First Observation of B° D*° Decays Sheldon Stone Jianchun Wang Syracuse University CLEO Plenary 05/11/01
Jianchun (JC) Wang2 The amplitude of B (or D) hadronic decays can be expressed as the product of two independent hadronic currents Factorization WW u d c q b q B WW 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 *
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/ ) 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, )
05/11/01Jianchun (JC) Wang4 Motivation WW u d c d b d BB D* + WW u d LLW compared B D* with the predictions based on a factorization model using , they agree within error of 15%
05/11/01Jianchun (JC) Wang5 Motivation WW u d c d b d BB D* + WW c u d d b d BB ++ D* WW u d c d b d BB D* + Possible contribution from other diagram WW u d c d b d BB + D* D* provides an estimate of extra diagram B (D** D* + ) / B (D** D* + ) = 1/2
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
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
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 )
05/11/01Jianchun (JC) Wang9 Distribution of 4 Mass Fit B yield in each bin No significant structure
05/11/01Jianchun (JC) Wang10 Reconstruction Efficiency Medium M : flat High M slow high efficiency Low M 4 tracks overlap low efficiency
05/11/01Jianchun (JC) Wang11 Effect on LLW Prediction Very small effect B D* LLW Prediction B D*
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) / Contribution: (0.42 0.47) events B D Branching fraction: unknown Efficiency: (17.1 5.7) / Contribution: (1.59 0.53) Br(%) events
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
05/11/01Jianchun (JC) Wang14 D* Invariant Mass Spectrum Two entries per event M D* (GeV) Events / 100 MeV D* D* D** Region
05/11/01Jianchun (JC) Wang15 The D** Final State N = 44 GeV < M D* < 2.6 GeV StateM (GeV) (MeV) Mode 3P03P0 ?? DD 1P11P D* 3P13P D* 3P23P D D*
05/11/01Jianchun (JC) Wang16 Spectrum of 3 Invariant Mass Two entries per event
05/11/01Jianchun (JC) Wang17 Spectrum of 3 Invariant Mass 2.3 GeV < M D* < 2.6 GeV No significant structure ( expecting a 1 )
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
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
05/11/01Jianchun (JC) Wang20 Cross Feed From Other Modes B D* Efficiency: (3.9 4.3) / Contribution: (0.42 0.47) events M B (GeV) Events / 2 MeV B D* B D Efficiency: (17.1 5.7) / Contribution: (1.59 0.53) Br(%) events