Minutes of the EW task force meeting held on June 14, 1996. ------------------------------------------------------------- 1. Run selection I ********************* It was found that the runs 37750 and 37751 were removed by mistake by the EW selection and the runs 37550 and 37551 which had to be removed have been left. Lee and Jacques have been informed. 2. Run selection II ********************* Andrea found that many tracks in the events of the fills 2618 and 2622 (runs 35482-->35518) have no ITC hits. Bill Cameron confirmed that the ITC data are unusable since the beginning of 1995 until run 35630 (included), due to the timing which was not set properly yet. The first GOOD fill/run for ITC is 2644/35635. It was agreed that these runs have to be removed from the EW/EA selections. Lee will comunicate this information to Jacques Boucrot to update the Scanbook database. 3. Run selection III *********************** The following prescriptions are suggested to obtain the OFFICIAL 1995 run list of the EW task force for the cross sections from Scanbook (ONCE the previously mentioned modification are done): Prescan : 1) selection by RUN : 35635/37063 (selecting 35635 has first run the runs affected by the ITC problem are discarded even if the SCANBOOK database has not been modified yet). 2) physics group selection : EA 3) No C.M. energy selection Peak : 1) selection by RUN : 37064/37853 or selection by year : 1995 LEP1 2) physics group selection : EW 3) C.M. energy : 91250 Peak+2 : 1) and 2) as Peak 3) C.M. energy : 93000 peak-2 : 1) and 2) as Peak 3) C.M. energy : 89500 Proceeding in this way the runs 37550, 37551 and 37755 will not be selected in any selection. This is has been decided to simplify the fit for the cross section. As a check you can compare your scanbook results with what is in the page "Data run selection, SRUN cards and summary files" from the EW page on WWW (once the last modifications are taken into account...). 4. Luminosity measurement (B.Bloch) ************************************* No further progress since the last Thursday meeting (the day before...). The evaluation of the systematic errors is in progress without major problem. The study of the correlation between 1994 and 1995 results is quite hard. 5. Results for Warsaw (M.Pepe and B. Pietrzyk) ****************************************************************** The dead-line for the paper is June 25th. We should have the numbers ready for the fit in advance. The tentative dead-line is the next EW task force meeting, next Friday. Bolek is in charge for the editing of the paper and, together with Frederic, of the fit. It is not clear if/when the LEP energy will be available. In any case , for luminosity and for the t-channel subtraction the present uncertainty of about 10 MeV is good enough.. Each subgroups will have to provide cross-section, number of events systematic and statistical errors for the four "energies". 6. Fitting procedure for the "EA only" runs (B. Pietrzyk) *********************************************************** The data collected during the runs when the luminosity were not available (EA.and..not.EW) will be used to measure Rl ,has agreed in the previous meetings. To avoid major changes in the fitting program, these data will be fitted by evaluating the luminosity for the number of hadrons and inflating the error on it (about 1%) to avoid artificial correlation with the total hadronic cross section. It was decided that for Warsaw ALSO the 1994 EA.and..not.EW data have to be analysed. 7. Asymmetries **************** At the last Thursday meeting the Collaboration took no decision on which data have to be used for the asymmetry results for Warsaw (1995 only or 1993,94,95). The measurement of the Bhabha asymmetry is going on. It has to be checked if it is possible to use cos(Theta) instead of cos(Theta*) to fit the angular distribution, since the ZFITTER correction are available only for cos(Theta). 8. UNIBAB (B.Bloch) ********************* it has been checked the recent UNIBAB MC productions done by Lee and Monica are not affected by the random number bug. Next meeting on Friday, June 21st at 11 a.m. in room 104-R-A10.