arXiv subjects

Qi-Fang Lü

Publications and source records attributed to Qi-Fang Lü.

At least 37 records · Page 2Linked to original sources

arXiv2021

Magic mixing angles for doubly heavy baryons

We study the so-called magic mixing angles for doubly heavy baryons. Defining that a magic mixing angle rotates states with definite $^{2S+1}(l_λ)_J$ to make them heavy-quark symmetric states, we derive the magic mixing angle only in the case $L_ρ=0$ between the heavy quark symmetric states with quantum numbers $\left(J, j_\ell\right)$ and the states with $\left(J, s_q+j_ρ\right)=\left(J, \{^4l_λ/^2l_λ\}\right)$ for a doubly heavy baryon in the standard $ρ-λ$ configuration, where $\vec j_\ell=\vec l_λ+\vec s_q$, $\vec s_ρ=\vec s_{Q1}+\vec s_{Q2}$, and $\vec j_ρ=\vec s_ρ+\vec L_ρ$. We discuss how this mixing angle affects model building for a doubly heavy baryon.

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arXiv2021

Triply-heavy tetraquarks in an extended relativized quark model

In this paper, we adopt an extended relativized quark model to investigate the triply-heavy tetrquarks systematically. The mass spectra are obtained by solving the four-body relativized Hamiltonian including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections. We find that all of the triply-heavy tetraquarks lie above the corresponding meson-meson thresholds, and thus no stable one exists. In particular, besides the spin-spin interactions, the Coulomb and confining potentials also contribute to the mass splittings in the $cb\bar c \bar q$ and $cb\bar b \bar q$ systems. Moreover, the whole mass spectra for triply heavy tetraquarks show quite similar patterns, which preserve the light flavor SU(3) symmetry and heavy quark symmetry well. Through the fall-apart mechanism, the triply-heavy tetraquarks may easily decay into the heavy quarkonium plus heavy-light mesons, which are good candidates for investigation in future experiments.

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arXiv2021

Possible Assignment of Excited Light $^3S_1$ Vector Mesons

We reanalyze the problems in the assignment of 3$^3S_1$ and 4$^3S_1$ light mesons, which have not yet been well established with the $q\bar{q}$ quark model. Regge trajectories and the $^3P_0$ decay model are used respectively to study the mass and width of the observed states and predict the missing ones. By comparing our calculations with the latest experiments, we suggest that the inconsistent data of $ρ(2150)$ may include two similar structures $ρ(4^3S_1)$ and $ω(4^3S_1)$. In addition, the problem of the $K^*(2^3S_1)$ assignment, with two observed states $K^*(1410)$ and $K^*(1680)$, is investigated, with several possible explanations.

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arXiv2021

Mass spectrum and strong decays of strangeonium in a constituent quark model

In this work we calculate the mass spectrum of strangeonium up to the $3D$ multiplet within a nonrelativistic linear potential quark model. Furthermore, using the obtained wave functions, we also evaluate the strong decays of the strangeonium states with the $^3P_0$ model. Based on our successful explanations of the well established states $ϕ(1020)$, $ϕ(1680)$, $h_1(1415)$, $f'_2(1525)$, and $ϕ_3(1850)$, we further discuss the possible assignments of strangeonium-like states from experiments by combining our theoretical results with the observations. It is found that some resonances, such as $f_2(2010)$ and $f_2(2150)$ listed by the Particle Data Group, and $X(2062)$ and $X(2500)$ newly observed by BESIII, may be interpreted as the strangeonium states. The possibility of $ϕ(2170)$ as a candidate for $ϕ(3S)$ or $ϕ(2D)$ cannot be excluded. We expect our results to provide useful references for looking for the missing $s\bar{s}$ states in future experiments.

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arXiv2021

Strong decays of the low-lying bottom strange baryons

In this work, the strong decay behaviors of the $λ-$mode low-lying $Ξ_{b}$ and $Ξ_{b}^\prime$ baryons are investigated within the $^3P_0$ model. Our results suggest that all of the low-lying $\bar 3_F$ states $Ξ_b(2S)$, $Ξ_b(1P)$, and $Ξ_b(1D)$ have small decay widths of less than 20 MeV, and these states have good potentials to be observed in the $Ξ_b^\prime π$ and $Ξ_b^{\prime *} π$ invariant masses. Further, most of the $6_F$ multiplets are relatively narrow and may decay into the $Ξ_b π$, $Ξ_b^\prime π$, $Ξ_b^{\prime *} π$, and $Λ_b \bar K$ final states. Considering the masses and strong decay behaviors, we can assign the newly observed $Ξ_{b}(6100)$ resonance as the $Ξ_b(1P)$ state with $J^P=3/2^-$ and interpret the $Ξ_{b}(6227)$ structure as the $J^P=3/2^-$ $Ξ_b^\prime(1P)$ state with a proper mixing angle. We expect that our predictions for these excited bottom strange baryons will provide helpful information for future experimental research.

