arXiv subjects

Li-Sheng Geng

Publications and source records attributed to Li-Sheng Geng.

At least 109 records · Page 6Linked to original sources

arXiv2022

Further understanding the nature of $a_0(1710)$ in the $D^+_s \to π^0 K^+ K^0_S$ decay

Based on our previous work about the role of $a_0(1710)$ in the $D_s^+\toπ^+K_S^0K_S^0$ decay [Phy. Rev. D 105, 116010 (2022)], we perform a further theoretical study of $a_0(1710)^+$ in the process $D^+_s \to π^0 a_0(1710)^+ \to π^0 K^+ K^0_S$. In addition to $a_0(1710)$, the contributions of $K^*$ and $a_0(980)$ are also taken into account. Firstly, we consider the contributions from the tree diagrams of $K^{*+} \to K^+π^0$ and $\bar{K}^{*0} \to π^0 \bar{K}^0$. Secondly, we describe the final state interaction of $K\bar{K}$ in the chiral unitary approach to study the contribution of $a_0(980)$, while the $a_0(1710)$ state is dynamically generated from the $K^*\bar{K}^*$ interaction, and then decays into $K^+\bar{K}^0$. Since the final $K^+ K_S^0$ state is in pure isospin $I=1$, the $D_s^+\toπ^0K^+K_s^0$ decay is an ideal process to study the $a_0(1710)^+$ and $a_0(980)^+$ resonances. Based on our theoretical calculations, it is found that the recent experimental measurements on the $K^+K^0_S$, $π^0K^+$, and $π^0 K_S^0$ invariant mass distributions can be well reproduced, which supports the molecular $K^*\bar{K}^*$ nature of the scalar $a_0(1710)$ resonance.

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arXiv2022

Hadronic molecules composed of a doubly charmed tetraquark state and a charmed meson

The three pentaquark states, $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, discovered by the LHCb Collaboration in 2019, can be arranged into a complete heavy quark spin symmetry multiplet of hadronic molecules of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$. In the heavy quark mass limit, the $Σ_{c}^{(\ast)}$ baryons can be related to the doubly charmed tetraquark states of isospin 1, i.e., $T_{\bar{c}\bar{c}}^{(\ast)}$( $T_{\bar{c}\bar{c}}^{0}$, $T_{\bar{c}\bar{c}}^{1}$, $T_{\bar{c}\bar{c}}^{2}$), via heavy antiquark diquark symmetry, which dictates that the $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ interactions are the same as the $\bar{D}^{(\ast)}T_{\bar{c}\bar{c}}^{(\ast)}$ interactions up to { heavy antiquark diquark symmetry} breakings. In this work, we employ the contact-range effective field theory to systematically study the $\bar{D}^{(\ast)}T_{\bar{c}\bar{c}}^{(\ast)}$ systems, and we show the existence of a complete heavy quark spin symmetry multiplet of hadronic molecules composed of a doubly charmed tetraquark state and a charmed meson. These are a new kind of hadronic molecules and, if discovered, can lead to a better understanding of the many exotic hadrons discovered so far. In addition, we summarise the triply charmed hexaquark states formed by different combinations of hadrons. In particular, we show that $\barΩ_{ccc}{p}$ system can bind by the Coulomb force, which is analogous to a hydrogenlike atom.

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arXiv2022

Nuclear binding energies in artificial neural networks

The binding energy (BE) or mass is one of the most fundamental properties of an atomic nucleus. Precise binding energies are vital inputs for many nuclear physics and nuclear astrophysics studies. However, due to the complexity of atomic nuclei and of the non-perturbative strong interaction, up to now, no conventional physical model can describe nuclear binding energies with a precision below 0.1 MeV, the accuracy needed by nuclear astrophysical studies. In this work, artificial neural networks (ANNs), the so called ``universal approximators", are used to calculate nuclear binding energies. We show that the ANN can describe all the nuclei in AME2020 with a root-mean-square deviation (RMSD) around 0.2 MeV, which is better than the best macroscopic-microscopic models, such as FRDM and WS4. The success of the ANN is mainly due to the proper and essential input features we identify, which contain the most relevant physical information, i.e., shell, paring, and isospin-asymmetry effects. We show that the well-trained ANN has excellent extrapolation ability and can predict binding energies for those nuclei so far inaccessible experimentally. In particular, we highlight the important role played by ``feature engineering'' for physical systems where data are relatively scarce, such as nuclear binding energies.

