arXiv subjects

Li-Sheng Geng

Publications and source records attributed to Li-Sheng Geng.

At least 73 records · Page 4Linked to original sources

arXiv2024

Evidence of the low-lying baryon $Σ^*(1/2^-)$ in the process $Λ_c^+\to ηπ^+Λ$

Motivated by the Belle measurements of the process $Λ_c^+\to ηπ^+Λ$, we investigate this process by considering the contributions from the $Λ(1670)$, $a_0(980)$, and $Σ(1385)$. In addition, we also consider the predicted low-lying baryon $Σ^*(1/2^-)$. Our results involving the $Σ^*(1/2^-)$ are favored by fitting to the Belle data of the $ηΛ$ and $π^+Λ$ invariant mass distributions. Furthermore, we predict the $ηπ^+$ invariant mass distribution and the angular distribution $dΓ/d{\rm cos}θ$, which are significantly different depending on whether or not the contribution from the $Σ^*(1/2^-)$ is considered. Finally, we show that, with the contribution from the $Σ^*(1/2^-)$, the calculated Dalizt plot agrees with the Belle measurements. Future precise measurements of the process $Λ_c^+\to ηπ^+Λ$ could shed further light on the existence of the low-lying $Σ^*(1/2^-)$.

hep-ph↗

arXiv2024

Productions of $X(3872)$/$Z_c(3900)$ and $X_2(4013)$/$Z_c(4020)$ in $Y(4220)$ and $Y(4360)$ decays

The two excited vector charmonium states $Y(4220)$ and $Y(4360)$ are difficult to be understood as pure $c\bar{c}$ charmonium states. Since they are located close to the mass thresholds of $\bar{D}D_{1}$ and $\bar{D}^*D_{1}$, they can be viewed as $\bar{D}D_{1}$ and $\bar{D}^*D_{1}$ molecules. Furthermore, recent studies indicated that the exotic states $X(3872)$/$Z_c(3900)$ and $X_2(4013)$/$Z_c(4020)$ are the isoscalar/isovector $\bar{D}D^{*}$ and isoscalar/isovector $\bar{D}^*D^{*}$ molecules, respectively. In this work, in the molecular picture, we employ the triangle diagram mechanism to study the productions of $ Z_{c}(3900) $ and $X(3872)$ in the pionic and radiative decays of $Y(4220)$, as well as their heavy-quark spin symmetry (HQSS) partners, i.e., the productions of $Z_{c}(4020)$ and $X_2(4013)$ in the pionic and radiative decays of $Y(4360)$. Using the effective Lagrangian approach, we obtain the ratios of the branching fractions $\mathcal{B}[Y(4360) \to Z_c(4020)π]/\mathcal{B}[Y(4220)\to Z_c(3900)π]=1.2$ and $\mathcal{B}[Y(4360)\to X_2(4013) γ]/\mathcal{B}[Y(4220)\to X(3872)γ]=0.5$, almost independent of model parameters, which indicate that the productions of $X_2(4013)$ and $Z_c(4020)$ in the radiative and pionic decays of $Y(4360)$ are likely to be measured in the future. The experimental studies of the predicted decay modes will help verify the molecular nature of $X(3872)$, $Z_c(3900)$, and $Y(4220)$. We hope the present work can stimulate experimental and further theoretical studies on these decay modes.

hep-ph↗

arXiv2024

Implication of a negative effective range on the $D\bar{D}^*$ interaction and the nature of $X(3872)$

A recent analysis of the LHCb data [Phys. Rev. D 105 (2022) L031503] obtained a sizable negative effective range for the $X(3872)$. This has attracted intensive discussions on whether $X(3872)$ can be deemed as a $D\bar{D}^*$ molecular state. This work explicitly demonstrates that the negative effective range of the $X(3872)$ does not contradict the molecular picture, adopting an effective field theory formulation of the $D\bar{D}^*$ interaction that can simultaneously reproduce the binding energy and effective range of the $X(3872)$. We elaborate on the implications of the large negative effective range of $X(3872)$ and the small binding energy on the underlying $D\bar{D}^*$ interaction. Such results are relevant for a better understanding of hadronic molecules and their binding mechanism.

