arXiv subjects

Qi-Fang Lü

Publications and source records attributed to Qi-Fang Lü.

At least 55 records · Page 3Linked to original sources

arXiv2019

Canonical interpretation of the newly observed $Λ_b(6146)^0$ and $Λ_b(6152)^0$ via strong decay behaviors

Stimulated by the newly observed $Λ_b(6146)^0$ and $Λ_b(6152)^0$ resonances, we investigate the strong decays of the low-lying singly bottom baryons within the quark pair creation model. Considering their masses and decay modes, we tentatively assign these states as the $λ-$ mode $Λ_b(2S)$, $Λ_b(1D)$, $Σ_b(2S)$, and $Σ_b(1P)$ states, and then estimate their strong decay widths. Compared with the experimental total widths and decay modes measured by the LHCb Collaboration, the $Λ_b(6146)^0$ and $Λ_b(6152)^0$ can be reasonably clarified into the $J^P=5/2^+$ and $J^P=3/2^+$ $Λ_b(1D)$ sates respectively, while other canonical assignments are disfavored. Other low-lying bottom states are also presented, where various narrow states may have good potential to be observed in future LHCb experiments.

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arXiv2019

Canonical interpretation of $Y(10750)$ and $Υ(10860)$ in the $Υ$ family

Inspired by the new resonance $Y(10750)$, we calculate the masses and two-body OZI-allowed strong decays of the higher vector bottomonium sates within both screened and linear potential models. We discuss the possibilities of $Υ(10860)$ and $Y(10750)$ as mixed states via the $S-D$ mixing. Our results suggest that $Y(10750)$ and $Υ(10860)$ might be explained as mixed states between $5S$- and $4D$-wave vector $b\bar{b}$ states. The $Y(10750)$ and $Υ(10860)$ resonances may correspond to the mixed states dominated by the $4D$- and $5S$-wave components, respectively. The mass and the strong decay behaviors of the $Υ(11020)$ resonance are consistent with the assignment of the $Υ(6S)$ state in the potential models.

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arXiv2019

The excited bottom-charmed mesons in a nonrelativistic quark model

Using the newly measured masses of $B_c(1S)$ and $B_c(2S)$ from the CMS Collaboration and the $1S$ hyperfine splitting determined from the lattice QCD as constrains, we calculate the $B_c$ mass spectrum up to the $6S$ multiplet with a nonrelativistic linear potential model. Furthermore, using the wave functions from this model we calculate the radiative transitions between the $B_c$ states within a constituent quark model. For the higher mass $B_c$ states lying above $DB$ threshold, we also evaluate the Okubo-Zweig-Iizuka (OZI) allowed two-body strong decays with the $^{3}P_{0}$ model. Our study indicates that besides there are large potentials for the observations of the low-lying $B_c$ states below the $DB$ threshold via their radiative transitions, some higher mass $B_c$ states, such as $B_c(2^3P_2)$, $B_c(2^3D_1)$, $B_c(3^3D_1)$, $B_c(4^3P_0)$, and the $1F$-wave $B_c$ states, might be first observed in their dominant strong decay channels $DB$, $DB^*$ or $D^*B$ at the LHC for their relatively narrow widths.

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arXiv2018

Interpretation of the newly observed $Σ_b(6097)^{\pm}$ and $Ξ_b(6227)^-$ states as the $P$-wave bottom baryons

The strong decays of the $P$-wave $Σ_b$, $Ξ_b'$ and $Ω_b$ baryons are investigated with a constituent quark model in the $j$-$j$ coupling scheme. The results show that the newly observed $Σ_b(6097)$ and $Ξ_b(6227)$ states by the LHCb collaboration can be assigned as the $λ$-mode $P$-wave singly bottom baryons. Given the heavy quark symmetry, both the $Σ_b(6097)$ and $Ξ_b(6227)$ states favor the light spin $j=2$ states with spin-parity numbers $J^P=3/2^-$ or $J^P=5/2^-$. More $P$-wave singly bottom baryons are most likely to be observed in future experiments for their relatively narrow width.

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arXiv2018

Newly observed $Ω(2012)$ state and strong decays of the low-lying $Ω$ excitations

Stimulated by the newly discovered $Ω(2012)$ resonance at Belle II, in this work we have studied the OZI allowed strong decays of the low-lying $1P$- and $1D$-wave $Ω$ baryons within the $^3P_0$ model. It is found that $Ω(2012)$ is most likely to be a $1P$-wave $Ω$ state with $J^P=3/2^-$. We also find that the $Ω(2250)$ state could be assigned as a $1D$-wave state with $J^P=5/2^+$. The other missing $1P$- and $1D$-wave $Ω$ baryons may have large potentials to be observed in their main decay channels.