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arXiv2022

Strangeness $S = -2$ baryon-baryon interactions and femtoscopic correlation functions in covariant chiral effective field theory

We study the baryon-baryon interactions with strangeness $S = -2$ and corresponding momentum correlation functions in leading order covariant chiral effective field theory. The relevant low energy constants are determined by fitting to the latest HAL QCD simulations, taking into account all the coupled channels. Extrapolating the so-obtained strong interactions to the physical point and considering both quantum statistical effects and the Coulomb interaction, we calculate the $ΛΛ$ and $Ξ^-p$ correlation functions with a spherical Gaussian source and compare them with the recent experimental data. We find remarkable agreement between our predictions and the experimental measurements by using the source radius determined in proton-proton correlations, which demonstrates the consistency between theory, experiment, and lattice QCD simulations. Moreover, we predict the $Σ^+Σ^+$, $Σ^+Λ$, and $Σ^+Σ^-$ interactions and corresponding momentum correlation functions. We further investigate the influence of the source shape and size of the hadron pair on the correlation functions studied and show that the current data are not very sensitive to the source shape. Future experimental measurement of the predicted momentum correlation functions will provide a non-trivial test of not only SU(3) flavor symmetry and its breaking but also the baryon-baryon interactions derived in covariant chiral effective field theory.

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arXiv2022

$Z_{cs}(3985)$ in next-to-leading-order chiral effective field theory -- the first truncation uncertainty analysis

We revisit the $D_s^-D^{*0}$/$D_s^{*-}D^0$ interaction and the $Z_{cs}(3985)$ state in chiral effective field theory(EFT) up to the next-to-leading order. We examine the relative importance of the leading-order contact, one-eta exchange, next-to-leading-order contact, and two-kaon-exchange contributions. We show that the leading-order and next-to-leading-order contact contributions play the most important role such that the $Z_{cs}(3985)$ state qualifies as a $D_s^-D^{*0}$/$D_s^{*-}D^0$ resonance. On the other hand, the weak one-eta-exchange and weakly energy-dependent two-kaon-exchange contributions are less important in dynamically generating the $Z_{cs}(3985)$ state, indicating that chiral EFT is less predictive in the present situation. Furthermore, we apply the Bayesian method to estimate chiral truncation uncertainties and find that they are of similar magnitude as their statistical counterparts. Our study shows that if $Z_c(3900)$ exists, then SU(3)-flavor symmetry also predicts $Z_{cs}(3985)$ with a certain robustness, i.e., both can be accommodated in the chiral EFT with dominant contact contributions.

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arXiv2022

Multi-hadron molecules: status and prospect

Starting from 2003, the discovery of a large amount of the so-called exotic hadronic states, i.e., the $XYZ$ states, the pentaquark states as well as the tetraquark states, have not only revived studies of hadron spectroscopy, but also hinted at the existence of new multi-hadron states made of hadrons other than nucleons and hyperons. We briefly comment on some of the latest studies on multi-hadron molecules in the light and heavy flavor sectors and highlight what should be done in the future.

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arXiv2022

Nucleon-nucleon interaction in the $^3S_1$-$^3D_1$ coupled channel for a pion mass of 469 MeV

In this work, we apply the relativistic chiral nuclear force to describe the state-of-the-art lattice simulations of the nucleon-nucleon scattering amplitude. In particular, we focus on the $^3S_1$-$^3D_1$ coupled channel for a pion mass of 469 MeV. We show that at leading order the relativistic chiral nuclear force can only describe $δ_{3S1}$ and $\varepsilon_1$ up to $T_\mathrm{lab.}\approx10$ MeV, while at the next-to-leading order it can do much better up to $T_\mathrm{lab}=200$ MeV. However, at the next-to-next-to-leading order, the description deteriorates, which can be attributed to the fact that the pion-mass dependence of the pion-nucleon couplings $c_{1,2,3,4}$ may not be negligible. Furthermore, all the studies consistently yield negative $δ_{3D1}$, contrary to the lattice QCD results which are positive but consistent with zero. The present study is relevant to a better understanding of the lattice QCD nucleon-nucleon force and more general baryon-baryon interactions.

