1. Heavy Flavor Averaging Group David Kirkby UC Irvine http://www.slac.stanford.edu/xorg/hfag/ http://belle.kek.jp/mirror/hfag/

2. D. Kirkby, UCI 2 Brief History HFAG is successor to LEP/SLD/CDF heavy- flavor working-groups. Established at May 2002 FPCP conf. as natural transfer of primary responsibility to Babar & Belle. Lesson from history [ t (B s ) from 1994 Moriond/LaThuile]: reliable averages require careful attention to methodology.

3. D. Kirkby, UCI 3 HFAG Mission Primary mission: provide averages of “heavy flavor” (B d,B s ) quantities for major conferences (summer/winter) and PDG. Secondary: standard reporting of analysis details standard reporting of analysis details develop & maintain averaging tools develop & maintain averaging tools build community consensus on methodology build community consensus on methodology develop new ways to summarize complex averages develop new ways to summarize complex averages

4. D. Kirkby, UCI 4 Organization b-hadron lifetimes B oscillations DG s V cb V ub B time-dependent Semileptonic decays Unitarity triangle Rare decays KEK, SLAC (flavor)CERN (flavour)

5. D. Kirkby, UCI 5 Methodology I Types of uncertainty & correlations handled: stat. syst1. syst2. syst3. syst4. … stat. syst1. syst2. syst3. syst4. … measurement A measurement B

6. D. Kirkby, UCI 6 Methodology II Assume that systematics correlated between measurements are due to unknown value of some external globally defined parameter. E.g., B lifetime used to determine B oscillation frequency.

7. D. Kirkby, UCI 7 Methodology III Approximate (n+1)- dim. likelihood with n-dim. likelihood, assuming external constraint on global param. more precise than internal constraint.

8. D. Kirkby, UCI 8 Issues Cannot handle statistical correlations (e.g., due to sample overlaps). Cannot combine multidim. results (e.g., simultaneous t-D m) How to combine measurements of same quantity made with different theoretical assumptions? (e.g., DG ).

9. D. Kirkby, UCI 9 Looking Ahead Convened task force to make recommendations on Dalitz analysis. Created new WG on b->c decays. Writeup of HFAG methodology & results on track for winter conferences. Involved in CKM2005 workshop.