arXiv subjects

Li-Sheng Geng

Publications and source records attributed to Li-Sheng Geng.

At least 55 records · Page 3Linked to original sources

arXiv2025

Flavor Physics at the CEPC: a General Perspective

We discuss the landscape of flavor physics at the Circular Electron-Positron Collider (CEPC), based on the nominal luminosity outlined in its Technical Design Report. The CEPC is designed to operate in multiple modes to address a variety of tasks. At the $Z$ pole, the expected production of 4 Tera $Z$ bosons will provide unique and highly precise measurements of $Z$ boson couplings, while the substantial number of boosted heavy-flavored quarks and leptons produced in clean $Z$ decays will facilitate investigations into their flavor physics with unprecedented precision. We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models. Our studies indicate that, with its highlighted advantages and anticipated excellent detector performance, the CEPC can explore beauty and $τ$ physics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments, potentially enabling the detection of new physics at energy scales of 10 TeV and above. This potential also extends to the observation of yet-to-be-discovered rare and exotic processes, as well as testing fundamental principles such as lepton flavor universality, lepton and baryon number conservation, etc., making the CEPC a vibrant platform for flavor physics research. The $WW$ threshold scan, Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard, especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements, and Flavor-Changing-Neutral-Current physics of Higgs boson and top quarks. We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals.

hep-ex↗

arXiv2025

Implication of the existence of $J^{PC}=0^{--}$ $\bar{D}_sDK$ bound state on nature of $D_{s0}^*(2317)$ and new configuration of exotic state

The discovery of numerous new hadrons over the past two decades has provided unprecedented opportunities to understand the non-perturbative QCD and hadron structure. Hadronic molecule picture plays an important role in explaining these new hadrons and enriching the configurations of exotic hadronic states. In this letter, using the model-independent $DK$ potential extracted from the relevant experimental data, a $J^{PC}=0^{--}$ $\bar{D}_sDK$ three-body hadronic molecule is predicted with a mass of $4310^{+14}_{-24}$ MeV. This state shows decoupling to conventional $c\bar{c}$ charmonia or the $\bar{D}_s D_{s0}^*(2317)$ two-body molecular state. It can be regarded as a compelling three-body hadronic molecular candidate. We further demonstrate that the $B^+ \to {D}^{*\pm}D^\mp K^+$ decays could be promising channels for searching for the predicted state in future high-luminosity LHCb runs.

hep-ph↗

arXiv2025

From bare two-nucleon interaction to nuclear matter and finite nuclei in a relativistic framework

Understanding nuclear forces, infinite nuclear matter, and finite nuclei within a unified framework has remained a central challenge in nuclear physics for decades. While most \textit{ab initio} studies employ nonrelativistic Schrödinger-equation frameworks, this work offers a relativistic perspective. Using a leading-order (LO) relativistic chiral interaction, we describe two-nucleon scattering via the Thompson equation, symmetric nuclear matter, and medium-mass nuclei (Ca, Ni, Zr, Sn) via the relativistic Brueckner-Hartree-Fock theory. Systematic uncertainties from regulator cutoffs and interaction parameters are analyzed. The empirical saturation region of nuclear matter is reproduced, and the binding energies and charge radii of medium-mass nuclei agree reasonably well with experimental data, significantly improving the ``Coester line". These results highlight that the relativistic approach, employing a leading-order chiral force with only four low-energy constants and no three-nucleon forces, can capture the most important dynamics and offer a complementary pathway to address longstanding challenges in nuclear \textit{ab initio} studies.

nucl-th↗

arXiv2025

Nuclear and neutron matter in the relativistic Brueckner-Hartree-Fock theory with next-to-leading order covariant chiral nuclear force

The symmetric nuclear matter and pure neutron matter are investigated by the relativistic Brueckner-Hartree-Fock (RBHF) theory with the covariant chiral nuclear forces up to the next-to-leading order~(NLO). A fitting scheme to ensure the naturalness of the low-energy constants is proposed, which plays a crucial role in the proper description of nuclear matter. With a momentum cutoff $Λ=590$ MeV, the empirical saturation energy and density, as well as the incompressibility coefficient at the saturation density are reproduced well. The EoSs show less dependence on the momentum cutoff and become softer at densities above saturation density, in comparison with the previous leading order results. Given the good description for the saturation properties of nuclear matter, the present work encourages future studies of the finite nuclei in the framework of the RBHF theory with the NLO covariant chiral nuclear forces.