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arXiv2022

Double-charm heptaquark states composed of two charmed mesons and one nucleon

Inspired by the experimental discoveries of $T_{cc}$, $Σ_c(2800)$, and $Λ_c(2940)$ and the theoretical picture where they are $DD^*$, $DN$, and $D^*N$ molecular candidates, we investigate the double charm heptaquark system of $DD^*N$. We employ the one-boson-exchange model to deduce the pairwise $D$-$D^*$, $D$-$N$, and $D^*$-$N$ potentials and then study the $DD^*N$ system with the Gaussian expansion method. We find two good hadronic molecular candidates with $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ and $\frac{1}{2}(\frac{3}{2}^-)$ $DD^*N$ with only $s$-wave pairwise interactions. The conclusion remains unchanged even taking into account the $S$-$D$ mixing and coupled channel effects. In addition to providing the binding energies, we also calculate the root-mean-square radii of the $DD^*N$ system, which further support the molecular nature of the predicted states. They can be searched for at the upcoming LHC run 3 and run 4.

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arXiv2022

Nuclear charge radii in Bayesian neural networks revisited

In this work, a refined Bayesian neural network (BNN) based approach with six inputs including the proton number, mass number, and engineered features associated with the pairing effect, shell effect, isospin effect, and ``abnormal" shape staggering effect of $^{181,183,185}$Hg, is proposed to accurately describe nuclear charge radii. The new approach is able to well describe the charge radii of atomic nuclei with $A\ge40$ and $Z\ge20$. The standard root-mean-square (rms) deviation is $0.014$ fm for both the training and validation data. In particular, the predicted charge radii of proton-rich and neutron-rich calcium isotopes are found in good agreement with data. We further demonstrate the reliability of the BNN approach by investigating the variations of the rms deviation with extrapolation distances, mass numbers, and isospin asymmetries.

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arXiv2022

Weak radiative hyperon decays in covariant baryon chiral perturbation theory

Weak radiative hyperon decays, important to test the strong interaction and relevant in searches for beyond the standard model physics, have remained puzzling both experimentally and theoretically for a long time. The recently updated branching fraction and first measurement of the asymmetry parameter of $Λ\to nγ$ by the BESIII Collaboration further exacerbate the issue, as none of the existing predictions can describe the data. We show in this letter that the covariant baryon chiral perturbation theory, with constraints from the latest measurements of hyperon non-leptonic decays, can well describe the BESIII data. The predicted branching fraction and asymmetry parameter for $Ξ^-\toΣ^-γ$ are also in agreement with the experimental data. We note that a more precise measurement of the asymmetry parameter, which is related with that of $Σ^+\to pγ$, is crucial to test Hara's theorem. We further predict the branching fraction and asymmetry parameter of $Σ^0\to nγ$, whose future measurement can serve as a highly nontrivial check on our understanding of weak radiative hyperon decay and on the covariant baryon chiral perturbation theory.

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arXiv2022

Theoretical study of the process $D^+_s \to π^+ K^0_S K^0_S$ and the isovector partner of $f_0(1710)$

We present a theoretical study of $a_0(1710)$, the isovector partner of $f_0(1710)$, in the process $D^+_s \to π^+ K^0_SK^0_S$. The weak interaction part proceeds through the charm quark decay process: $c(\bar{s}) \to (s + \bar{d} + u)(\bar{s})$, while the hadronization part takes place in two mechanisms, differing in how the quarks from the weak decay combines into $πK^*$ with a quark-antiquark pair $q\bar{q}$ with the vacuum quantum numbers. In addition to the contribution from the tree diagram of the $K^{*+} \to π^+ K^0_S$, we have also considered the $K^*\bar{K}^*$ final-state interactions within the chiral unitary approach to generate the intermediate state $a_0(1710)$, then it decays into the final states $K^0_SK^0_S$. We find that the recent experimental measurements on the $K^0_SK^0_S$ and $π^+K^0_S$ invariant mass distributions can be well reproduced, and the proposed mechanism can provide valuable information on the nature of scalar $f_0(1710)$ and its isovector partner $a_0(1710)$.

