Abstract
The recent LHCb data on $B_s^0\to J/\psi p\bar{p}$ revealed a new pentaquark-like $P_c(4337)^+$ structure, while finding no evidence for $P_c(4312)^+$ discovered earlier in $\Lambda_b^0\to J/\psi p K^-$. Though puzzling, the data actually offer an important hint to understand the nature of the pentaquark candidates. We develop a model to analyze the $B_s^0\to J/\psi p\bar{p}$ data. We find that a $\Sigma_c\bar{D}$ one-loop mechanism causes a threshold cusp that fits well the $P_c(4337)^+$ peak. Also, the $\Sigma_c\bar{D}$ and $\Lambda_c\bar{D}^{*}$ threshold cusps interfere with each other to reproduce an oscillating behavior in the proton helicity angle distribution. These results combined with our earlier analysis on $\Lambda_b^0\to J/\psi p K^-$ indicate that $P_c(4312)^+$ and $P_c(4337)^+$ are created by different interference patterns between the $\Sigma_c\bar{D}$ and $\Lambda_c\bar{D}^{*}$ (anomalous) threshold cusps. The proposed scenario consistently explains why the $P_c(4312)^+$ and $P_c(4337)^+$ peaks appear in $\Lambda_b^0\to J/\psi p K^-$ and $B_s^0\to J/\psi p\bar{p}$, respectively, but not vice versa or both.
Highlights
Since the discovery of Xð3872Þ [1], we have witnessed many experimental observations of exotic hadron candidates that are not categorized in the conventional constituent quark structures such as qqand qqq; see Refs. [2,3,4,5,6,7,8,9] for reviews
We find that a ΣcDone-loop mechanism causes a threshold cusp that fits well the Pcð4337Þþ peak
These results combined with our earlier analysis on Λ0b → J=ψpK− indicate that Pcð4312Þþ and Pcð4337Þþ are created by different interference patterns between the ΣcDand ΛcD Ã threshold cusps
Summary
Since the discovery of Xð3872Þ [1], we have witnessed many experimental observations of exotic hadron candidates that are not categorized in the conventional constituent quark structures such as qqand qqq; see Refs. [2,3,4,5,6,7,8,9] for reviews. Many theoretical attempts have been made to interpret the candidates as hadronic molecules [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39], compact multiquarks [40,41,42,43,44,45,46,47,48], or hadrocharmonia [49,50,51] Difficulties of these interpretations lie in: (i) We poorly understand hadron interactions and formation mechanisms of the exotic hadrons; (ii) resonances are expected to appear in different processes, this is often not the case, and their appearances seem to be highly process dependent. In this paper, taking advantage of these characteristics of the kinematical effects, we propose a scenario on how one can consistently explain pentaquark candidates Pc’s observed in the recently measured Λ0b and B0s decay processes.
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