nucl-th↗

arXiv2025

Pole trajectories of the $Λ(1405)$ helps establish its dynamical nature

The $Λ(1405)$ has been one of the most controversial exotic baryons. If the $Λ(1405)$ possesses a two-pole molecular structure, these poles are expected to evolve differently towards the SU(3) limit. From an analysis of a recent LQCD simulation on the $πΣ-\bar{K}N$ scattering for $I=0$ and the study of the quark mass dependence of the octet baryon masses, we determine for the first time the trajectories of these poles towards the symmetric point over the $\mathrm{Tr}[M]=C$ trajectory accurately. At $m_π\simeq 200$ MeV, our results are consistent with the lattice simulations, and the extrapolations to the physical point, based on the NLO chiral Lagrangians, agree well with existing experimental analyses. We predict qualitatively similar trajectories at LO and up to NLO, consistent with the LO interaction's dominance. At the SU(3) symmetric point of this trajectory, both poles are on the physical sheet, and the lower pole is located at $E^{(1)}=1573(6)(6)$ MeV, becoming a SU(3) singlet, while the higher pole at $E^{(8a)}=1589(7)(5)$ MeV couples to the octet representation. Moreover, we make predictions in $I=1$ for the $Σ^*$ resonance. We find a resonance pole that evolves into a bound state around $m_π=415$ MeV in this sector. The results presented here are crucial to shed light on the molecular nature of exotic strange baryon resonances and can be tested in future LQCD simulations.

hep-ph↗

arXiv2025

Strong decays of $a_0$, $f_0$, $f_2$, and $K^*_2$ resonances as dynamically generated states of two vector mesons

The two-body strong decays of the $f_0(1500)$, $f_0(1710)$, $a_0(1710)$, $f_2(1270)$, $f_2'(1525)$, and $K_2^*(1430)$ resonances are investigated, assuming them as dynamically generated states of two vector mesons via $s$-wave interactions. The partial decay widths of all the possible two-body pseudoscalar meson-pseudoscalar meson final states are calculated considering the triangular diagrams. It is found that the ratios of branching fractions are similar to the previous results for most channels, which were obtained by using the real-axis method and considering the box diagrams. However, there are also differences. In addition, our focus is on the partial decay widths. More precise experimental measurements are needed to test the model calculations and determine the nature of these scalar and tensor mesons. It is anticipated that the BES\uppercase\expandafter{\romannumeral3}, Belle\uppercase\expandafter{\romannumeral2} and LHCb collaborations will conduct these measurements in the future.

hep-ph↗

arXiv2025

Two-pole structures in QCD -- a universal phenomenon governed by chiral dynamics

We illustrate how the two-pole structures of the $Λ(1405)$ emerge from the underlying universal chiral dynamics that describe the coupled-channel interactions between octet baryons and pseudo-Nambu-Goldstone bosons. Specifically, we attribute this phenomenon to the form of the leading-order chiral potential, which is of the Weinberg-Tomozawa type. We reveal how the underlying chiral dynamics can be exposed by examining the light-quark mass evolution of the two poles. The latest lattice QCD simulations have indeed found evidence for the existence of the two poles of $Λ(1405)$, in qualitative agreement with our predictions. We briefly mention a recent work in which lattice QCD simulations are studied more quantitatively, along with a proposal for how the SU(3) flavor content of the two poles of $Λ(1405)$ can be experimentally verified.

hep-ph↗

arXiv2025

In-medium $ΛN$ interactions with leading order covariant chiral hyperon/nucleon-nucleon forces

In-medium $ΛN$ interactions are crucial in hypernuclei and neutron star physics. In this work, we study the in-medium $ΛN$ interaction within the relativistic Brueckner-Hartree-Fock (RBHF) framework, employing the leading-order covariant chiral hyperon/nucleon-nucleon forces for the first time. We demonstrate that a consistent description of both the experimental cross-section data and the `empirical value' of the $Λ$ single-particle potential can be achieved. This contrasts with the majority of studies in the non-relativistic framework, where higher-order two-body chiral forces are typically required. This study offers a new perspective on the in-medium $ΛN$ interactions, urgently needed in relativistic \textit{ab initio} hypernuclear physics studies.

nucl-th↗

arXiv2025

Constraining the hidden-charm pentaquark predictions and discriminating the $P_c(4440)$ and $P_c(4457)$ spins through the effective range expansion

