arXiv subjects

Feng-Xiao Liu

Publications and source records attributed to Feng-Xiao Liu.

9 recordsLinked to original sources

arXiv2026

Singly heavy tetraquarks

In this work, we carry out a systematic study of the spectra of the $1S$-wave states for the whole singly-heavy tetraquark systems within a semi-relativistic hybrid quark potential model, in which both the one-gluon exchange (OGE) and one-boson exchange (OBE) interactions are included. Furthermore, the fall-apart decays are evaluated with the quark exchange model by combining the obtained spectra. It is found that besides the OGE potentials, the OBE potentials play crucial roles for describing the spectrum. All of our obtained states lie far above the lowest dissociation meson-meson threshold. They are compact states with relatively narrow fall-apart widths $\sim 1-120$~MeV. The $D_{s0}(2317)$, $D_{s1}(2460)$, $T_{b\bar{s}}(5568)$, and $T_{c\bar{s}}(2327)$ resonances reported from experiments cannot be explained as compact tetraquarks. While the $T_{\bar{c}\bar{s}0}(2870)$ and $T_{c\bar{s}0}(2900)$ favor the tetraquark states with $IJ^P=00^+$ and $10^+$, i.e. $T_{(\bar{c}\bar{s}[ud])0^+}^0(2919)$ and $T_{(cn\{\bar{s}\bar{n}\})0^+}^{1}(2922)$, respectively. More singly-heavy tetraquark states have good potentials to be observed in some of their dominant decay channels in experiments.

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arXiv2026

Fully-strange tetraquarks: fall-apart decays and experimental candidates

We presents a systematic analysis of the fall-apart decays for the $1S$, $1P$, and $2S$-wave fully-strange tetraquark states. It shows that most of the fully-strange tetraquark states have a relatively narrow fall-apart decay width of $\mathcal{O}(10)$ MeV. The newly observed axial-vector state $X(2300)$ at BESIII may favor the low-lying $1S$-wave $1^{+-}$ state $T_{(4s)1^{+-}}(2323)$, while the $X(2500)$ resonance observed in the earlier BESIII experiment may favor the low-lying $1P$-wave $0^{-+}$ state $T_{(4s)0^{-+}}(2481)$. Some fully-strange tetraquark states predicted in theory can be searched for in their dominant fall-apart decay channels in experiment, such as $ϕϕ$, $ϕϕ(1680)$, $η^{(\prime)}ϕ$, $η^{(\prime)}h_1(1415)$, and $ϕf_2^{\prime}(1525)$, to which they have relatively large couplings.

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arXiv2025

Decoding spin-parity quantum numbers and decay widths of double $J/ψ$ exotic states

We derive helicity amplitudes for the fully charmed tetraquark states decays into vector meson pair under two types of models, where the one is from quark model and the other one is from diquark model. The decay angular distributions have been given by the cascade decays $T_{4c}\to J/ψ(D_{(s)}^*)+J/ψ(\bar{D}_{(s)}^*)$ along with $J/ψ\to μ^++μ^-$ or $D_{(s)}^*\to D_{(s)}+π$, showing that spin-0 and spin-2 states can be distinguished. We also find that the spin-0 state decay to $J/ψ$-pair exhibits a higher degree of quantum entanglement than that in spin-2 state decays. These findings will assist in experimentally differentiating various spin-parity states, determining decay widths and unveiling undiscovered hadronic states within existing structures, thereby shedding light on the internal properties of double $J/ψ$ exotic states.

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arXiv2024

All-heavy pentaquarks

In a nonrelativistic potential quark model framework, we carry out a calculation of the mass spectrum for the low-lying $1S$ all-heavy pentaquark state by adopting the explicitly correlated Gaussian method. The obtained states are compact and lie far above the lowest dissociation baryon-meson threshold. Moreover, using the obtained masses and wave functions we evaluate the fall-apart decay properties within a quark-exchange model. The results show that the $1S$ all-heavy pentaquark states have a fairly narrow fall-apart width, which scatters in the range of $\sim0.1-4.0$ MeV. Their dominant fall-apart decay channels may be ideal for searching for their signals in future experiments.

