Abstract
A measurement of the decay time dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented, along with measurements of the $T$-odd triple-product asymmetries. In this decay channel, the CP-violating weak phase arises from the interference between $B_s^0$-$\bar{B}_s^0$ mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $3.0\, fb^{-1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0 \to \phi\phi$ decays is obtained. The CP-violating phase is measured to be ${\phi_s =-0.17\pm0.15\mathrm{\,(stat)}\pm0.03\mathrm{\,(syst)}}$ rad. The triple-product asymmetries are measured to be ${A_U=-0.003\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$ and ${A_V=-0.017\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$. Results are consistent with the hypothesis of CP conservation.
Highlights
The B0s → φφ decay is forbidden at tree level in the Standard Model (SM) and proceeds predominantly via a gluonic b → sssloop process
Interference between the B0s-B 0s oscillation and decay amplitudes leads to a CP asymmetry in the decay time distributions of B0s and B 0s mesons, which is characterized by a CP-violating weak phase
Acceptance functions are included in Rthe decay timedependent fit through the 15 integrals εðΩÞfkðΩÞdΩ, where fk are the angular functions given in Table I and εðΩÞ is the efficiency as a function of the set of helicity angles, Ω
Summary
The B0s → φφ decay is forbidden at tree level in the Standard Model (SM) and proceeds predominantly via a gluonic b → sssloop (penguin) process. A recent analysis of B0s → J=ψπþπ− decays using the full LHCb run I data set of 3.0 fb−1 has measured the CP-violating phase to be 0.070 Æ 0.068ðstatÞ Æ 0.008ðsystÞ rad [7]. Triple-product asymmetries are formed from T-odd combinations of the momenta of the final-state particles Such asymmetries provide a method of measuring CP violation in a decay time integrated method that complements the decay time-dependent measurement [9]. In the heavy quark limit, fL is expected to be the dominant polarization due to the vector-axial structure of charged weak currents [2] This is found to be the case for tree-level B decays measured at the B factories [11,12,13,14,15,16]. The results presented in this paper supersede previous measurements of the CP-violating phase [17] and T-odd triple-product asympmffieffi tries [19], made using 1.0 fb−1 of data collected at a s 1⁄4 7 TeV
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