Recent b physics results from OPAL David Waller, Carleton University for the OPAL Collaboration EPS Conference HEP2003 Heavy Flavour Physics Session Aachen, Germany 17 July 2003

July 17, 2003EPS Conference D. Waller/Carleton U.2 Outline –Object, motivation –Method –Results Charm counting in beauty decays –Object, motivation –Method –Results Conclusions Analyses of Z 0 data!

July 17, 2003EPS Conference D. Waller/Carleton U.3 Semileptonic decay of b hadrons to orbitally excited D mesons Measure D **0 are L=1 orbitally excited charm mesons. –Measure narrow J q = 3/2 states (D 1 0, D 2 *0 ). –Wide J q = 1/2 states not visible with statistics. Reconcile difference between measured inclusive and exclusive semileptonic branching ratios. Reduce uncertainty in |V cb |. Test HQET predictions. Object Motivation

July 17, 2003EPS Conference D. Waller/Carleton U.4 Semi-leptonic decay of b hadrons to orbitally excited D mesons: Method Identify high p lepton ( ,e) –high efficiency and purity for p  > 3 GeV/c, p e > 2 GeV/c Exclusively reconstruct D **0 D **0 D *+  **- D 0  + slow K -  + (  +  - ) Background cuts to remove fake  **- (  from fragmentation) –main background from decays plus fake  **- –ANN (p, p T, d0/σ d0 ) to select  **- 3 mm

July 17, 2003EPS Conference D. Waller/Carleton U.5 D **0 – D *+ mass difference Combine D 0→ K  and K3  channels to reduce uncertainty due to background. Unbinned ML fit to determine number of D 1 and D 2 * events (B.-W.  Gaussian). Number of wrong sign and right sign background events fit simultaneously.

July 17, 2003EPS Conference D. Waller/Carleton U.6 Results for

July 17, 2003EPS Conference D. Waller/Carleton U.7 Charm counting in b decays: Object and Motivation Object:(1) measure with inclusive method. (2)use to calculate average number of c plus anti- c quarks per b quark decay, n c. Motivation: compare experimental value of n c to theoretical prediction: n c = 1.20 ± 0.06 (Neubert & Sachrajda) Use PDG values

July 17, 2003EPS Conference D. Waller/Carleton U.8 Charm counting in b decays: Inclusive method Differentiate b→1 charm from b→2 charm using topology. Impact parameter significance, S (=d 0 /σ d0 ), of tracks from D decay greater than S of tracks from b decay. In b→2 charm most tracks from D decay. Combine S of tracks in jet into single joint probability variable: P J

July 17, 2003EPS Conference D. Waller/Carleton U.9 Charm counting in b decays: Probability Density Functions and Fits 1 and 2 charm PDFs for –ln(P J ) for different track multiplicities (TM) Hatched = 2 charm Green = 1 charm Red = 0 charm, charmonium, bckgd

July 17, 2003EPS Conference D. Waller/Carleton U.10 Charm Counting in b decays: Results measured for each year separately. Results for each year combined → consistent. Two dominant systematics from physics modelling: –charged particle multiplicity in fragmentation (±6.2%) –neutral K and  multiplicities in D decays ( %) combined with and to yield n c

July 17, 2003EPS Conference D. Waller/Carleton U.11 Conclusion Results of these recent OPAL charm counting and analyses consistent with previous measurements and theoretical predictions. this result: pink band Semileptonic B decays to narrow L=1 D mesons This result: ALEPH (1997): CLEO (1998): This result: ALEPH (1997): CLEO (1998):

July 17, 2003EPS Conference D. Waller/Carleton U.12 Key variables

July 17, 2003EPS Conference D. Waller/Carleton U.13 Cross check of results  angle between  **- and  slow in rest frame of D *+. Signal peaks at higher |cos(  )| while background is flat. peak sidebands

July 17, 2003EPS Conference D. Waller/Carleton U.14 Extra slide: charm counting