------------------------------------------------------------- Minutes of the meeting of the Heavy Flavour Steering group | ------------------------------------------------------------- 7 June 2000 (CERN) Status of the Summer99 paper: ============================= Detailed comments have been received from W. Venus. Several of the points raised by Wilbur concern aspects of our work which need to be solved/improved for the next releases of averaged numbers. The present version has been sent to the EP preprint responsible (june 19th). It can be accessed on: http://lephfs.web.cern.ch/LEPHFS/heavy_flavour_99_06.ps General infos: ============== - I. I. Bigi was expected to be at CERN between June 22 and July 10. Unfortunately he is unable to come. Contacts via email have to be developed. - P. Roudeau will present "LEP b-physics results" at the CERN LEP feast in October. Answers to questions on our activities: ======================================= These answers to questions formulated in Autumn 99 are not yet publicly available. This has to be finalized before end of June. Activities related to Summer2000 results: ========================================= We are expected: -to update present averages using new measurements, -to improve existing procedures, knowing that there are some aspects of our work which need further efforts, -to develop new sections (mentioned during previous group meetings) As a general request can we quote always the chi2/ndf (or the fit probability) when we produce averages? *** Lifetimes: Lucia di Ciaccio -------------- Lucia who was unable to attend the meeting send us answers on the points which were listed before the meeting: 1) - be prepared to use a different for B. It would be also of interest to evaluate if results depend on the assumed shape of the fragmentation function (for the same ). This maybe studied on simulation using the shapes which are favoured by data at present. 2) - produce an average b-lifetime using exclusive lifetimes and production rates (a very-very-very old request) 3) - give more details on systematics when averaging Bs and Lb lifetimes 4) - expend the section on comparisons between measured and expected b-hadron lifetimes. Lucia considers that there is no problem to fulfill the requirements 1, 3 and 4. There is the hope that G. Barker (Delphi) joins the lifetime group and works on point 2. There is an additional point which has to be addressed: -take into account the expected difference between taub(sl) and taub(incl) when computing the average. A value for the ratio taub(sl)/taub(incl) is quoted at present in Summer99 but is not used when computing the global average. This number has to be checked by the lifetime group and included when computing the average. At present the values of the lifetimes obtained with B--> J/Psi X are not included using a very weak argument ("because they probably correspond to a different mixture of b-hadron species"). This has to be reconsidered and, if needed, an uncertainty for this difference in sample composition has to be evaluated. *** b-rates: (O. Schneider, CH. Weiser) ------------ It is proposed to include the new measurement of CLEO of the branching fraction: BR(Lc --> p K pi). *** b-oscillations: O. Schneider ------------------- -Several results are expected on Bs oscillations and a new measurement of Dmd (OPAL) -New activities can be started and volunteers are welcome (required..). They concern: +Delta(gamma(Bd)) by comparing results on Chid (CLEO), which depend on Delta(Gamma), and on Dmd +a limit on the CP asymmetry in B decays: several measurements are available and statistically limited. -Answers on questions concerning analyses on Dms and on their combination have been made circulating within the oscillation group by Olivier. -A link between the B oscillation web-page and the Delta(Gamma(Bs)) page will be created so that the latter will be publicly accessible. *** Vcb: R. Hawkings -------- Some work remains to be done on the effect of D** in B--> D*+ l nu decays. It would be nice also to have an unfolded distribution of the ISGW form factor. *** Vub: M. Battaglia -------- Nothing new to be expected. Answers on Vub analyses are expected to be available publicly soon. *** New section on sin(2*beta) average: --------------------------------------- It is proposed to use the result shown in Taipei by R. Forty which combines measurements from CDF, ALEPH and OPAL on the B--> J/Psi K0s decay channel. We need the green light from CDF colleagues whose measurement is dominating the average to proceed further. The present idea is to have an "official" CDF-LEP-SLD number for Summer Conferences. *** New section on the rho, eta CKM parameters fit: P. Roudeau, A. Stocchi --------------------------------------------------- A first version of this section was made available before the meeting. http://lephfs.web.cern.ch/LEPHFS/summer_00_01.ps Numbers will be updated with new results available before the conferences. It has been proposed to quote also results without including Vub from CLEO. It has been proposed to quote the names of theorists, experts in lattice QCD, as reference people for the central values and uncertainties on the parameters taken from theory in this business. The names of G. Martinelli and his group, with whom close contacts already exist, have been proposed. New plots have to be prepared and a new version of this section is expected soon. The results expected