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arXiv2018

Strong decays of higher charmonium states into open-charm meson pairs

The open-charm strong decays of higher charmonium states up to the mass of the $6P$ multiplet are systematically studied in the $^3P_0$ model. The wave functions of the initial charmonium states are calculated in the linear potential (LP) and screened potential (SP) quark model. The decay widths for most of the well-established charmonium states above the open-charm thresholds can be reasonably described. By comparing our quark model calculations with the experimental observations we also discuss the nature of some of the newly observed charmonium-like states. It is found that (i) the $ψ(4415)$ may favor the $ψ(4S)$ or $ψ_1(3D)$ assignment. There may exist two highly overlapping vector charmonium states around 4.4 GeV; (ii) In the LP model the $J^{PC}=1^{--}$ $Y(4660)$ resonance and the $J^{PC}=0^{++}$ $X(4500)$ resonance may be assigned as the $ψ(5S)$ and $χ_{c0}(4P)$, respectively; (iii) The newly observed state $X^*(3860)$ can be assigned as the $χ_{c0}(2P)$ state with a narrow width of about $30$ MeV; (iv) It seems to be difficult to accommodate the $X(4140)$ and $X(4274)$ states in the same potential model as excited $χ_{c1}$ states. (v) The $X(3940)$ resonance can be assigned as the $η_c(3S)$ state; (vi) The vector charmonium-like states $Y(4230/4260,4360)$ and scalar $X(4700)$ cannot be described by any conventional charmonium states self-consistently in our model.

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arXiv2018

Strong decay of $Λ_c(2940)$ as a $2P$ state in the $Λ_c$ family

Considering the mass, parity and $D^0 p$ decay mode, we tentatively assign the $Λ_c(2940)$ as the $P-$wave states with one radial excitation. Then, via studying the strong decay behavior of the $Λ_c(2940)$ within the $^3P_0$ model, we obtain that the total decay widths of the $Λ_{c1}(\frac{1}{2}^-,2P)$ and $Λ_{c1}(\frac{3}{2}^-,2P)$ states are 16.27 MeV and 25.39 MeV, respectively. Compared with the experimental total width $27.7^{+8.2}_{-6.0}\pm0.9^{+5.2}_{-10.4}~\rm{MeV}$ measured by LHCb Collaboration, both assignments are allowed, and the $J^P=\frac{3}{2}^-$ assignment is more favorable. Other $λ-$mode $Σ_c(2P)$ states are also investigated, which are most likely to be narrow states and have good potential to be observed in future experiments.

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arXiv2018

A new decay mode of higher charmonium

We calculate the $Λ_c\barΛ_c$ partial decay width of the excited vector charmonium states around 4.6 GeV with the quark pair creation model. We find that the partial decay width of the $Λ_c\barΛ_c$ mode can reach up to several MeV for $ψ(4S,~5S,~6S)$. In contrast, the partial $Λ_c\barΛ_c$ decay width of the states $ψ(3D,~4D,~5D)$ is less than one MeV. If the enhancement $Y(4630)$ reported by the Belle Collaboration in $Λ_c\barΛ_c$ invariant-mass distribution is the same structure as $Y(4660)$, the $Y(4660)$ resonance is most likely to be a $S$-wave charmonium state.

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arXiv2017

Strong decays of the 1P and 2D doubly charmed states

We perform a systematical investigation of the strong decay properties of the low-lying $1P$- and $2D$-wave doubly charmed baryons with the $^3P_0$ quark pair creation model. The main predictions include: (i) in the $Ξ_{cc}$ and $Ω_{cc}$ family, the $1P~ρ$ mode excitations with $J^P=1/2^-$ and $3/2^-$ should be the fairly narrow states. (ii) For the $1P~λ$ mode excitations, $|^2P_λ\frac{3}{2}^-\rangle$ and $|^4P_λ\frac{3}{2}^-\rangle$ have a width of $Γ\sim150$ MeV, and mainly decay into the $J^P=3/2^+$ ground state. Meanwhile, $|^2P_λ\frac{1}{2}^-\rangle$ and $|^4P_λ\frac{5}{2}^-\rangle$ are the narrow states with a width of $Γ\sim40$ MeV, and mainly decay into the ground state with $J^P=1/2^+$. (iii) The $2D_{ρρ}$ states mainly decay via emitting a heavy-light meson if their masses are above the threshold of $Λ_cD$ or $Ξ_cD$, respectively. Their strong decay widths are sensitive to the masses and can reach several tens MeV. (iv) The $2D_{λλ}$ states may be broad states with a width of $Γ>100$ MeV. It should be emphasized that the states with $J^P=3/2^+$ and $5/2^+$ mainly decay into the ground state with $J^P=3/2^+$ plus a light-flavor meson, while the states with $J^P=1/2^+$ and $7/2^+$ mainly decay into the ground state with $J^P=1/2^+$ plus a light-flavor meson.