hep-ph↗

arXiv2024

Investigations on the weak decays of $D\bar{B}$ molecules

The decays of exotic states discovered experimentally always proceed via the strong and electromagnetic interactions. Recently, a tetraquark state with the quark content $bc\bar{q}\bar{q}$ was predicted by Lattice QCD simulations. It is below the mass threshold of $D\bar{B}$, which can only decay via the weak interaction. In this work, based on the decay mechanism of $T_{cc}$ as a $DD^*$ molecule, we propose that the decays of the $bc\bar{q}\bar{q}$ tertaquark state as a $D\bar{B}$ molecule proceed via the Cabibbo-favored weak decays of the $\bar{B}$ or $D$ meson, accompanied by the tree-level decay modes and the triangle decay modes. Our results indicate that the branching fraction of the $D\bar{B}$ molecule decaying into $π^+ K^{-} \bar{B}^0$ is sizable, which is a good channel to observe the $D\bar{B}$ molecule in future experiments.

hep-ph↗

arXiv2024

Likely existence of bound states and the Efimov effect in the triple-$J/ψ$ system

The ground-breaking discovery of the first fully charmed tetraquark state $X(6900)$ in the $J/ψJ/ψ$ invariant mass distribution by the LHCb collaboration has inspired intensive theoretical studies. Various interpretations, such as molecular states, compact tetraquark states, and coupled-channel effects, have been proposed for these states. Of particular interest is the ongoing search for the triple-$J/ψ$ state--a fully-charmed hexaquark state. To deepen our understanding of the triple-$J/ψ$ state and to guide future experimental searches, we study the triple-$J/ψ$ system in this work employing the Gaussian expansion method and the $J/ψJ/ψ$ potential parameterized to yield a shallow bound state, as suggested in several theoretical works. Our results support a triple-$J/ψ$ bound state, even in cases where the attractive interaction between the two $J/ψ$ mesons is very weak. Moreover, our analysis implies the Efimov effect in the triple-$J/ψ$ system. In addition, we extend our investigation to the triple-$Υ(1S)$ system and obtain results similar to those for the triple-$J/ψ$ system.

hep-ph↗

arXiv2024

Unveiling the $a_0(1710)$ nature in the process $J/ψ\to {\bar{K}}^0K^+ρ^- $

We have investigated the process $J/ψ\to {\bar{K}}^0K^+ρ^-$ by taking into account the $S$-wave ${K^*\bar{K}^*}$, $ρω$, and $ρϕ$ final-state interactions, where the scalar meson $a_0(1710)$ is generated. In addition, we also take into account the contributions from the scalar $a_0(980)(\to \bar{K}^0K^+)$ and the intermediate resonances $K_1(1270)^{-}(\to {\bar{K}}^0ρ^-) $ and $K_1(1270)^{0}(\to K^+ρ^-)$. Our results show that, in the ${\bar{K}^0K^+}$ invariant mass distribution, a clear peak structure around 1.8~GeV appears, which could be associated with the scalar $a_0(1710)$, however, no significant structure of the $a_0(980)$ is observed. On the other hand, one can find clear peaks of the $K_1(1270)$ in the ${\bar{K}}^0ρ^-$ and $K^+ρ^-$ invariant mass distributions. The future precise measurement of this process by the BESIII and Belle II Collaborations and the planned Super Tau-Charm Facility (STCF) in the future could shed light on the nature of $a_0(1710)$.

hep-ph↗

arXiv2024

Identifying the two-pole structure of the $Λ(1405)$ using an SU(3) flavor filter

We propose a novel method to identify the two-pole structure of the $Λ(1405)$. The two poles owe their origin to different quark flavor irreducible representations in the meson-baryon coupled-channel interactions, thus they should be individually manifested in reactions that provide good flavor eigenstate sources. Hadronic decays of charmonia into $\barΛΣπ$ and $\barΛ(1520)Σπ$ are such reactions, and the flavor octet and singlet poles can be approximately singled out in these two decay modes. This SU(3) flavor filter works even considering the flavor symmetry breaking. With the huge charmonium data sets collected, it is therefore promising to solve the long-standing $Λ(1405)$ puzzle employing the proposed flavor filter.

