论文标题
$ x $和$ z_ {cs} $ in $ b^+\ to j/ψϕk^+$ as $ s $ - 波阈值cusps和替代旋转 - 准则分配给$ x（4274）$和$ x（4500）$
$X$ and $Z_{cs}$ in $B^+\to J/ψϕK^+$ as $s$-wave threshold cusps and alternative spin-parity assignments to $X(4274)$ and $X(4500)$
论文作者
论文摘要
最近，LHCB对$ b^+\ to j/ψϕk^+$的幅度分析表明，基于Breit-Wigner共振描述所有峰结构的假设，这表明存在异国$ x $和$ z_ {cs} $ hadrons的存在。但是，光谱中的所有峰和下降都位于相关的梅森 - 膜阈值，阈值运动尖端可能会引起此类结构。这表明了独立振幅分析的重要性以及适当考虑运动效应的重要性，这就是我们在这项工作中所做的。我们的型号适合$ J/ψX$，$ J/ψK^+$，以及$ K^+ϕ $同时不变的质量分布，表明所有$ x $，$ z_ {cs} $，并且可以用普通的$ s $ - $ wave threshold cusps来很好地描述。 $ x（4274）$和$ x（4500）$结构的旋转 - 准则分别为$ 0^ - $和$ 1^ - $，而不是$ 1^+$和$ 0^+$和$ 0^+$。考虑到所有相关的阈值尖，拟合参数的数量似乎大大减少。 LHCB数据需要$ d_s^{（*）} \ bar {d}^{*} $在我们的模型中散射长度与零一致，不利于$ d_s^{（*）} \ bar {d}^{*}^{*} $ molecule的$ z_ $ z_ 220 $ z_ {cs $ z_ {并且，通过SU（3）关系，与先前的晶格QCD结果一致。
Recent LHCb's amplitude analysis on $B^+\to J/ψϕK^+$ suggests the existence of exotic $X$ and $Z_{cs}$ hadrons, based on an assumption that Breit-Wigner resonances describe all the peak structures. However, all the peaks and also dips in the spectra are located at relevant meson-meson thresholds where threshold kinematical cusps might cause such structures. This points to the importance of an independent amplitude analysis with due consideration of the kinematical effects, and this is what we do in this work. Our model fits well $J/ψϕ$, $J/ψK^+$, and $K^+ϕ$ invariant mass distributions simultaneously, demonstrating that all the $X$, $Z_{cs}$, and dip structures can be well described with the ordinary $s$-wave threshold cusps. Spin-parity of the $X(4274)$ and $X(4500)$ structures are respectively $0^-$ and $1^-$ from our model, as opposed to $1^+$ and $0^+$ from the LHCb's. With all relevant threshold cusps considered, the number of fitting parameters seems to be significantly reduced. The LHCb data requires $D_s^{(*)}\bar{D}^{*}$ scattering lengths in our model to be consistent with zero, disfavoring $D_s^{(*)}\bar{D}^{*}$ molecule interpretations of $Z_{cs}(4000)$ and $Z_{cs}(4220)$ and, via the SU(3) relation, being consistent with previous lattice QCD results.
