论文标题
在$ pk^{ - } $ sepsprum中观察$λη$阈值，$λ_{c}^{c}^{+} \ rightarrow p k^{ - }π^{+} $衰减
Observation of a Threshold Cusp at the $Λη$ Threshold in the $pK^{-}$ Mass Spectrum with $Λ_{c}^{+} \rightarrow p K^{-} π^{+}$ Decays
论文作者
论文摘要
我们在$ pk^{ - } $不变质量频谱中观察到狭窄的峰值结构，附近$λη$阈值。在150万$λ_{c}^{+} \ rightArrow p k^{ - }π^{+} $衰减的150万事件中清楚地看到了这一峰。我们尝试两种方法来解释这种结构：作为新的共鸣，作为$λη$阈值的尖端。最佳拟合度是通过flatt $ \ rm {\ acute {e}} $函数的连贯总和和$χ^2/{\ rm n.d.f} = 257/243 $（$ P = 0.25 $）的恒定背景振幅的函数，而对breit-wigner functions则是$ 7 $ 7 $ 7 $。最佳拟合将结构解释为$λη$阈值的尖端，并且所获得的参数与已知的$λ（1670）$的已知属性一致。该观察结果给出了从光谱形状中的黑龙中阈值尖端的首次识别。
We observe a narrow peaking structure in the $pK^{-}$ invariant-mass spectrum near the $Λη$ threshold. The peak is clearly seen in 1.5 million events of $Λ_{c}^{+} \rightarrow p K^{-} π^{+}$ decay using the $980~{\rm fb^{-1}}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the $Λη$ threshold. The best fit is obtained with a coherent sum of a Flatt$\rm{\acute{e}}$ function and a constant background amplitude with the $χ^2/{\rm n.d.f}=257/243$ ($p = 0.25$), while the fits to Breit-Wigner functions are unfavored by more than 7$σ$. The best fit explains the structure as a cusp at the $Λη$ threshold, and the obtained parameters are consistent with the known properties of $Λ(1670)$. The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.
