Model-Independent Observation of Exotic Contributions to $B^0\to J/\psi K^{+}{\pi }^{-}$ Decays

An angular analysis of $B^0\to J/\psi K^{+}{\pi }^{-}$ decays is performed, using proton-proton collision data corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$ collected with the LHCb detector. The $m(K^{+}{\pi }^{-})$ spectrum is divided into fine bins. In each $m(K^{+}{\pi }^{-})$ bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by $K^{*}$ resonances is examined, making minimal assumptions about the $K^{+}{\pi }^{-}$ system. The data reject the $K^{*}$-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the $m(J/\psi {\pi }^{-})$ vs $m(K^{+}{\pi }^{-})$ plane suggests structures near $m(J/\psi {\pi }^{-})=4200$ and 4600 MeV.

Figure 1

Spectrum of $K_J^{*}$ resonances from Ref. [10], with the vertical span of the boxes indicating $\pm {\mathrm{\Gamma }}_0$, where ${\mathrm{\Gamma }}_0$ is the width of each resonance. The horizontal dashed lines mark the $m(K^{+}{\pi }^{-})$ physical region for $B^0\to J/\psi K^{+}{\pi }^{-}$ decays, whereas the dot-dashed lines mark the specific region, $m(K^{+}{\pi }^{-})\in [1085,1445]\mathrm{MeV}$, employed for determining the significance of exotic contributions.

Figure 2

Comparison of $m(J\psi {\pi }^{-})$ in the $m(K^{+}{\pi }^{-})\in [1085,1265]\mathrm{MeV}$ region between the background-subtracted data and simulated events weighted by moments models with $J_{\max }^k=2$ and $J_{\max }^k=15$.

Figure 3

Likelihood-ratio test for exotic significance. The data shows a $10\sigma$ deviation from the pseudoexperiments generated according to the null hypothesis ($K_J^{*}$-only contributions).

Figure 4

Background-subtracted 2D distribution of $m(J/\psi {\pi }^{-})$ vs $m(K^{+}{\pi }^{-})$ in the region $m(K^{+}{\pi }^{-})\in [745,1545]\mathrm{MeV}$. The intensity ($z$-axis) scale has been highly truncated to limit the strong $K^{*}(892{)}^0$ contribution.