Pavel Krokovny Heidelberg University on behalf of LHCb collaboration

1. Search for New Physics in CP violating measurements at LHCb Pavel Krokovny Heidelberg University on behalf of LHCb collaboration • Introduction • LHCb experiment • Physics results • bS measurements • prospects • Conclusion

2. Why CP violation? • CP violating parameters are well predicted by the Standard Model • Good sensitivity to New Physics • Huge statistics allows to perform a precise measurements

3. LHCb features • Large bb cross section & acceptance: huge statistics • Efficient trigger: reducing very high background • Excellent vertexing: resolving fast Bs oscillation • Good tracking & PID: signal reconstruction & background suppression

4. fS measurement in BS mixing • Bs->J/Yf is dominated by tree diagram. (penguin contribution is in order of 10-3-10-4) • Interference between direct & mixing decays gives a CP violating phase fS=fM-2fD. • fS in SM is small and well predicted: fS=0.03630.017 • Good sensitivity for New Physics: fS=fSSM+fSNP

5. Angular analysis

6. Flavor tagging • Need to determine BS flavor at production time. • Two methods: Same Side (Kaon flavor) and Opposite Side (other B flavor) • Two key parameters: efficiency (e) and dilution factor D=(1-2w) • Effective tagging power proportional to eD2 • OST is calibrated on data using self-tagged B decays: B+gD*+mn, J/YK+ • SST calibration: using double tag method

7. Flavor tagging performance • Flavor tagger was tuned using 48K B0->D*-m+n events • Then we check performance on 6K B0->D-p+ events • eeff(SS+OS) = 4.31.0 % • compatible with MC expectation • Dmd = 0.4990.0320.003 ps-1 • world average: 0.5070.005 ps-1 Mixing in B0gD-p+ LHCb-Conf 2011-010

8. BSgJ/Yf signal Bs mass 75728 events Lifetime LHCb-Conf 2011-006

9. fS result • Feldman-Cousins method used to get CL contours in fS-DG plane • Statistical errors only(systematic effects found to small in comparison with statistical uncertainty) LHCb-Conf 2011-006

10. fS prospects Expectation!

11. Additional channels for fs • BsgJ/Y f0 • J/Y f0 is CP even eigenstate: angular analysis not needed. • Measurement of fS to come soon. (error ~1.5 of J/Yf) First observation! Phys.Let.B698:115, 2011

12. g measurements • Two set of methods to measure g: • loop diagram: Bghh (possible NP contribution) • tree diagram: BgDK (theoretically clean) • Difference in results will indicate for New Physics.

13. /K /K Bd/s Bd/s /K /K gfrom Bghh Large penguins contributions in both decays Method: Measure time-dependent CP asymmetry for B and BsKK and exploit U-spin flavor symmetry for P/T ratio (R. Fleischer). Take fs, fd from J/,J/Ks can resolve g

14. K-p+ K+p- K+p- K-p+ Direct CPV in Bghh 37 pb-1 ACP(BdgKp)=-0.0880.0110.007 (world average: -0.0980.12) ACP(BSgKp)=0.270.080.02 CDF: 0.390.17 LHCb-Conf-2011-042

15. Favored:VcbVus* Vcs*Vub: suppressed u s Common final state K- K- s u u b B- B- b c c u f D0 D0 u u gfrom BgDK Interference between tree-level decays; theoretically clean Parameters: g,rB, δ • Three methods for exploiting interference (choice of D0 decay modes): • Gronau, London, Wyler (GLW): Use CP eigenstates, e.g. D0  h+ h - • Atwood, Dunietz, Soni (ADS): Use doubly Cabibbo-suppressed decays, e.g. D0  K+π- • Dalitz plot analysis of 3-body D0 decays, e.g.Ks π+ π-

16. ADS method D. Atwood, I. Dunietz and A. Soni, PRL 78, 3357 (1997); PRD 63, 036005 (2001) Enhancement of СР-violationdue to use ofCabibbo-suppressedD decays B–D0K–- color allowed, D0K+π– - doublyCabibbo-suppressed B–D0K–- color suppressed, D0K+π– - Cabibbo-allowed Interfering amplitudes are comparable Measured quantities:

17. ADS analysis at LHCb 4.0s significance RADS=(1.660.390.24) 10-2 AADS=-0.390.170.02 World average: 1.60.3 (w/o LHCb) World average: -0.580.21 LHCb-Conf 2011-044

18. Conclusion • LHCb shown a good performance in B & charm physics. • B-factories & Tevatron sensitivity overtaken or matched on many topics using 2010 data only. • No sign of New Physics yet . • Great potential to search for New Physics in next years!

19. Backup

20. Control Channels B+ J/ K+ • Tagging calibration (opposite side) B0 J/ K*0 • Kinematically similar to BsJ/ • Angular acceptance checks: Polarization amplitudes • Check of tagging performance

21. J/Yf amplitudes

22. LHCb data taking LHCb collected 37 pb-1 in 2010, and 670 pb-1 in 2011 One day of operation now corresponds to whole 2010 statistics!

23. B mixing Due to the different values of CKM couplings the Bs mixes faster then the Bd Bd mixing Bs mixing b b Bs mixing d s t t 5.1 x 1011 Hz 1.8 x 1013 Hz Bd Bs Bd Bs W W W W Bd → Bd Bd → Bd Bs → Bs Bs → Bs s d t b t b Both the Bd and Bs mixing have been precisely measured in experiments

24. BS mixing formalism

25. Additional channels for fs Pure penguin decays Br(BsgK*K*)=(1.950.470.51 0.29)10-5 First observation! LHCb-Conf 2011-019

26. Lifetime measurement for BsgK+K-

27. CPV in charm • Indirect CPV: mixing rate of D0gD0 and D0gD0 differ • Direct CPV: amplitudes for D0/D0 differ, mixture of mixing and decay diagram. • The SM predicts very small CPV in charm: O(10-4). • Can be up to O(10-2) in some NP models. • Good prospects to search NP in charm! • Promising modes: CS modes with penguin contribution:

28. Charge asymmetry in D0gh+h- • Production and soft pion asymmetry cancel in ARAW(f)-ARAW(g) • There is no detection asymmetry in D0gh+h-

29. D0gh+h- ACP results • Fit the mass difference: M(D*)-M(D0) • Result: ACP(KK)-ACP(pp)= (-0.280.700.25) % • Belle: (-0.860.600.07)% • BaBar: (+0.240.62)% naïve difference • CDF: (-0.460.33)%w/o systematic LHCb-Conf 2011-023