Tuesday 22 September 1998
                                               Ian Tomalin


                MINUTES OF THE 21TH BEW MEETING
               =================================

Agenda
========

   I. Tomalin  : Current activities of BEW group.
                 Discussion of proposal from LEP EW group
                 for averaging LEP2 EW results.

   F. Teubert  : Status of 189 GeV cross section analyses
                 (on behalf of M.N. Minard).

   D. Schlatter: S-matrix fit results using to f-fbar data
                 (on behalf of M.N. Minard).

   I. Tomalin  : Z' limits (on behalf of M.Swynghedauw)


I. Tomalin: Current activities of BEW group.
===============================================
  * Draft 1 of BEW paper (130-183 GeV) in preparation.
    (Difermion cross-sections and asymmetries plus limits on 
     physics beyond SM).
  * T. Metcalf's analysis for excited leptons approaching completion.
  * E. Simopoulou's direct search for leptoquarks also nearly done.
  * Single top production awaits 189 GeV data before update.

Future work:
  & Update cross sections and asymmetries at 189 GeV.
  & Try to improve analyses (qq, bb, cc, Qfb)
  & Implement and test new MC from Jadach which contains accurate
    description of ISR/FSR interference.
  & Reconsider definition of cross-section.
  & Look for s-channel resonances by studying difermion cross sections
    vs. sqrt(s').

=> Plenty to do if new people interested in joining group !!!

I. Tomalin: Proposal from LEP EW group for averaging LEP2 EW results.
=====================================================================
  DELPHI has proposed that the LEP EW working group produce 
officially approved averages of LEP2 cross sections and asymmetries,
and use these to provide combined limits on contact interactions etc.
Idea seems good, but ALEPH needs an opinion on how it should be done.

F. Teubert: Status of 189 GeV cross section analyses
=====================================================
  Work presented from M.-N. Minard using 107 pb**-1 of data.
For sqrt(s'/s) > 0.9, preliminary qq cross section is 19.36 +- 0.42 pb,
compared with SM prediction of 19.17 pb. Must work to reduce size
of systematic errors.
  For selected events with Thrust < 0.75, data/MC = 0.76 +- 0.07 !
(=> missing WW).
  Marie-Noelle reconstructs isolated photons using PECO (with correction 
for ECAL saturation of ENERGY*(1.+0.00076*ENERGY)). This gives good 
agreement between data and MC (GAL306) for both the energy of ISR photons 
produced in radiative returns to the Z, and the total visible mass. By 
contrast, using ENFLW (GAMPEK) photons gives much worse agreement.

  Additional info: 
    * GAL307 contains much better desciption of HCAL than GAL306. 
      Will reduce mean visible energy by about 1 GeV.

D. Schlatter: S-matrix fit
===========================
  Dieter gave results of 8 parameter S-matrix fit from Marie-Noelle.
Z mass determined from LEP1 data, with Z-gamma interference measured
using high energy data now has similar errors to that obtained with
Z-gamma interference taken from theory.
  Long discussion with 2 main objections analysis:
    i) Need study of effects of ISR, box diagrams etc, as was done
       at 133 GeV.
   ii) Result is only valid if no new physics at LEP2. However in
       this case, could Z-gamma interference differ from SM ?
       
I. Tomalin: Z' limits
======================
  Ian showed limits on Z' from M.Swynghedauw. Limit on sequential
Z' is now 980 GeV, which beats CDF. Limits on E6 and LR models
in range 320-500 GeV. Not as good as CDF (570-630 GeV). Will go in
paper if finished.