Meson-exchange Potentials Research Articles

Heavy exotic hadrons near thresholds: [formula omitted] and its partners

Recent accelerator experiments have reported unexpected states known as exotic hadrons, whose properties cannot be explained by the conventional picture. In 2022, the LHCb collaboration reported the doubly charmed tetraquark Tcc+ which is a genuine exotic states whose minimal quark content is ccūd̄. We consider the Tcc state as a DD∗ hadronic molecule. The one meson exchange potentials are employed as for the hadron interactions, and a bound state properties is investigated. Furthermore, the superflavor symmetry predicts a new pentaquark state D̄Ξcc from Tcc, which is obtained by replacing a D(∗) meson with a Ξcc(∗) baryon. We also study a possible existence of the D̄Ξcc bound state, and its properties.

Coupled-channel description of charmed heavy hadronic molecules within the meson-exchange model and its implication

Motivated by the first observation of the double-charm tetraquark Tcc+(3875) by the LHCb Collaboration, we investigate the nature of Tcc+ as an isoscalar DD* hadronic molecule in a meson-exchange potential model incorporated by the coupled-channel effects and three-body unitarity. The D0D0π+ invariant mass spectrum can be well-described and the Tcc+ pole structure can be precisely extracted. Under the hypothesis that the interactions between the heavy flavor hadrons can be saturated by the light meson-exchange potentials, the near-threshold dynamics of Tcc+ can shed light on the binding of its heavy-quark spin symmetry (HQSS) partner D*D* (I=0) and on the nature of other heavy hadronic molecule candidates such as X(3872) and Zc(3900) in the charmed-anticharmed systems. The latter states can be related to Tcc+ in the meson-exchange potential model with limited assumptions based on the SU(3) flavor symmetry relations. The combined analysis, on the one hand, indicates the HQSS breaking effects among those HQSS partners, and on the other hand, highlights the role played by the short and long-distance dynamics for the near threshold D(*)D(*) and D(*)D¯(*)+c.c. systems. Published by the American Physical Society 2024

The S- and P-Wave Low-Lying Baryons in the Chiral Quark Model

The $1S$, $2S$, $1P$ and $2P$ states of light baryons are investigated within the chiral quark model, paying particular attention to the well-known order reverse problem of $1P$ and $2S$ states. Besides a nonperturbative linear-screened confining interaction and a perturbative one-gluon exchange between quarks, we incorporate the Goldstone-boson exchanges taking into account not only the full octet of pseudoscalar mesons but also the scalar one. The scalar meson exchange potential simulates the higher order multi-pion exchange terms that appear in the chiral Lagrangian and its omission has been already admitted as a deficiency of the original model in describing, for instance, the $\rho-\omega$ splitting. The numerical approach to the three body bound state problem is the so-called Gau\ss ian expansion method, which is able to get a precision as good as Faddeev calculations. With a set of parameters fixed to different hadron and hadron-hadron observables, we find that the chiral potential could play an important role towards the issue on the mass order reverse problem. We extend our calculation to the $qqQ$ and $qQQ$ sectors (with $q$ representing a light $u$-, $d$-, or $s$-quark and $Q$ denoting the charm quark or the bottom one) in which many new states have been recently observed. Some tentative assignments are done attending to the agreement between theoretical and experimental masses; however, we admit that other sources of information are needed in order to make strong claims about the nature of these states.

Maximum Mass of Hybrid Stars in the Quark Bag Model

The effect of model parameters in the equation of state for quark matter on the magnitude of the maximum mass of hybrid stars is examined. Quark matter is described in terms of the extended MIT bag model including corrections for one-gluon exchange. For nucleon matter in the range of densities corresponding to the phase transition, a relativistic equation of state is used that is calculated with two particle correlations taken into account based on using the Bonn meson-exchange potential. The Maxwell construction is used to calculate the characteristics of the first order phase transition and it is shown that for a fixed value of the strong interaction constant $\alpha_s$, the baryon concentrations of the coexisting phases grow monotonically as the bag constant B increases. It is shown that for a fixed value of the strong interaction constant $\alpha_s$, the maximum mass of a hybrid star increases as the bag constant $B$ decreases. For a given value of the bag parameter $B$, the maximum mass rises as the strong interaction constant $\alpha_s$ increases. It is shown that the configurations of hybrid stars with maximum masses equal to or exceeding the mass of the currently known most massive pulsar are possible for values of the strong interaction constant $\alpha_s>0.6$ and sufficiently low values of the bag constant.

