Tuesday 2nd February 1999
                                              Ian Tomalin

                MINUTES OF THE 26TH BEW MEETING
               =================================

Agenda
=======
  Electroweak results for Winter Conferences -

  Marie-Noelle Minard : Hadronic cross section at 189 GeV 
  Corinne Goy         : Heavy quark production at 183/189 GeV 
  Elsa Merle          : Dilepton production at 189 GeV    


Marie-Noelle Minard : Hadronic cross section at 189 GeV 
========================================================

Using 173.59 pb**-1, cross section for sqrt(s'/s) > 0.9 and
|cos(theta)| < 0.95 is 18.76 +- 0.34 +- 0.14 pb. 
Compare with SM prediction of 19.29 pb.
  Major systematic uncertainty is PYTHIA/JETSET difference in ISR 
simulation. Major backgrounds are radiative qq (7.6%) and WW (5.8%).

 Note: (i) ENFLW algorithm modified - 
         (a) E/pi ratio multiplied by factor 1.2 for track enters
             ECAL crack.
         (b) 5% correction to ECAL endcap wires in MC
 => Visible mass spectrum agrees better in data and MC.

Still to be understood: cross section in bin 0.9 < |cos(theta)! < 0.95
is much smaller than expected.

Corinne Goy : Heavy quark production at 183/189 GeV 
===================================================

Measurement of R_b at 189 GeV. Require QIPBTAG event prob < 1.0e-4.
Also require both jets of event to have |cos(theta)! < 0.9.
  => 260 events selected, with 41.4% bb efficiency.
Backgrounds: udsc (33.1), qq rad. (5.6), ZZ (5.5) and WW(2.1).
  => R_b = 0.153 +- 0.011 +- 0.008
Compared with SM = 0.170

  Systematic error dominated by measurement of R_b at Z0 peak
using same method with 1998 calibration data. (Was 5% wrong).

Also presented measurement of A_FB(cc) at 183 GeV. For details
of this see ALEPH note 99-002. Using cc selection of BEW paper,
get 153 events, of which 75 are background.
  Measure quark charges using 7 variable neural network.
Inputs = rapdity weighted jet charge, lepton/kaon charge, pi_soft
from D* decay etc.
  Efficiency to get cc event charge correct is 81%, compared
with 76% using jet charge alone.

  => A_FB(cc) = 0.95 +- 0.27 +- 0.11
compared with SM = 0.62.

Elsa Merle : Dilepton production at 189 GeV    
============================================
  Dilepton results at 189 GeV obtained using same technique as
BEW paper: 
  For sqrt(s'/s) > 0.9 and |cos(theta)! < 0.95 -

     mu+mu-: sigma = 2.66 +- 0.13 +- 0.06 pb   (SM = 2.69 pb)
             A_FB  = 0.581 +- 0.037 +- 0.012   (SM = 0.57)

   tau+tau-: sigma = 2.39 +- 0.15 +- 0.05 pb   (SM = 2.78 pb)
             A_FB  = 0.569 +- 0.051 +- 0.046   (SM = 0.57)

e+e-, -0.9 < cos(theta*) < 0.9: sigma = 83.4 +- 0.7 +- 0.7  (SM = 88.6)

e+e-, -0.9 < cos(theta*) < 0.7: sigma = 17.0 +- 0.3 +- 0.2   (SM = 17.7)

 => Measured e+e- cross sections are well below SM predictions.
This discrepancy occurs at small polar angles to the beam axis, which 
suggests that it is a detector effect, not new physics.
Strong phi dependence of the track momenta is seen in this region,
but this has only a very small effect on the cross sections.
Further investigation needed.