arXiv subjects

Lu Meng

Publications and source records attributed to Lu Meng.

At least 73 records · Page 4Linked to original sources

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 $Ξ_c\bar{D}^{(\ast)}$.

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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.

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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.

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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.

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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....

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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.

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arXiv2019

Light pseudoscalar meson and doubly charmed baryon scattering lengths with heavy diquark-antiquark symmetry

We adopt the heavy baryon chiral perturbation theory (HBChPT) to calculate the scattering lengths of $ϕB_{cc}^{(*)}$ up to $\mathcal{O}(p^3)$, where $ϕ$ is the pseudoscalar mesons. The recoil effect and the mass splitting between the spin-$1\over 2$ and spin-$3\over 2$ doubly charmed baryons are included. In order to give the numerical results, we construct the chiral Lagrangians with heavy diquark-antiquark (HDA) symmetry in a formally covariant approach. Then, we relate the low energy constants (LECs) of the doubly charmed baryons to those of $D^{(*)}$ mesons. The LECs for the $ϕD^{(*)}$ scattering are estimated in two scenarios, fitting lattice QCD results and using the resonance saturation model. The chiral convergence of the first scenario is not good enough due to the the large strange quark mass and the presence of the possible bound states, virtual states and resonance. The final results for two scenarios are consistent with each other. The interaction for the $[πΞ^{(*)}_{cc}]^{(1/2)}$, $[KΞ^{(*)}_{cc}]^{(0)}$, $[KΩ^{(*)}_{cc}]^{(1/2)}$, $[ηΞ^{(*)}_{cc}]^{(1/2)}$, $[ηΩ^{(*)}_{cc}]^{(0)}$ and $[\bar{K}Ξ^{(*)}_{cc}]^{(0)}$ channels are attractive. The most attractive channel $[\bar{K}Ξ^{(*)}_{cc}]^{(0)}$ may help to form the partner states of the $D_{s0}^*(2317)$ ($D_{s1}(2460)$) in the doubly heavy sector.

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arXiv2019

Possible Molecular States Composed of Doubly Charmed Baryons with Couple-channel Effect

We systematically investigate the possible molecular states composed of (1) two spin-$\frac{3}{2}$ doubly charmed baryons, and (2) a pair of spin-$\frac{3}{2}$ and spin-$\frac{1}{2}$ doubly charmed baryons. The one-boson-exchange (OBE) model is used to describe the potential between two baryons. The channel mixing effect is considered for the systems with the same quantum number $(I(J^P))$ but different total spin ($S$) and orbital angular momenta ($L$). We also study the channel mixing effect among the systems composed of various doubly charmed baryons if they have the same quantum number. Many of the systems are good candidates of molecular states.

hep-ph↗

arXiv2019

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

In this work, we employ the heavy hadron chiral perturbation theory (HHChPT) to calculate the $Σ_c\bar{D}^{(*)}$ potentials to the next-to-leading order. The contact, the one-pion exchange and the two-pion exchange interactions are included. Besides, the mass splittings between the heavy quark spin symmetry (HQSS) multiplets are kept in calculations. Our result shows that neglecting the heavy quark symmetry (HQS) violation effect may be misleading to predict the potentials between the charmed hadrons. We perform numerical analysis with three scenarios. In the first scenario, we relate the low-energy constants (LECs) in the contact terms of $Σ_c\bar{D}^{(*)}$ to those of nucleon systems, and reproduce the $P_c(4312)$ and $P_c(4440)$ as loosely bound states. In the second scenario, we vary the unknown LECs and find a small parameter region in which $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ can coexist as molecular states. In the third scenario, we include the coupled-channel effect on the basis of scenario II, and notice that the three $P_c$ states can be reproduced as molecular states simultaneously in a large region of parameters. Our analytical results can be used for the chiral extrapolations in lattice QCD. With the lattice QCD results in the future as inputs, the identification of the $P_c$ states and predictions for other systems would be more reliable.

