
                                                 Tuesday 16th May 2000
 
 
                   MINUTES OF THE 43rd BEW MEETING
                   ===============================

 
  Agenda 
  ------
 
   1. First look to 2000 data  (hadrons) :  M.-N. Minard 
 
   2. First look to 2000 data  (leptons) :  I. De Bonis
 
 
  
 
  First look to 2000 data  (hadrons) :  M.-N. Minard 
  --------------------------------------------------
 
  Data taken between 200 and 208 GeV amount to L = 24.038 pb-1
  Analysis restricted to E > 201 GeV corresponding to L = 22.124 pb-1
  and an average energy of 204.6

  Backgrounds and efficiencies based on 202GeV MC
 
  * Inclusive analysis: (sqrt(s'/s) > 0.1)
 
    1992 events,  Backgrounds : 18.3% WW, 2.3% ZZ, 2.3% Zee, 4.1% gamgam
    signal efficiency  82.4 %
 
    Cross section : 79.123 +- 2.038 pb measured ; 79.97 pb Z_fitter expectation
 
  * Exclusive analysis (sqrt(s'/s) > 0.9)
 
     328 events,  Backgrounds : 6.6% WW, 1.64% ZZ, 0.05% Zee, 0.01% gamgam,
     rad. background 4.05%,  signal efficiency  87.4 %
 
     Cross section : 15.55 +- 0.896 pb measured ; 15.67 pb Z_fitter expectation


 

  First look to 2000 data  (leptons) :  I. De Bonis
  -------------------------------------------------

  All data (200 - 208) analysed corresponding to L = 23.89 pb-1 and
  an average energy of 204.4 GeV.  202 GeV MC used. 
  
 
  mu+ mu- :
  =========
  * Incl. analysis  (sqrt(s'/s) > 0.1)
   
    efficiency = 92% , backgr = 11 % 
    Cross section :  4.71 +- 0.50 pb  measured ; 6.46 pb expected

  * Excl. analysis  (sqrt(s'/s) > 0.9)
   
    efficiency = 96% , backgr = 5 % 
    Cross section :  2.0 +- 0.3 pb measured ; 2.24 pb expected 
 
  e+ e-  :
  ========
  * Incl. analysis  (-0.9 < cos(th*) < 0.9 )
   
    efficiency = 80% , backgr = 11 % 
    Cross section :  75.2 +- 2.2 pb  measured ; 75.8 pb expected
   
  * Excl. analysis (-0.9 < cos(th*) < 0.7 )
   
    efficiency = 94% , backgr = 13 % 
    Cross section :  15.1 +- 0.9  measured ; 15.2 expected 
  

  tau+ tau-  :
  ============
  * Incl. analysis  ( (sqrt(s'/s) > 0.1)

    efficiency = 35% , backgr = 17 % 
    Cross section :  7.8 +- 0.9 pb measured ; 6.46 pb expected
   
  * Excl. analysis   (sqrt(s'/s) > 0.9)

    efficiency = 60% , backgr = 20 % 
    Cross section :  2.5 +- 0.5 pb measured ; 2.26 pb expected 
  

  
  Discussion : Within ALEPH a strategy should be worked out on how 
               to combine the data taken at the different high
               energy points. 
   
               Updated results should be presented at next Thursday meeting. 


  A. O. B. 
  --------
     New members in the BEW group :
       -  Jordi Burguet-Castell (Ecole. Poly.)
       -  Richard Hill (Imperial College)
       -  Joachim Meyer (DESY)
     
     Next meeting : 13/6/2000  14:30