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Shi-Lin Zhu

Publications and source records attributed to Shi-Lin Zhu.

At least 109 records · Page 6Linked to original sources
arXiv2020

Strong decays of fully-charm tetraquarks into di-charmonia

We study strong decays of the possible fully-charm tetraquarks recently observed by LHCb, and calculate their relative branching ratios through the Fierz rearrangement. Together with our previous QCD sum rule study [Phys. Lett. B 773, 247 (2017)], our results suggest that the broad structure around $6.2$-$6.8$ GeV can be interpreted as an $S$-wave $cc\bar c \bar c$ tetraquark state with $J^{PC} = 0^{++}$ or $2^{++}$, and the narrow structure around 6.9 GeV can be interpreted as a $P$-wave one with $J^{PC} = 0^{-+}$ or $1^{-+}$. These structures were observed in the di-$J/ψ$ invariant mass spectrum, and we propose to confirm them in the di-$η_c$, $J/ψh_c$, $η_c χ_{c0}$, and $η_c χ_{c1}$ channels. We also propose to search for their partner states having the negative charge-conjugation parity in the $J/ψη_c$, $J/ψχ_{c0}$, $J/ψχ_{c1}$, and $η_c h_c$ channels.

hep-ph↗
arXiv2020

Probing hidden-charm decay properties of $P_c$ states in a molecular scenario

The $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ observed by the LHCb Collaboration are very likely to be $S$-wave $Σ_c\bar{D}^{(*)}$ molecular candidates due to their near-threshold character. In this work, we study the hidden-charm decay modes of these $P_c$ states, $P_c\to J/ψp(η_cp)$, using a quark interchange model. The decay mechanism for the $P_c\to J/ψp(η_cp)$ processes arises from the quark-quark interactions, where all parameters are determined by the mass spectra of mesons. We present our results in two scenarios. In scenario I, we perform the dynamical calculations and treat the $P_c$ states as pure $Σ_c \bar D^{(*)}$ molecules. In scenario II, after considering the coupled channel effect between different flavor configurations $Σ^{(*)}_c\bar D^{(*)}$, we calculate these partial decay widths again. The decay patterns in these two scenarios can help us to explore the molecular assignment and the inner flavor configurations for the $P_c$ states. In particular, the decay widths of $Γ(P_c(4312)\toη_cp)$ are comparable to the $J/ψp$ decay widths in both of these two scenarios. Future experiments like LHCb may confirm the existence of the $P_c(4312)$ in the $η_cp$ channel.

hep-ph↗
arXiv2020

$D^{(\ast)}N$ interaction and the structure of $Σ_c(2800)$ and $Λ_c(2940)$ in chiral effective field theory

We study the $DN$ and $D^\ast N$ interactions to probe the inner structure of $Σ_c(2800)$ and $Λ_c(2940)$ with the chiral effective field theory to the next-to-leading order. We consider the contact term, one-pion-exchange and two-pion-exchange contributions to characterize the short-, long- and mid-range interactions of the $D^{(\ast)}N$ systems. The low energy constants of the $D^{(\ast)}N$ systems are related to those of the $N\bar{N}$ interaction with quark level Lagrangian that inspired by the resonance saturation model. The $Δ(1232)$ degree of freedom is also included in the loop diagrams. The attractive potential in the $[DN]_{J=1/2}^{I=1}$ channel is too weak to form bound state, which indicates the explanation of $Σ_c(2800)$ as the compact charmed baryon is more reasonable. Meanwhile, the potentials of the isoscalar channels are deep enough to yield the molecular states. We obtain the masses of the $[DN]_{J=1/2}^{I=0}$, $[D^\ast N]_{J=1/2}^{I=0}$ and $[D^\ast N]_{J=3/2}^{I=0}$ systems to be $2792.0$ MeV, $2943.6$ MeV and $2938.4$ MeV, respectively. The $Λ_c(2940)$ is probably the isoscalar $D^\ast N$ molecule considering its low mass puzzle. Besides, the $Λ_c(2940)$ signal might contain the spin-$\frac{1}{2}$ and spin-$\frac{3}{2}$ two structures, which can qualitatively explain the significant decay ratio to $D^0p$ and $Σ_cπ$. We also study the $\bar{B}^{(\ast)}N$ systems and predict the possible molecular states in the isoscalar channels. We hope experimentalists could hunt for the open charmed molecular pentaquarks in the $Λ_c^+π^+π^-$ final state.

hep-ph↗
arXiv2020

Spectrum of the strange hidden charm molecular pentaquarks in chiral effective field theory