The Weinberg compositeness criterion dictates that a pure shallow bound state is characterized by a large scattering length $a_0\gg\mathcal{O}(1/β)$ and a positive effective range $r_0$ that naturally scales to the size of $\mathcal{O}(1/β)$, where $1/β$ signifies the interaction range. In constructing the contact-range effective field theory (EFT) up to the next-to-leading order to describe the pentaquarks $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ observed by the LHCb collaboration in 2019, we match the effective range $r_0$ at single-channel situation for these pentaquarks with the low-energy couplings within the EFT framework. Three different schemes are used to connect the couplings with the effective range. We find positive effective ranges $r_0$ of the natural size of $\mathcal{O}(1/β)$ for the spin configurations $J^P=\frac{3}{2}^-$ for $P_c(4440)$ and $J^P=\frac{1}{2}^-$ for $P_c(4457)$ within the molecular $\bar{D}^* Σ_c$ description. Additionally, predictions from the power counting for low-energy couplings or Wilsonian coefficients suggest that, under heavy quark spin symmetry, the broad $P_c(4380)$ resonance, discovered by the LHCb collaboration in 2015, when considered as part of the single-channel $\bar{D}^{(*)} Σ_c^{(*)}$ molecular system alongside $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$, has a mass of approximately $4376$ $\rm{MeV}$.

hep-ph↗

arXiv2025

Status and prospect of weak radiative hyperon decays

Weak radiative hyperon decays represent a rich interplay between weak interactions and the internal structure of baryons, offering profound insights into Quantum Chromodynamics and weak interactions. Recent experimental observations, particularly from BESIII, have revealed deviations from theoretical predictions. These deviations could signal new physics or the need for refined theoretical models incorporating intermediate resonance effects. This review discusses recent theoretical advancements and key experimental findings, focusing on recent measurements from BESIII and their implications for strong interactions and baryon structure.

hep-ph↗

arXiv2025

Effect of a repulsive three-body interaction on the $DD^{(*)}K$ molecule

The hadronic molecular picture of the observed exotic states has inspired numerous investigations into few-body systems. Recently, the lattice effective field theory studied the effect of a three-body interaction on the binding energy of the $DD^{*}K$ system, revealing an intriguing phenomenon in the binding energy. This work uses the Gaussian expansion method to explore the underlying physics. Our results show that as the repulsive three-body interaction strengthens, the spatial size of the $DD^{(*)}K$ bound state gradually increases. Further enhancement of the three-body interaction causes the $DD^{(*)}K$ three-body bound state to break into a $D^{(*)}K$ two-body bound state, accompanied by a distant $D$ meson. The identical nature of the two $D$ mesons leads to the fact that the $DDK$ system consistently resembles an isosceles triangle-shaped spatial configuration.

nucl-th↗

arXiv2025

Relativistic chiral nuclear forces: status and prospects

Understanding nuclear structure, reactions, and the properties of neutron stars from \textit{ab initio} calculations from the nucleon degrees of freedom has always been a primary goal of nuclear physics, in which the microscopic nuclear force serves as the fundamental input. So far, the Weinberg chiral nuclear force, first proposed by the Nobel laureate Weinberg, has become the \textit{de facto} standard input for nuclear \textit{ab initio} studies. However, compared to their non-relativistic counterparts, relativistic \textit{ab initio} calculations, which describe better nuclear observables, have only begun. The lack of modern relativistic nucleon-nucleon interactions is an important issue restricting their development. In this work, we briefly review the development and status of the Weinberg chiral nuclear force, as well as its limitations. We further present a concise introduction to the relativistic chiral nuclear force, show its description of the scattering phase shifts and observables such as differential cross sections, and demonstrate its unique features. Additionally, we show that the relativistic framework could be naturally extended to the antinucleon-nucleon interaction.

nucl-th↗

arXiv2024

Three ways to decipher the nature of exotic hadrons: multiplets, three-body hadronic molecules, and correlation functions

In the past two decades, a plethora of hadronic states beyond the conventional quark model of $q\bar{q}$ mesons and $qqq$ baryons have been observed experimentally, which motivated extensive studies to understand their nature and the non-perturbative strong interaction. Since most of these exotic states are near the mass thresholds of a pair of conventional hadrons, the prevailing picture is that they are primarily hadronic molecules. In principle, one can verify the molecular nature of these states by thoroughly comparing their masses, decay widths, and production rates in a particular picture with experimental data. However, this is difficult or impossible. First, quantum mechanics allows for the mixing of configurations allowed by symmetries and quantum numbers. Second, data are relatively scarce because of their small production rates and the many difficulties in the experimental measurements. As a result, other alternatives need to be explored. This review summarizes three such approaches that can help disentangle the nature of the many exotic hadrons discovered. In the first approach, based on the molecular interpretations for some exotic states, we study the likely existence of multiplets of hadronic molecules related by various symmetries, such as isospin symmetry, SU(3)-flavor symmetry, heavy quark spin/flavor symmetry, and heavy antiquark diquark symmetry. In the second approach, starting from some hadronic molecular candidates, one can derive the underlying hadron-hadron interactions. With these interactions, one can study related three-body systems and check whether three-body bound states/resonances exist. In the third approach, one can turn to the femtoscopy technique to derive the hadron-hadron interactions, hence inaccessible. This technique provided an unprecedented opportunity to understand the interactions between unstable hadrons.

