The nature of the three narrow $P_c$ states, i.e., $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, is under intense discussion since their discovery from the updated analysis by LHCb. In this work we extend our previous coupled-channel approach [Phys. Rev. Lett. \bf{124}, 072001 (2020)] by including the $Λ_c\bar{D}^{(*)}$ and $η_cp$ as explicitly in addition to the $J/ψp$, as required by unitarity and heavy quark spin symmetry (HQSS). Since inelastic parameters are very badly constrained by the current data, three schemes are considered: (a) scheme I with pure contact interactions and without the $Λ_c\bar D^{(*)}$ interactions, (b) scheme II, where the one-pion exchange is added to scheme I, and (c) scheme III, where the $Λ_c \bar D^{(*)}$ are included in addition. It is shown that to obtain cutoff independent results, OPE in the multichannel system is to be supplemented with $S$-$D$ mixing contact terms. We demonstrate that the experimental data for the $J/ψp$ invariant mass distribution are consistent with the interpretation of the $P_c(4312)$ and $P_c(4440)/P_c(4457)$ as $Σ_c\bar{D}$ and $Σ_c \bar{D}^{*}$ hadronic molecules, respectively, and that the data show clear evidence for a new narrow $P_c(4380)$, as a $Σ_c^*\bar D$ molecule, which should exist as a consequence of HQSS. While two equally good solutions are found in scheme I, only one of these solutions with the quantum numbers of the $P_c(4440)$ and $P_c(4457)$ being $J^P=3/2^-$ and $1/2^-$, respectively, survives the requirement of regulator independence once the OPE is included. Moreover, we predict the line shapes in the elastic and inelastic channels and demonstrate that those related to the $P_c(4440)$ and the $P_c(4457)$ in the corresponding $Σ_c^{(*)}\bar{D}$ and $η_cp$ mass distributions allow one to confirm the quantum numbers given above, once the data are available.
Understanding the nature of the heavy pentaquarks and searching for them in pion-induced reactions
利用开粲强子再散射图研究了反应$π^- p \to π^- J/ψp$。由于再散射振幅中存在三角形奇异性（TS），TS峰可以模拟$J/ψp$不变质量分布中的类五夸克共振，这可能会给我们对奇异态性质的理解带来模糊性.由于TS机制具有高度的过程依赖性，在不同过程中寻找重五夸克态可以帮助我们澄清这些不确定性。
Revealing the nature of double-strangeness pentaquark states via femtoscopic correlation functions
School of Physics, Beihang University（北京航空航天大学物理学院）；Institute for Advanced Study in Nuclear Energy & Safety, College of Physics and Optoelectronic Engineering, Shenzhen University（深圳大学物理与光电工程学院核能与安全高等研究院）；Universidade de Sao Paulo, Instituto de Física（圣保罗大学物理研究所）；Universidade Federal de São Paulo（圣保罗联邦大学）；Peng Huanwu Collaborative Center for Research and Education, Beihang University（北京航空航天大学彭桓武教研中心）；Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所南方核科学理论中心）
In this article, we construct the color singlet-singlet type five-quark currents with the isospins $(I,I_3)=(\frac{1}{2},\frac{1}{2})$ and $(\frac{3}{2},\frac{1}{2})$ unambiguously to explore the $\bar{D}Σ_c$, $\bar{D}Σ_c^*$, $\bar{D}^*Σ_c$ and $\bar{D}^*Σ_c^*$ pentaquark states via the QCD sum rules for the first time, where the $\bar{D}$, $Σ_c$, $\cdots$ represent the color-singlet clusters having the same quantum numbers as the corresponding physical mesons or baryons. The numerical results support assigning the $P_c(4312)$, $P_c(4380)$, $P_c(4440)$ and $P_c(4457)$ as the $\bar{D}Σ_c$, $\ba…
The effects of the $Σ_c\bar{D}^*$-$Λ_{c}(2595)\bar{D}$ coupled-channel dynamics and various one-boson-exchange (OBE) forces for the LHCb pentaquark states, $P_c(4440)$ and $P_c(4457)$, are reinvestigated. Both the pion and $ρ$-meson exchanges are considered for the $Σ_c\bar{D}^*$-$Λ_{c}(2595)\bar{D}$ coupled-channel dynamics. It is found that the role of the $Λ_{c}(2595)\bar{D}$ channel in the descriptions of the $P_c(4440)$ and $P_c(4457)$ states is not significant with the OBE parameters constrained by other experimental sources. The naive OBE models with the short-distance $δ(\vec{r})$ term…
We study hidden-flavor pentaquarks, $Q\bar Q qqq$, based on a constituent quark-model with a standard quark-quark interaction that reproduces the low-energy meson and baryon spectra. We make use of dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A detailed comparison is made with other results in the literature and with experimental data. Our results show a different pattern for open-flavor and hidden-flavor pentaquarks, as suggested by the data. Further implications about the existence of quarkonia bound to nuclei are discus…