hep-ph↗

arXiv2024

The $Ω(2012)$ as a hadronic molecule

Recently, a new excited baryon state, $Ω(2012)$, was observed in the invariant mass spectra of $K^-Ξ^0$ and $K^0_S Ξ^-$ by the Belle Collaboration. This state has a narrow width ($\sim 6$ MeV) compared to other baryon states with a similar mass. In this paper, we provide a mini-review on the $Ω(2012)$ state from the molecular perspective, where it appears to be a dynamically generated state with spin-parity $3/2^-$ from the coupled-channels interactions of the $\bar{K} Ξ(1530)$ and $ηΩ$ in $s$-wave and $\bar{K} Ξ$ in $d$-wave. Additionally, alternative explanations for the $Ω(2012)$ resonance are also discussed.

hep-ph↗

arXiv2024

Saturation of nuclear matter in the relativistic Brueckner Hatree-Fock approach with a leading order covariant chiral nuclear force

Nuclear saturation is a crucial feature in nuclear physics that plays a fundamental role in understanding various nuclear phenomena, ranging from properties of finite nuclei to those of neutron stars. However, a proper description of nuclear saturation is highly nontrivial in modern nonrelativistic~\textit{ab initio}~studies because of the elusive three-body forces. In this letter, we calculate the equation of state for nuclear matter in the relativistic Brueckner-Hartree-Fock (RBHF) framework with the leading order covariant chiral nuclear force. We show that a simultaneous description of the nucleon-nucleon scattering data and the saturation of the symmetric nuclear matter can be achieved. In this regard, the relativistic effects nicely explain the saturation of nuclear matter. As a result, the present study based on the covariant chiral nuclear force shows that in the RBHF framework, one can achieve saturation with a leading order covariant chiral nuclear force with only two-body forces, in contrast to the vast majorities of studies in the non-relativistic framework, where the next-to-next-to-leading order two-body and three-body chiral forces are needed. This study sets the foundation for studying nuclear saturation with the covariant chiral force in the RBHF framework, which allows for a systematic understanding of one of the key features of nuclear physics more microscopically.

nucl-th↗

arXiv2024

Analysis of $B_s^0 \to X(3872) [ψ(2S)] π^+π^- (K^+ K^-)$ decays

We have phenomenologically investigated the decays $B_s^0 \to X(3872) π^+π^- (K^+ K^-)$ and $B_s^0 \to ψ(2S) π^+ π^- (K^+K^-)$. In our analysis, the scalar meson $f_0(980)$ is formed through the final state interactions of coupled channels $ππ$ and $K\bar{K}$. Our findings indicate that the $π^+π^-$ invariant mass distribution of the $B_s^0 \to ψ(2S)π^+π^-$ decay can be accurately reproduced. Furthermore, we have explored the $π^+π^- (K^+ K^-)$ invariant mass distribution of the $B_s^0 \to X(3872) π^+π^- (K^+ K^-)$ decay, accounting for the different production mechanisms between $X(3872)$ and $ψ(2S)$, up to a global factor. It is found that the production rates for $X(3872)$ and $ψ(2S)$ are much different, which indicates that the structure of $X(3872)$ is more complicated than the $ψ(2S)$, which is a conventional $c\bar{c}$ state. Additionally, we have considered the contributions from $f_0(1500)$ to $π^+π^-$ and the $ϕ$ meson to $K^+ K^-$ in our analysis. Utilizing the model parameters, we have calculated the branching fraction of $B_s^0 \to X(3872) K^+ K^-$, and anticipate that the findings of our study can be experimentally tested in the future.

hep-ph↗

arXiv2024

Productions of $D^*_{s0}(2317)$ and $D_{s1}(2460)$ in $B_{(s)}$ and $Λ_b(Ξ_b)$ decays