We calculate the effective potentials of the $Ξ_c\bar{D}^{(\ast)}$, $Ξ_c^\prime\bar{D}^{(\ast)}$ and $Ξ_c^\ast\bar{D}^{(\ast)}$ systems with the chiral effective field theory up to the next-to-leading order. We simultaneously consider the short-, intermediate- and long-range interactions. With the newly observed $P_c$ spectra as inputs, we construct the quark-level contact Lagrangians to relate the low energy constants to those of $Σ_c\bar{D}^{(\ast)}$ with the help of quark model. Our calculation indicates there are seven bound states in the $I=0$ strange hidden charm $[Ξ_c^\prime\bar{D}^{(\ast)}]_J~(J=\frac{1}{2},\frac{3}{2})$ and $[Ξ_c^\ast\bar{D}^{(\ast)}]_J~(J=\frac{1}{2},\frac{3}{2},\frac{5}{2})$ systems. Our analyses also disfavor the $Λ_c\bar{D}^{(\ast)}$ bound states. However, we obtain three new hadronic molecules in the isoscalar $[Ξ_c\bar{D}^{(\ast)}]_J~(J=\frac{1}{2},\frac{3}{2})$ systems. The masses of $[Ξ_c\bar{D}]_{1/2}$, $[Ξ_c\bar{D}^{\ast}]_{1/2}$ and $[Ξ_c\bar{D}^{\ast}]_{3/2}$ are predicted to be $4319.4^{+2.8}_{-3.0}$ MeV, $4456.9^{+3.2}_{-3.3}$ MeV and $4463.0^{+2.8}_{-3.0}$ MeV, respectively. We also notice the one-eta-exchange influence is rather feeble. Binding solutions in the $I=1$ channels are nonexistent. We hope the future analyses at LHCb can seek for these new $P_{cs}$s in the $JψΛ$ final states, especially near the thresholds of $Ξ_c\bar{D}^{(\ast)}$.

hep-ph↗
arXiv2019

The hidden-charm strong decays of the $Z_c$ states

Inspired by BESIII's measurement of the decay $Z_c(3900)^{\pm}\rightarrow ρ^{\pm}η_c$, we calculate the branching fraction ratio between the $ρη_c$ and $πJ/ψ$ decay modes for the charged states $Z_c(3900)$, $Z_c(4020)$ and $Z_c(4430)$ using a quark interchange model. Our results show that (i) the ratio $R_{Z_c(3900)}=\frac{\mathcal{B}(Z_c(3900)^{\pm}\rightarrow ρ^{\pm}η_c)}{\mathcal{B}(Z_c(3900)^{\pm}\rightarrow π^{\pm}J/ψ)}$ is 1.3 and 1.6 in the molecular and tetraquark scenarios respectively, which is roughly consistent with the experimental data $R^{\mathrm{exp}}=2.2\pm0.9$. (ii) The ratios $\frac{Γ[Z_c(3900)\rightarrow ρη_c]}{Γ[Z_c(4020)\rightarrow ρη_c]}$ and $\frac{Γ[Z_c(3900)\rightarrow πJ/ψ]}{Γ[Z_c(4020)\rightarrow πJ/ψ]}$ are about 12.5 and 24.2, respectively in the molecular scenario. In contrast, these ratios are about 1.2 in the tetraquark scenario. The non-observation of the $Z_c(4020)$ signal in the $πJ/ψ$ decay mode strongly indicates that $Z_c(3900)$ and $Z_c(4020)$ are molecule-like signals which arise from the $D^{(*)}{\bar D}^{(*)}$ hadronic interactions.

hep-ph↗
arXiv2019

$Σ_cN$ interaction in chiral perturbation theory

We adopt the heavy baryon chiral perturbation theory to calculate the $Σ_cN$ interaction to the next-to-leading order. We consider the contact interactions, one-pion-exchange contributions, two-pion-exchange diagrams, and renormalization effects of the vertices, masses and wave functions. With the pion mass dependent expression, we fit the $Σ_cN$ interaction from HAL QCD calculation with $m_π\approx 410$ MeV and $m_π\approx 570$ MeV, and then extrapolate it to the physical pion mass. The $^3S_1(I=1/2)$ $Σ_{c}N$ interaction is weakly attractive but no bound solution is found. We also propose a quark model to estimate the leading order $Σ_cN$ contact interaction with the $NN$ interaction as input. This approach combining the quark model and the chiral effective field theory predicts a very attractive interaction in $^1S_0(I=3/2)$ $Σ_{c}N$ channel and a two-body bound state.