The three pentaquark states, $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, discovered by the LHCb Collaboration in 2019, are widely recognized as $\bar{D}^{(\ast)}Σ_{c}$ hadronic molecules. Together with their four $\bar{D}^{(*)}Σ_{c}^{\ast}$ partners dictated by heavy quark spin symmetry they present a complete multiplet of hadronic molecules of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$. It is widely recognized that to understand their nature, other discovery channels play an important role. In this work, we investigate two three-body decay modes of the $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ molecules. The tree…
Within the chiral unitary approach and with the constraints of heavy quark spin symmetry, we study the coupled channel interactions of ${\bar D}^{(*)}Σ_c^{(*)}$ channels, close to whose thresholds three pentaquark-like $P_c$ states have been reported by the LHCb Collaboration. In the present work, we take into account the contributions of pion exchanges via box diagrams to the interaction potentials, and therefore lift the degeneracy in the masses of ${\bar D}^*Σ_c^{(*)}$ spin multiplets. Fitting the $J/ψp$ invariant mass distributions in the $Λ_b^0 \to J/ψK^- p$ decay, we find that the LHCb p…
In this work, we report on a theoretical study of possible pentaquark states $Λ^0_b(5912)$ and $Λ^0_b(5920)$ in the $γp\to{}Λ_b^{0(*)}B^+$ reactions within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole and $t$-channel $\bar{B}^{{*}-}$ exchange, the contact term contribution are also included. Our theoretical approach is based on the chiral unitary theory where the $Λ^0_b(5912)$ and $Λ^0_b(5920)$ resonances are dynamically generated. Within the coupling constants of the $Λ^0_b(5912)$ and $Λ^0_b(5920)$ to $\bar{B}p$ and $\bar{B}^{*}p$ channe…
We have recently studied hidden-charm pentaquarks, $c\bar c qqq$, using dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A pattern was obtained that compares well with the experimental data. We extend our description to other flavor sectors which can be framed within the same type of structures discussed in the original paper. A detailed comparison is made with other results in the literature and with experimental data. Predictions will be a useful tool to discriminate between different models of multiquark system dynamics.
Hidden charm pentaquarks and the nature of $P_{c}$ states observed at LHCb
Hunan Normal University（湖南师范大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
We investigate the possibility of studying the strange hidden-charm pentaquark state $P_{cs}(4459)$ by photon-induced reactions on a proton target in an effective Lagrangian approach. The production process is described by the $t$-channel $K^{-}$ exchange, the $u$-channel $Λ$ exchange, the contract term, and the $s$- channel nucleon pole. Our theoretical approach is based on the assumption that $P_{cs}(4459)$ with $J^{P}=1/2^{-}$ or $J^{P}=3/2^{-}$ can be interpreted as a molecule composed of $\bar{D}^{*}Ξ_c$. Using the coupling constants of the $P^{J^P}_{cs}$ to $γΛ$ and $K^{-}p$ channels obt…
We demonstrate that triangle singularity (TS) and box singularity (BS) mechanisms can produce unique narrow enhancements at the $Λ_c\bar{D}$ and $Λ_c\bar{D}^*$ thresholds in the invariant mass spectra of $J/ψp$ and $J/ψpπ$, respectively. Taking into account that such mechanisms only depend on the initial $Σ_c^{(*)}\bar{D}^{(*)}$ interactions near threshold within the TS or BS kinematic regimes, the $Λ_c\bar{D}$ and $Λ_c\bar{D}^*$ threshold enhancements can be regarded as a feed-down phenomenon originated from both the heavier pentaquark decays and the $Σ_c^{(*)}\bar{D}^{(*)}$ scatterings from …
Understanding the nature of the hidden charm pentaquark(like) signals in the LHCb data for $Λ_b^0\to J/ψp K^-$ is a central problem of hadron spectroscopy. We propose a scenario completely different from previous ones such as hadron molecules and compact pentaquarks. We identify relevant double triangle mechanisms with leading or lower-order singularities. The associated anomalous threshold cusps at the $Σ_c^{(*)}\bar{D}^{(*)}$ thresholds are significantly more singular than the ordinary ones. Then we demonstrate that the double triangle amplitudes reproduce the peak structures of $P_c(4312)^+…
