------------------------------------------------------------- Minutes of the meeting of the Heavy Flavour Steering group | ------------------------------------------------------------- 5 March 2001 (CERN) Averages for Winter Conferences: =============================== No new results are expected from CDF/LEP/SLD Collaborations. Averages obtained at the time of Beauty 2000 are thus still valid. Contacts have been established, after an initiative from W. Yao(PDG), with BaBar and BELLE Collaborations to produce averages on Bd, B+ lifetimes and on Dmd. Contact persons from these collaborations have been nominated. Olivier and Lucia have agreed to help them to produce these averages using existing programs developed by the Lifetimes and Oscillations groups. Documentation on these programs has been provided and data has been delivered in a suitable form. It is expected to have averages for Moriond QCD including BaBar and BELLE results (produced by Lucia and Olivier). This activity has to be considered as a natural extension of our work if we want that CDF/LEP/SLD data be incorporated in a correct way in future averages. This is not to be considered as results that would be included in our final report. Summer 2000 report: =================== Comments have been received from Richard and new plots have been prepared by Olivier. Comments on the new sections (6, 9, 10) and on the sections in which people have more expertise are expected within two weeks (before March 20). ================================== During the discussion the following points have been raised: - Vcb: we stick to the approach explained in Summer99. Elisabetta will provide a new version. The Appendix F will be part of the main text. - Section on the unitarity triangle: too detailed, it has to be shortened as much as possible, keeping it self-contained (discussions on the choice of values for the different parameters can be removed, making appropriate references) - Section 10 on CP violation: it is proposed to expand it including limits obtained with inclusive lepton events. Richard will provide new text + numbers. - New results from b-factories (lifetimes, oscillations, sin(2 beta)). It has to be said in the introduction, quoting appropriate references, that such quantities have been produced by BaBar and BELLE. The new value for sin(2 beta) obtained at B-factories can be quoted in the section on the Unitarity triangle. - the sensitivity needed for 3 and 5 sigma measurements of Dms will be given. - b-fractions: updated values will be provided by Christian Comments about the CKM-mini-workshop: ===================================== At the initiative of PDG a Workshop was organized in LBL with the aim at providing recommandations for the next PDG issue on the way to extract values for the CKM parameters. This workshop was held in December 2000. Elisabetta and Marco were co-conveners of the Vcb and Vub groups and were present at LBL. Fabrizio Palla, P. Roudeau and O. Schneider have contributed to the meeting through a video-conference link. Discussions were mostly on the determination of Vub and Vcb and there was no much time to discuss other quantities nor the global fit of CKM parameters. Recommandations have been prepared by the conveners: E. Barberio and M. Artuso for Vcb, M. Battaglia and L. Gibbons for Vub. Reports are available on request from the authors. There has been an extensive discussion on the inclusive V_ub determination addressing specific criticisms widely voiced in the past by a part of the community. The recommandation to the PDG is to treat on equal footing the exclusive and inclusive determinations by two separate listings. Since the dominant uncertainties arise from model systematics that are difficult to be reliably estimated at present, the aim of extracting a single average value cannot be satisfied at this stage. The procedure followed reflects the confidence we have in the overall uncertainty given the agreement among the results obtained but will not push the uncertainties below an experimentally verified level. On Vcb I think that one can say that a lot of discussions happen, involving theorists (which were not contributing initially in this workshop). This was extremely painful and the final recommandation was not shared by all people involved in the process. We have obtained that the inclusive Vcb measurement was considered at least on an equal footing as compared with the exclusive measurement. We have not a clear idea about what is coming next. Who is writing the new sections for PDG? Who will be a referee for these sections? Since our meeting, we received the following information from Weiming (who was contacted by Marco): "The mini-reviews will follow either after this summer or early next year. In any case, if you have any suggestions regarding the mini-reviews writers, please let me know." Future of our activity: ======================= We aim at producing a final report by end 2001/beginning 2002 which is expected to appear as a Physics Report. As this report will be based on published (or accepted for publication) results, it is important that Collaborations have a clear idea about the results that could be included in this report (and eventually speed up some analyses). Averaged results have also to be delivered with all needed information so that they can be included in future averages. In particular a breakdown of all contributions to the uncertainty has to be produced (full correlation matrix). For the final report we have also to conclude on an update of b-quark fragmentation parameters and on a possible new section on B**. As already mentioned, it has been realized that it is important if a structure similar to the present Steering group exists, in future, with representatives from the different experiments involved in the averages. Contacts have started to develop with BaBar and BELLE. A new organization has to be prepared with interested people and we have to take care of the fact that present CDF/LEP/SLD results are correctly incorporated. At present Lucia and Olivier contribute to this transition phase. Next meetings: ============= The following dates have been retained: -18 May 9h00 (to finalize issues on b-fragmentation parameters updates) - 6 July 9h00 (before Summer conferences) - 8 October 14h00 (to finalize our last report) Sincerely yours ______________________________________________________________________