to appear in this section are the following: - comparison between the regions selected in the (rho, eta) plane by b-physics and by epsilon-K. The quantitative comparison is done by considering the value of BK. deduced from the values of rho and eta obtained from b-physics, that you need to get the correct value of epsilonK and the value of BK obtained by lattice QCD. BK(b-physics)=0.80+0.15-0.17 <--> BK(lattice)=0.87+-0.06+-0.13 - value of fBd*sqrt(BBd) obtained from all constraints but Dmd: fBd*sqrt(BBd)=(232 +- 13)MeV <--->fBd*sqrt(BBd)(lattice)=(210+-25+30-10)MeV - expected prob. dist for Delta(ms), having removed the present limit from the set of constraints - expected prob. dist for Vub, having removed the present measurements from the set of constraints - results on rho, eta, angles, ... using all constraints. *** New section on the average number of c and cbar quarks in b-decays: P. R. ----------------------------------------------------------------------- It is of interest to try to have an official number on this quantity because: +several different values can be found in various publications. +there is not an official average on this quantity; the LEPEWWG has produced an official result for b-->cbar-->l which includes a subset of the measurements which can be used to determine . +there are a few points which need to be better explained or updated in this exercise as the contribution of Xic baryons and of the charmonium. An exercise has been done (P. Roudeau) which includes all measurements and accounts for correlations within individual experiments and in-between experiments. RESULTS INCLUDE: -MEASTS. OF CHARMED MESON RATES IN B DECAYS (ALEPH,DELPHI,OPAL,CLEO) D0 +D+ +Ds lc+ +Xic (CLEO)= 1.070 +-0.039 +- 0.041 D0 +D+ +Ds lc+ +Xic (LEP )= 1.117 +-0.039 +- 0.059 Average: 1.082 +- 0.055 estimated charmonium rate: 2.42 +-0.32 % Average CLEO/LEP including charmonium: 1.130 +-0.055 -INCLUSIVE 0C AND 2C RESULT FROM DELPHI WHICH GIVES FOR NC+NCBAR: 1.151 +-0.047 Average with previous result: 1.142 +-0.036 (M. Elsing HEP99 quotes: 1.149+-0.036 without including the inclusive CLEO result) -EXCLUSIVE DDBAR FINAL STATES MEASURED BY ALEPH AND CLEO P(W--> Xc) is the probability for the W to couple to csbar and to give a charmed particle Xc in the final state. P(W-->D0+D+)% P(W__>Ds)% P(W-->Lc)% ALEPH 11.0 +-3.8 +-0.7 16.8 +-4.4 +-5.1 0.8 +-0.3 CLEO 7.2 +-2.0 +-0.2 7.8 +-3.1 +-2.9 Average 8.0 +-1.8 8.7 +-4.3 There are some differences if one compares with the similar table quoted by the Heavy Flavour group of the LEPEWWG (LEPHF/98-01): P(W-->D0+D+)% P(W__>Ds)% P(W-->Lc)% ALEPH 11.3 +-3.7 17.4 +-4.1 0.9 +-0.1 CLEO 8.1 +-2.3 8.3 +-2.7 Average 9.0 +-1.9 11.0 +-2.2 The main difference comes from P(W-->Ds) in which the large common syst. coming from Br(Ds-->Phi pi) is included in the error matrix when I do the average whereas I think that it is added afterwards (not shown in the Table) by the LEPEWWG. (WE EXPECT NEW RESULTS FROM DELPHI AND SLD ON EXCLUSIVE DDBAR STATES, THIS YEAR) AVERAGE OF B-->DDBARX FROM CLEO+ALEPH: 1.19 +- 0.05 (THIS VALUE IS, IN THE END QUITE CLOSE TO THE RESULT OF 1.19+-0.04 QUOTED BY THE LEPEWWG, BECAUSE OF COMPENSATION OF LOCAL DIFFERENCES, AND TO THE VALUE OF M. ELSING: 1.201+-0.037). AVERAGE OF ALL RESULTS: STILL TO BE DONE. A written version will be available this week (26-30/06/2000). It is proposed to include a figure showing this measurement in the plane (BRsl(b--> l X), ) and corresponding expectations from theory. **** Discussion on "how to proceed"?: ------------------------------------- Results are expected to be delivered for Osaka before the 1rst of July. This leaves time to produce averaged values. Before this date it would be nice if the different groups conclude on: +what can be done concerning the inclusive lifetime average (see the points listed before) +add or not BR(Lc --> pKpi) from CLEO in b-rates +Decide to have or not a CDF-LEP average on sin(2*beta) +decide to have or not a section on +possible improvements in D** treatment in exclusive Vcb determination It seems too late to use an updated value for and for the shape of the b-fragmentation function. This has to be postponed after Summer but included in the release of the Summer200 EP preprint. We have to be prepared that results may not be available so early before the Conference. The main concern is on Bs oscillations for which several updates are expected. Olivier will be available until the 21st of July to produce combined results, after this date, O. Leroy has agreed to take this charge. A.O.B.: ======= M. Battaglia reports on a discussion he had with W. Yao on the possibility to produce "world wide" averages for CKM matrix elements to appear in the next versions of PDG. It is envisaged by Weiming to organize a steering group under the PDG flag and our working groups will be invited to contribute. This idea was received positively. As a result of a first discussion, if this idea is pursued by Weiming, it maybe envisaged that LEP groups contribute during the next 1 or 2 years to explain what they did and to make sure that LEP results are properly included. This point will be on the agenda for the next meeting, expecting more infos from Marco. Next meeting: July 12th ============ We hope to be able to finalize results. Answers to last year's questions have to be publicly available. Sincerely yours ______________________________________________________________________