Recent studies show that $D_{s0}^{\ast}(2317)$ and $D_{s1}(2460)$ contain large molecular components. In this work, we employ the naive factorization approach to calculate the production rates of $D_{s0}^{\ast}(2317)$ and $D_{s1}(2460)$ as hadronic molecules in $B_{(s)}$ and $Λ_b(Ξ_b)$ decays, where their decay constants are estimated in the effective Lagrangian approach. With the so-obtained decay constants $f_{D_{s0}^{\ast}(2317)}$ and $f_{D_{s1}(2460)}$, we calculate the branching fractions of the $b$-meson decays $B_{(s)}\to \bar{D}_{(s)}^{(*)}D_{s0}^*$ and $B_{(s)}\to \bar{D}_{(s)}^{(*)}D_{s1}$ and the $b$-baryon decays $Λ_b(Ξ_{b}) \to Λ_c(Ξ_{c}) D_{s0}^*$ and $Λ_b(Ξ_{b}) \to Λ_c(Ξ_c) D_{s1}$. Our results show that the production rates of $D_{s0}^{\ast}(2317)$ and $D_{s1}(2460)$ in the $B_s$, $Λ_b$ and $Ξ_b$ decays are rather large that future experiments could observe them. In particular, we demonstrate that one can extract the decay constants of hadronic molecules via the triangle mechanism because of the equivalence of the triangle mechanism to the tree diagram established in calculating the decays $B \to \bar{D}^{(*)}D_{s0}^{\ast}(2317)$ and $B \to \bar{D}^{(*)}D_{s1}(2460)$.

hep-ph↗

arXiv2024

Productions of $X(3872)$, $Z_c(3900)$, $X_2(4013)$, and $Z_c(4020)$ in $B_{(s)}$ decays offer strong clues on their molecular nature

The exotic states $X(3872)$ and $Z_c(3900)$ have long been conjectured as isoscalar and isovector $\bar{D}^*D$ molecules. In this work, we first propose the triangle diagram mechanism to investigate their productions in $B$ decays as well as their heavy quark spin symmetry partners, $X_2(4013)$ and $Z_c(4020)$. We show that the large isospin breaking of the ratio $\mathcal{B}[B^+ \to X(3872) K^+]/\mathcal{B}[B^0 \to X(3872) K^0] $ can be attributed to the isospin breaking of the neutral and charged $\bar{D}^*D$ components in their wave functions. For the same reason, the branching fractions of $Z_c(3900)$ in $B$ decays are smaller than the corresponding ones of $X(3872)$ by at least one order of magnitude, which naturally explains its non-observation. A hierarchy for the production fractions of $X(3872)$, $Z_c(3900)$, $X_2(4013)$, and $Z_c(4020)$ in $B$ decays, consistent with all existing data, is predicted. Furthermore, with the factorization ansatz we extract the decay constants of $X(3872)$, $Z_c(3900)$, and $Z_c(4020)$ as $\bar{D}^*D^{(*)}$ molecules via the $B$ decays, and then calculate their branching fractions in the relevant $B_{(s)}$ decays, which turn out to agree with all existing experimental data. The mechanism we proposed is useful to elucidate the internal structure of the many exotic hadrons discovered so far and to extract the decay constants of hadronic molecules,which can be used to predict their production in related processes.

hep-ph↗

arXiv2023

Dynamical origin of universal two-pole structures and their light quark mass evolution

Two-pole structures refer to the fact that two dynamically generated states are located close to each other between two coupled channels and have a mass difference smaller than the sum of their widths. Thus, the two poles overlap in the invariant mass distribution of their decay products, creating the impression that only one state exists. This phenomenon was first noticed for the $Λ(1405)$ and the $K_1(1270)$, and then for several other states. This report explicitly shows how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between a heavy matter particle and a pseudo-Nambu-Goldstone boson. Furthermore, we predict similar two-pole structures in other systems dictated by chiral symmetry, such as the isospin $1/2$ $\bar{K}Σ_c-πΞ'_c$ coupled channel, awaiting experimental discoveries.

hep-ph↗

arXiv2023

Systematic studies of $DDKK$ and $D\bar{D}K\bar{K}$ four-hadron molecules

Assuming that $D_{s0}^{*}(2317)$ is a $DK$ molecular state with a binding energy of 45 MeV, we investigate the existence of four-hadron molecules, $DDKK$ and $D\Bar{D}K\Bar{K}$, with the Gaussian expansion method. Their binding energies are $138\sim155$ MeV and $123\sim163$ MeV below the mass thresholds of $DDKK$ and $D\Bar{D}K\Bar{K}$. The $D\Bar{D}K\Bar{K}$ state has a decay width of $36\sim54$ MeV due to the complex $K\Bar{K}$ interaction. Further theoretical studies of and experimental searches for such four-hadron molecules can help deepen the understanding of the nonperturbative strong interaction in a nontrivial way.

