arXiv subjects

Wen-Nian Liu

Publications and source records attributed to Wen-Nian Liu.

6 recordsLinked to original sources

arXiv2026

Mass relations in heavy hadrons from Jensen-like inequalities

We demonstrate that mass inequalities for hadrons with one or more heavy quarks arise primarily from the concavity of binding energies in the quark model, reflecting short-range Coulombic interactions and long-range confinement. Empirical two-body bindings $B_{i\bar{j}}$ are extracted from spin-averaged meson masses, ensuring model independence and direct use of experimental data. Fitting these as functions of reduced mass $μ_{ij}$ reveals a critical confinement scale of 1.34~fm where bindings turn positive. The concave $B(1/μ)$ justifies Jensen-like inequalities under flavor permutation, reproducing relations like $m_{x\bar{y}} > \frac{1}{2}(m_{x\bar{x}} + m_{y\bar{y}})$ and baryon analogs, including $m_{xyz} > \frac{1}{3}(m_{xxx} + m_{yyy} + m_{zzz})$. Hadron mass decomposition validates $ΔM_{\textrm{EXP}} \approx ΔB + ΔC$ with $σ\sim 2.07$~MeV for mesons and baryons. Promoting inequalities to equalities, we predict masses for unobserved heavy baryons (e.g., $M(Ω_{b}^{\ast})=6076.6\,$MeV, $M(Ξ_{cc}^{\ast})=3703.6\,$MeV and $M(Ω_{cc}^{\ast})=3802.4\,$MeV) and identify favored quark-exchange scattering channels.

hep-ph↗

arXiv2026

Compactness, mass spectra, and strong stability of singly heavy tetraquarks

We propose a Coulomb-like parameterization in terms of bag radius of the short-range chromo-electric interaction between heavy quarks and strange quarks within the framework of the MIT bag model for hadrons including multiquark systems and re-examine mass spectra of doubly and fully heavy baryons self-consistently and variationally. Building upon this, we apply this approach to systematically investigate the mass spectra and $S$-wave strong decay stability of singly heavy tetraquark systems, including $nQ\bar{n}\bar{n}$, $nQ\bar{s}\bar{n}$, $Qs\bar{n}\bar{n}$, $sQ\bar{s}\bar{n}$, and $sQ\bar{s}\bar{s}$ (with $Q=c,b$). Choosing the bag confinement energy as a compactness criterion, the bag radius is shown to be close to the confinement uplimit of the radius, $R_c = 5.615\,\text{GeV}^{-1}$, for the compact singly charmed systems,and for these systems some high-spin states are unlikely to form compact structures, while several others do exhibit potential for compactnessNotably, computation indicates that the state $T_{nc\bar{s}\bar{n}}(0^+,2.925)$ emerges as a compact tetraquark with relatively large strong decay width, a plausible candidate of the observed tetrquark $T_{c\bar{s}0}^{a}(2900)$.

hep-ph↗

arXiv2025

Prospects for compact hexaquarks under the limitation imposed by quark confinement

The limitation of flavor constituents for compact multiquarks is crucial for understanding the strong interaction at the low energy scale. Utilizing the MIT bag model that incorporates perturbative interactions and confinement energy $E_{\rm CON}$, we derive a critical bag radius $R_c=5.61\,$GeV$^{-1}$ from the condition $E_{\rm CON} < 0$ at zero temperature and zero baryon density, which aligns with the string-breaking distance of 1.2--1.4$\,$fm. Applying this framework to 6-, 7-, and 8-quark systems, we find the bag radii $R_0$ to be highly sensitive to relativistic effects from light quarks, leading to the exclusion of most heavy-light flavor configurations (e.g., $n^3\bar{c}^3$, $n^3\bar{n}\bar{c}^2$) due to positive $E_{\rm CON}$ and radii exceeding the critical radius. Color-spin wavefunctions are constructed using Young tableaux to evaluate interaction matrices and OZI-superallowed decays. Broad decay widths in fully heavy systems for OZI-superallowed modes could arise from wavefunction overlaps due to heavy flavor symmetry, suggesting possible narrow widths for $nnb\bar{b}\bar{b}\bar{b}$ and $nnn\bar{b}\bar{b}\bar{b}$ hexaquarks. This phenomenological approach provides insights into the limitations on multiquarks imposed by confinement. It recommends experimental searches at LHCb for these states.

