Short Biased Minutes of

W meeting 16/2/2000 in TH Auditorium from 9 am to 1:40 pm

1) RacoonWW (Stefan Dittmaier)

Very nice and informative presentation on RacoonWW (stands for Radiative Corrections ON e+e-WW). The file with the transparencies is available online (click here) . RacoonWW can give either CC03 or 4f+gamma final states (CC03 only for YFSWW, see previous minutes). Full O(alpha) corrections are related to O(10**3-10**4) diagrams ! A considerable reduction of the number of diagrams is obtained by the Double Pole Approximation. The expected precision is 0.5% to be compared to the 2% of GENTLE (this was calculated by comparing to Jegerlener 1989). A public version of the program will be available in a few weeks, but final numbers for the total cross section and the BR are available now. A further issue is related to the recombination of FRS photons which potentially could shift the W mass, particularly in the sl channel. This requires further studies with realistic experimental cuts. Shifts of a few tenth of MeV on the mass peak can be observed, but, as poitend out in the last minutes, we take at least partially in account this effect by using Photos in the MC through the reweighting method. A comparison with YFSWW on this issue is under way.

2) YFSWW vs Gentle (Reisaburo)

You can see the diff YFSWW vs Gentle and vs RacoonWW by clicking here . It should be pointed out that a difference of 0.5% is already present for KoralW-Gentle. The new YFSWW and RacoonWW calculations predict -1.8 to -2.8% decrease in the total cross section from Gentle for Ecms above 170 GeV. This is due to the inclusion of non-leading (non-universal) O(alpha) EW radiative corrections for off-shell W-pair production. Detailed comparisons are still going on.

3) 1999 WW cross section : preliminary result for the Winter Conferences (Maria)

The final preliminary result for the x-section in the individual channels and the BR has been presented and approved for the thursday meeting. It has been suggested to plot the new DPA theo x-section (see above) and also give Vcs.

4) Status of Single W (Vincent)

The problem with the Calo systematics at 189 GeV is sorted out (was a bug, sical was errouneously rescaled). The old selection has been applied to 19X data and a nice plot x-sect vs energy is available. We need to agree with the other 4 exp on a common definition for the x-sect (this has already happened with the exception of the lvlv channel). This should happen fast (otherwise we will apply a default which will become "de facto" the common definition). In the next 15 days Vincent will work on the improved selection for final approval 1st of March. Unlikely to have the delta(Kgamma) for Moriond.

5) The W mass in the semilept tau channel (Helenka)

Very preliminary results for the 19X data for the Winter Conf have been presented. Seems all in shape with some problem of convergence at 202 GeV. On the other hand as far as 189 GeV final results for the paper are concerned the silver and bronze categories seem to be very sensitive to fragmentation systematics. This appears both as large numbers and large errors, and as few common events when HERWIG vs JETSET is applied. This is particularly unfortunate as the fragm error is common to all experiments. It has been decided to widraw these recovered evts from the paper while these effects are being understood.

6) TGC at 189 GeV. OO2 news (Manel)

The difference in the expected error between OO2 and Log-Likelihood is understood. It was due both to the absence of a Chi2 prob cut (>0.005) and to the presence of bkg fluctuations which can be reduced by a window cut. The O1_iterative approach seems to be a bit worst for delta(kappa_gamma). The fit to data after this tuning gives results very similar to that already presented last time.

7) Status of TGC paper (Jorgen)

The text has been revised. The problem related to expected errors for the OO is solved (see above). The calibration curves for the LL are done, a problem has appeared in the calib curve for re_G4Z. This is related to the normalization of the PDF (Lambda integral in Tim transparencies) for non-standard model values. The proper error on Lambda is under evaluation. Fits OO2 for taus and lvlv are under preparation. Paper ready by next week. Will present the status at the thursday of march, the 2nd.

8) Colour Reconnection news at 189 GeV (Eric)

In the draft 1 of the paper we have averaged the result of Excalibur with KoralW. However the dependence to the % of reconnected evts seems not the same. A deeper investingation has given evidences of problems in the interface between Excalibur and SK1. We have to widraw Exc/SK1 from the paper and use KoralW only. Colour reconnected Herwig is under production.

9) Status of leptonic mass and width for 1999 data (Guillame and Barbara)

Very preliminary plots and numbers for 19X data are available. Needs to solve instabilities in the width for the electron channel and to understand if an apparent difference between the 192/200 and 196/202 samples for the muons can be explained by data quality differences. In the process of understanding the data quality a problem has been found for the Ri estimator for electrons (dE/dX calibration ?) and a few evts with masked digital hcal chains in the mc have appeared (in principle impossible, bug ? After the meeting it has been clarified that the masked digital chains were actually planes with no HV, and that the effect was the same discussed at the software meeting of 4/2/2000 , see the soft meeting minutes).

10) Status of 4q mass for 1999 data (Jeremy)

The numbers for the 4q channel are quite stable. It has been observed a dependence on the energy of the efficiency and purity of the NN14 . There is a degradation of performance as long as one gets far from 189 GeV. Retraining will be necessary for the final results.

11) Status of MC production (Jason).

A detailed list of the various samples, including specification of Linux samples has been given by Jason (see transparencies).

12) W mass from OO method (Andrea)

Very detailed investigation of the intrinsinc limits of the statistical sensitivity on the W mass measurement have led back to the concept of Optimal Observable. Unfortunately the best OO yields interesting and useful results on the MC thruth but gets degraded at the reco level. All this is described in detail in the transparencies of Andrea, please have a look to them by clicking here.

WW Meeting in Heidelberg

Pre-registrations will open the 21st of February

see forthcoming ALNEWS