1. 12/14/021 Measurements of the Branching Fractions and Helicity Amplitudes in B  D*  Decays Authors: Guangpei Chen, Roy A. Briere Intended for: PRD (RC) Committee: Dave Cinabro, Tom Ferguson, Jianchun Wang Introduction  Decay chain studied: B  D*  , D*  D ,       ( D   K   +, K   + , K   +  +   )  Measure: branching fractions, a 2 /a 1 (color-suppressed/color-enhanced), |H  |, |H  |, |H  |,  ,  ,  L /  |H  | 2  |H  | 2 +|H  | 2 +|H  | 2 ) )  History: CLEO 94(PRD), with joint (cos  D*, cos   ) fit, 0.89 fb  data. CLEO CONF 98, with joint (cos  D*, cos  ,  ) fit, 3.1 fb  data.

2. 12/14/022 Important features on reconstruction  CLEO II and II.V data are treated separately in branching fraction measurement, and put together in helicity fit. Three D  modes are fitted together but with different resolutions and acceptances.  In D  K   +  mode, Dalitz weight selection, and  energy- dependent mass width used.  A  energy-dependent E B resolution used, showing as a linear function of cos  .  Cut on  S (sphericity angle) and R 2.  For events with multiple B candidates, the one with smallest |  E| is chosen. N( B   D*   ) = 462  26 N( B  D*    ) = 563  26

3. 12/14/023 Unbinned Maximum likelihood fit  Signal probability distribution: P ji S (M,m,cos  D*,cos  ,  )  Gaussian function for M B.  BW with Blatt-Weiskopf form factor for m .  The differential cross-section along with detector acceptance for angular distribution. The detector acceptance are weighted according to helicity amplitudes with several iterations.  Bkg probability distribution: P ji B (M,m,cos  D*,cos  ,  )  ARGUS function for M B.  Flat distribution for m .  Angular distribution of B mass sideband event, fit with function P 2 (cos  D* )  P 2 (cos   )  P 1 (cos(  )) for angular distribution.

4. 12/14/024 Branching fractions  All candidates with 5.20 < M B < 5.30 GeV/c 2 are included in the fit. Angular distributions are ignored.  B(B   D*   ) = ( 0.98  0.06  0.16  0.05 )% B(B  D* +   ) = ( 0.68  0.03  0.09  0.02 )%  a 2 /a 1 = 0.27  0.03  0.05  0.06  First systematic errors:  The number of BB pairs (2%).  The background shape (3%).  Monte Carlo statistics (1-2%).  Detection efficiency (10-18)%.  Second systematic errors are from uncertainty of branching fractions, and fraction of charge/neutral B pair production (a 2 /a 1 measurement only).

5. 12/14/025 Extraction of Helicity Amplitude B   D*   B  D* +    Only B events in the B signal region are included in the fit.  The number of signal and background are fixed.  Detector acceptance are helicity dependent, a weighting technique used with several iterations until the helicity amplitudes converge.

6. 12/14/026 Helicity Amplitudes  Systematic errors: the acceptance parameterization, detector smearing, background level and shape, non-resonant    contribution, and the polarization dependence on the mass of the   meson.  The results indicate possible non-trivial helicity amplitude phases with significance of 3.19  and 2.75 , respectively. 0.31  0.12  0.040.65  0.16  0.04  0.322  0.025  0.0160.306  0.030  0.025 |H  | 1.42  0.27  0.041.02  0.28  0.11  0.107  0.031  0.0110.122  0.040  0.010 |H  | 0.941  0.009  0.0060.944  0.009  0.009 |H  | B  D* +   B   D*   Quantity

7. 12/14/027 Longitudinal Polarization   L /  (B   D*   ) = 0.892  0.018  0.016   L /  (B  D* +   ) = 0.885  0.016  0.012  The fraction of longitudinal polarization for B  D* +   is in good agreement with the HQET prediction using factorization and the measurements of the semileptonic form factors.

8. 12/14/028

9. 9 Other Significant Questions  Fit iterations: takes about 8 iterations; converge to the same point using fully longitudinal or no polarization initial value;  Weighted acceptance  Background angular distribution: try flat distribution; B side band data, B side band MC, MC under B peak are compared, differences are small;  Number of BKG events: consistent with fit in two regions