5 Jan 03S. Bailey / BaBar : B decays to Measure gamma1 B Decays to Measure  Stephen Bailey Harvard University for the BaBar Collaboration PASCOS 2003 Mumbai, India

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma2 Background  CP violation with B 0 ->  K S (sin2  ) is well established  Agrees with Standard Model  Now we need to overconstrain the unitarity triangle to check consistency  = arg(V ud V ub * / V cd V cb *)  = -arg(V ub ) in standard phase convention  Results from BaBar at PEP-II: e + e - ->  (4S) -> BB bar  ~88 million BB bar pairs   

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma3 Many Methods – none are easy  Amplitude relationships with B - -> D 0 CP K - and friends  “Squashed” amplitude triangles: BR(B -  D 0 bar K - ) << BR(B -  D 0 K - )  Interference involving doubly Cabibbo suppressed D 0 decays  sin(2  +  ) with B 0 -> D ( * ) -  +,  +, a 1 +, …  Cabibbo suppressed B 0 -> D ( * )+  -  Use B 0 -> D s ( * )  and SU(3) to estimate B 0 -> D ( * )+  -  Progress on both full and partial reconstruction techniques  B -> , K , KK  Several options with various theoretical trade-offs

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma4 B   D 0 CP K  and friends  D 0 CP = (D 0  D 0 bar ) /  2 : CP even or odd decays, e.g. K + K -  Measure sides of amplitude triangles to determine   2 A(B - -> D 0 CP K - ) = A(B - -> D 0 K - )  A(B - -> D 0 bar K - )  2 A(B - -> D 0 CP K - ) = A(B - -> D 0 K - )  |A(B - -> D 0 bar K - )| e - i  e i   Sensitivity to  depends on r = |A(B - -> D 0 bar K - )| / |A(B - -> D 0 K - )| strong phase weak phase

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma5 B -  D 0 K -  Use D 0 -> K -  +, K -  +  -  +, K -  +  0 hep-ex/ B -> D 0  with kaon ID cut and 3  m ES cut B -> D 0 K D 0 -> K  only PDG: BF(B - -> D 0  - ) = (5.3  0.5)x10 -3 (81M BB bar pairs; 75 fb -1 )

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma6 B   D 0 CP K   B   D 0 [K + K  ] K   36.8  8.4  4.0 signal events  B   D 0 [     ] K   Upcoming  backgrounds from B ->  K hep-ex/

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma7  Direct CP asymmetry from D 0 CP states: strong phase weak phase B   D 0 CP K  and friends A CP = 0.17  /-0.07 hep-ex/ (81M BB bar pairs; 75 fb -1 )

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma8 B -  D 0 bar K -  Hard: BR(B -  D 0 bar K - ) << BR(B -  D 0 K - )  Interference from doubly Cabibbo suppressed D 0 decays:  B - -> D 0 bar K - (small) --> K +  - (big)  B - -> D 0 K - (big) --> K +  - (small)  Plan:  Measure B - -> D 0 (bar) K - w/ D 0 bar -> K +  -, K +  -  +  -, K +  -  0  Measure Multiple D 0 CP modes  See Gronau, hep-ph/

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma9 B   D 0 CP K  Summary  B - -> D 0 K - measured  R(B -> D 0 K/D 0  ) = (8.31  0.35  0.20)%  D 0 CP -> K + K - : initial results available  Direct Asymmetry: A CP = 0.17  /-0.07  More modes (e.g. D 0 CP ->  ) in progress  More data coming too…  Cabibbo suppressed modes in progress… hep-ex/ (81M BB bar pairs; 75 fb -1 )

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma10 sin(2  +  ) with B 0  D ( * )   Both D ( * )+  - and D ( * )-  + from B 0 and B 0 bar  Interference -> CP violation  B 0 B 0 bar mixing : e -i 2   b -> u : V ub ~ e -i   Large difference in branching fractions:  BF favored (B 0 -> D ( * )-  + ) ~ 3x10 -3  BF suppressed (B 0 -> D ( * )+  - ) ~  Small CP violating effect expected (2%)  Measure one weak phase (2  +  ) and a strong phase (  ) for each mode in standard phase convention

