1. 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

2. 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!

3. 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

4. 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

5. 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.

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

7. 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

8. 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

9. 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

10. 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. +7.2 - 4.6

11. 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):

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

13. 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

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