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arXiv2017

Regge-like relation and a universal description of heavy-light systems

Using the Regge-like formula $(M-m_Q)^2=πσL$ between hadron mass $M$ and angular momentum $L$ with a heavy quark mass $m_Q$ and a string tension $σ$, we analyze all the heavy-light systems, i.e., $D/D_s/B/B_s$ mesons and charmed and bottom baryons.Numerical plots are obtained for all the heavy-light mesons of experimental data whose slope becomes nearly equal to 1/2 of that for light hadrons. Assuming that charmed and bottom baryons consist of one heavy quark and one light cluster of two light quarks (diquark), we apply the formula to all the heavy-light baryons including recently discovered $Ω_c$'s and find that these baryons experimentally measured satisfy the above formula. We predict the average mass values of $B$, $B_s$, $Λ_b$, $Σ_c$, $Ξ_c$, and $Ω_c$ with $L=2$ as 6.01, 6.13, 6.15, 3.05, 3.07, and 3.34 GeV, respectively. Our results on baryons suggest that these baryons can be safely regarded as heavy quark-light cluster configuration. We also find a universal description for all the heavy-light mesons as well as baryons, i.e., one unique line is enough to describe both of charmed and bottom heavy-light systems. Our results suggest that instead of mass itself, gluon flux energy is essential to obtain a linear trajectory.

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arXiv2017

Mass spectra and radiative transitions of doubly heavy baryons in a relativized quark model

We study the mass spectra and radiative decays of doubly heavy baryons within the diquark picture in a relativized quark model. The mass of the $J^P=1/2^+$ $Ξ_{cc}$ ground state is predicted to be 3606 MeV, which is consistent with the mass of $Ξ_{cc}^{++}(3621)$ newly observed by the LHCb collaboration. The predicted mass gap between two $S$ wave states, $Ξ_{cc}^*$ ($J^P=3/2^+$) and $Ξ_{cc}$ ($J^P=1/2^+$), is 69 MeV. Furthermore, the radiative transitions of doubly heavy baryons are also estimated by using the realistic wave functions obtained from relativized quark model. The radiative decay widths of $Ξ_{cc}^{*++} \to Ξ_{cc}^{++}γ$ and $Ξ_{cc}^{*+} \to Ξ_{cc}^+γ$ are predicted to be about 7 and 4 keV, respectively. These predictions of doubly heavy baryons can provide helpful information for future experimental searches.

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arXiv2017

Strong and radiative decays of the doubly charmed baryons

We have systematically studied the strong and radiative decays of the low-lying $1P$-wave doubly charmed baryons. Some interesting observations are: (i) The states $Ξ_{cc}^*$ and $Ω_{cc}^*$ with $J^P=3/2^+$ have a fairly large decay rate into the $Ξ_{cc}γ$ and $Ω_{cc}γ$ channels with a width $\sim 15$ and $\sim7$ keV, respectively. (ii) The lowest lying excited doubly charmed baryons are dominated by the $1P$ $ρ$ mode excitations, which should be quite narrow states. They decay into the ground state with $J^P=1/2^+$ through the radiative transitions with a significant ratio. (iii) The total decay widths of the first orbital excitations of $λ$ mode ($1P_λ$ states with $J^P=1/2^-$, $3/2^-$, $5/2^-$) are about $Γ\sim100$ MeV, and the ratio between the radiative and hadronic decay widths is about $\mathcal{O}(10^{-3})$.

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arXiv2016

String point of view for heavy-light mesons

An approximate rotational symmetry of a heavy-light meson is viewed from a string picture. Using a simple string configuration, we derive a formula, $(M-m_c)^2=πσL$, whose coefficient of the r.h.s. is just 1/2 of that of a light meson with two light quarks. A numerical plot is obtained for $D$ mesons of experimental data as well as several theoretical models, which shows good agreement with this formula.

