arXiv subjects
Publications and source records attributed to Di Ben.
Recently, the BESIII Collaboration claimed that their observed $X(2370)$ ($J^{PC}=0^{-+}$) is predominantly a glueball state based on several arguments. However, we find these arguments to be flawed and the conclusion unjustified. Instead, we demonstrate that all observed properties of the $X(2370)$ can be naturally explained by a $\bar\Sigma\Sigma$ molecule dominated state.
This study estimates the contributions of hidden-strangeness hadronic molecular states ($N(2080)3/2^-$, $N(2270)3/2^-$) to $\phi$ production and hidden-charm $P_c$ states to $J/\psi$ production in $pp$ collisions. The calculated cross-sections reach $\sim 10~\mu b$ for $pp\to pp\phi$ and $\sim 0.1~nb$ for $pp\to pp J/\psi$ at energies $\sim 2$~GeV above threshold. We also compute the spin density matrix element $\rho_{00}$ and the decay angular distributions for $\phi\to K^+K^-$ and $J/\psi\to\mu^+\mu^-$. To support future experiments, we conduct Monte Carlo simulations for the four-body final states of $pp\to ppK^+K^-$ and $pp\to pp\mu^+\mu^-$. The resulting lab-frame distributions are expected to inform detector design at facilities like the High-Intensity heavy-ion Accelerator Facility (HIAF) and the proposed Chinese Advanced Nuclear Physics Research Facility (CNUF), enabling more precise measurements and tighter theoretical constraints. Furthermore, to explain the STAR collaboration's result on $\phi$ meson spin alignment in heavy-ion collisions, we propose a novel mechanism involving hidden-strangeness molecular states, testable with future high-statistics $pp\to pp\phi$ data.
We study hidden- and open-strange pentaquark configurations in the hadronic molecular picture with QCD sum rules. Starting from the baryon octet combined with an $s\bar{s}$ pair, we construct 21 interpolating currents with $J=1/2$ and $3/2$. In the analysis, contributions up to dimension 11 are included in the operator product expansion, and both parity-projected spectra and the chiral-even and chiral-odd Lorentz structures are examined. No bound-state solution is found in the $J^P=1/2^-$ sector, although several channels generate resonance masses near nearby thresholds or poorly established strange baryons. In the $J^P=3/2^-$ sector, the $\Sigma\phi$ and $\Xi K^\ast$ currents both support a near-threshold bound-state solution around $2.2$ GeV, suggesting a possible molecular configuration with channel mixing. In contrast, positive-parity sectors are more difficult to identify the corresponding states. In addition, our results favor the spin-parity assignments $J^P=3/2^-$ for $\Sigma(2250)$, $J^P=1/2^-$ for $\Sigma(2455)$, $\Sigma(2620)$, and $\Xi(2370)$, and $J^P=3/2^+$ for $\Xi(2250)$. These results provide a systematic QCD sum rule study of strange pentaquark molecular candidates in the strange sector.
Our previous studies revealed evidence of the strange molecular partners of $P_c$ states, $N(2080)3/2^-$ and $N(2270)3/2^-$, in the $\gamma p \to K^{*+} \Sigma^0 / K^{*0} \Sigma^+$ and $\gamma p \to \phi p$ reactions. Motivated by the differential cross-section data for $\gamma p \to K^+ \Sigma^0$ from CLAS 2010, which exhibits some bump structures at $W \approx$ 1875, 2080 and 2270 MeV, we extend our previous analysis by investigating the effects of $N(1535)1/2^-$, $N(1875)3/2^-$, $N(2080)1/2^- \&\ 3/2^-$ and $N(2270)1/2^- , 3/2^- \&\ 5/2^-$, as strange partners of $P_c$ molecular states, in the reactions $\gamma p \to K^+ \Sigma^0$ and $\gamma p \to K^0 \Sigma^+$. The theoretical model employed in this study utilizes an effective Lagrangian approach in the tree-level Born approximation. It contains the contributions from $s$-channel with exchanges of $N$, $\Delta$, $N^*$ (including the hadronic molecules with hidden strangeness), and $\Delta^*$; $t$-channel; $u$-channel; and the generalized contact term. The results based on the final fitted parameters are in good agreement with all available experimental data of both cross-sections and polarization observables for $\gamma p \to K^+ \Sigma^0$ and $\gamma p \to K^0 \Sigma^+$. Notably, the $s$-channel exchanges of molecules significantly contribute to the bump structures in cross-sections for $\gamma p \to K \Sigma$ at $W \approx$ 1900, 2080 and 2270 MeV, and show considerable coherence with contributions from $s$-channel exchanges of general resonances to construct the overall structures of cross-sections. More abundant experiments, particularly for the reaction $\gamma p \to K^0 \Sigma^+$, are necessary to further strengthen the constraints on the theoretical models.