Hidden-charm pentaquarks as a meson-baryon molecule with coupled channels for D¯(*)Λc and D¯(*)Σc(*)

The recent observation of two hidden-charm pentaquark states by LHCb collaborations prompted us to investigate the exotic states close to the $\bar{D}\Lambda_{\rm c}$, $\bar{D}^{\ast}\Lambda_{\rm c}$, $\bar{D}\Sigma_{\rm c}$, $\bar{D}\Sigma^{\ast}_{\rm c}$, $\bar{D}^{\ast}\Sigma_{\rm c}$ and $\bar{D}^{\ast}\Sigma^{\ast}_{\rm c}$ thresholds. We therefore studied the hadronic molecules that form the coupled-channel system of $\bar{D}^{(\ast)}\Lambda_{\rm c}$ and $\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$. As the heavy quark spin symmetry manifests the mass degenerations of $\bar{D}$ and $\bar{D}^\ast$ mesons, and of $\Sigma_{\rm c}$ and $\Sigma^\ast_{\rm c}$ baryons, the coupled channels of $\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$ are important in these molecules. In addition, we consider the coupling to the $\bar{D}^{(\ast)}\Lambda_{\rm c}$ channel whose thresholds are near the $\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$ thresholds, and the coupling to the state with nonzero orbital angular momentum mixed by the tensor force. This full coupled channel analysis of $\bar{D}^{(\ast)}\Lambda_{\rm c}-\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$ with larger orbital angular momentum has never been performed before. By solving the coupled-channel Schr\"odinger equations with the one meson exchange potentials that respected to the heavy quark spin and chiral symmetries, we studied the hidden-charm hadronic molecules with $I(J^P)=1/2(3/2^\pm)$ and $1/2(5/2^\pm)$. We conclude that the $J^P$ assignment of the observed pentaquarks is $3/2^+$ for $P^+_{\rm c}(4380)$ and $5/2^-$ for $P^+_{\rm c}(4450)$, which is agreement with the results of the LHCb analysis. In addition, we give predictions for other $J^P=3/2^\pm$ states at 4136.0, 4307.9 and 4348.7 MeV in $J^P=3/2^-$, and 4206.7 MeV in $J^P=3/2^+$, which can be further investigated by means of experiment.

Time reversal invariance violating and parity conserving effects in proton-deuteron scattering

Time reversal invariance violating and parity conserving effects for low-energy elastic neutron-deuteron scattering are calculated for meson exchange and effective field theory type potentials in a distorted wave-born approximation using realistic hadronic wave functions, obtained by solving three-body Faddeev equations in configuration space.

Mass spectra of dimesonic states in light flavour sector

Masses of the dimesonic (meson-antimeson) molecular states are calculated using Yukawa like and meson exchange potential in semi-relativistic approach. The digamma decay width of the dimesonic systems are evaluated using the spectroscopic parameters. Many states such as $f{}_{0}$(980), $h{}_{1}$(1380), $a{}_{0}$(1450), $f{}_{0}$(1500), $f{}_{2}'$(1525), $f{}_{2}$(1565), $a{}_{2}$(1700), $f{}_{0}$(1710), $f{}_{2}$(1810), $f{}_{2}$(2010) have shown the signature of dimesonic molecules. Their masses and digamma widths are in good agreement with other theoretical results as well as experimental measurements.

Exotic baryons as a hadronic molecule in the heavy quark region

We study the hadronic molecules formed by the coupled-channel system of D (*) Λ c and D (*) Σ c (*) , inspired by the two hidden-charm pentaquark states observed by LHCb collaborations in 2015. In these molecules, the coupled channels of D (*) Σ c (*) are important because the thresholds of these channels are approximately degenerated by the heavy quark spin symmetry. In addition, we consider the coupling to the D (*) Λ c channel whose thresholds are close to the D (*) Σ c (*) thresholds, and the coupling to the state with l ≠ 0 mixed by the tensor force. By solving the coupled-channel Schrodinger equations with the one meson exchange potentials, we study the hidden-charm hadronic molecules with I(J P ) = 1/2(3/2 ± ) and 1/2(5/2 ± ). We conclude that the J P assignment of the observed pentaquarks is 3/2 + for P + c (4380) and 5/2 − for P + c (4450), which is agreement with the results of the LHCb analysis. In addition, we give predictions for other J P = 3/2 ± states.

Hadron interferences in the proton-induced coherentη-meson-production reaction on a scalar-isovector nucleus

The coherent $\eta$ meson energy $E_\eta$ distribution spectra in the proton nucleus reaction have been calculated to investigate the $\pi^0 - \eta$ mesons' interference, in addition to the study of resonance $N^*$ dynamics in the nucleus. The elementary reaction occurring in the nucleus is assumed to proceed as $ pN \to pN^* $; $ N^* \to N\eta $. Born terms in the intermediate state is also considered. In a scalar-isovector nucleus, this reaction occurs because of $\pi^0$ and $\eta$ meson exchange interactions for the forward going proton and $\eta$ meson; other meson exchange potentials do not contribute in this process. The sensitivity of the cross section to the hadron nucleus interactions, and the beam energy dependence of the cross section are studied for this reaction.

