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Heavy Flavor Averaging Group

Heavy Flavor Averaging Group. David Kirkby UC Irvine. http://www.slac.stanford.edu/xorg/hfag/ http://belle.kek.jp/mirror/hfag/. Brief History. HFAG is successor to LEP/SLD/CDF heavy-flavor working-groups.

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Heavy Flavor Averaging Group

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

  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(Bs) from 1994 Moriond/LaThuile]: reliable averages require careful attention to methodology.

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

  4. Organization CERN (flavour) KEK, SLAC (flavor) b-hadron lifetimes B oscillations DGs Vcb Vub B time-dependent Semileptonic decays Unitarity triangle Rare decays

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

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

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

  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.

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