Average Strong-phase Differences Research Articles

Measurement of the D \u2192 K\u2212\u03c0+\u03c0+\u03c0\u2212 and D \u2192 K\u2212\u03c0+\u03c00 coherence factors and average strong-phase differences in quantum-correlated Doverline{D} decays

The decays D → K−π+π+π− and D → K−π+π0 are studied in a sample of quantum-correlated Doverline{D} pairs produced through the process e+e− → ψ(3770) → Doverline{D} , exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fb−1. Here D indicates a quantum superposition of a D0 and a {overline{D}}^0 meson. By reconstructing one neutral charm meson in a signal decay, and the other in the same or a different final state, observables are measured that contain information on the coherence factors and average strong-phase differences of each of the signal modes. These parameters are critical inputs in the measurement of the angle γ of the Unitarity Triangle in B− → DK− decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3π = {0.52}_{-0.10}^{+0.12} and {R}_{K{pi pi}^0} = 0.78 ± 0.04, with values for the average strong-phase differences that are {delta}_D^{K3pi }=left({167}_{-19}^{+31}right){}^{circ} and {delta}_D^{K{pi pi}^0}=left({196}_{-15}^{+14}right){}^{circ} , where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D → K−π+π+π− to yield results that will allow for a more sensitive measurement of γ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6°.

Improved sensitivity to the CKM phase γ through binning phase space in B− → DK−, D → K+π−π−π+ decays

A binning scheme is proposed for D→K+π−π−π+ phase space that will improve the sensitivity of a B−→DK− analysis to the angle γ of the Cabibbo-Kobayashi-Maskawa Unitarity Triangle. The scheme makes use of amplitude models recently reported by the LHCb collaboration. Assuming that a four-bin scheme optimised on the models retains a similar sensitivity when applied in data, it is estimated that the statistical uncertainty on γ from the B-meson sample so far collected by the LHCb experiment will be as low as 5 degrees. This will be one of the most precise results available for any single decay mode in a B−→DK− measurement. Quantum-correlated DD¯ data accumulated by the CLEO-c experiment are analysed to provide first constraints on the coherence factors and average strong-phase differences in the four bins, which are necessary inputs for the measurement. These constraints are compared with the predictions of the model, and consequences for the measurement of γ are discussed.

Improved determination of the D → K − π + π + π − coherence factor and associated hadronic parameters from a combination ofe+e−→ψ(3770)→cc¯andpp→cc¯Xdata

Measurements of the coherence factor $R_{K3\pi}$, the average strong-phase difference $\delta^{K3\pi}_D$ and mean amplitude ratio $r_D^{K3\pi}$ for the decay $D \to K^-\pi^+\pi^+\pi^-$ are presented. These parameters are important inputs to the determination of the unitarity triangle angle $\gamma$ in $B^- \to DK^-$ decays, where $D$ designates a superposition of $D^0$ and $\bar{D}{}^0$ mesons decaying to a common final state. The results are based on a combined fit to observables obtained from a re-analysis of the CLEO-c $\psi(3770)$ data set and those measured in a $D^0\bar{D}^0$ mixing study performed by the LHCb collaboration.

New determination of the [formula omitted] and [formula omitted] coherence factors and average strong-phase differences

Measurements of the coherence factors (RKππ0 and RK3π) and the average strong-phase differences (δDKππ0 and δDK3π) for the decays D0→K−π+π0 and D0→K−π+π+π− are presented. These parameters are important inputs to the determination of the unitarity triangle angle γ in B∓→DK∓ decays, where D designates a D0 or D¯0 meson decaying to a common final state. The measurements are made using quantum correlated DD¯ decays collected by the CLEO-c experiment at the ψ(3770) resonance, and augment a previously published analysis by the inclusion of new events in which the signal decay is tagged by the mode D→KS0π+π−. The measurements also benefit from improved knowledge of external inputs, namely the D0D¯0 mixing parameters, rDKπ and several D-meson branching fractions. The measured values are RKππ0=0.82±0.07, δDKππ0=(164−14+20)°, RK3π=0.32−0.28+0.20 and δDK3π=(225−78+21)°. Consideration is given to how these measurements can be improved further by using the larger quantum-correlated data set collected by BESIII.

Determination of theD0→K−π+π0andD0→K−π+π+π−coherence factors and average strong-phase differences using quantum-correlated measurements

The first measurements of the coherence factors (R_Kpipi0 and R_K3pi) and the average strong-phase differences (delta_D^Kpipi0 and delta_D^K3pi) for D0->K-pi+pi0 and D0->K-pi+pi+pi- are presented. These parameters can be used to improve the determination of the unitarity triangle angle gamma in B^- -> DK^- decays, where D is a D^0 or Dbar^0 meson decaying to the same final state. The measurements are made using quantum-correlated, fully-reconstructed D^0Dbar^0 pairs produced in e+e- collisions at the psi(3770) resonance. The measured values are: R_Kpipi0=0.84+/-0.07, delta_D^Kpipi0=(227+14-17) deg, $R_K3pi=0.33+0.20-0.23, and delta_D^K3pi=(114+26-23) deg. These results indicate significant coherence in the decay D0->K-pi+pi0, whereas lower coherence is observed in the decay D0->K-pi+pi+pi-. The analysis also results in a small improvement in the knowledge of other D-meson parameters, in particular the strong-phase difference for D0->K-pi+, delta_D^Kpi, and the mixing parameter, y.

Flavour physics at CLEO-c

Three CLEO-c results related to flavour-physics are presented: the determination of the strong-phase difference between D0->K+pi- and D0->K-pi+, delta, the measurement of the coherence parameter and average strong-phase difference between D0->K+pi-pi-pi+ and D0 -> K-pi+pi+pi- and measurements of the variation of strong-phase difference between D0 and D0bar decays to K0Spi+pi- over phase space. All measurements are important for determining the unitarity triangle angle gamma from B->D(*)K(*) decays. Furthermore, the measurement of delta is important for interpreting D0-D0bar mixing.