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arXiv2016

Masses of open charm and bottom tetraquark states in a relativized quark model

We study the masses of open charm and bottom tetraquark states within the diquark-antidiquark scenario in the relativized quark model proposed by Godfrey and Isgur. The diquark and antidiquark masses are firstly solved by relativized quark potential, and then treated as the usual antiquark and quark, respectively. The masses of tetraquark states are obtained by solving the Schrödinger-type equation between the new diquark and antidiquark. We find the masses of $sq\bar b\bar q$ tetraquark configuration are much higher than that of $X(5568)$. This conclusion disfavors the possibility of $X(5568)$ as a tetraquark state within the diquark-antidiquark scenario. Further experimental searches are needed to clarify the nature of the signal observed by D0 collaboration.

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arXiv2016

Puzzle of the $Λ_c$ spectrum

There is a puzzle in the $Λ_c^+$ family, i.e., one member with $J^P=3/2^+$ is missing in a $L=2$ multiplet which the heavy quark effective theory predicts, and $J^P$'s of $Λ_c(2765)^+$ and $Λ_c(2940)^+$ are unknown. Using a light diquark picture to calculate baryon masses, we study possible assignments of two $Λ_c$'s with unknown $J^P$ and the missing $Λ_c^+$ with $3/2^+$ for $L=2$, and we find the most probable possibility that the peak corresponding to $Λ_c(2880)^+$ actually includes a missing member with spin $3/2^+$ for $L=2$ and that quantum numbers of $Λ_c(2765)^+$ and $Λ_c(2940)^+$ are $2S(1/2^+)$ and $2P(1/2^-)$, respectively.

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arXiv2016

Strong decays of the $X(2500)$ newly observed by the BESIII Collaboration

Basing on the observation of a new $J^{PC}=0^{-+}$ state, $X(2500)$, in the partial wave analysis of the decay $J/ψ\rightarrowγX\rightarrow γϕϕ$ performed by the BESIII Collaboration, we have evaluated the strong decays of the $X(2500)$ as the $4^1S_0$ and $5^1S_0$ $s\bar{s}$ states in the $^3P_0$ meson decay model. The predicted total decay width for the $4^1S_0$ $s\bar{s}$ is about 894.5 MeV, and the one for the $5^1S_0$ $s\bar{s}$ is about 271.1 MeV, which is in agreement with the experimental data $Γ_{X(2500)}=230^{+64+56}_{-35-33}$ MeV. By considering the mass and the total strong decay width of the $X(2500)$, we propose that the $X(2500)$ state can be interpreted as a candidate of the $5^1S_0$ $s\bar{s}$ state.

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arXiv2016

Excited bottom and bottom-strange mesons in the quark model

In order to understand the possible $q\bar{q}$ quark-model assignments of the $B_J(5840)$ and $B_J(5960)$ recently reported by the LHCb Collaboration, we evaluate mass spectra, strong decays, and radiative decays of bottom and bottom-strange mesons in a nonrelativistic quark model. Comparing these predictions with the relevant experimental results, we suggest that the $B_J(5840)$ and $B_J(5960)$ can be identified as the $B(2^1S_0)$ and $B(1^3D_3)$, respectively, and the $B(5970)$ reported by the CDF Collaboration can be interpreted as the $B(2^3S_1)$ or $B(1^3D_3)$. Further precise measurements of the width, spin and decay modes of the $B(5970)$ are needed to distinguish these two assignments. These predictions of bottom and bottom-strange mesons can provide useful information to further experimental investigations.

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arXiv2016

The $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$ in the relativized quark model

We investigate the masses of $cs \bar c \bar s$ tetraquark states in a diquark-antidiquark picture employing the relativized quark model proposed by Godfrey and Isgur. Only the antitriplet diquark states in color space are calculated. The diquark masses are obtained with the relativized potential firstly, and then the diquark and antidiquark are treated as the usual antiquark and quark, respectively, and the masses of the tetraquark states are obtained by solving the Schrödinger equation with the relativized potential between the diquark and antidiquark. The theoretical uncertainties induced by screening effects are also taken into account. It is found that the resonance of $X(4140)$ can be regarded as the $cs \bar c \bar s$ tetraquark ground states, and the $X(4700)$ can be assigned as the $2S$ excited tetraquark state. When the internal excited diquarks are taken into account, the resonance of $X(4500)$ can be explained as the tetraquark composed of one $2S$ scalar diquark and one scalar antidiquark. In our approach, the $X(4274)$ cannot be explained as a tetraquark state, however, it can be a good candidate of the conventional $χ_{c1}(3^3P_1)$ state. In addition, other charmonium-like states $χ_{c0}(3915)$, $X(4350)$, $X(4630)$ and $X(4660)$, as the $cs \bar c \bar s$ tetraquark states, are also discussed.

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