Advances in experimental study of time-dependent CP violation in neutral B meson decays

Neutral B mesons exhibit fascinating features of flavour oscillation and time-dependent CP violation, providing an ideal window to probe the origin and mechanism of CP violation. The LHCb experiment at the Large Hadron Collider is well suited for study of time-dependent CP violation in neutral B meson decays, owing to the copious production of B-0 and Bs0 mesons, and the excellent performance of the LHCb detector in tracking, vertexing and particle identification. In the first two running periods, the LHCb experiment has accumulated a large sample of proton-proton collision data collected at center-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb(-1). Fruitful study of time-dependent CP violation in both B-0 and Bs0 meson decays has been carried out at LHCb. In the B-0 sector, the LHCb experiment has overtaken the B factories, achieving the highest precision in a series of key measurements. A recent study of B0 -> J/psi KS0 and B0 ->psi(2S)KS0 decays using the full Run 1 and Run 2 sample gives sin2 beta=0.717 +/- 0.013 +/- 0.008, which are consistent both with previous results from BaBar, Belle and LHCb and with the standard model predictions. The B-0 mass difference is measured to be triangle m(d)=0.5050 +/- 0.0021 +/- 0.0010 ps-1 using B0 -> D(*)-mu+nu mu decays. CP-violating parameters for the decay B0 ->pi+pi- are measured to be S-pi pi = -0.672 +/- 0.034, C-pi pi = -0.320 +/- 0.038. The Bs0 sector was largely unexplored before the LHC. The LHCb experiment has made vast efforts to study B(s)(0)oscillation and time-dependent CP violation. The Bs0 mass difference has been very precisely determined to be triangle m(s)=17.7683 +/- 0.0051 +/- 0.0032 ps-1 using B-s(0)-> Ds-pi+ decays. The sign of the B(s)(0)decay width difference triangle Gamma s is determined to be positive using part of 2011 data, and the two-fold ambiguity in the previous measurements of phi s and triangle Gamma s is completely resolved. The B(s)(0)mixing phase phi s is a core measurement at LHCb, which has been extensively pursued using tree-level b -> cc<overline>s decays, such as B-s(0)-> J/psi phi and B-s(0)-> J/psi pi+pi-. The latest update of the B-s(0)-> J/psi phi analysis using the full Run 1 and Run 2 data sample leads to phi s=-0.039 +/- 0.022 +/- 0.006 rad and triangle Gamma s=0.0845 +/- 0.0044 +/- 0.0024 ps-1, which are the most precise measurements and consistent with the standard model predictions. Vanishing time-dependent CP violation is found in several loop-level b -> s transitions, such as B-s(0)->phi phi and B-s(0)->phi gamma, as expected in the standard model. Nonzero time-dependent CP asymmetry in Bs0 meson decays was first observed by LHCb in the process B-s(0)-> K+K-, which receives sizable contributions from both tree-level and loop-level diagrams. The latest LHCb measurements of CP-violating parameters in B-s(0)-> K+K- decays are SKK=0.139 +/- 0.032 and CKK=0.172 +/- 0.031. Time-dependent CP violation in B-s(0)-> Ds -/+ K +/- decays is measured by LHCb and used to determine the CKM angle gamma using the measured phi s value, yielding gamma=(74 +/- 11)degrees, which is in good agreement with other gamma determinations. These findings have greatly enriched our understanding of flavour physics and CP violation, and made huge impacts on tests of the standard model. The global CKM analysis that includes the recent high-precision LHCb measurements confirms the validity of the CKM mechanism and significantly improves precision of the CKM parameters. The LHCb experiment entered the third running period in 2022 with the recently upgraded detector. Looking ahead, LHCb aims to collect 50 fb(-1) of data in the coming decade and eventually accumulate 300 fb(-1) after a phase-2 upgrade. With such massive amount of data, many key measurements of CP violation and CKM elements will be measured with unprecedented precision. For example, using 50 (300) fb(-1) of data, LHCb will be able to measure sin2 beta with a precision of 0.006 (0.003), the B(s)(0)mixing phase phi s with a precision of 0.008 (0.004) rad, the CP-violating phase in B-s(0)->phi phi with a precision of 0.026 (0.011) rad, and the CKM angle gamma in B-s(0)-> Ds+K- decays with a precision of 4.4 degrees (1.5 degrees). Furthermore, time-dependent CP violation in certain heavily-suppressed decays of neutral B mesons, such as B0 -> KS0 mu+mu-, B-s(0)->phi mu+mu-, B0 ->rho 0 mu+mu-, B0 ->rho 0 gamma and Bs0 ->mu+mu-, will become accessible at LHCb, offering new opportunities for testing the standard model and probing new physics.