Patrice presented a first look at the WW cross section. 14pb-1 was analysed for centre of mass energies in the range 200-208 GeV. The averaged centre of mass energy (luminosity weighted over runs) is 203.9 GeV. '99 selection algorithms have been applied, signal efficiency taken from 202 GeV MC WW events (cross section vary by less than 50pb-1 over the considered range). Ecm dependence of background rates has been taken into account. The old software has been compared to the new common software, leading to exactly the same result for the fully and semi-leptonic channels. For the 4q channel, the new software includes a new training of the NN at 196 GeV Ecm. The new software will be used from now on.

Patrice presented some inclusive distribution of variables entering the 4q NN. Given the limited statistics available, no difference between data and MC expectations is observed. The 4q cross section (8.1 +- 0.9 pb) agrees with the Gentle expectation (8.0 pb). For the semi and fully leptonic channels, the cross-sections are also in agreement with Gentle's prediction.

It was suggested to check lepton identification performances.

As the WW cross section variation with Ecm is very weak, it was decided , given the present available statistics to give only the cross section at the mean centre of masse energy.

Oliver gave a short summary of the Aleph presentation on particle flow studies given at the WW00 workshop. With different selections (the standard NN14 one and an L3 based one), Aleph confirms that inter jet particle flow distributions are sensitive to colour reconnection. Several fragmentation models (Jetset, Herwig, Ariadne) were also tested, inter jet particle flow is less sensitive to fragmentation than to colour reconnection (for the SKI model with full reconnection).

Oliver then presented further studies performed after the workshop. He showed the L3 based selection, introduces a larger reduction of the fraction of reconnected events (5-10%) compared to 1-2% for the NN14 selection but does not reject colour reconnected events. The mean ratio R of particle flow (between jets from a same W)/(jets from different Ws) has a linear dependence with the fraction of colour reconnected events. Data (189 GeV only) tend to prefer low probability of reconnection (<50% at 1 sigma). The shape of the R distribution has also been compared between data and MC, similar conclusion holds.

The following action list has been suggested :

• optimisation the 4q selection,
• optimisation of the discriminant variable (ratio, asymmetry, momentum weighted particle flow…),
• particle flow should also been looked at for Bose-Einstein effects,
• what are the correlations between bins (if any?).

Eric presented some personal impressions from the workshop. A discussion took place, from which a few possible actions listed below were formulated :

TGC : some discussion should take place within Aleph on the lep TGC combination (3D?, combination of systematics,…) this will be discussed at the Heidelberg meeting. Neutral and Quartic couplings should be look at. Kinematical information from single-W should be used to derive TGC limits.

W mass : There should be a critical reading of the Delphi MLBZ note (A. Venturi + …). The aleph reweighting based method to evaluate fragmentation error should be complete (for Heidelberg?). Gerald's MC tuning should be documented in an aleph note of possible.

FSI : The particle flow analysis should definitively be continued. Interplay between color reconnection fraction and fragmentation parameters (like m₀) should be looked at (see for example fig. 15 of the original SK paper). Cooperation with the other experiments on understanding the difference between analyses (including Crete files and background) should continue.

Bolek gave a short summary of his WW00 talk (which was very well received). At the workshop L3 and Delphi presented some studies on the impact of background, leading to contradictory conclusions. Bolek will have a look at this effect in view of trying to clarify the point.

Frederic gave some informations, transmitted by Rick and Selvam, about the W meeting in Heidelberg. People should arrive on Sunday the 28^th of May and leave Wednesday the 29^th, as meetings will take place Monday and Tuesday full day. There will be more precise practical information (travel, hotels, …) very soon on the web.