Abstract
The first full amplitude analysis of $B^+\to J/\psi \phi K^+$ with $J/\psi\to\mu^+\mu^-$, $\phi\to K^+K^-$ decays is performed with a data sample of 3 fb$^{-1}$ of $pp$ collision data collected at $\sqrt{s}=7$ and $8$ TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into $\phi K^+$, and four $J/\psi\phi$ structures are observed, each with significance over $5$ standard deviations. The quantum numbers of these structures are determined with significance of at least $4$ standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed $X(4140)$ state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the $K^{*}(1680)^+\to\phi K^+$ transition.
Highlights
In 2008 the CDF Collaboration presented 3.8σ evidence for a near-threshold Xð4140Þ → J=ψφ mass peak in Bþ → J=ψφKþ decays1 referred to as Yð4140Þ in the literature, with width Γ 1⁄4 11.7 MeV [1].2 Much larger widths are expected for charmonium states at this mass because of open flavor decay channels [2], which should make the kinematically suppressed X → J=ψφ decays undetectable
The Xð4140Þ structure was observed by the CMS Collaboration (5σ) [25]. Evidence for it was reported in Bþ → J=ψφKþ decays by the D0 Collaboration (3σ) [26]
An amplitude analysis of the decay Bþ → J=ψφKþ is presented for the first time, with additional results for, and containing more detailed description of, the work presented in Ref. [33]
Summary
In 2008 the CDF Collaboration presented 3.8σ evidence for a near-threshold Xð4140Þ → J=ψφ mass peak in Bþ → J=ψφKþ decays referred to as Yð4140Þ in the literature, with width Γ 1⁄4 11.7 MeV [1].2 Much larger widths are expected for charmonium states at this mass because of open flavor decay channels [2], which should make the kinematically suppressed X → J=ψφ decays undetectable. In an unpublished update to their Bþ → J=ψφKþ analysis [29], the CDF Collaboration presented 3.1σ evidence for a second relatively narrow J=ψφ mass peak near 4274 MeV. This observation has received attention in the literature [30,31]. If genuine J=ψφ states are present, it is crucial to determine their quantum numbers to aid their theoretical interpretation Both of these tasks call for a proper amplitude analysis of Bþ → J=ψφKþ decays, in which the observed mφK and mJ=ψφ masses are analyzed simultaneously with the distributions of decay angles, without which the resolution of different resonant contributions is difficult, if not impossible. An amplitude analysis of the decay Bþ → J=ψφKþ is presented for the first time, with additional results for, and containing more detailed description of, the work presented in Ref. [33]
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