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arXiv2021

Branching fractions of $B^-\to D^-X_{0,1}(2900)$ and their implications

The exotic states $X_{0,1}(2900)$ with the quark flavor of $cs\bar{u}\bar{d}$ are recently observed in the mass spectrum of $D^+K^-$ in $B^-\to D^-D^+K^-$ by the LHCb collaboration. To explore the nature of $X_{0,1}(2900)$, except for analyzing their masses and decay widths as usually did in literatures, the study of their production mechanism in $B$-meson weak decays would provide another important information. The amplitude of $B^-\to D^- X_{0,1}$ is non-factorizable. We consider the final-state-interaction effects and calculate them via the rescattering mechanism. The measured branching fractions of $B^-\to D^- X_{0,1}$ are revealed. It is manifested by ${B}^-\to Λ_c^-Ξ_c^{(\prime)0}$ and $Λ_b^0\to P_c^+K^-$ that the rescattering mechanism can result in the relatively large branching fractions. The similar processes of $B^-\to π^-X_{0,1}$ are also analyzed. The isospins of $X_{0,1}$ can be investigated by $B\to DX_{0,1}^{\pm,0}$ decays.

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arXiv2020

Open charm and bottom tetraquarks in an extended relativized quark model

In present work, we systematically calculate the mass spectra of open charm and bottom tetraquarks $q q\bar q \bar Q$ within an extended relativized quark model. The four-body relativized Hamiltonians including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved by using the variational method. It is found that the predicted masses of four $0^+$ $ud\bar s \bar c$ states are 2765, 3065, 3152, and 3396 MeV, which disfavor the assignment of the newly observed $X_0(2900)$ as a compact tetraquark. Moreover, the whole mass spectra of the open charm and bottom tetraquarks show quite similar patterns, which preserve the light flavor SU(3) symmetry and heavy quark symmetry well. In addition, our results suggest that the flavor exotic states $nn\bar s \bar c$, $nn\bar s \bar b$, $ss\bar n \bar c$, and $ss\bar n \bar b$ and their antiparticles can be searched in the heavy-light meson plus kaon final states by future experiments. More theoretical and experimental efforts are needed to investigate these singly heavy tetraquarks.

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arXiv2020

Masses of fully heavy tetraquarks $QQ \bar Q \bar Q$ in an extended relativized quark model

Inspired by recent measurement of possible fully charmed tetraquarks in LHCb Collaboration, we investigate the mass spectra of fully heavy tetraquarks $QQ \bar Q \bar Q$ in an extended relativized quark model. Our estimations indicate that the broad structure around 6.4 GeV should contain one or more ground $cc \bar c \bar c$ tetraquark states, while the narrow structure near 6.9 GeV can be categorized as the first radial excitation of $cc \bar c \bar c$ system. Moreover, with the wave functions of the tetraquarks and mesons, the strong decays of tetraquarks into heavy quarkonium pair are qualitatively discussed, which can be further checked by the LHCb and CMS Collaborations.

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arXiv2020

Masses of doubly heavy tetraquarks $T_{QQ^\prime}$ in a relativized quark model

In the present work, the mass spectra of doubly heavy tetraquarks $T_{QQ^\prime}$ are systematically investigated in a relativized quark model. The four-body systems including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved within the variational method. Our results suggest that the $IJ^P=01^+$ $bb \bar u \bar d$ state is 54 MeV below the relevant $\bar B \bar B$ and $\bar B \bar B^*$ thresholds, which indicates that both strong and electromagnetic decays are forbidden, and thus this state can be a stable one. Its large hidden color component and small root mean square radius demonstrate that it is a compact tetraquark rather than a loosely bound molecule or point-like diquark-antidiquark structure. Our predictions of the doubly heavy tetraquarks may provide valuable information for future experimental searches.

