Φφ Decay Research Articles

A description of χcJ → VV decays within the effective field theory framework

We study χcJ → VV decays using the QCD effective field theory approach. The helicity suppressed decay amplitudes are also considered. The colour-singlet contributions of these amplitudes suffer from the endpoint singularities, it is shown that they can be absorbed into renormalisation of the nonfactorisable colour-octet matrix element. The latter can be associated with the colour-octet component of the charmonium wave function. The heavy quark spin symmetry makes it possible to establish the relationships between colour-octet matrix elements for different states χcJ up to higher order corrections in small velocity v. This allows us to estimate the polarisation parameters for χc2→ VV using data for χc0,1→ VV. This analysis is carried out for the available data on the χcJ→ ϕϕ decays.

Helicity amplitude analysis of χcJ→ ϕϕ

Using (447.9 ± 2.3) million ψ(3686) events collected with the BESIII detector, the decays of χcJ→ ϕϕ (J = 0, 1, 2) have been studied via the decay ψ(3686) → γχcJ. The branching fractions of the decays χcJ→ ϕϕ (J = 0, 1, 2) are determined to be (8.59 ± 0.27 ± 0.20) × 10−4, (4.26 ± 0.13 ± 0.15) × 10−4, and (12.67 ± 0.28 ± 0.33) × 10−4, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process ψ(3686) → γχcJ, χcJ→ ϕϕ, ϕ → K+K−, the polarization parameters of the χcJ→ ϕϕ decays are determined for the first time.

Measurement of CP violation in the {B}_s^0to phi phi decay and search for the B0\u2192 \u03d5\u03d5 decay

A measurement of the time-dependent CP-violating asymmetry in {B}_s^0to phi phi decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.0 fb−1 collected by the LHCb experiment at centre-of-mass energies sqrt{s} = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 {B}_s^0to phi phi decays is obtained. The CP-violating phase {phi}_s^{soverline{s}s} is measured to be −0.073 ± 0.115(stat) ± 0.027(syst) rad, under the assumption it is independent of the helicity of the ϕϕ decay. In addition, the CP-violating phases of the transverse polarisations under the assumption of CP conservation of the longitudinal phase are measured. The helicity-independent direct CP-violation parameter is also measured, and is found to be |λ| = 0.99 ± 0.05(stat) ± 0.01(syst). In addition, T-odd triple-product asymmetries are measured. The results obtained are consistent with the hypothesis of CP conservation in overline{b}to overline{s}soverline{s}s transitions. Finally, a limit on the branching fraction of the B0 → ϕϕ decay is determined to be mathcal{B}left({B}^0to phi phi right)<2.7times {10}^{-8} at 90 % confidence level.

Charmless b-meson and b-baryon decays at LHCb

The latest LHCb results for charmless b-meson and b-baryon decays, using Run I data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, are presented. The search for charmless three-body decays of the Λb0 and Ξb0 baryons to the final states Λh+h'- (h(') = π or K) results in the first observation of Λ0b → ΛK+π- and Λb0 → ΛK+K- decays and measurements of their branching fractions and CP asymmetries, as well as evidence of the Λb0 → Λπ+π- decay and limits on the branching fractions of Ξb0 baryon decays. The first observation of Λb0 → Λϕ decay is also reported and the branching fraction and triple-product asymmetries are measured. The search for Λb0 → Λη' and Λb0 → Λη decays yields evidence for the latter and upper limits on the former. A measurement of the branching fraction of Bs0→ ϕϕ decay and a limit on the B0→ ϕϕ mode are also presented. The decay Bs0→Ks0K* (892)0 is observed for the first time and its branching fraction measured.

Measurement of the [formula omitted] mixing phase using [formula omitted

Using 3 fb−1 of collision data collected by the LHCb collaboration in proton-proton collisions the Bs0 mixing phase, ϕs in the Bs0→ϕϕ decay mode is determined to be ϕs=−0.17±0.15(stat)±0.03(syst). This is consistent with the Standard Model expectation that CP violation in this channel is small.

Final state interaction effect in the pure annihilation B→ϕϕ decay

We analyzed the process of [Formula: see text] decay in quantum chromodynamics factorization (QCDF) and final state interaction (FSI). In QCDF for this decay we have only the annihilation graph and we expected small branching ratio. Then we considered FSI effect as a sizable correction where the intermediate states are [Formula: see text], K+ K–, and [Formula: see text] mesons. To consider the amplitudes of these intermediate states, the QCDF approach was used. The experimental branching ratio of [Formula: see text] is less than 2 × 10–7 and our results are 0.04 × 10–7 and 1.54 × 10–7 from QCDF and FSI, respectively.

Recent results on CP violation B0s meson decays

Measurements of CP violation in B0s mesons decays provide an excellent method to test the prediction of the Standard Model and search for effect of new physics beyond it. With the first 1 fb−1 √ of data collected in pp collisions at √s = 7TeV the LHCb experiment performed the world best precision measurements of the CP-violating phase φs and on the decay width difference ΔΓs. The analysis of the B0s → φφ decay and the measurement of the B0s lifetime in decays to CP eigenstates are also presented.

Studies of Hadronic B Decays at LHCb

Hadronic B decays are important decays for CP-violation studies and to search for beyond the Standard Model (SM) effects. CP-violation results obtained from the decays B→DK where D represents D0 or D¯0 and from the decays B→hh where h denotes K or π are presented. The B→DK decay modes are due to tree level diagrams while the B→hh are sensitive to loop diagrams and thus to New Physics. Results from a full angular analysis of the BS0→ϕϕ decay modes are also presented as well as the effective lifetime measurement using the BS0→KK mode. The analyses presented here are based on 1.0 fb−-1 pp collision data collected in 2011 with the LHCb detector.

Study on Bd → ϕ KS Decay in EDQS Model

We study Bd → ϕKS decay in extra down-type quarks (EDQS) model with a non-universal Z boson associated with flavor changing neutral currents (FCNCs) at the tree level. With the up-to-date experimental data of Br(Bd → ϕKS), SϕKS, and AϕKS, we derive the bounds on the Z-b-s coupling parameter |Ubs| and the new weak phase ϕ, using the constrained parameter spaces, we finally give predictions for Bs → ϕϕ decay, which could be tested at the Fermilab Tevatron and the LHC-b experiments.

Mechanisms for [formula omitted] decays

Exclusive decays of χcJ(J=0,2) into ϕϕ are investigated in the framework of perturbative quantum chromodynamics (pQCD) and P03 quark pair creation model. The results show that these two mechanisms exhibit a quite different behavior in evaluating the decay width for the χc0 and χc2. In pQCD method with non-relativistic (NR) approximation, while the calculated χc2→ϕϕ decay width is comparable with measured one, the result for the χc0→ϕϕ decay width is suppressed and much smaller than experimental value. However, in P03 quark pair creation model, the situation is reversed: the decay width of χc0→ϕϕ is greatly enhanced and can reproduce the large measured value, while the contribution to the χc2→ϕϕ decay width is small. The results suggest that while the pQCD mechanism is the dominant mechanism for χc2→ϕϕ decay, the P03 quark pair creation mechanism is the dominant one for χc0→ϕϕ decay.