nucl-th↗
arXiv2019

Isospin violating decay $D^*_s \to D_s π^0$ in chiral perturbation theory

We systematically calculate the isospin violating decay, $D_s^*\to D_sπ^0$, with the heavy meson chiral perturbation theory up to $\mathcal{O}(p^3)$ including the loop diagrams. The $\mathcal{O}(p^3)$ tree level amplitudes contain four undetermined LECs. We use two strategies to estimate them. With the nonanalytic dominance approximation, we get $Γ[D_s^\ast\to D_sπ^0]=(3.38\pm0.12)$ eV. With the naturalness assumption, we give a possible range of the isospin violating decay width, $[1.11-6.88]$ eV. We find that the contribution of the $\mathcal{O}(p^3)$ corrections might be significant.

hep-ph↗
arXiv2019

Interactions between two heavy mesons within heavy meson chiral effective field theory

We have studied the interactions between two heavy mesons ($D^{(*)}$-$D^{(*)}$, $\bar D^{(*)}$-$\bar D^{(*)}$, $B^{(*)}$-$B^{(*)}$, or $\bar B^{(*)}$-$\bar B^{(*)}$) within heavy meson chiral effective field theory and investigated possible molecular states. The effective potentials are obtained with Weinberg's scheme up to one-loop level. At the leading order, four body contact interactions and one pion exchange contributions are considered. In addition to two pion exchange diagrams, we include the one-loop chiral corrections to contact terms and one pion exchange diagrams at the next-to-leading order. The effective potentials both in momentum space and coordinate space are investigated and discussed extensively. The possible molecular states are also studied and the binding energies are provided by solving the Schrodinger equation. The results will be helpful for the experimental search for the doubly-heavy molecular states.

hep-ph↗
arXiv2019

Hidden charm pentaquark states and $Σ_c^{(*)}\bar{D}^{(*)}$ interaction in chiral perturbation theory

We adopt the chiral perturbation theory to calculate the $Σ_{c}^{(*)}\bar{D}^{(*)}$ interaction to the next-to-leading order (NLO) and include the couple-channel effect in the loop diagrams. We reproduce the three $P_c$ states in the molecular picture after including the $Λ_{c}\bar{D}^{(*)}$ intermediate states. We also discuss some novel observations arising from the loop diagrams.

hep-ph↗
arXiv2019

Three body open flavor decays of higher vector charmonium and bottomonium

With an extended quark pair creation model we systematically study the OZI-allowed three body open flavor decays of higher vector charmonium and bottomonium states. We obtain that the $BB^*π$ and $B^*B^*π$ partial decay widths of $Υ(10860)$ are consistent with experiment, and the corresponding partial decay widths of $Υ(11020)$ can reach up to 2$\sim$3 MeV. Meanwhile the partial widths of $DD^*π$ and $D^*D^*π$ modes for most higher vector charmonium states can reach up to several MeV.

hep-ph↗
arXiv2019

Hidden-charm and hidden-bottom molecular pentaquarks in chiral perturbation theory

The newly observed $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ at the LHCb experiment are very close to the $Σ_c\bar{D}$ and $Σ_c\bar{D}^\ast$ thresholds. In this work, we perform a systematic study and give a complete picture on the interactions between $Σ_c^{(\ast)}$ and $\bar{D}^{(\ast)}$ systems in the framework of heavy hadron chiral perturbation theory, where the short-range contact interaction, long-range one-pion-exchange contribution, and intermediate-range two-pion-exchange loop diagrams are all considered. We first investigate the three $P_c$ states without and with considering the $Λ_c$ contribution in the loop diagrams. It is difficult to simultaneously reproduce the three $P_c$s unless the effect of $Λ_c$ is included. The coupling between $Σ_c^{(\ast)}\bar{D}^{(\ast)}$ and $Λ_c\bar{D}^{(\ast)}$ channels is crucial for the formation of these $P_c$s. Our calculation supports the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ to be the $S$-wave hidden-charm $[Σ_c\bar{D}]_{J=1/2}^{I=1/2}$, $[Σ_c\bar{D}^\ast]_{J=1/2}^{I=1/2}$ and $[Σ_c\bar{D}^\ast]_{J=3/2}^{I=1/2}$ molecular pentaquarks, respectively. Our calculation disfavors the spin assignment $J^P=\frac{1}{2}^-$ for $P_c(4457)$ and $J^P=\frac{3}{2}^-$ for $P_c(4440)$, because the excessively enhanced spin-spin interaction is unreasonable in the present case. We obtain the complete mass spectra of the $[Σ_c^{(\ast)}\bar{D}^{(\ast)}]_J$ systems with the fixed low energy constants. Our result indicates the existence of $[Σ_c^{\ast}\bar{D}^{\ast}]_J~(J=\frac{1}{2},\frac{3}{2},\frac{5}{2})$ hadronic molecules. The previously reported $P_c(4380)$ might be a deeper bound one. Additionally, we also study the hidden-bottom $Σ_b^{(\ast)}B^{(\ast)}$ systems, and predict seven bound molecular states, which could serve as a guidance for future experiments....

