First Observation of ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ Oscillations in ${D}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ Decays and Measurement of the Associated Coherence Parameters

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First Observation of $D^{0} - {\bar{D}}^{0}$ Oscillations in $D^{0} \to K^{+} π^{-} π^{+} π^{-}$ Decays and Measurement of the Associated Coherence Parameters

R. Aaij et al. (LHCb Collaboration)

Phys. Rev. Lett. 116, 241801 – Published 17 June 2016

Abstract

Charm meson oscillations are observed in a time-dependent analysis of the ratio of $D^{0} \to K^{+} π^{-} π^{+} π^{-}$ to $D^{0} \to K^{-} π^{+} π^{-} π^{+}$ decay rates, using data corresponding to an integrated luminosity of $3.0 {fb}^{- 1}$ recorded by the LHCb experiment. The measurements presented are sensitive to the phase-space averaged ratio of doubly Cabibbo-suppressed to Cabibbo-favored amplitudes $r_{D}^{K 3 π}$ and the product of the coherence factor $R_{D}^{K 3 π}$ and a charm mixing parameter $y_{K 3 π}^{'}$ . The constraints measured are $r_{D}^{K 3 π} = (5.67 \pm 0.12) \times 10^{- 2}$ , which is the most precise determination to date, and $R_{D}^{K 3 π} y_{K 3 π}^{'} = (0.3 \pm 1.8) \times 10^{- 3}$ , which provides useful input for determinations of the CP-violating phase $γ$ in $B^{\pm} \to D K^{\pm}$ , $D \to K^{\mp} π^{\pm} π^{\mp} π^{\pm}$ decays. The analysis also gives the most precise measurement of the $D^{0} \to K^{+} π^{-} π^{+} π^{-}$ branching fraction, and the first observation of $D^{0}$ – ${\bar{D}}^{0}$ oscillations in this decay mode, with a significance of 8.2 standard deviations.

Received 24 February 2016

DOI:https://doi.org/10.1103/PhysRevLett.116.241801

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