Lu Meng

Bio: Lu Meng is an academic researcher from Ruhr University Bochum. The author has contributed to research in topics: Tetraquark & Order (ring theory). The author has an hindex of 3, co-authored 5 publications receiving 36 citations.

Probing the long-range structure of the T c c + with the strong and electromagnetic decays

Abstract: Very recently, the LHCb Collaboration reported the doubly charmed tetraquark state ${T}_{cc}^{+}$ below the ${D}^{*+}{D}^{0}$ threshold about 273 keV. As a very near-threshold state, its long-distance structure is very important. In the molecular scheme, we relate the coupling constants of ${T}_{cc}^{+}$ with ${D}^{*0}{D}^{+}$ and ${D}^{*+}{D}^{0}$ to its binding energy and mixing angle of two components with a coupled-channel effective field theory. With the coupling constants, we investigate the kinetically allowed strong decays ${T}_{cc}^{+}\ensuremath{\rightarrow}{D}^{0}{D}^{0}{\ensuremath{\pi}}^{+}$, ${T}_{cc}^{+}\ensuremath{\rightarrow}{D}^{+}{D}^{0}{\ensuremath{\pi}}^{0}$ and radiative decays ${D}^{+}{D}^{0}\ensuremath{\gamma}$. Our results show that the decay width of ${T}_{cc}^{+}\ensuremath{\rightarrow}{D}^{0}{D}^{0}{\ensuremath{\pi}}^{+}$ is the largest one, which is just the experimental observation channel. Our theoretical total strong and radiative widths are in favor of the ${T}_{cc}^{+}$ as a $|{D}^{*+}{D}^{0}⟩$ dominated bound state. The total strong and radiative width in the single channel limit and isospin singlet limit are given as ${59.7}_{\ensuremath{-}4.4}^{+4.6}\text{ }\text{ }\mathrm{keV}$ and ${46.7}_{\ensuremath{-}2.9}^{+2.7}\text{ }\text{ }\mathrm{keV}$, respectively. Our calculation is cutoff-independent and without prior isospin assignment. The absolute partial widths and ratios of the different decay channels can be used to test the structure of ${T}_{cc}^{+}$ state when the updated experimental results are available.

Decoding the nature of Z c s ( 3985 ) and establishing the spectrum of charged heavy quarkoniumlike states in chiral effective field theory

Abstract: We study the newly observed charmoniumlike state ${Z}_{cs}(3985)$ in the framework of chiral effective field theory. The interaction kernel of the ${\overline{D}}_{s}{D}^{*}/{\overline{D}}_{s}^{*}D$ system is calculated up to the next-to-leading order with the explicit chiral dynamics. With the fitted parameters extracted from the ${Z}_{c}(3900)$ data as inputs, the mass, width, and event distributions of the ${Z}_{cs}(3985)$ are very consistent with the experimental measurements. Our studies strongly support the ${Z}_{cs}(3985)$ as the partner of the ${Z}_{c}(3900)$ in the ${\mathrm{SU}(3)}_{f}$ symmetry and the ${\overline{D}}_{s}{D}^{*}/{\overline{D}}_{s}^{*}D$ molecular resonance with the same dynamical origin as the other charged heavy quarkoniumlike states. We precisely predict the resonance parameters of the unobserved states in ${\overline{D}}_{s}^{*}{D}^{*}$, ${B}_{s}^{*}\overline{B}/{B}_{s}{\overline{B}}^{*}$, and ${B}_{s}^{*}{\overline{B}}^{*}$ systems, and establish a complete spectrum of the charged charmoniumlike and bottomoniumlike states with the $I({J}^{P})$ quantum numbers $1({1}^{+})$ and $\frac{1}{2}({1}^{+})$, respectively.

Predicting the D‾s(*)Ds(*) bound states as the partners of X(3872)

Abstract: In this work, we investigate the SU(3) flavor symmetry, heavy quark spin symmetry and their breaking effects in the di-meson systems. We prove the existence of the [ D ‾ s ∗ D s ∗ ] 0 + + , [ D ‾ s ∗ D s / D ‾ s D s ∗ ] 1 + - , and [ D ‾ s ∗ D s ∗ ] 1 + - bound states as the consequence of two prerequisites in the SU(3) flavor symmetry and heavy quark spin symmetry. The first prerequisite, the X ( 3872 ) as the weakly D ‾ ∗ D / D ‾ D ∗ bound state is supported by its mass and decay branching ratios. The second prerequisite, the existence of the [ D ‾ s D s ] 0 + + bound state is supported by the lattice QCD calculation and the observation of χ c 0 ( 3930 ) by the LHCb Collaboration. We hope the future experimental analyses can search for these bound states in the B → D ( s ) ( * ) D ‾ ( s ) ( * ) h processes (h denotes the light hadrons). The [ D ‾ s ∗ D s ∗ ] 0 + + bound state is also expected to be reconstructed in the J / ψ ϕ final state in the B → J / ψ ϕ K decay.

