1. First Observation of B°  D*°         Decays Sheldon Stone Jianchun Wang Syracuse University CLEO Plenary 05/11/01

2. Jianchun (JC) Wang2  The amplitude of B (or D) hadronic decays can be expressed as the product of two independent hadronic currents Factorization WW u d c q b q B WW l c q b q B  This can be compared to semileptonic decays  Test of factorization  B  D* + h  decay width:  ,  , a 1  (Starting from   by D. Bortoletto & S. Stone)  B  D* + h  polarization:  ,  , D S * 

3. 05/11/01Jianchun (JC) Wang3 Mechanism of Factorization Ligeti, Luke, and Wise (LLW) propose to study the mechanism of factorization by examining the differential decay rate as a function of X invariant mass in B  D  *  X ( HEP-PH/0103020 ) The large number of color ( N C ) limit  “its accuracy is not expected to decrease as the X invariant mass increases” Perturbative QCD  “corrections should grow with the X invariant mass” Our recent measurement B  D*(4  , D ( * )   is ideal for this study (CLEO 01-5, CBX 00-16, 00-33, 00-68 )

4. 05/11/01Jianchun (JC) Wang4 Motivation WW u d c d b d BB  D* + WW u d    LLW compared B  D*        with the predictions based on a factorization model using         , they agree within error of 15%

5. 05/11/01Jianchun (JC) Wang5 Motivation WW u d c d b d BB         D* + WW c u d d b d BB ++ D*  WW u d c d b d BB   D* + Possible contribution from other diagram WW u d c d b d BB   + D*  D*         provides an estimate of extra diagram B (D**   D* +  ) / B (D**   D*  + ) = 1/2

6. 05/11/01Jianchun (JC) Wang6 Selection Criteria  ,K  normal selection, 3  dE/dX consistency   mass constraint, photon in good barrel  B: beam constrained mass, | cos  B | < 0.8  Further background suppression :  b 2 < 5 B  D*        , D*  D  D  K   

7. 05/11/01Jianchun (JC) Wang7 The D*         Final State N = 64  16 E B sidebands ( 4  < |  E B | < 6   = 14 MeV E B signal ( |  E B | < 2 

8. 05/11/01Jianchun (JC) Wang8 The D*          Final State  E B Sidebands  E B Signal N = 0.8  13.6 B+B+ u bd c         D* + WW No Signal as expected ( ub  cd )

9. 05/11/01Jianchun (JC) Wang9 Distribution of 4  Mass Fit B yield in each bin No significant structure

10. 05/11/01Jianchun (JC) Wang10 Reconstruction Efficiency  Medium M  : flat  High M    slow   high efficiency  Low M   4  tracks overlap  low efficiency

11. 05/11/01Jianchun (JC) Wang11 Effect on LLW Prediction Very small effect B  D*         LLW Prediction B  D*        

12. 05/11/01Jianchun (JC) Wang12 Cross Feed From Other Modes B  D*         Branching fraction: (1.72  0.14  0.14)% Efficiency: (3.9  4.3) / 40000 Contribution: (0.42  0.47) events B  D          Branching fraction: unknown Efficiency: (17.1  5.7) / 40000 Contribution: (1.59  0.53)  Br(%) events

13. 05/11/01Jianchun (JC) Wang13 B (B   D*         )  B (B  D*         ) = (0.30  0.07  0.06) % ( B (B  D*         )  = (1.72  0.14  0.24)% )  Systematic errors ( ~ 20%)  5.4% from slow   2.2% per charged track (coherent)  11% on background shape  4.7% on D*  D  branching fraction  2.3% on D  K    branching fraction  6.3% (4 events) cross-feed background

14. 05/11/01Jianchun (JC) Wang14 D*  Invariant Mass Spectrum Two entries per event M D*  (GeV) Events / 100 MeV D*   D*   D** Region

15. 05/11/01Jianchun (JC) Wang15 The D**        Final State N = 44  12 2.3 GeV < M D*   < 2.6 GeV StateM (GeV)  (MeV) Mode 3P03P0 ?? DD 1P11P1 2.42218.9 D*  3P13P1 2.461290 D*  3P23P2 2.45923 D  D* 

16. 05/11/01Jianchun (JC) Wang16 Spectrum of 3  Invariant Mass   Two entries per event

17. 05/11/01Jianchun (JC) Wang17 Spectrum of 3  Invariant Mass  2.3 GeV < M D*   < 2.6 GeV No significant structure ( expecting a 1  )

18. 05/11/01Jianchun (JC) Wang18 Summary  We made the first observation of B  D*        , and measured the branching fraction to be (0.30  0.07  0.06) %  The reaction has a large component of D**   D*    No effects on LLW mechanism of factorization study CBX 01-21, Draft 01-21

19. 05/11/01Jianchun (JC) Wang19 Distribution of  E-M B E B :  = 14 MeV Signal: |  E B | < 2  Sideband: 4  < |  E B | < 6  M D4  :  = 2.7 MeV Signal: |  D4  –5.28 | < 2  Sideband: |  D4  –5.23 | < 10 

20. 05/11/01Jianchun (JC) Wang20 Cross Feed From Other Modes B  D*         Efficiency: (3.9  4.3) / 40000 Contribution: (0.42  0.47) events M B (GeV) Events / 2 MeV B  D*         B  D          Efficiency: (17.1  5.7) / 40000 Contribution: (1.59  0.53)  Br(%) events