Measurement of CP violation in B0 → J/ψKS0 and B0 → ψ(2S)KS0 decays

Abstract

Abstract

A measurement is presented of decay-time-dependent CP violation in the decays B0 → J/ψ K S 0 and B0 → ψ(2S)K S 0 , where the J/ψ is reconstructed from two electrons and the ψ(2S) from two muons. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. The CP -violation observables are measured to be

A measurement is presented of decay-time-dependent CP violation in the decays B⁰ → J/ψK[subscript S]⁰ and B⁰ → ψ(2S)K[subscript S]⁰, where the J/ψ is reconstructed from two electrons and the ψ(2S) from two muons. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb⁻¹. The CP-violation observables are measured to be C(B⁰ → J/ψ K[subscript S]⁰) = 0.12 ± 0.07 ± 0.02, S(B⁰ → J/ψ K[subscript S]⁰) = 0.83 ± 0.08 ± 0.01, C(B⁰ → ψ(2S)[subscript S]⁰) = −0.05 ± 0.10 ± 0.01, S(B⁰ → ψ(2S)K[subscript S]⁰) = 0.84 ± 0.10 ± 0.01, where C describes CP violation in the direct decay, and S describes CP violation in the interference between the amplitudes for the direct decay and for the decay after B⁰−B¯⁰ oscillation. The first uncertainties are statistical and the second are systematic. The two sets of results are compatible with the previous LHCb measurement using B0 → J/ψ K S0 decays, where the J/ψ meson was reconstructed from two muons. The averages of all three sets of LHCb results are C(B⁰ → (cc ¯)K[subscript S]⁰) = − 0.017 ± 0.029, S(B⁰ → (cc ¯) K[subscript S]⁰ = 0.760 ± 0.034, under the assumption that higher-order contributions to the decay amplitudes are negligible. The uncertainties include statistical and systematic contributions.

C

B 0

→ J / ψ

K S 0

= 0.12 ± 0.07 ± 0.02 ,

S

B 0

→ J / ψ

K S 0

= 0.83 ± 0.08 ± 0.01 ,

C

B 0

→ ψ

2 S

K S 0

= − 0.05 ± 0.10 ± 0.01 ,

S

B 0

→ ψ

2 S

K S 0

= 0.84 ± 0.10 ± 0.01 ,

$$ \begin{array}{l}C\left({B}^0\to J/\psi \kern0.5em {K}_{\mathrm{S}}^0\right)=0.12\pm 0.07\pm 0.02,\\ {}S\left({B}^0\to J/\psi \kern0.5em {K}_{\mathrm{S}}^0\right)=0.83\pm 0.08\pm 0.01,\\ {}C\left({B}^0\to \psi (2S){K}_{\mathrm{S}}^0\right)=-0.05\pm 0.10\pm 0.01,\\ {}S\left({B}^0\to \psi (2S){K}_{\mathrm{S}}^0\right)=0.84\pm 0.10\pm 0.01,\end{array} $$

where C describes CP violation in the direct decay, and S describes CP violation in the interference between the amplitudes for the direct decay and for the decay after

B 0

−

B ¯

0

$$ {B}^0-{\overline{B}}^0 $$ oscillation. The first uncertainties are statistical and the second are systematic. The two sets of results are compatible with the previous LHCb measurement using B0 → J/ψ K S 0 decays, where the J/ψ meson was reconstructed from two muons. The averages of all three sets of LHCb results are

C

B 0

→

c

c ¯

K S 0

= − 0.017 ± 0.029 ,

S

B 0

→

c

c ¯

K S 0

= 0.760 ± 0.034 ,

$$ \begin{array}{l}C\left({B}^0\to \left[c\overline{c}\right]{K}_{\mathrm{S}}^0\right)=-0.017\pm 0.029,\\ {}S\left({B}^0\to \left[c\overline{c}\right]{K}_{\mathrm{S}}^0\right)=0.760\pm 0.034,\end{array} $$

under the assumption that higher-order contributions to the decay amplitudes are negligible. The uncertainties include statistical and systematic contributions.