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arXiv2022

Roles of $a_0(980)$, $Λ(1670)$, and $Σ(1385)$ in the $Λ_c^+ \to ηΛπ^+$ decay

Recently, the Belle Collaboration has measured the $Λ_c^+ \to ηΛπ^+$ decay and reported the $ηΛ$ and $Λπ^+ $ invariant mass distributions, which show the clear signals of the resonances $Λ(1670)$ and $Σ(1385)$, respectively. Based on our previous works [Eur. Phys. J. C 76 (2016) 496 and Phys. Rev. D 95 (2017) 074024], we re-analyze this process by considering the $S$-wave $ηΛ$ and $ηπ^+$ final state interactions within the chiral unitary approach, which dynamically generate the $Λ(1670)$ and $a_0(980)$, respectively. Our results are in good agreement with the Belle measurements, which supports the molecular nature of the $Λ(1670)$ and $a_0(980)$. In addition, the $ηπ^+$ invariant mass distributions are also computed and a cusp structure of $a_0(980)$ is cleary shown around the $K\bar{K}$ mass threshold.

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arXiv2022

Triple-charm molecular states composed of $D^D^D$ and $D^D^D^*$

Inspired by the newly observed $T_{cc}^+$ state, we systematically investigate the $S$-wave triple-charm molecular states composed of $D^*D^*D$ and $D^*D^*D^*$. We employ the one-boson-exchange model to derive the interactions between $D(D^*)$ and $D^*$ and solve the three-body Schrödinger equations with the Gaussian expansion method. The $S$-$D$ mixing and coupled channel effects are carefully assessed in our study. Our results show that the $I(J^P)=\frac{1}{2}(0^-,1^-,2^-)$ $D^*D^*D$ and $I(J^P)=\frac{1}{2}(0^-,1^-,2^-,3^-)$ $D^*D^*D^*$ systems could form bound states, which can be viewed as three-body hadronic molecules. We present not only the binding energies of the three-body bound states, but also the root-mean-square radii of $D $-$D^*$ and $D^*$-$D^*$, which further corroborate the molecular nature of these states. These predictions could be tested in the future at LHC or HL-LHC.

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arXiv2022

Three-body molecules $\bar{D}\bar{D}^{\ast}Σ_{c}$- understanding the nature of $T_{cc}$, $P_{c}(4312)$, $P_{c}(4440)$ and $P_{c}(4457)$

The nature of the three pentaquark states, $P_{c}(4312)$, $P_{c}(4440)$ and $P_{c}(4457)$, discovered by the LHCb Collaboration in 2019, is still under debate, although the $\bar{D}^{(\ast)}Σ_{c}$ molecular interpretation seems to be the most popular. In this work, by adding a $\bar{D}$ meson into the $\bar{D}^{\ast}Σ_{c}$ pair, we investigate the mass and decay width of the three-body molecules $\bar{D}\bar{D}^{\ast}Σ_{c}$ and explore the correlation between the existence of the $\bar{D}\bar{D}^{\ast}Σ_{c}$ molecules with the existence of $\bar{D}^{(\ast)}Σ_{c}$ and $\bar{D}^{\ast}\bar{D}$ two-body molecules. The latter can be identified with the doubly charmed tetraquark state $T_{cc}$ recently discovered by the LHCb Collaboration. Based on the molecular nature of $P_{c}(4312)$, $P_{c}(4440)$, $P_{c}(4457)$, and $T_{cc}$, our results indicate that there exist two three-body bound states of $\bar{D}\bar{D}^{\ast}Σ_{c}$ with $I(J^{P})=1(1/2^{+})$ and $I(J^{P})=1(3/2^{+})$, and binding energies $37.24$ MeV and $29.63$ MeV below the $\bar{D}\bar{D}^{\ast}Σ_{c}$ mass threshold. In addition, we find that the mass splitting of these two three-body molecules are correlated to the mass splitting of $P_{c}(4440)$ and $P_{c}(4457)$, which offers a non-trivial way to reveal the molecular nature of these states. The partial widths of two $\bar{D}\bar{D}^{\ast}Σ_{c}$ molecules decaying into $J/ψp \bar{D}$ and $J/ψp \bar{D}^{\ast}$ are found to be several MeV. We recommend the experimental searches for the $\bar{D}\bar{D}^{\ast}Σ_{c}$ molecules in the $J/ψp \bar{D}$ and $J/ψp \bar{D}^{\ast}$ invariant mass distributions.