hep-ph↗

arXiv2023

Correlation function for the $a_0(980)$

We have conducted a model independent analysis of the $K^+ \bar{K}^0$ pair correlation function obtained from ultra high energy $pp$ collisions, with the aim of extracting the information encoded in it related to the $K\bar{K}$ interaction and the coupled channel $π^+ η$. With the present large errors at small relative $K^+\bar{K}^0$ momenta, we find that the information obtained about the scattering matrix suffers from large uncertainties. Even then, we are able to show that the data imply the existence of the $a_0$ resonance, $a_0(980)$, showing as a strong cusp close to the $K\bar{K}$ threshold. We also mention that the measurement of the $π^+ η$ correlation function will be essential in order to constrain more the information on $K\bar{K}$ dynamics that can be obtained from correlation functions.

hep-ph↗

arXiv2023

Stripping triangle loops: Discussion of $D_s^+\to ρ^+η\to π^+π^0η$ in $a_0(980)$ production

We address a general problem in the evaluation of triangle loops stemming from the consideration of the range of the interaction involved in some of the vertices, as well as the energy dependence of the width of some unstable particles in the loop. We find sizeable corrections from both effects. We apply that to a loop relevant to the $D_s^+ \to π^+ π^0 η$ decay, and find reductions of about a factor of $4$ in the mass distribution of invariant mass of the $πη$ in the region of the $a_0(980)$. The method used is based on the explicit analytical evaluation of the $q^0$ integration in the $d^4q$ loop integration, using Cauchy's residues method, which at the same time offers an insight on the convergence of the integrals and the effect of form factors and cutoffs.

hep-ph↗

arXiv2023

Theoretical study of scalar meson $a_0(1710)$ in the $η_c \to {\bar{K}}^0K^+π^- $ reaction

We investigate the process $η_c \to {\bar{K}}^0K^+π^-$ by taking into account the $S$-wave ${K^*\bar{K}^*}$ and $ρω$ interactions within the unitary coupled-channel approach, where the scalar meson $a_0(1710)$ is dynamically generated. In addition, the contributions from the intermediate resonances $K_0^*(1430)^{-}\to {\bar{K}}^0π^- $ and $K_0^*(1430)^{0}\to K^+π^-$ are also considered. We find a significant dip structure around 1.8~GeV, associated to the $a_0(1710)$, in the ${\bar{K}^0K^+}$ invariant mass distribution, and the clear peaks of the $K_0^*(1430)$ in the ${\bar{K}}^0π^-$ and $K^+π^-$ invariant mass distributions, consistent with the {\it BABAR} measurements. We further estimate the branching fractions $\mathcal{B}(η_c \to \bar{K}^{*0}K^{\ast+}π^-)= 5.5\times10^{-3}$ and $\mathcal{B}(η_c \to ωρ^+π^-)= 7.9\times10^{-3}$. Our predictions can be tested by the BESIII and BelleII experiments in the future.

hep-ph↗

arXiv2023

Two-pole structures as a universal phenomenon dictated by coupled-channel chiral dynamics

In the past two decades, one of the most puzzling phenomena discovered in hadron physics is that a nominal hadronic state can actually correspond to two poles on the complex energy plane. This phenomenon was first noticed for the $Λ(1405)$, then for $K_1(1270)$, and to a lesser extent for $D_0^*(2300)$. In this Letter, we show explicitly how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between heavy matter particles and pseudo Nambu-Goldstone bosons. In particular, the fact that two poles appear in between the two dominant coupled channels can be attributed to the particular form of the leading order chiral potentials of the Weinberg-Tomozawa form. Their lineshapes overlap with each other because the degeneracy of the two coupled channels is only broken by explicit chiral symmetry breaking of higher order. We predict that for light-quark~(pion) masses heavier than their physical values (e.g., about 200 MeV in the $Λ(1405)$ case studied), the lower pole becomes a virtual state, which can be easily verified by future lattice QCD simulations. Furthermore, we anticipate similar two-pole structures in other systems, such as the isopin $1/2$ $\bar{K}Σ_c-πΞ'_c$ coupled channel, which await for experimental discoveries.

hep-ph↗