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arXiv2024

Hidden and double charm-strange tetraquarks and their decays in a potential quark model

We carry out a systematic study of the $1S$-wave hidden and double charm-strange tetraquarks $cs\bar{c}\bar{s}$ and $cc\bar{s}\bar{s}$ in a nonrelativistic potential quark model framework with the explicitly correlated Gaussian method, and the mass spectra, color-spin configurations and possible decay modes are obtained. We find that although these states are all above their open flavor thresholds, their rearrangement decay widths are rather narrow which can be understood by the mismatching of the wave functions between the initial and final states. It implies that the tetraquarks of $cs\bar{c}\bar{s}$ and $cc\bar{s}\bar{s}$ may have a good chance to exist as genuine tetraquark states. It also shows that the color-spin configurations of the $cs\bar{c}\bar{s}$ and $cc\bar{s}\bar{s}$ systems are quite different. We find that for a physical state of $cs\bar{c}\bar{s}$ its color configurations can be dominated by either the $|11\rangle_{c}$ or $|88\rangle_{c}$ ones. It suggests that some hidden charm-strange tetraquark states may strongly couple to two color-singlet hadrons if the kinematics and dynamics allow. In contrast, we find that the color configurations $|11\rangle_{c}$ and $|88\rangle_{c}$ in a double charm-strange $cc\bar{s}\bar{s}$ state are rather compatible. It may suggest that an overall color-singlet tetraquark (i.e. a genuine color-singlet) should always play a role in the $T_{cc\bar{s}\bar{s}}$ states. Discussions taking into account some experimental candidates are presented, and suggestions on further experimental searches are also made.

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arXiv2024

Fully-heavy tetraquark states and their evidences in the LHC observations

Stimulated by the exciting progress on the observations of the fully-charmed tetraquarks at LHC, we carry out a combined analysis of the mass spectra and fall-apart decays of the $1S$-, $2S$-, and $1P$-wave $cc\bar{c}\bar{c}$ states in a nonrelativistic quark model (NRQM). It is found that the $X(6600)$ structure observed in the di-$J/ψ$ invariant mass spectrum can be explained by the $1S$-wave state $T_{(4c)0^{++}}(6550)$. This structure may also bear some feed-down effects from the higher $2S$ and/or $1P$ tetraquark states. The $X(6900)$ structure observed in both the di-$J/ψ$ and $J/ψψ(2S)$ channels can be naturally explained by the $2S$-wave state $T_{(4c)0^{++}}(6957)$. The small shoulder structure around $6.2-6.4$ GeV observed at CMS and ATLAS may be due to the feed-down effects from some $1P$-wave states with $C=-1$ and/or some $2S$-wave states with $J^{PC}=0^{++}$. Other decay channels are implied in such a scenario and they can be investigated by future experimental analyses. Considering the large discovery potential at LHC, we also present predictions for the $bb\bar{b}\bar{b}$ states which can be searched for in the future.

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arXiv2023

Charmed-strange tetraquarks and their decays in a potential quark model

In the framework of a nonrelativistic potential quark model, we investigate the mass spectrum of the $1S$-wave charmed-strange tetraquark states of $cn\bar{s}\bar{n}$ and $cs\bar{n}\bar{n}$ ($n=u$ or $d$) systems. The tetraquark system is solved by a correlated Gaussian method. With the same parameters fixed by the meson spectra, we obtained the mass spectra for the $1S$-wave tetraquark states. Furthermore, based on the predicted tetraquark spectra we estimate their rearrangement decays in a quark-exchange model. We find that the rearrangement decays of the tetraquarks may be mainly driven by the spin-spin interactions. The resonances $X_0(2900)^0$ and $T^a_{c\bar{s}0}(2900)^{++/0}$ reported from LHCb may be assigned to be the lowest $1S$-wave tetraquark states $\bar{T}_{cs0}^f(2818)$ and $T^{a}_{c\bar{s}0}(2828)$ classified in the quark model, respectively. It also allows us to extract the couplings for the initial tetraquark states to their nearby $S$-wave interaction channels. We find that some of these couplings turn out to be sizeable. Following the picture of the wavefunction renormalization for the near-threshold strong $S$-wave interactions, the sizeable coupling strengths can be regarded as an indication of their dynamic origins as candidates for hadronic molecules. Furthermore, our predictions suggest that signals for the $1S$-wave charmed-strange tetraquark states can also be searched in the other channels, such as $D^0K^+$, $D^+K^+$, $D^{*+}K^-$, $D^{*+}K^+$, $D^{*0}K^+$, $D^0\bar{K}^{*0}$, $D_s^+ρ^0$, etc.