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma11 sin(2  +  ) : B 0  D s ( * )   | ( * ) | = ~ 0.02  Use B 0 -> D s ( * )+  - to estimate |A(B 0 -> D ( * )+  - )| via SU(3) symmetry  Introduces theoretical uncertainty  B 0 -> D s +  -  Use D s + ->  +, K s K +, K* bar K +  21.4  5.1 signal events  BF(B 0 -> D s +  - ) = (3.2  0.9  1.0) x  84M BB bar pairs; 78 fb -1  BF(B 0 -> D s * +  - ) < 4.1 x [90% CL] hep-ex/ |A(B 0 bar -> D ( * )-  + )| |A(B 0 -> D ( * )-  + )| too small to measure w/ current data

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma12 sin(2  +  ) : Fully reconstructed B 0  D ( * )   Fully reconstruct both D  and D*   Time evolution for each state f arg( D+  - ) = -(2  +  +  arg( D-  + ) = -(2  +  -   Four ’s include one weak phase (2  +  ) and two strong phases (  ( * ) ) arg( D*+  - ) = -(2  +  +  *  arg( D*-  + ) = -(2  +  -  * 

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma13 sin(2  +  ) : Fully reconstructed B 0  D ( * )   We have thousands of fully reconstructed B 0 -> D  and B 0 -> D*   The sin(2  +  ) fitter is being studied  The results aren’t unblinded yet  m ES from B 0 -> D -  + with 5.2 fb -1  very clean signal  now we have almost 20x more data 5.2 fb -1 B 0  D -  +

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma14 sin(2  +  ) : Partially reconstructed B 0  D*   Another method: Partial D* reconstruction  Reconstruct low momentum  in D* -> D , but not rest of D  More signal events, but also more background  N(tagged) > events in full dataset 20.3 fb -1 : only a fraction of the current data, but shows approximate S/B

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma15 sin(2  +  ) : Partially reconstructed B 0  D*   Unreconstructed D daughters could affect tag side vertex position measurement  Validate partial reco. method with a lifetime measurement  (B 0 ) = (1.510   0.041) ps (with 20.7 fb -1 )  cf PDG  (B 0 ) = ( ) ps  hep-ex/ submitted to PRD  Proceeding with sin(2  +  ) fit, results not unblinded yet…

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma16 B 0  , K , KK  Amplitude relationships with B -> , K , KK may also measure or constrain   Theoretical interpretation is complicated:  Penguins  Rescattering contributions  SU(3) symmetry breaking  etc.  For a recent brief review, see Fleischer, hep-ph/  For now we’ll quote branching fractions (BF) and Asymmetries (A) and let you plug the numbers into your favorite theory…

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma17 B 0  , K , KK ModeBF x A B 0 ->  0  0 < 3.6 [90% CL] B 0 ->  +   0.6  0.2 S= 0.02  0.34 ; C=  0.25 B 0 -> K 0   1.5   0.36  0.09 B 0 -> K +   0.9    B 0 -> K + K - < 0.6 [90% CL] B+ ->  +    0.02 B + -> K +    0.09  0.01 B + -> K 0    0.10  0.02 B + -> K + K 0 bar < 1.3 [90% CL] hep-ex/ hex-ex/ hex-ex/ hep-ex/ (81 fb -1 except K 0  +, K + K 0 bar : 54 fb -1 )

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma18 Many More Modes  Exploring many other modes which could measure  or 2  +  :  B -> D ( * ) K ( * )  B -> D ( * ) K S  B -> D K S   B -> D ( * ) K ( * )   Dalitz analysis of B ->   etc.

5 Jan 03S. Bailey / BaBar : B decays to Measure gamma19 Outlook  The Good News: We’re making progress  B - -> D 0 CP K -  Several sides of amplitude triangles measured  A CP = 0.17  /-0.07  sin(2  +  ) with B 0 -> D ( * )   Decay modes reconstructed  Lifetime measurement checks method  sin(2  +  ) fit results in progress  B 0 -> , K , KK  Many branching fractions measured  Need theoretical input for interpretation  Final story will likely involve:  B factory measurements of many decay modes  Hadronic accelerator results with B s decays  Theoretical input