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arXiv2020

Canonical interpretations of the newly observed $Ξ_c(2923)^0$, $Ξ_c(2939)^0$ and $Ξ_c(2965)^0$ resonances

Three neutral resonances $Ξ_c(2923)^0$, $Ξ_c(2939)^0$ and $Ξ_c(2965)^0$ have been observed in the $Λ_c^+ K^-$ mass spectrum by the LHCb Collaboration. Given the $Ξ_c$ and $Ξ_c^\prime$ mass spectra predicted by the constituent quark models, these three resonances are tentatively treated as the $λ-$mode $Ξ_c(2S)$, $Ξ_c^\prime(2S)$, $Ξ_c^{\prime *}(2S)$, and $Ξ_c^\prime(1P)$ states, and their strong decay behaviors are calculated within the $^3P_0$ model. Our results indicate that the $Ξ_c(2923)^0$ and $Ξ_c(2939)^0$ can be clarified into the $J^P=3/2^-$ and $5/2^-$ $Ξ_c^\prime(1P)$ states respectively, and the $Ξ_c(2965)^0$ can be regarded as the $J^P=1/2^+$ $Ξ_c^\prime(2S)$ state. Also, we suggest that the previous observed $Ξ_c(2930)$ may be the overlap of two structures $Ξ_c(2923)$ and $Ξ_c(2939)$, and the $Ξ_c(2970)$ should be the same state as $Ξ_c(2965)$. Other theoretical information on the missing $Ξ_c(2S)$, $Ξ_c^{\prime *}(2S)$, and $Ξ_c^\prime(1P)$ states may be helpful for future experimental searches.

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arXiv2020

The newly observed $Λ_b(6072)^0$ structure and its $ρ-$mode nonstrange partners

Inspired by the newly observed $Λ_b(6072)$ structure, we investigate its strong decay behaviors under various assignments within the $^3P_0$ model. Compared with the mass and total decay width, our results suggest that the $Λ_b(6072)$ can be regarded as the lowest $ρ-$mode excitation in $Λ_b$ family. Then, the strong decays of $ρ-$mode nonstrange partners for the $Λ_b(6072)$ are calculated. It is found that the $J^P=5/2^-$ $Λ_b$ and $Λ_c$ states are relatively narrow, and mainly decay into the $Σ_b^{(*)} π$ and $Σ_c^{(*)} π$ final states, respectively. These two states have good potentials to be observed in future experiments, which may help us to distinguish the three-quark model and diquark model.

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arXiv2020

All-heavy tetraquarks

In this work we study the mass spectra of the fully-heavy tetraquark systems, i.e. $cc\bar{c}\bar{c}$, $bb\bar{b}\bar{b}$, $bb\bar{c}\bar{c}/cc\bar{b}\bar{b}$, $bc\bar{c}\bar{c}/cc\bar{b}\bar{c}$, $bc\bar{b}\bar{b}/bb\bar{b}\bar{c}$, and $bc\bar{b}\bar{c}$, within a potential model by including the linear confining potential, Coulomb potential, and spin-spin interactions. It shows that the linear confining potential has important contributions to the masses and is crucial for our understanding of the mass spectra of the fully-heavy tetraquark systems. For the fully-heavy tetraquarks $Q_1Q_2\bar{Q}_3\bar{Q}_4$ our explicit calculations suggest that no bound states can be formed below the thresholds of any meson pairs $(Q_1\bar{Q}_3)$-$(Q_2\bar{Q}_4)$ or $(Q_1\bar{Q}_4)$-$(Q_2\bar{Q}_3)$. Thus, we do not expect narrow fully-heavy tetraquark states to be existing in experiments.

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arXiv2020

The $ss \bar s \bar s$ tetraquark states and the newly observed structure $X(2239)$ by BESIII Collaboration

We investigate the mass spectrum of the $ss \bar s \bar s$ tetraquark states within the relativized quark model. By solving the Schrödinger-like equation with the relativized potential, the masses of the $S-$ and $P-$wave $ss \bar s \bar s$ tetraquarks are obtained. The screening effects are also taken into account. It is found that the observed resonant structure $X(2239)$ in the $e^+e^- \to K^+K^-$ process by BESIII Collaboration can be assigned as a $P-$wave $1^{--}$ $ss \bar s \bar s$ tetraquark state. Furthermore, the radiative transition and strong decay behaviors of this structure are also estimated, which can provide helpful information for future experimental searches.

