Heavy Flavor Averaging Heavy Flavor Averaging GroupGroup

David KirkbyDavid Kirkby

UC IrvineUC Irvine

http://www.slac.stanford.edu/xorg/hfag/http://belle.kek.jp/mirror/hfag/

22D. Kirkby, UCID. Kirkby, UCI

Brief HistoryBrief History

HFAG is successor to LEP/SLD/CDF HFAG is successor to LEP/SLD/CDF heavy-flavor working-groups.heavy-flavor working-groups.

Established at May 2002 FPCP conf. as Established at May 2002 FPCP conf. as natural transfer of primary natural transfer of primary responsibility to Babar & Belle.responsibility to Babar & Belle.

Lesson from history [Lesson from history [(B(Bss) from 1994 ) from 1994 Moriond/LaThuile]: reliable averages Moriond/LaThuile]: reliable averages require careful attention to require careful attention to methodology.methodology.

33D. Kirkby, UCID. Kirkby, UCI

HFAG MissionHFAG Mission

Primary mission: provide averages of Primary mission: provide averages of “heavy flavor” (B“heavy flavor” (Bdd,B,Bss) quantities for major ) quantities for major conferences (summer/winter) and PDG.conferences (summer/winter) and PDG.

Secondary:Secondary: standard reporting of analysis detailsstandard reporting of analysis details develop & maintain averaging toolsdevelop & maintain averaging tools build community consensus on methodologybuild community consensus on methodology develop new ways to summarize complex develop new ways to summarize complex

averagesaverages

44D. Kirkby, UCID. Kirkby, UCI

OrganizationOrganization

b-hadron lifetimes

B oscillations

s

Vcb

Vub

B time-dependent

Semileptonic decays

Unitarity triangle

Rare decays

KEK, SLAC (flavor)

CERN (flavour)

55D. Kirkby, UCID. Kirkby, UCI

Methodology IMethodology I

Types of uncertainty & correlations Types of uncertainty & correlations handled:handled:

stat.

syst1.

syst2.

syst3.

syst4.

…

stat.

syst1.

syst2.

syst3.

syst4.

…measurement A measurement B

66D. Kirkby, UCID. Kirkby, UCI

Methodology IIMethodology II

Assume that systematics correlated Assume that systematics correlated between measurements are due to between measurements are due to unknown value of some external unknown value of some external globally defined parameter.globally defined parameter.

E.g., B lifetime used to determine B E.g., B lifetime used to determine B oscillation frequency.oscillation frequency.

77D. Kirkby, UCID. Kirkby, UCI

Methodology IIIMethodology III

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

88D. Kirkby, UCID. Kirkby, UCI

IssuesIssues

Cannot handle statistical correlations Cannot handle statistical correlations (e.g., due to sample overlaps).(e.g., due to sample overlaps).

Cannot combine multidim. results Cannot combine multidim. results (e.g., simultaneous (e.g., simultaneous m)m)

How to combine measurements of How to combine measurements of same quantity made with different same quantity made with different theoretical assumptions? (e.g., theoretical assumptions? (e.g., ).).

99D. Kirkby, UCID. Kirkby, UCI

Looking AheadLooking Ahead

Convened task force to make Convened task force to make recommendations on Dalitz analysis.recommendations on Dalitz analysis.

Created new WG on b->c decays.Created new WG on b->c decays.

Writeup of HFAG methodology & Writeup of HFAG methodology & results on track for winter results on track for winter conferences.conferences.

Involved in CKM2005 workshop.Involved in CKM2005 workshop.