hep-ph↗
arXiv2019

Possible interpretations of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$

Based on our previous QCD sum rule studies on hidden-charm pentaquark states, we discuss possible interpretations of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$, which were recently observed by LHCb. Our results suggest that the $P_c(4312)$ can be well interpreted as the $[Σ_c^{++} \bar D^-]$ bound state with $J^P = 1/2^-$, while the $P_c(4440)$ and $P_c(4457)$ can be interpreted as the $[Σ_c^{+} \bar D^0]$ bound state with $J^P = 1/2^-$, the $[Σ_c^{*++} \bar D^{-}]$ and $[Σ_c^{+} \bar D^{*0}]$ bound states with $J^P = 3/2^-$, or the $[Σ_c^{*+} \bar D^{*0}]$ bound state with $J^P = 5/2^-$. We propose to measure their spin-parity quantum numbers to verify these assignments.

hep-ph↗
arXiv2019

A possible explanation of the threshold enhancement in the process $e^+e^-\rightarrow Λ\barΛ$

Inspired by the recent measurement of the process $e^+e^-\rightarrow Λ\barΛ$, we calculate the mass spectrum of the $ϕ$ meson with the GI model. For the excited vector strangeonium states $ϕ(3S,~4S,~5S,~6S)$ and $ϕ(2D,~3D,~4D,~5D)$, we further investigate the electronic decay width with the Van Royen-Weisskopf formula, and the partial widths of the $Λ\barΛ$, $Ξ^{-(*)}\barΞ^+$, and $Σ^{+(*)}\barΣ^{-(*)}$ decay modes with the extended quark pair creation model. We find that the electronic decay width of the $D$-wave vector strangeonium is about $3\sim8$ times larger than that of the $S$-wave vector strangeonium. Around 2232 MeV the partial decay width of the $Λ\barΛ$ mode can reach up to several MeV for $ϕ(3^3S_1)$, while the partial $Λ\barΛ$ decay width of $ϕ(2^3D_1)$ is $\mathcal{O}(10^{-3})$ keV. If the threshold enhancement reported by the BESIII Collaboration arises from the strangeonium meson, this state is very likely to be the $ϕ(3^3S_1)$ state. We also note that the $Λ\barΛ$ and $Σ^{+}\barΣ^{-}$ partial decay widths of the states $ϕ(3^3D_1)$ and $ϕ(4^3S_1)$ are about several MeV, respectively, which are enough to be observed in future experiments.

hep-ph↗
arXiv2019

The strong decay patterns of $Z_c$ and $Z_b$ states in the relativized quark model

Employing the relativized quark model and the quark-interchange model, we investigate the decay of the charged heavy quarkonium-like states $Z_c(3900)$, $Z_c(4020)$, $Z_c(4430)$, $Z_b(10610)$ and $Z_b(10650)$ into the ground and radially excited heavy quarkonia via emitting a pion meson. The $Z_c$ and $Z_b$ states are assumed to be hadronic molecules composed of open-flavor heavy mesons. The calculated decay ratios can be compared with the experimental data, which are useful in judging whether the molecule state assignment for the corresponding $Z_c$ or $Z_b$ state is reasonable or not. The theoretical framework constructed in this work will be helpful in revealing the underlying structures of some exotic hadrons.

