Pavel Krokovny Heidelberg University on behalf of LHCb collaboration Introduction LHCb experiment Physics results  S measurements  prospects Conclusion Search for New Physics in CP violating measurements at LHCb

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

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

 S measurement in B S mixing Bs->J/  is dominated by tree diagram. (penguin contribution is in order of ) Interference between direct & mixing decays gives a CP violating phase  S =  M -2  D.  S in SM is small and well predicted:  S =  Good sensitivity for New Physics:  S =  S SM +  S NP

Angular analysis

Flavor tagging Need to determine B S flavor at production time. Two methods: Same Side (Kaon flavor) and Opposite Side (other B flavor) Two key parameters: efficiency (  ) and dilution factor D=(1-2  ) Effective tagging power proportional to  D 2 OST is calibrated on data using self-tagged B decays: B +  D* + , J/  K + SST calibration: using double tag method

Flavor tagging performance Flavor tagger was tuned using 48K B 0 ->D* -  + events Then we check performance on 6K B 0 ->D -  + events  eff (SS+OS) = 4.3  1.0 % compatible with MC expectation  m d =   ps -1 world average:  ps -1 Mixing in B 0  D -  + LHCb-Conf

B S  J/  signal LHCb-Conf  28 events Bs mass Lifetime

 S result Feldman-Cousins method used to get CL contours in  S -  plane Statistical errors only (systematic effects found to small in comparison with statistical uncertainty) LHCb-Conf

 S prospects Expectation!

Additional channels for  s Bs  J/  f 0 J/  f 0 is CP even eigenstate: angular analysis not needed. Measurement of  S to come soon. (error ~1.5 of J/  ) First observation! Phys.Let.B698:115, 2011

 measurements Two set of methods to measure  : loop diagram: B  hh (possible NP contribution) tree diagram: B  DK (theoretically clean) Difference in results will indicate for New Physics.

 from B  hh Large penguins contributions in both decays B d/s  /K B d/s Method: Measure time-dependent CP asymmetry for B      and B s  K  K  and exploit U-spin flavor symmetry for P/T ratio (R. Fleischer). Take  s,  d from J/ ,J/  K s  can resolve 

Direct CPV in B  hh K+-K+- K-+K-+ A CP (B d  K  )=   (world average:  0.12) A CP (B S  K  )=0.27  0.08  0.02 CDF: 0.39  0.17 K+-K+- K-+K-+ LHCb-Conf pb -1

 from B  DK Interference between tree-level decays; theoretically clean Parameters: , r B, δ Three methods for exploiting interference (choice of D 0 decay modes): Gronau, London, Wyler (GLW): Use CP eigenstates, e.g. D 0  h + h - Atwood, Dunietz, Soni (ADS): Use doubly Cabibbo-suppressed decays, e.g. D 0  K + π - Dalitz plot analysis of 3-body D 0 decays, e.g. K s π + π - V cs * V ub : suppressed Favored: V cb V us * b u s uu b u c D0D0 K-K- B-B- B-B- u s u c D0D0 f Common final state K-K-

ADS method D. Atwood, I. Dunietz and A. Soni, PRL 78, 3357 (1997); PRD 63, (2001) Enhancement of СР-violation due to use of Cabibbo-suppressed D decays B –  D 0 K – - color allowed, D 0  K + π – - doubly Cabibbo-suppressed B –  D 0 K – - color suppressed, D 0  K + π – - Cabibbo-allowed Interfering amplitudes are comparable Measured quantities:

ADS analysis at LHCb 4.0  significance R ADS =(1.66  0.39  0.24) World average:  0.21 A ADS =-0.39  0.17  0.02 World average: 1.6  0.3 (w/o LHCb) LHCb-Conf

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!

Backup

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

J/  amplitudes

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!

B mixing d b b d W t t W BdBd BdBd Due to the different values of CKM couplings the B s mixes faster then the B d s b b s W t t W BsBs BsBs B d → B d B d mixing B s mixing B s → B s B s mixing Both the B d and B s mixing have been precisely measured in experiments 5.1 x Hz1.8 x Hz

B S mixing formalism

Additional channels for  s Pure penguin decays First observation! LHCb-Conf Br(Bs  K*K*)=(1.95  0.47  0.51  0.29)10 -5

Lifetime measurement for Bs  K + K -

CPV in charm Indirect CPV: mixing rate of D 0  D 0 and D 0  D 0 differ Direct CPV: amplitudes for D 0 /D 0 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:

Charge asymmetry in D 0  h + h - Production and soft pion asymmetry cancel in A RAW (f)  A RAW (g) There is no detection asymmetry in D 0  h + h -

D 0  h + h - A CP results Fit the mass difference: M(D*)-M(D 0 ) Result: A CP (KK)  A CP (  )= (  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