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arXiv2019

Hadronic Molecular States Composed of Spin-$3\over 2$ Singly Charmed Baryons

We investigate the possible deuteron-like molecules composed of a pair of charmed spin-$\frac{3}{2}$ baryons, or one charmed baryon and one charmed antibaryon within the one-boson-exchange (OBE) model. For the spin singlet and triplet systems, we consider the couple channel effect between systems with different orbital angular momentum. Most of the systems have binding solutions. The couple channel effect plays a significant role in the formation of some loosely bound states. The possible molecular states of $Ω_c^*Ω_c^*$ and $Ω_c^*\barΩ_c^*$ might be stable once produced.

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arXiv2018

Magnetic moments of the spin-${3\over 2}$ singly heavy baryons

We calculate the magnetic moments of spin-$3\over 2$ singly charmed baryons in the heavy baryon chiral perturbation theory (HBChPT). The analytical expressions are given up to $\mathcal{O}(p^3)$. The heavy quark symmetry is used to reduce the number of low energy constants (LECs). With the lattice QCD simulation data as the magnetic moments of the charmed baryons, the numerical results are given up to $\mathcal{O}(p^3)$ in three scenarios. In the first scenario, we use the results in the quark model as the leading order input. In the second scenario, we use the heavy quark symmetry and neglect the contribution of heavy quark. In the third scenario, the heavy quark contribution is considered on the basis of the scenario II and the magnetic moments of singly bottom baryons are given as a by-product.

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arXiv2018

The radiative decays of the singly heavy baryons in chiral perturbation theory

In the framework of the heavy baryon chiral perturbation theory (HBChPT), we calculate the radiative decay amplitudes of the singly heavy baryons up to the next-to-next-to-leading order (NNLO). In the numerical analysis, we adopt the heavy quark symmetry to relate some low energy constants (LECs) with those LECs in the calculation of the magnetic moments. We use the results from the lattice QCD simulation as input. With a set of unified LECs, we obtain the numerical (transition) magnetic moments and radiative decay widths. We give the numerical results for the spin-$1\over 2$ sextet to the spin-$1\over 2$ antitriplet up to the next-to-leading order (NLO). The nonvanishing $Γ(Ξ_c^{'0} \rightarrow Ξ^0_cγ)$ and $Γ(Ξ_c^{*0} \rightarrow Ξ^0_c γ)$ solely arise from the U-spin symmetry breaking, and do not depend on the lattice QCD inputs up to NLO. We also systematically give the numerical analysis of the magnetic moments of the spin-$1\over 2$, spin-$3\over 2$ sextet and their radiative decay widths up to NNLO. In the heavy quark limit, the radiative decays between the sextet states happen through the magnetic dipole (M1) transitions, while the electric quadrupole (E2) transition does not contribute. We also extend the same analysis to the single bottom baryons.

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arXiv2018

Magnetic moments of the spin-$1\over 2$ singly charmed baryons in chiral perturbation theory

We systematically derive the analytical expressions of the magnetic moments of the spin-$1\over 2$ singly charmed baryons to the next-to-next-to-leading order in the heavy baryon chiral perturbation theory (HBChPT). We discuss the analytical relations between the magnetic moments. We estimate the-low energy constants (LECs) in two scenarios. In the first scenario, we use the quark model and Lattice QCD simulation results as input. In the second scenario, the heavy quark symmetry is adopted to reduce the number of the independent LECs, which are then fitted using the data from the Lattice QCD simulations. We give the numerical results to the next-to-leading order for the antitriplet charmed baryons and to the next-to-next-to-leading order for the sextet states.

hep-ph↗

arXiv2018

Possible hadronic molecules composed of the doubly charmed baryon and nucleon

We perform a systematical investigation of the possible deuteron-like bound states with configuration $Ξ_{cc}N (\bar{N})$, where $N(\bar{N})$ denotes the nucleon (anti-nucleon), in the framework of the one-boson-exchange-potential model. In the spin-triplet sector we take into account both the ${}^3S_1$ and ${}^3D_1$ channels due to non-vanishing tensor force. There exist several candidates of the loosely bound molecular states for the $Ξ_{cc}N$ and $Ξ_{cc}\bar{N}$ systems, which lie below the threshold of $Λ_cΛ_c$ or $Λ_c{\barΛ}_c$. We also investigate the possible loosely bound states with configurations $Λ_cN(\bar{N})$ and $Σ_cN(\bar{N})$. These molecular candidates may be searched for at Belle II and LHC in the near future.