hep-ph↗
arXiv2019

Hidden-charm pentaquarks and $P_c$ states

Recently, the LHCb Collaboration reported three $P_c$ states in the ${J/ψ}p$ channel. We systematically study the mass spectrum of the hidden charm pentaquark in the framework of an extended chromomagnetic model. For the $nnnc\bar{c}$ pentaquark with $I=1/2$, we find that (i) the lowest state is $P_{c}(4327.0,1/2,1/2^{-})$ [We use $P_{c}(m,I,J^{P})$ to denote the $nnnc\bar{c}$ pentaquark], which corresponds to the $P_{c}(4312)$. Its dominant decay mode is $Λ_{c}\bar{D}^{*}$. (ii) We find two states in the vicinity of $P_{c}(4380)$. The first one is $P_{c}(4367.4,1/2,3/2^{-})$ and decays dominantly to $N{J/ψ}$ and $Λ_{c}\bar{D}^{*}$. The other one is $P_{c}(4372.4,1/2,1/2^{-})$. Its dominant decay mode is $Λ_{c}\bar{D}$, and its partial decay width of $Nη_{c}$ channel is comparable to that of $N{J/ψ}$. (iii) In higher mass region, we find $P_{c}(4476.3,1/2,3/2^{-})$ and $P_{c}(4480.9,1/2,1/2^{-})$, which correspond to $P_{c}(4440)$ and $P_{c}(4457)$. In the open charm channels, both of them decay dominantly to the $Λ_{c}\bar{D}^{*}$. (iv) We predict two states above $4.5~\text{GeV}$, namely $P_{c}(4524.5,1/2,3/2^{-})$ and $P_{c}(4546.0,1/2,5/2^{-})$. The masses of the $nnnc\bar{c}$ state with $I=3/2$ are all over $4.6~\text{GeV}$. Moreover, we use the model to explore the $nnsc\bar{c}$, $ssnc\bar{c}$ and $sssc\bar{c}$ pentaquark states.

hep-ph↗
arXiv2019

Radiative transitions and magnetic moments of the charmed and bottom vector mesons in chiral perturbation theory

In this work, we systematically study the radiative decays and magnetic moments of the charmed and bottom vector mesons with chiral perturbation theory up to one-loop level. We present the results in SU(2) and SU(3) cases with the mass splitting in loop diagrams kept and unkept, respectively. The obtained decay rates for $D^\ast$ and $B^\ast$ mesons in SU(3) case with the mass splitting kept are: $Γ_{\bar{D}^{\ast 0}\to \bar{D}^0γ}=16.2^{+6.5}_{-6.0}$ keV, $Γ_{D^{\ast-}\to D^-γ}=0.73^{+0.7}_{-0.3}$ keV, $Γ_{D_s^{\ast-}\to D_s^-γ}= 0.32^{+0.3}_{-0.3}$ keV, and $Γ_{B^{\ast+}\to B^+γ}=0.58^{+0.2}_{-0.2}$ keV, $Γ_{B^{\ast0}\to B^0γ}=0.23^{+0.06}_{-0.06}$ keV, $Γ_{B_s^{\ast0}\to B_s^0γ}=0.04^{+0.03}_{-0.03}$ keV. The decay width for $D^{\ast-}\to D^-γ$ is consistent with the experimental measurement. As a byproduct, the full widths of $\bar{D}^{\ast0}$ and $D_s^{\ast-}$ are $Γ_{\mathrm{tot}}(\bar{D}^{\ast0})\simeq77.7^{+26.7}_{-20.5}~\mathrm{keV}$ and $ Γ_{\mathrm{tot}}(D_s^{\ast-})\simeq0.62^{+0.45}_{-0.50}~\mathrm{keV}$, respectively. We also calculate the magnetic moments of the heavy vector mesons. The analytical chiral expressions derived in our work shall be helpful for the extrapolations of lattice QCD simulations in the coming future.

hep-ph↗
arXiv2019

Spectrum of the fully-heavy tetraquark state $QQ\bar Q' \bar Q'$

In this work, we systematically calculate the mass spectra of the $S$-wave fully heavy tetraquark states $bb\bar b\bar b$, $cc\bar c\bar c$, and $bb\bar c\bar c$ in two nonrelativistic quark models. A tetraquark state may be an admixture of a $6_c-\bar 6_c$ state and a $\bar 3_c-3_c$ one, where $6_c-\bar 6_c$($\bar 3_c-3_c$) denotes the color configuration with a $6_c$ ($\bar 3_c$) diquark and a $\bar 6_c$ ($3_c$) antidiquark. For the tetraquark states $bb\bar b\bar b$ and $cc\bar c\bar c$ with $J^{PC}={0^{++}}$, the $6_c-\bar 6_c$ state is lower than the $\bar 3_c-3_c$ one in both the two quark models, while the order of the $bb\bar c\bar c$ states depend on models. The $6_c-\bar 6_c$ and $\bar 3_c-3_c$ mixing effects are induced by the hyperfine interactions between the diquark and antidiquark, while the contributions from the one-gluon-exchange (OGE) Coulomb or the linear confinement potentials vanish for the $QQ\bar Q'\bar Q'$ system. With the couple-channel effects, we obtain the similar mass spectra. The numerical results show that the ground $QQ\bar Q'\bar Q'$ ($Q=b,c$ and $Q'=b,c$) tetraquark states are located above the corresponding scattering states, which indicates that there may not exist a bound state in the scheme of the two quark models.

hep-ph↗