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arXiv2020

Strong decays of the newly observed narrow $Ω_b$ structures

Motivated by the newly observed narrow structures $Ω_b(6316)^-$, $Ω_b(6330)^-$, $Ω_b(6340)^-$, and $Ω_b(6350)^-$ in the $Ξ_b^0 K^-$ mass spectrum, we investigate the strong decays of the low-lying $Ω_b$ states within the $^3P_0$ model systematically. According to their masses and decay widths, the observed $Ω_b(6316)^-$, $Ω_b(6330)^-$, $Ω_b(6340)^-$, and $Ω_b(6350)^-$ resonances can be reasonably assigned as the $λ-$mode $Ω_b(1P)$ states with $J^P=1/2^-, 3/2^-, 3/2^-$, and $5/2^-$. Meanwhile, the remaining $P-$wave state with $J^P=1/2^-$ should have a rather broad width, which can hardly be observed by experiments. For the $Ω_b(2S)$ and $Ω_b(1D)$ states, our predictions show that these states have relatively narrow total widths and mainly decay into the $Ξ_b \bar K$, $Ξ_b^\prime \bar K$ and $Ξ_b^{\prime*} \bar K$ final states. These abundant theoretical predictions may be valuable for searching more excited $Ω_b$ states in future experiments.

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arXiv2020

Strong decays of the higher excited $Λ_Q$ and $Σ_Q$ baryons

In this work, we preform a systematic study of the strong decays for the higher singly heavy baryon resonances $Λ_Q(3S)$, $Λ_Q(2P)$, $Λ_Q(2D)$, $Λ_Q(1F)$, $Σ_Q(3S)$, $Σ_Q(2P)$, $Σ_Q(2D)$, and $Σ_Q(1F)$ within the $^3P_0$ model. Our results show that most of the $λ-$mode higher excited $Λ_Q$ and $Σ_Q$ states have a relatively narrow width, and mainly decay into two-body final states with one heavy meson plus one light baryon. Our calculations provide abundant theoretical information and demonstrate the general feature for these higher states, which may be valuable for future experimental searches and establishing the singly heavy baryon spectrum.

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arXiv2019

Triply charmed and bottom baryons in a constituent quark model

In this work, we study the mass spectrum of the $Ω_{ccc}$ and $Ω_{bbb}$ baryons up to the $N=2$ shell within a nonrelativistic constituent quark model (NRCQM). The model parameters are adopted from the determinations by fitting the charmonium and bottomonium spectra in our previous works. The masses of the $Ω_{ccc}$ and $Ω_{bbb}$ baryon states predicted in present work reasonably agree with the results obtained with the Lattice QCD calculations. Furthermore, to provide more knowledge of the $Ω_{ccc}$ and $Ω_{bbb}$ states, we evaluate their radiative decays with the available masses and wave functions from the potential model.

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arXiv2019

$Ω$ baryon spectrum and their decays in a constituent quark model

Combining the recent developments of the observations of $Ω$ sates we calculate the $Ω$ spectrum up to the $N=2$ shell within a nonrelativistic constituent quark potential model. Furthermore, the strong and radiative decay properties for the $Ω$ resonances within the $N=2$ shell are evaluated by using the masses and wave functions obtained from the potential model. It is found that the newly observed $Ω(2012)$ resonance is most likely to be the spin-parity $J^P=3/2^-$ $1P$-wave state $Ω(1^{2}P_{3/2^{-}})$, it also has a large potential to be observed in the $Ω(1672)γ$ channel. Our calculation shows that the 1$P$-, 1$D$-, and 2$S$-wave $Ω$ baryons have a relatively narrow decay width of less than 50 MeV. Based on the obtained decay properties and mass spectrum, we further suggest optimum channels and mass regions to find the missing $Ω$ resonances via the strong and/or radiative decay processes.

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arXiv2019

Interpretation of the newly observed $Λ_b(6146)^{0}$ and $Λ_b(6152)^0$ states in a chiral quark model

The strong decays of the low-lying $λ$-mode $Λ_b(1D,2S)$ and $Σ_b(2S)$ states are studied in a chiral quark model. We find that: (i) the newly observed $Λ_b(6146/6152)$ resonances in the $Λ_bπ^+π^-$ spectrum by the LHCb Collaboration might be explained with the $λ$-mode $Λ_b(1D)$ states in the quark model. It should be emphasized that whether the structure in the $Λ_bπ^+π^-$ spectrum correspond to two states or one state should be further clarified with more observations in future experiments. (ii) The $Λ_b(2S)$ $|J^P = \frac{1}{2}^+,0\rangle$ state mainly decays into $Σ_b^*π$ channel, which may be an ideal channel for searching for this $Λ_b(2S)$ state in future experiments. (iii) The $Σ_b(2S)$ $|J^P = \frac{1}{2}^+,1 \rangle$ and $|J^P = \frac{3}{2}^+,1 \rangle$ dominantly decay into $Λ_bπ$ with $Γ\simeq 3.82$ MeV and $Γ\simeq 4.72$ MeV, respectively.

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