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arXiv2018

Magnetic moments of the spin-${3\over 2}$ doubly heavy baryons

In this work, we investigate the chiral corrections to the magnetic moments of the spin-$3\over 2$ doubly charmed baryons systematically up to next-to-next-to-leading order with the heavy baryon chiral perturbation theory. The numerical results are given up to next-to-leading order: $μ_{Ξ^{*++}_{cc}}=1.72μ_{N}$, $μ_{Ξ^{*+}_{cc}}=-0.09μ_{N}$, $μ_{Ω^{*+}_{cc}}=0.99μ_{N}$. As a by-product, we have also calculated the magnetic moments of the spin-$3\over 2$ doubly bottom baryons and charmed bottom baryons: $μ_{Ξ^{*0}_{bb}}=0.63μ_{N}$, $μ_{Ξ^{*-}_{bb}}=-0.79μ_{N}$, $μ_{Ω^{*-}_{bb}}=0.12μ_{N}$, $μ_{Ξ^{*+}_{bc}}=1.12μ_{N}$, $μ_{Ξ^{*0}_{bc}}=-0.40μ_{N}$, $μ_{Ω^{*0}_{bc}}=0.56μ_{N}$.

hep-ph↗

arXiv2017

Radiative decays of the doubly charmed baryons in chiral perturbation theory

We have systematically investigated the spin-$\frac{3}{2}$ to spin-$\frac{1}{2}$ doubly charmed baryon transition magnetic moments to the next-to-next-to-leading order in the heavy baryon chiral perturbation theory (HBChPT). Numerical results of transition magnetic moments and decay widths are presented to the next-to-leading order: $μ_{Ξ_{cc}^{*++}\rightarrowΞ_{cc}^{++}}=-2.35μ_{N}$, $μ_{Ξ_{cc}^{*+}\rightarrowΞ_{cc}^{+}}=1.55μ_{N}$, $μ_{Ω_{cc}^{*+}\rightarrowΩ_{cc}^{+}}=1.54μ_{N}$, $Γ_{Ξ_{cc}^{*++}\rightarrowΞ_{cc}^{++}}=22.0$ keV, $Γ_{Ξ_{cc}^{*+}\rightarrowΞ_{cc}^{+}}=9.57$ keV, $Γ_{Ω_{cc}^{*+}\rightarrowΩ_{cc}^{+}}=9.45$ keV.

hep-ph↗

arXiv2017

Magnetic moments of the doubly charmed and bottomed baryons

The chiral corrections to the magnetic moments of the spin-$\frac{1}{2}$ doubly charmed baryons are systematically investigated up to next-to-next-to-leading order with heavy baryon chiral perturbation theory (HBChPT). The numerical results are calculated up to next-to-leading order: $μ_{Ξ^{++}_{cc}}=-0.25μ_{N}$, $μ_{Ξ^{+}_{cc}}=0.85μ_{N}$, $μ_{Ω^{+}_{cc}}=0.78μ_{N}$. We also calculate the magnetic moments of the other doubly heavy baryons, including the doubly bottomed baryons (bbq) and the doubly heavy baryons containing a light quark, a charm quark and a bottom quark ($\{bc\}q$ and $[bc]q$): $μ_{Ξ^{0}_{bb}}=-0.84μ_{N}$, $μ_{Ξ^{-}_{bb}}=0.26μ_{N}$, $μ_{Ω^{-}_{bb}}=0.19μ_{N}$, $μ_{Ξ^{+}_{\{bc\}q}}=-0.54μ_{N}$, $μ_{Ξ^{0}_{\{bc\}q}}=0.56μ_{N}$, $μ_{Ω^{0}_{\{bc\}q}}=0.49μ_{N}$, $μ_{Ξ^{+}_{[bc]q}}=0.69μ_{N}$, $μ_{Ξ^{0}_{[bc]q}}=-0.59μ_{N}$, $μ_{Ω^{0}_{[bc]q}}=0.24μ_{N}$.

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