First measurement of the CP-violating phase in Bs0 → J / ψ ( → e + e - ) ϕ decays

The European Physical Journal C - Particles and Fields. 2021. Vol. 81. No. 11. Article 1026.

LHCb C., Arzymatov K., Belavin V., Borisyak M., Boldyrev A., Derkach D., Hushchyn M., Karpov M., Kazeev N., Maevskiy A., Ratnikov F., Ryzhikov A., Ustyuzhanin A.

A flavour-tagged time-dependent angular analysis of {{B} ^0_{s}} \!\rightarrow {{J /\psi }} \phi decays is presented where the {J /\psi } meson is reconstructed through its decay to an e ^+e ^- pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8\text {\,Te V} , corresponding to an integrated luminosity of 3 \text {\,fb} ^{-1} . The C\!P-violating phase and lifetime parameters of the {B} ^0_{s} system are measured to be {\phi _{{s}}} =0.00\pm 0.28\pm 0.07\text {\,rad}, {\Delta \Gamma _{{s}}} =0.115\pm 0.045\pm 0.011\text {\,ps} ^{-1} and {\Gamma _{{s}}} =0.608\pm 0.018\pm 0.012\text {\,ps} ^{-1} where the first uncertainty is statistical and the second systematic. This is the first time that C\!P-violating parameters are measured in the {{B} ^0_{s}} \!\rightarrow {{J /\psi }} \phi decay with an e ^+e ^- pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.

Keywords: физика высоких энергий, Experimental High Energy Physics and Elementary Particles Physics