Implications of the Zcs(3985) and Zcs(4000) as two different states

Abstract: Recently, the hidden charm tetraquark states Z cs ( 3985 ) and Z cs ( 4000 ) with strangeness were observed by the BESIII and LHCb collaborations, respectively, which are great breakthroughs for exploring exotic quantum chromodynamics (QCD) structures. The first and foremost question is whether they are the same state. In this work, we explore the implications of the narrower state Z cs ( 3985 ) in BESIII and the wider one Z cs ( 4000 ) in LHCb as two different states. Within a solvable nonrelativistic effective field theory, we include the possible violations of heavy quark spin symmetry and SU(3) flavor symmetry in a comprehensive approach. If Z cs ( 3985 ) and Z cs ( 4000 ) are two different states, our results show that Z cs ( 4000 ) / Z cs ( 3985 ) is the pure ( | D ‾ s ∗ D 〉 + / - | D ‾ s D ∗ 〉 ) / 2 state, and the SU(3) flavor partner of Z c ( 3900 ) is Z cs ( 4000 ) rather than the Z cs ( 3985 ) . Another two important consequences are the existence of a tensor D ‾ s ∗ D ∗ resonance with mass about 4126 MeV and width 13 MeV, and the suppression of the decay mode Z cs ( 3985 ) → J / ψ K . The two consequences can be tested in experiments and distinguish the two-state interpretation from the one-state scheme.

Revisit the isospin violating decays of X ( 3872 )

Abstract: In this work, we revisit the isospin violating decays of $X(3872)$ in a coupled-channel effective field theory. In the molecular scheme, the $X(3872)$ is interpreted as the bound state of ${\overline{D}}^{*0}{D}^{0}/{\overline{D}}^{0}{D}^{*0}$ and ${D}^{*\ensuremath{-}}{D}^{+}/{D}^{\ensuremath{-}}{D}^{*+}$ channels. In a cutoff-independent formalism, we relate the coupling constants of $X(3872)$ with the two channels to the molecular wave function. The isospin violating decays of $X(3872)$ are obtained by two equivalent approaches, which amend some deficiencies about this issue in literature. In the quantum field theory approach, the isospin violating decays arise from the coupling constants of $X(3872)$ to two dimeson channels. In the quantum mechanics approach, the isospin violating is attributed to wave functions at the origin. We illustrate that how to cure the insufficient results in literature. Within the comprehensive analysis, we bridge the isospin violating decays of $X(3872)$ to its inner structure. Our results show that the proportion of the neutral channel in $X(3872)$ is over 80%. As a by-product, we calculate the strong decay width of $X(3872)\ensuremath{\rightarrow}{\overline{D}}^{0}{D}^{0}{\ensuremath{\pi}}^{0}$ and radiative one $X(3872)\ensuremath{\rightarrow}{\overline{D}}^{0}{D}^{0}\ensuremath{\gamma}$. The strong decay width and radiative decay width are about 30 keV and 10 keV, respectively, for the binding energy from $\ensuremath{-}300\text{ }\text{ }\mathrm{keV}$ to $\ensuremath{-}50\text{ }\text{ }\mathrm{keV}$.

An updated review of the new hadron states

Abstract: The past decades witnessed the golden era of hadron physics. Many excited open heavy flavor mesons and baryons have been observed since 2017. We shall provide an updated review of the recent experimental and theoretical progresses in this active field. Besides the conventional heavy hadrons, we shall also review the recently observed open heavy flavor tetraquark states X(2900) and Tcc+(3875) as well as the hidden heavy flavor multiquark states X(6900), Pcs(4459)0 , Zcs(3985)− , Zcs(4000)+ , and Zcs(4220)+ . We will also cover the recent progresses on the glueballs and light hybrid mesons, which are the direct manifestations of the non-Abelian SU(3) gauge interaction of the Quantum Chromodynamics in the low-energy region.

Coupled-channel approach to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>T</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mi>c</mml:mi></mml:mrow><mml:mo>+</mml:mo></mml:msubsup></mml:math> including three-body effects

