Status and progress of the HFLAV-Tau group activities Alberto Lusiani Scuola Normale Superiore and INFN, sezione di Pisa
Status and progress of the HFLAV-Tau group activities Outline 1 Introduction 2 Tau Branching Fractions Fit 3 Lepton Universality 4 Determination of | V us | from Tau Decays 5 Further investigations on | V us | from fi → s inclusive 6 HFLAV Tau LVF combinations 7 Summary Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 2 / 46
Status and progress of the HFLAV-Tau group activities Introduction HFLAV Tau sub-group (HFLAV = Heavy Heavy Flavour Averaging Group) (new acronym since 2017) I Tau sub-group established since 2008, http://www.slac.stanford.edu/xorg/hflav/tau/ membership B A B AR • Swagato Banerjee (Victoria → Louisville) • A. L. (convener) • J. Michael Roney (Victoria) Belle • Kiyoshi Hayasaka (Nagoya → Niigata) • Hisaki Hayashii (Nara) • Boris Shwartz (Budker) LHCb • Marcin Chrząszcz (Zürich / Cracow) (since 2014) Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 3 / 46
Status and progress of the HFLAV-Tau group activities Introduction Introduction HFLAV-Tau goals I provide up-to-date tau lepton properties world averages (especially when one can improve over PDG standard averages) I exploit at best all relevant experimental information I provide some useful elaborations of tau data ( e.g. , charged weak current lepton universality, | V us | computed from tau data) recent history 2014 • summer 2014 HFLAV report (arXiv preprint) 2016 • summer 2016 HFLAV report (arXiv preprint) • PDG tau branching fraction fit provided by HFLAV-Tau group since 2016 • PDG tau BRs mini-review since 2016 co-authored by 2 HFLAV members 2017 • acronym changed from HFAG to HFLAV • spring 2017 HFLAV report submitted for refereed publication • very minor refinements w.r.t. summer 2016 release Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 4 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 5 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit HFLAV Tau Branching Fraction Fit Features I use published statistical and systematic correlations I aim to avoid error scale factors as used by PDG, including relevant systematic effects I global minimum ffl 2 fit using constraint equations (see later) systematic dependencies of results from external parameters I experimental measurements typically depend on external parameters [ e.g. , ff ( e + e − → fi + fi − ) , ” and ! branching fractions, other fi branching fractions] I identify dependencies from external parameters, typically from systematics tables I update results values and uncertainties according to updates of external parameters common systematics across different experimental results I two or more results may depend on the same external parameters (also across different publications and different experiments) e.g. : may depend on estimated integrated luminosity, ff ( e + e − → fi + fi − ) I account for statistical correlations induced by common systematics Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 6 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit HFLAV Tau Branching Fraction Fit Features (2) example of constraint equations I B ( fi → h� ) = B ( fi → ı� ) + B ( fi → K� ) ( h = ı; K ) I B ( fi − → ı − ı + ı − � ) = B [ fi − → ı − ı + ı − � ( ex: K S → ı + ı − )] + B ( fi − → ı − K S � ) · B ( K S → ı + ı − ) » – B ( fi → — ¯ �� ) = [ B ( fi → — ¯ �� )] I B ( fi → e ¯ �� ) [ B ( fi → e ¯ �� )] I unitarity constraint (not used for HFLAV-Tau fit, used for PDG BR fits) properties of PDG fit before 2016 that differ from HFLAV fit I unitarity constraint I does not usually consider effects of external parameters dependencies I uses error scale factors (complex procedure used for scale factors in global fit) Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 7 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit Main Changes from 2014 to 2016-2017 I no new experimental input (there were several in the 2014 report) I removed two old preliminary results I Γ 35 = B ( fi → ıK 0 S � ) , B A B AR , ICHEP 2008 I Γ 40 = B ( fi → ıK 0 S ı 0 � ) , B A B AR , DPF 2009 I removed result B [ fi → K 0 S ( particles ) − ] , Belle, 2014 I information in the paper does not allow computing consistent correlations with the other esclusive results in the same paper; the 2014 report included some inconsistent estimate, which made the results covariance matrix negative-definite I ALEPH 1998 Γ 46 ( fi − → ı − K 0 ¯ K 0 � fi ) has been removed because 100% correlated with other esclusive results I several minor constraint imperfections were fixed I all fixes have negligible effects on | V us | , lepton-universality tests, . . . Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 8 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit Tau Branching Fractions Fit results I 170 measurements, 88 constraint equations I fit 135 quantities: 47 BRs, 88 derived quantities (ratios of linear combinations of BRs) I ffl 2 = d.o.f. = 137 = 123 , CL = 17 : 79% (was 16.45% in 2014) I 5.44 error scale factor for inconsistent B A B AR and Belle B ( fi − → K − K − K + � fi ) as in 2014 I consistent with unitarity within 0.1% uncertainty, residual = (0 : 03 ± 0 : 10)% Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 9 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit 2016 fit inputs results by experiment experiment number of results ALEPH 39 CLEO 35 BaBar 23 OPAL 19 Belle 15 DELPHI 14 L3 11 CLEO3 6 TPC 3 ARGUS 2 HRS 2 CELLO 1 Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 10 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit HFLAV spring 2017 basis modes B ( fi → : : : ) HFLAV spring 2017 B ( fi → : : : ) HFLAV spring 2017 ı − K − K + � fi — − ¯ 0 : 1434 ± 0 : 0027 � — � fi 17 : 3917 ± 0 : 0396 ı − K − K + ı 0 � fi e − ¯ 0 : 0061 ± 0 : 0018 � e � fi 17 : 8162 ± 0 : 0410 ı − ı 0 ”� fi ı − � fi 0 : 1386 ± 0 : 0072 10 : 8103 ± 0 : 0526 K − ”� fi K − � fi 0 : 0155 ± 0 : 0008 0 : 6960 ± 0 : 0096 K − ı 0 ”� fi ı − ı 0 � fi 0 : 0048 ± 0 : 0012 25 : 5023 ± 0 : 0918 ı − ¯ K 0 ”� fi K − ı 0 � fi 0 : 0094 ± 0 : 0015 0 : 4327 ± 0 : 0149 ı − ı + ı − ”� fi ( ex. K 0 ) ı − 2 ı 0 � fi ( ex. K 0 ) 0 : 0218 ± 0 : 0013 9 : 2424 ± 0 : 0997 K − !� fi K − 2 ı 0 � fi ( ex. K 0 ) 0 : 0410 ± 0 : 0092 0 : 0640 ± 0 : 0220 h − ı 0 !� fi ı − 3 ı 0 � fi ( ex. K 0 ) 0 : 4058 ± 0 : 0419 1 : 0287 ± 0 : 0749 K − ffi� fi K − 3 ı 0 � fi ( ex. K 0 ; ” ) 0 : 0044 ± 0 : 0016 0 : 0428 ± 0 : 0216 ı − !� fi 1 : 9544 ± 0 : 0647 h − 4 ı 0 � fi ( ex. K 0 ; ” ) 0 : 1099 ± 0 : 0391 K − ı − ı + � fi ( ex. K 0 ; ! ) ı − ¯ 0 : 2923 ± 0 : 0067 K 0 � fi 0 : 8386 ± 0 : 0141 K − ı − ı + ı 0 � fi ( ex. K 0 ; !; ” ) 0 : 0410 ± 0 : 0143 K − K 0 � fi 0 : 1479 ± 0 : 0053 a − 1 ( → ı − ‚ ) � fi 0 : 0400 ± 0 : 0200 ı − ¯ K 0 ı 0 � fi 0 : 3812 ± 0 : 0129 ı − 2 ı 0 !� fi ( ex. K 0 ) 0 : 0071 ± 0 : 0016 K − ı 0 K 0 � fi 0 : 1502 ± 0 : 0071 2 ı − ı + 3 ı 0 � fi ( ex. K 0 ; ”; !; f 1 ) ı − ¯ 0 : 0013 ± 0 : 0027 K 0 ı 0 ı 0 � fi ( ex. K 0 ) 0 : 0234 ± 0 : 0231 3 ı − 2 ı + � fi ( ex. K 0 ; !; f 1 ) 0 : 0768 ± 0 : 0030 ı − K 0 S K 0 S � fi 0 : 0233 ± 0 : 0007 K − 2 ı − 2 ı + � fi ( ex. K 0 ) 0 : 0001 ± 0 : 0001 ı − K 0 S K 0 L � fi 0 : 1047 ± 0 : 0247 2 ı − ı + !� fi ( ex. K 0 ) 0 : 0084 ± 0 : 0006 ı − ı 0 K 0 S K 0 S � fi 0 : 0018 ± 0 : 0002 3 ı − 2 ı + ı 0 � fi ( ex. K 0 ; ”; !; f 1 ) 0 : 0038 ± 0 : 0009 ı − ı 0 K 0 S K 0 L � fi 0 : 0318 ± 0 : 0119 K − 2 ı − 2 ı + ı 0 � fi ( ex. K 0 ) 0 : 0001 ± 0 : 0001 K 0 h − h − h + � fi ¯ 0 : 0222 ± 0 : 0202 ı − f 1 � fi ( f 1 → 2 ı − 2 ı + ) 0 : 0052 ± 0 : 0004 ı − ı − ı + � fi ( ex. K 0 ; ! ) 8 : 9704 ± 0 : 0515 ı − 2 ı 0 ”� fi 0 : 0193 ± 0 : 0038 ı − ı − ı + ı 0 � fi ( ex. K 0 ; ! ) 2 : 7694 ± 0 : 0711 1 − Γ All 0 : 0355 ± 0 : 1031 h − h − h + 2 ı 0 � fi ( ex. K 0 ; !; ” ) 0 : 0976 ± 0 : 0355 note: a linear combination sums up to 1 Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 11 / 46
Status and progress of the HFLAV-Tau group activities Tau Branching Fractions Fit Measurement pulls, pulls probability - HFLAV spring 2017, no scaling 24 14 22 Number of measurements Number of measurements 20 12 18 10 16 14 8 12 10 6 8 4 6 4 2 2 0 0 −6 −5 −4 −3 −2 −1 0 1 2 3 4 5 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Pull Probability I two outliers: B A B AR and Belle B ( fi → K − K − K + � fi ) results I (pull probabilities expressed as n. of Gaussian sigma’s) Alberto Lusiani, SNS – PHIPSI 2017, 26-29 June 2017, Mainz, Germany 12 / 46
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