In this article, we systematically discuss the decay patterns of the hidden-strange hadronic molecular state $N(2270)$ which is assumed as an S-wave $K^\ast\Sigma^\ast$ shallow bound state with its possible quantum numbers $J^P$ which are ${1/2}^-$, ${3/2}^-$ and ${5/2}^-$. By using the effective Lagrangian approach and considering pseudo-scalar meson and vector meson exchanges, we have thoroughly calculated and discussed the decay behavior of the $N(2270)$ molecular state, including hadronic and radiative decay and the cutoff dependence, for different $J^P$ values. For all three cases, $K^\ast \Lambda$, $K^\ast \Sigma$, and $\rho N$ final states are always included as the main decay channels. However, the $K \Lambda$, $\pi N$ and $\pi \Delta$ final states exhibit notable differences. These different decay properties will provide valuable guidance for future experimental searches and aid in distinguishing different $J^P$ assumptions and understanding their internal structures.
In the present work, we re-analyze the available data for $\gamma p\to K^{\ast +}\Sigma^0$ and $\gamma p \to K^{\ast 0}\Sigma^+$ by considering the contributions from the $N(2080){3/2}^-$ and $N(2270)3/2^-$ molecules instead of any nucleon resonances in the $s$ channel, where the $N(2080)3/2^-$ was proposed to be a $K^\ast \Sigma$ molecule as the strange partner of the $P_c^+(4457)$ hadronic molecular state, and the $N(2270)3/2^-$ was assumed to be a $K^*\Sigma^*$ molecule as the strange partner of the $\bar{D}^\ast \Sigma^\ast_c$ bound states that are predicated as members in the same heavy-quark spin symmetry multiplet as the $P_c$ states. It turns out that all the available cross-section data can be well reproduced, indicating that the molecular structures of the possible $N(2080){3/2}^-$ and $N(2270)3/2^-$ states are compatible with the available data for $K^\ast\Sigma$ photoproduction reactions. Further analysis shows that for both $\gamma p\to K^{\ast +}\Sigma^0$ and $\gamma p \to K^{\ast 0}\Sigma^+$ reactions, the $N(2080){3/2}^-$ exchange provides dominant contributions to the cross-sections in the near-threshold energy region, and significant contributions from the $N(2270)3/2^-$ exchange to the cross-sections in the higher energy region are also found. Predictions of the beam asymmetry $\Sigma$, target asymmetry $T$, and recoil baryon asymmetry $P$ are presented and compared with those from our previous work. Measurements of the data on these observables are called on to further constrain the reaction mechanisms of $K^\ast\Sigma$ photoproduction reactions and to verify the molecular scenario of the $N(2080){3/2}^-$ and $N(2270)3/2^-$ states.
In hadron spectrum physics, the partial wave analysis is a primary method used to extract properties of hadronic resonances. The covariant orbital-spin coupling scheme holds unique advantages over other partial wave methods due to its Lorentz covariant form and determined orbital-spin quantum numbers. This paper presents a general form of the covariant orbital-spin coupling scheme based on the irreducible tensor of the homogeneous proper Lorentz group and its little groups. A systematic procedure for constructing partial wave amplitude in a Lorentz covariant way is provided, which can be applied to both massive and massless particles. Specific examples are also included.