Abstract: A coupled-channel approach is applied to the charged tetraquark state ${T}_{cc}^{+}$ recently discovered by the LHCb Collaboration. The parameters of the interaction are fixed by a fit to the observed line shape in the three-body ${D}^{0}{D}^{0}{\ensuremath{\pi}}^{+}$ channel. Special attention is paid to the three-body dynamics in the ${T}_{cc}^{+}$ due to the finite life time of the ${D}^{*}$. An approach to the ${T}_{cc}^{+}$ is argued to be self-consistent only if both manifestations of the three-body dynamics, the pion exchange between the $D$ and ${D}^{*}$ mesons and the finite ${D}^{*}$ width, are taken into account simultaneously to ensure that three-body unitarity is preserved. This is especially important to precisely extract the pole position in the complex energy plane whose imaginary part is very sensitive to the details of the coupled-channel scheme employed. The ${D}^{0}{D}^{0}$ and ${D}^{0}{D}^{+}$ invariant mass distributions, predicted based on this analysis, are in good agreement with the LHCb data. The low-energy expansion of the ${D}^{*}D$ scattering amplitude is performed and the low-energy constants (the scattering length and effective range) are extracted. The compositeness parameter of the ${T}_{cc}^{+}$ is found to be close to unity, which implies that the ${T}_{cc}^{+}$ is a hadronic molecule generated by the interactions in the ${D}^{*+}{D}^{0}$ and ${D}^{*0}{D}^{+}$ channels. Employing heavy-quark spin symmetry, an isoscalar ${D}^{*}{D}^{*}$ molecular partner of the ${T}_{cc}^{+}$ with ${J}^{P}={1}^{+}$ is predicted under the assumption that the $D{D}^{*}\text{\ensuremath{-}}{D}^{*}{D}^{*}$ coupled-channel effects can be neglected.

Probing the long-range structure of the T c c + with the strong and electromagnetic decays

Abstract: Very recently, the LHCb Collaboration reported the doubly charmed tetraquark state ${T}_{cc}^{+}$ below the ${D}^{*+}{D}^{0}$ threshold about 273 keV. As a very near-threshold state, its long-distance structure is very important. In the molecular scheme, we relate the coupling constants of ${T}_{cc}^{+}$ with ${D}^{*0}{D}^{+}$ and ${D}^{*+}{D}^{0}$ to its binding energy and mixing angle of two components with a coupled-channel effective field theory. With the coupling constants, we investigate the kinetically allowed strong decays ${T}_{cc}^{+}\ensuremath{\rightarrow}{D}^{0}{D}^{0}{\ensuremath{\pi}}^{+}$, ${T}_{cc}^{+}\ensuremath{\rightarrow}{D}^{+}{D}^{0}{\ensuremath{\pi}}^{0}$ and radiative decays ${D}^{+}{D}^{0}\ensuremath{\gamma}$. Our results show that the decay width of ${T}_{cc}^{+}\ensuremath{\rightarrow}{D}^{0}{D}^{0}{\ensuremath{\pi}}^{+}$ is the largest one, which is just the experimental observation channel. Our theoretical total strong and radiative widths are in favor of the ${T}_{cc}^{+}$ as a $|{D}^{*+}{D}^{0}⟩$ dominated bound state. The total strong and radiative width in the single channel limit and isospin singlet limit are given as ${59.7}_{\ensuremath{-}4.4}^{+4.6}\text{ }\text{ }\mathrm{keV}$ and ${46.7}_{\ensuremath{-}2.9}^{+2.7}\text{ }\text{ }\mathrm{keV}$, respectively. Our calculation is cutoff-independent and without prior isospin assignment. The absolute partial widths and ratios of the different decay channels can be used to test the structure of ${T}_{cc}^{+}$ state when the updated experimental results are available.

Unified description of the hidden-charm tetraquark states Z c s ( 3985 ) , Z c ( 3900 ) , and X ( 4020 )

Abstract: The newly observed hidden-charm tetraquark state ${Z}_{cs}(3985)$, together with ${Z}_{c}(3900)$ and $X(4020)$, are studied in the combined theoretical framework of the effective range expansion, compositeness relation, and the decay width saturation. The elastic effective-range-expansion approach leads to sensible results for the scattering lengths, effective ranges, and the compositeness coefficients, i.e., the probabilities to find the two-charm-meson molecule components in the tetraquark states. The coupled-channel formalism by including the $J/\ensuremath{\psi}\ensuremath{\pi}$ and $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ to fulfill the constraints of the compositeness relation and the decay width confirms the elastic effective-range-expansion results for the ${Z}_{c}(3900)$, by using the experimental inputs for the ratios of the decay widths between $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ and $J/\ensuremath{\psi}\ensuremath{\pi}$. With the results from the elastic effective-range-expansion study as input for the compositeness, we generalize the discussions to the ${Z}_{cs}(3985)$ by including the $J/\ensuremath{\psi}{K}^{\ensuremath{-}}$ and ${D}_{s}^{\ensuremath{-}}{D}^{*0}/{D}_{s}^{*\ensuremath{-}}{D}^{0}$ and predict the partial decay widths of the $J/\ensuremath{\psi}{K}^{\ensuremath{-}}$. Similar calculations are also carried out for the $X(4020)$ by including the ${h}_{c}\ensuremath{\pi}$ and ${D}^{*}{\overline{D}}^{*}$, and the partial decay widths of the ${h}_{c}\ensuremath{\pi}$ is predicted. Our results can provide useful guidelines for future experimental measurements.