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arXiv2025

Resonant Singly Heavy Pentaquarks in the MIT Bag Model: Mass Spectra and Strong Decays

Exploring the limits of color interactions in multiquark states is an important topic. Based on the bag confinement picture of hadrons, we find that for singly heavy pentaquarks, the bag confinement radius precisely falls within the range of color interaction limits provided by lattice QCD, approximately 1.17--1.29$\,\text{fm}$. This leads us to believe that singly heavy pentaquark states have the potential to form resonant states. Inspired by singly heavy baryons, we consider the mirror pentaquarks of singly heavy baryons. Furthermore, we adopt the MIT bag model, taking into account chromomagnetic and color-electric interactions between heavy and strange quarks, to calculate the mass spectrum of singly heavy pentaquarks configured as $qqqQ\bar{q}$ and analyze the stability of their S-wave two-body strong decays. We show that for the singly heavy pentaquark system, the masses are generally about $500\, \text{MeV}$ higher than the corresponding mirror baryon ground state masses, which is consistent with conclusions drawn from chiral methods. We also provide a mass mapping relationship between singly heavy pentaquarks and singly heavy baryons based on light quark flavor symmetry. The analysis of strong decays indicates that these singly heavy pentaquarks are unstable with respect to strong decays, which is consistent with our initial hypothesis.

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arXiv2025

Searching for compact pentaquark state within the bag model framework

The search for the compact limit of multi-quark states is a challenging issue. Within the framework of the MIT bag model, we propose an effective limit bag radius of $R_{c} = 5.615 \, \text{GeV}^{-1}$(or $1.11 \, \text{fm}$) for bound states . When the bag radius of a hadron falls below this value, the bag binding energy satisfies $E_{B} < 0$, indicating that the system has a compact intention. We consider various combinations of different numbers and ratios of heavy and light quarks, indicating that the bag radius of hadrons depending on the number of quarks is suppressed by the presence of heavy quarks. Focusing on five-quark combinations, we find that the average bag radius of $nncc\bar{c}$ is below the threshold $R_{c}$. We take into account color-magnetic interactions and calculate the mass, magnetic moment, binding energy, and relative strong decay width for the $nnQQ\bar{Q}$ system. We show that the binding energies of most states in the flavor combination $nncc\bar{c}$ are approximately $-20 \, \text{MeV}$, whereas states involving bottom quarks have binding energies around $-120 \, \text{MeV}$, with some decay widths suppressed by the decay constant. Additionally, the $nQQQ\bar{Q}$ system exhibits even deeper binding. Our results support the compact intention of $nnQQ\bar{Q}$ and suggest that the $nQQQ\bar{Q}$ configuration demonstrates even stronger compactness.

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arXiv2020

Regge behaviors in orbitally excited spectroscopy of charmed and bottom baryons

Stimulated by recent progress made by the LHCb Collaboration in discoveries of new bottom baryons, e.g., the $Ξ_{b}(6227)^{-}$ and the $Σ_{b}(6097)^{\pm}$, we re-examine the orbitally excited spectrum of the charmed and bottom baryons using Regge approach in the heavy quark-diquark picture. The results indicate that the spin-averaged mass spectrum of the orbitally-excited charmed and bottom baryons can be described by a linear Regge relation, which is derived from the rotating QCD string model. By giving further mass-splitting analysis of spin-dependent interactions, we explain the baryons $Ξ_{b}(6227)^{-}$ and the $Σ_{b}(6097)^{\pm}$,and the $Σ_{c}(2800)$ and $Ξ_{c}^{\prime }(2930)$ to be the $1P$%-wave baryons, all with the spin-parity $J^{P}=3/2^{-}$ preferably. Mass prediction of the bottom baryon $Ξ_{b}$ in its P- and D-waves are presented, providing clues for the coming experiments like the LHCb to find them.

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