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arXiv2022

Kaon, Nucleon and $Δ^*$ Resonances with Hidden Charm

In this presentation we discuss the generation of hadrons with an exotic quark content and hidden charm emerging from three-body interactions. To be more specific, we have studied the $KD\bar{D}^*/K\bar D D^*$ and $ND\bar{D}^*/N\bar{D}D^*$ systems and predicted states generated from the respective three-body dynamics. In the case of the $KD\bar{D}^*/K\bar D D^*$ system we predict the formation of a meson state with mass around $4307$ MeV and quantum numbers $I(J^P) = 1/2(1^-)$, $K^*(4307)$, and from the study of the $ND\bar{D}^*/N\bar{D}D^*$ system we found $N^*$ states with masses in the range $4400\sim 4600$ MeV, width of $2\sim 20$ MeV and positive parity.

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arXiv2022

An accurate relativistic chiral nucleon-nucleon interaction up to the next-to-next-to-leading order

We report on the construction of an accurate relativistic chiral nucleon-nucleon interaction up to the next-to-next-to-leading (NNLO) order. We compare the so-obtained neutron-proton phaseshifts with the next-to-next-to-next-to-leading order (N$^3$LO) nonrelativistic ones and we show that up to $T_\mathrm{lab.}=200$ MeV, the relativistic chiral nuclear force can describe the PWA93 phaseshifts and inelasticities as well as its N$^3$LO nonrelativistic counterparts. As a result, the relativistic chiral nuclear force can be readily used for relativistic ab initio nuclear structure, reaction, as well astrophysical studies.

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arXiv2022

Accurate relativistic chiral nucleon-nucleon interaction up to NNLO

We construct a relativistic chiral nucleon-nucleon interaction up to the next-to-next-to-leading order in covariant baryon chiral perturbation theory. We show that a good description of the $np$ phase shifts up to $T_\mathrm{lab}=200$ MeV and even higher can be achieved with a $\tildeχ^2/\mathrm{d.o.f.}$ less than 1. Both the next-to-leading order results and the next-to-next-to-leading order results describe the phase shifts equally well up to $T_\mathrm{lab}=200$ MeV, but for higher energies, the latter behaves better, showing satisfactory convergence. The relativistic chiral potential provides the most essential inputs for relativistic ab initio studies of nuclear structure and reactions, which has been in need for almost two decades.

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arXiv2022

Test of the hyperon-nucleon interaction within leading order covariant chiral effective field theory

Motivated by the recent experimental measurements of differential cross sections of the $Σ^{-}p$ elastic scattering in the momentum range of $470$ to $850$ MeV$/c$ by the J-PARC E$40$ experiment, we extend our previous studies of $S=-1$ hyperon-nucleon interactions to relatively higher energies up to $900$ MeV$/c$ for both the coupled-channel $Λp\rightarrow(Λp, Σ^{+}n, Σ^{0}p)$, $Σ^{-}p\rightarrow(Λn, Σ^{0}n, Σ^{-}p)$ and single-channel $Σ^{+}p\rightarrowΣ^{+}p$ reactions. We show that although the leading order covariant chiral effective field theory is only constrained by the low energy data, it can describe the high energy data reasonably well, in particular, the J-PARC E40 differential cross sections. The predicted cusp structure close to the $ΣN$ threshold in the $Λp\to Λp$ reaction agrees with the latest ALICE observation as well as with the results of the next-to-leading order heavy baryon chiral effective theory. On the other hand, the comparison with the latest CLAS data on the $Λp$ cross sections between 0.9 and 2.0 GeV$/c$ clearly indicates the need of higher order chiral potentials for such high momenta. This is also the case for the latest J-PARC data on the $Σp \rightarrow Λn$ differential cross sections. Nevertheless, even for these cases, the predictions are in qualitative agreement with the data, albeit with large uncertainties, implying that the predicted total and differential cross sections are of relevance for ongoing and planned experiments.

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