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arXiv2021

Higher mass spectra of the fully-charmed and fully-bottom tetraquarks

In this work, we calculate the higher mass spectra for the $2S$- and $1D$-wave fully-charmed and fully-bottom tetraquark states in a nonrelativistic potential quark model. The $2S$-wave fully-charmed/bottom tetraquark states lie in the mass range of $\sim (6.9,7.1)$/$(19.7,19.9)$ GeV, apart for the highest $0^{++}$ state $T_{(cc\bar{c}\bar{c})0^{++}}(7185)$/ $T_{(bb\bar{b}\bar{b})0^{++}}(19976)$. Most of the $2S$-wave states highly overlap with the high-lying $1P$-wave states. The masses for the $1D$-wave fully-charmed/bottom tetraquarks are predicted to be in the range of $\sim (6.7,7.2)/(19.5,20.0)$ GeV. The mass range for the $D$-wave tetraquark states cover most of the mass range of the $P$-wave states and the whole mass range of the $2S$-wave states. The narrow structure $X(6900)$ recently observed at LHCb in the di-$J/ψ$ invariant mass spectrum may be caused by the $1P$-, or $2S$-, or $1D$-wave $T_{cc\bar{c}\bar{c}}$ states. The vague structure $X(7200)$ may be caused by the highest $2S$-wave state $T_{(cc\bar{c}\bar{c})0^{++}}(7185)$, two low-lying $3S$-wave states $T_{(cc\bar{c}\bar{c})0^{++}}(7240)$ and $T_{(cc\bar{c}\bar{c})2^{++}}(7248)$, and/or the high-lying $1D$-wave states with masses around 7.2 GeV and $J^{PC}=0^{++},1^{++},2^{++},3^{++}$, or $4^{++}$. While it is apparent that the potential quark model calculations predict more states than the structures observed in the di-$J/ψ$ invariant mass spectrum, our calculations will help further understanding of the properties of these fully-heavy tetraquark states in their strong and magnetic interactions with open channels based on explicit quark model wave functions.

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arXiv2021

Fully-strange tetraquark $ss\bar{s}\bar{s}$ spectrum and possible experimental evidence

In this work we construct 36 tetraquark configurations for the $1S$-, $1P$-, and $2S$-wave states, and make a prediction of the mass spectrum for the tetraquark $ss\bar{s}\bar{s}$ system in the framework of a nonrelativistic potential quark model without the diquark-antidiquark approximation. The model parameters are well determined by our previous study of the strangeonium spectrum. We find that the resonances $f_0(2200)$ and $f_2(2340)$ may favor the assignments of ground states $T_{(ss\bar{s}\bar{s})0^{++}}(2218)$ and $T_{(ss\bar{s}\bar{s})2^{++}}(2378)$, respectively, and the newly observed $X(2500)$ at BESIII may be a candidate of the lowest mass $1P$-wave $0^{-+}$ state $T_{(ss\bar{s}\bar{s})0^{-+}}(2481)$. Signals for the other $0^{++}$ ground state $T_{(ss\bar{s}\bar{s})0^{++}}(2440)$ may also have been observed in the $ϕϕ$ invariant mass spectrum in $J/ψ\toγϕϕ$ at BESIII. The masses of the $J^{PC}=1^{--}$ $T_{ss\bar{s}\bar{s}}$ states are predicted to be in the range of $\sim 2.44-2.99$ GeV, which indicates that the $ϕ(2170)$ resonance may not be a good candidate of the $T_{ss\bar{s}\bar{s}}$ state. This study may provide a useful guidance for searching for the $T_{ss\bar{s}\bar{s}}$ states in experiments.

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