Systematic investigation of the spectroscopy and decay behaviors of doubly-charmed pentaquarks

TL;DR

This work investigates the spectroscopy and decay of doubly-charmed pentaquarks using a heavy quark–light diquark four-body model with a nonrelativistic constituent quark Hamiltonian and Gaussian expansion method. By constructing complete flavor-color-spin wave functions and solving the four-body problem, the authors predict mass spectra in the $4.7$–$5.4$ GeV range, RMS radii of $1.1$–$1.6$ fm, and significant color-spin mixing from hyperfine interactions. They compute rearrangement decay widths via the quark-interchange model and find all states are unstable, with several narrow resonances ($<10$ MeV) and many broader states ($15$–$70$ MeV) decaying to a singly-charmed meson and a singly-charmed baryon. The results identify concrete experimental signatures across multiple flavor configurations that can guide future searches at LHCb, Belle II, and BESIII. The study provides a detailed map of the doubly-charmed pentaquark landscape and emphasizes the role of compact multiquark dynamics and color-spin mixing in shaping their spectra and decays.

Abstract

Building upon the discoveries of the $Ξ^{++}_{cc}(3621)$ and $T^{+}_{cc}(3875)$, we undertake a comprehensive investigation into the mass spectra, internal structures, and decay properties of doubly-charmed pentaquarks. By treating the two light quarks as a tightly bound diquark, the five-body system reduces to a four-body heavy quark-heavy quark-diquark-antiquark configuration. Within the constituent quark model framework, we calculate their mass spectra in the range of 4.7-5.4 GeV and corresponding internal mass contributions via the Gaussian expansion method. The root-mean-square radii, typically between 1.1-1.6 fm, indicate compact spatial structures. Furthermore, we also calculate the rearrangement decay widths via the quark-interchange model, finding that all states are unstable and decay into a singly-charmed baryon and a singly-charmed meson. Several narrow resonances have been identified, some of which have a total width even below 10 MeV. We hope that our study could provide valuable guidance for future theoretical investigations and experimental searches targeting doubly-charmed pentaquarks.

Figures (5)

• Figure 1: Spatial coordinates defined for the $P_{cc}$ doubly-charmed pentaquark system and its two-body decays into a meson-baryon $BC$ final state via quark rearrangement. Here, the $BC$ final state can form via two quark rearrangement pathways: $B_{1}C_{1}$ ($[c_{2}\bar{q}][c_{1}(q_{1}q_{2})]$) and $B_{2}C_{2}$ ($[c_{1}\bar{q}][c_{2}(q_{1}q_{2})]$), as illustrated in the figure.
• Figure 2: The quark-interchange diagrams for $P_{cc}$ decaying into meson-baryon final state at the quark level. The curve line denotes the (di)quark–(anti)quark interactions.
• Figure 3: Relative positions for the $cc[nn]\bar{n}$ (a) and $cc[nn]\bar{s}$ (b) pentaquarks labeled with horizontal solid lines, e.g. $5101(\Gamma=13)$ represents the mass and total decay width of the corresponding state (units: MeV). The numbers below the horizontal lines, e.g. $7:2:3$, represent the relative branching ratios of the corresponding state. The black and red horizontal lines represent the pentaquarks with $I_{nn}=1$ and $0$, respectively. The dotted lines denote various $S$-wave baryon-meson thresholds, and the superscripts (subscript) of the labels, e.g. $(\Sigma^{*}_{c}D^{*})^{5/2,3/2,1/2}_{3/2,1/2}$, represent the possible total angular momenta (isospin) of the channels. The solid dots of different colors where the vertical dashed lines with arrows intersect the horizontal solid lines represent the allowed rearranged S-wave decay processes. If a vertical dashed line with an arrow intersects a horizontal solid line without a solid dot, it means that corresponding decay process is forbidden for relevant state.
• Figure 4: Relative positions for the $cc[ss]\bar{n}$ (a) and $cc[ss]\bar{s}$ (b) pentaquarks labeled with horizontal solid lines, e.g. $5351~(\Gamma=17)$ represents the mass and total decay width of the corresponding state (units: MeV). The numbers below the horizontal lines, e.g. $4.3:2:3$, represent the relative branching ratios of the corresponding state. The dotted lines denote various $S$-wave baryon-meson thresholds, and the superscripts of the labels, e.g. $(\Omega^{*}_{c}D^{*})^{5/2,3/2,1/2}$, represent the possible total angular momenta of the channels. The solid dots of different colors where the vertical dashed lines with arrows intersect the horizontal solid lines represent the allowed rearranged S-wave decay processes. If a vertical dashed line with an arrow intersects a horizontal solid line without a solid dot, it means that corresponding decay process is forbidden for relevant state.
• Figure 5: Relative positions for the $cc[ns]\bar{n}$ (a) and $cc[ns]\bar{s}$ (b) pentaquarks labeled with horizontal solid lines, the labels, e.g. $5237(\Gamma=14)$ represents the mass and total decay width of the corresponding state (units: MeV). The numbers below the horizontal lines, the labels, e.g. $2.4:1:1.5$, represent the relative branching ratios of the corresponding state. The dotted lines denote various $S$-wave baryon-meson thresholds, and the superscripts of the labels, e.g. $(\Xi^{*}_{c}D^{*})^{5/2,3/2,1/2}$, represent the possible total angular momenta of the channels. The solid dots of different colors where the vertical dashed lines with arrows intersect the horizontal solid lines represent the allowed rearranged S-wave decay processes. If a vertical dashed line with an arrow intersects a horizontal solid line without a solid dot, it means that corresponding decay process is forbidden for relevant state.