Measurement of sin(2 b ) in the decays B 0  D ( * ) D ( * )

1. Measurement of sin(2b) in the decays B0 D(*)D(*) Douglas Roberts University of Maryland

2. Physics Motivation • Prediction of Standard Model: • The CP asymmetries in all Bd decays that do not involve direct b u or b  d transitions have to be the same. • This implies that CP asymmetries in B D(*)D(*), which is bc(cd), should be the same as seen in BJ/yKS, which is bc(cs) • Both measurements related to sin(2b) • Any difference in measurements would indicate non-Standard Model contributions

3. SUSY with gluino masses of ~100-300 GeV can lead to deviations from SM asymmetry prediction in B D(*)D(*) measurable by BABAR†. Looking for ~10% difference in asymmetry measurement (Standard Model uncertainty). Depends on ratio of tree and penguin matrix elements in B D(*)D(*), so would need good calculation of hadronic matrix elements One can also potentially measure the angle g in these decays via the interference of the tree and penguin‡ †for example, Y. Grossman and M. Worah, Phys. Lett.B395, 241 (1997) ‡A. Datta, D. London, Phys. Lett. B584, 81 (2004) Physics Motivation (cont.)

4. DD Analysis Group • University of Maryland • Vincent Lillard (Graduate Student, graduated Spring 2004) • Chung Khim Lae (Graduate Student) • Jacob Anderson (Graduate Student) • Chunhui Chen (Postdoc) • Douglas Roberts (Faculty) • UC Irvine • Maarten Bruinsma (Postdoc) • Caltech • Justin Albert (Postdoc) • Tim Pietenko (Graduate Student)

5. Reconstruction of B0D*+D*- • We reconstruct B0 mesons exclusively using a number of D* and D decay modes: • D*+D0p+, D*+D+p0 • D0K-p+, K-p+p0, K-p+p-p+, KSp+p- • D+K-p+p+, KSp+, K-K+p+ • Total of 22 mode combinations used • Results based on 1999-2004 data • 210 fb-1, about 200 million BB pairs

6. Signal Observation, B0D*+D*- • 270 ± 19 events in the signal region • Purity of ~75% • Branching Fraction: • (8.1±0.6±1.0)×10-4 • Preliminary • Also see signals in: • D*+D*- • D+D- • D+D0 • D*0D*+ • D*0D+ • D*0D*+

7. BABAR • B0 D*+ D*- D0 + D0 - K _+ K+ -  +  - 2 1 1 3 4 3 5 2 8 5 6 7 6 7 4 B0D*+D*- Data Event

8. Transversity Amplitudes in B0D*+D*- • The vector-vector final state of B0D*+D*- is not a pure CP eigenstate. • Assuming factorization CP-odd P-wave component could be of the order 5%. • We can measure this directly, however • RT is fraction of CP-odd component, given by: • Will present preliminary result at Heavy Flavor 9 conference

9. Angular Distribution • Time dependent full angular • distribution for B0 D*+ D*- : • Integrating over time, B flavor, q1, ftr • get one dimensional pdf in terms of Rt: (A┴-A┴ for B0 decay) CP-odd component CP-even component • The above pdf does NOT take detector acceptance into account! (previous measurements measured bias in MC and added to final result) We choose to put efficiency directly into PDF….

10. Results - Rt • B0 D*+ D*- is found • to be mostly CP-even Rt = 0.125  0.044(stat)  0.007(syst) • Shown is the projection of events with mES > 5.27 GeV/c2 • Background parameter consistent with fits to • sideband events: b2 = -0.16 ± 0.17 • 500 toy experiments show goodness of fit:

11. Angular Distribution • Time dependent full angular • distribution for B0 D*+ D*- : • Time dependent amplitudes: • Generalized comparison: let’s assume penguin contributions are negligable (only one ) (and |q/p| = 1 so that |A0|2 = |l|2 |A0|2 ) Now, integrating over all three angles… (–) CP dilution factor: K = 1 – 2Rt (–) (+ ) • Time dependent asymmetry: S = -K sin2b C

12. Allowing Penguins… • If penguin diagrams are non-negligible, this leads to different l||, l0, l┴ Note: a common value of |l| or Im(l) cannot be factored! (–) • Now the decay rate • can be written as a function • of qtr and time: (–) (–) Mixture of CP-even(+) and CP-odd(-) contributions dilute sin(Dmt) coeff.!

13. Results – CP fit C = 0.06 ±0.17(stat)± 0.03(syst) sin2b = 0.75 ±0.25(stat) ± 0.03(syst) • Charmonium sin2b = 0.685 ± 0.032 • World Average

14. Summary • CP asymmetries consistent with charmonium results • Assuming no penguin contribution

15. Future Prospects • Measurement of CP asymmetries and RT submitted to PRL(hep-ex/0505092) • Have seen evidence for other B0D(*)+D(*)- decay modes useful for CP studies • We are beginning a more comprehensive program to measure all decays of the type BD(*)D(*) • Both charged and neutral B • Will help get a handle on penguin contributions • Look at color-suppressed decays • Currently working on a paper draft that included branching ratio measurements (or limits) for all 10 modes of the type B  D(*)D(*) • This will be an excellent compliment to our measurement of sin2b in B0J/yKS! • Dr. Chen has started looking at BD(*)D(*)K decays • Potential to measure cos2b

16. The BaBar Silicon Vertex Tracker

17. Maryland Involvement in the BABAR Silicon Vertex Tracker (SVT) • The Maryland group has had continued involvement in the calibration and maintenance of the SVT • D. Roberts, V. Lillard, C.K. Lae, together with a group from LBL and UC Santa Cruz, have been working on the internal, in situ, alignment of the SVT • Involves measuring location and orientation of 340 silicon wafer with an accuracy < 5 mm • Improvements in vertex resolution seen during past year have improved many analyses, including CP measurements and lifetimes

18. SVT Local Alignment • We have developed a fitting tool used for alignment that fits e+e- m+m- events as a single track using the know beam boost parameters. • This provides very accurate measurements of the track orbit, and allows tracks to be fit in the SVT alone. • Reduces errors on alignment parameters by close to factor of 10 for same statistical sample of events • With about 100,000 m-pair events together with some cosmic tracks, we are able to measure alignment to a few microns • Position resolution is >10mm

19. SVT Operations • Graduate students V. Lillard and C.K. Lae and postdoc C. Chen have all served as SVT Operations Managers • C. Chen in early part of 2004 • C.K. Lae currently serving • Operations Managers are responsible for the day-to-day operations of the SVT • Check data quality • First ones to get paged when something goes wrong • Serve for a 3 month term • C. Chen is currently serving as the Operations Coordinator • Responsible for training the Op. Managers • Expected to be more of an expert than the managers and should be able to deal with more serious problems

20. SVT System Management • Since May of 2003, D. Roberts has been acting as one of the two SVT system managers • Responsible for current operation of SVT • Coordinating software and hardware development • Planning for future detector upgrades • Recently pushed through a successful plan to upgrade to the radiation monitoring and protection system • System was installed summer of 2004, and has been functioning as expected • During the 2006 shutdown, we could have the opportunity for an intervention of the SVT (i.e. take it apart and fix/replace any problem components) • Over past year or so, we have done a risk/benefit analysis of performing an intervention. • Conclusion was that the SVT is functioning fine as is, risk of damage not outweighed by benefit. • Actively involved in understanding performance of the SVT in the upcoming high-luminosity runs of PEP-II • Impact of radiation to lifetime of SVT • Impact on physics of higher detector occupancy • Integration with redesigned interaction region