Studies of the resonance structure in D 0 → K ∓ π ± π ± π ∓ decays

Abstract

Amplitude models are constructed to describe the resonance structure of $D^0\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D^0\to K^{+}{\pi }^{-}{\pi }^{-}{\pi }^{+}$ decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb experiment, corresponding to an integrated luminosity of 3.0 $f{b}^{-1}$ . The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes $D^0\to a_1{\left(1260\right)}^{+}{K}^{-}$ and $D^0\to K_1{(1270/1400)}^{+}{\pi }^{-}$ being prominent in $D^0\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D^0\to K^{+}{\pi }^{-}{\pi }^{-}{\pi }^{+}$ , respectively. Precise measurements of the lineshape parameters and couplings of the $a_1{\left(1260\right)}^{+}$ , $K_1{\left(1270\right)}^{-}$ and $K{\left(1460\right)}^{-}$ resonances are made, and a quasi model-independent study of the $K{\left(1460\right)}^{-}$ resonance is performed. The coherence factor of the decays is calculated from the amplitude models to be $R_{K3\pi }=0.459\pm 0.010\left(\mathrm{stat}\right)\pm 0.012\left(\mathrm{syst}\right)\pm 0.020\left(\mathrm{model}\right)$ , which is consistent with direct measurements. These models will be useful in future measurements of the unitary-triangle angle $\gamma$ and studies of charm mixing and $CP$ violation.