- Discussion ---------- The following topics have been discussed: 1) sprime definition : ----------------- It might be better to use the inv. mass of the outgoing fermion pair for the sprime definition. If looking at the OPAL method one sees that the error on the efficiency correction is of the order of the correction --> one introduces a theoretical error into the measurement. Frederic has arguments that the O(alpha) correction for the interference is not the best. He should give a formal presentation about his arguments at one of the following meetings. It is also an open question if the tag efficiency is really the same with and without interference. To decide between 0.85 and 0.9 for the sprime-cut the contact interaction fits should be performed for both options, looking then for the better limits. In the case of Bhabhas one should possibly consider a cut on pseudorapidity. 2) four-fermion processes : ---------------------- The OPAL method is very difficult to understand. Frederic should try to understand the section in the OPAL paper on this topic and give a presentation. The questions are: What is in the Monte Carlo? How do we define the x-sections? 3) Rb : It is not clear if Mario Antonelli is measuring also Rb. -- He will give a presentation in October. 4) The fitting programs for contact interactions and leptoquarks should be combined into a single one. 5) What should we measure in addition? For example : alpha (like OPAL). We agree that it is not worth doing it, as we don't reach the necessary precision to really make it an interesting measurement. Marie-Noelle suggests to measure Rs (maybe a student will do that). Is Mario measuring also AFB(b)? 6) Should we write a paper now or later, including the 183 data? We agree that we should wait until the end of the year. For example, the ISR problem in Pythia is being solved, which could result in a reduction of the systematic error. 7) W-background : ------------ Should we leave the background in or subtract it, i.e. select WW events and reject them? The second approach seems to be one to be preferred. However, what should be done (by Marie-Noelle) is to produce a plot of the efficiencies and errors vs. the sprime-cut. This could answer a lot of questions. 8) KORALZ : ------- We need a KORALZ production at 133 GeV and a production with the new Pythia version 6. Maybe also "WW events" should be generated below the threshold. Guenther will take care of this. 9) Marc is doing an analysis for Zprime, with a different selection scheme. He should present his work at one of the following meetings. 10) Christos is looking at single lepto-quark production. 11) Marie-Noelle should give a presentation in Oxford about the status of the x-section measurements.
- Next meeting ---> in Oxford during the ALEPH week
Guenther Dissertori
Fri, Oct 03 , 03:00:38 MET DST 1997