hep-ph↗

arXiv2024

Studying the heavy quark spin symmetry multiplet of hadronic molecules $\bar{D}^{()}Σ_c^{()}$ in the three-body decays of $\bar{D}^{(*)}Λ_c π$

The decay behavior of an exotic state can be used to probe its internal structure. We note that the hidden-charm pentaquark states, $P_ψ^{N}(4312)$, $P_ψ^{N}(4440)$, and $P_ψ^{N}(4457)$, have only been observed in the $J/ψp$ channel. In this work, we employ the effective Lagrangian approach to systematically investigate the two-body and three-body decays of the heavy quark spin symmetry multiplet of hadronic molecules $\bar{D}^{(*)}Σ_c^{(*)}$. Our results show that the partial decay widths of the hidden-charm pentaquark molecules into $\bar{D}^{(*)}Λ_c π$ are sizable so that $\bar{D}^{(*)}Λ_c π$ are promising channels to search for them, which can help clarify their molecular nature.

hep-ph↗

arXiv2024

Reexamination of antinucleon-nucleon interactions in covariant chiral effective field theory

Motivated by the recent progress in developing high-precision relativistic chiral nucleon-nucleon interactions, we study the antinucleon-nucleon interaction in a hybrid approach where the real part of the potential is constructed in the leading-order covariant chiral effective field theory, and the imaginary part is described following the procedure adopted in the heavy baryon chiral effective field theory. The phase shifts and inelasticities with $J\leq 1$ are obtained and compared to those calculated in the next-to-leading order heavy baryon chiral effective field theory. For most partial waves, the descriptions of phase shifts and inelasticities in the hybrid approach are comparable to those in the next-to-leading order heavy baryon chiral effective field theory, confirming the relatively faster convergence of the relativistic approach observed in the nucleon-nucleon sector. In addition, we search for bound states/resonances near the $\bar{N}N$ threshold and find several structures that can be associated with those states recently observed by the BESIII Collaboration.

nucl-th↗

arXiv2024

Study of the exotic three-body $N D^* \bar{K}^*$ system

We have studied the $N D^* \bar{K}^*$ system in the framework of the Fixed Center Approximation to the Faddeev equations, taking the exotic $D^* \bar{K}^* $ system as the cluster and allowing the N to interact with the components of the cluster. Previous studies have determined the existence of three states of spin $0,1,2$ for the $D^* \bar{K}^* $ system, the one of spin $0$ associated to the $X_0(2900)$ state observed by the LHCb collaboration. From this perspective, we find five states with total spin $1/2,3/2,5/2$, with bindings from $10$ to $30$ MeV and widths below $60$ MeV, which could be well identified. We also discuss the decay channels of these states that should help in future experimental searches of these states.

hep-ph↗

arXiv2024

Review of the low-lying excited baryons $Σ^*(1/2^-)$

Strong empirical and phenomenological indications exist for large sea-quark admixtures in the low-lying excited baryons. Investigating the low-lying excited baryon $Σ^*(1/2^-)$ is important to determine the nature of the low-lying excited baryons. We review the experimental and theoretical progress on the studies of the $Σ^*(1/2^-)$. Although several candidates have received intensive discussions, such as $Σ(1620)$ and $Σ(1480)$, their existence needs further confirmation. Following the prediction of the unquenched quark models for the $Σ^*(1/2^-)$, many theoretical works suggested the existence of these states in various processes. Future experimental measurements could shed light on the existence of the low-lying excited $Σ^*(1/2^-)$ state.

hep-ph↗

arXiv2024

Theoretical study of $N(1535)$ and $Σ^*(1/2^-)$ in the Cabibbo-favored process $Λ_c^+ \to p \bar{K}^0η$

Motivated by the recent experimental measurements, we have investigated the Cabibbo-favored process $Λ_c^+ \to p \bar{K}^0η$, where the $N(1535)$ resonance is dynamically generated from the $S$-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach. The contributions from the intermediate $N(1650)$ and the predicted low-lying baryon $Σ^*(1/2^-)$ are also considered. In addition, a Breit-Wigner amplitude for the $N(1535)$ resonance is checked. By comparing with the measured $ηp$, $\bar{K}^0 η$, and $p \bar{K}^0$ invariant mass squared distributions, our results support the interpretation of $N(1535)$ as a dynamically generated state. Furthermore, we demonstrate that, with the contribution from $Σ^*(1/2^-)$ taken into account, the calculated invariant mass spectrum agrees with the Belle measurements. Future precise measurements of the $Λ_c^+\to p \bar{K}^0η$ process can further elucidate the existence of the low-lying baryon $Σ^*(1/2^-)$.

hep-ph↗