Nucleon-nucleon interaction: A typical/concise review

Nearly a recent century of work is divided to Nucleon-Nucleon (NN) interaction issue. We review some overall perspectives of NN interaction with a brief discussion about deuteron, general structure and symmetries of NN Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN interaction models, as frameworks to build NN potentials, are reviewed concisely. We try to include and study almost all well-known potentials in a similar way, discuss more on various commonly used plain forms for two-nucleon interaction with an emphasis on the phenomenological and meson-exchange potentials as well as the constituent-quark potentials and new ones based on chiral effective field theory and working in coordinate-space mostly. The potentials are constructed in a way that fit NN scattering data, phase shifts, and are also compared in this way usually. An extra goal of this study is to start comparing various potentials forms in a unified manner. So, we also comment on the advantages and disadvantages of the models and potentials partly with reference to some relevant works and probable future studies.

Four-Body Faddeev–Yakubovsky Equations Using Two-Cluster RGM Kernels: Applications to 4N and 4α Systems

Four-cluster Faddeev–Yakubovsky calculations using two-cluster RGM kernels are carried out for identical clusters. A precise ground-state energy of the α-particle, predicted by the quark-model nucleon–nucleon (NN) interaction fss2, is Eα = −26.61 MeV, including approximate effects of the Coulomb force and the charge dependence of the 2N force. The missing −1.7 MeV in the experimental value −28.3 MeV is about half of 3–4 MeV, predicted by modern meson-exchange 2N potentials, implying that almost half of 3–4 MeV is attributed to the off-shell effect of our nonlocal NN interaction fss2. As to the applications to four-α system, a method to eliminate the Faddeev redundant components from the basic Faddeev–Yakubovsky equations is proposed.

Nucleon-meson couplings in a one-boson-exchange potential using noncritical string theory

A noncritical holographic QCD model constructed in the six dimensional anti--de Sitter (AdS${}_{6}$) supergravity background is employed to study a baryon. It is shown that the size of the baryon is of order one with respect to the $\ensuremath{\lambda}$, however, it is smaller than the scale of the dual QCD. An effective four-dimensional action for the nucleon is obtained in terms of the meson exchange potentials. All meson-nucleon couplings in the noncritical AdS${}_{6}$ background are calculated. Results obtained using our model are compared with predictions of four modern phenomenological interaction models. Also, our numerical results are compared with the results of the Sakai-Sugimoto (SS) model which indicate that the noncritical holographic QCD model can be a good toy to calculate the meson-nucleon couplings.

Few-nucleon systems interacting via non-local quark-model baryon-baryon interaction

Low- and medium-energy nucleon-deuteron scattering less than the incident energy 65 MeV per nucleon is examined by using the quark-model nucleon-nucleon interaction fss2. The off-shell effect of this non-local interaction yields a part of the attractive effect given by the three-nucleon force in the standard description by meson-exchange potentials. The triton binding energy and the spin-doublet scattering length are well described by fss2 without introducing the three-nucleon force. The nucleon analyzing power is slightly improved from the results by the AV18 potential, but the so-called Ay puzzle in the low-energy region still remains. Similar reduction of the peak heights by the Coulomb force is also seen in the vector analyzing power of the deuteron, iT11(θ). Other observables are rather similar to the predictions by meson-exchange potentials, including discrepancies of deuteron breakup differential cross sections from experiment for some particular kinematical configurations. The systematic KVI data of the 1H(d⃗, 2p)n scattering at Ed = 130 MeV are reasonably reproduced for breakup differential cross sections and deuteron analyzing powers.

Meson-exchange model for theΛΛ¯interaction

In the present work, we apply the one-boson-exchange potential model to investigate the possibility of $Y(2175)$ and $\ensuremath{\eta}(2225)$ as bound states of $\ensuremath{\Lambda}\overline{\ensuremath{\Lambda}}(^{3}S_{1})$ and $\ensuremath{\Lambda}\overline{\ensuremath{\Lambda}}(^{1}S_{0})$, respectively. We consider the effective potential from the pseudoscalar $\ensuremath{\eta}$ exchange and ${\ensuremath{\eta}}^{\ensuremath{'}}$ exchange, the scalar $\ensuremath{\sigma}$ exchange, and the vector $\ensuremath{\omega}$ exchange and $\ensuremath{\phi}$ exchange. The $\ensuremath{\eta}$- and ${\ensuremath{\eta}}^{\ensuremath{'}}$-meson-exchange potential is a repulsive force for the state $^{1}S_{0}$ and attractive for $^{3}S_{1}$. The results depend very sensitively on the cutoff parameter of the $\ensuremath{\omega}$ exchange (${\ensuremath{\Lambda}}_{\ensuremath{\omega}}$) and least sensitively on that of the $\ensuremath{\phi}$ exchange (${\ensuremath{\Lambda}}_{\ensuremath{\phi}}$). Our result suggests the possible interpretation of $Y(2175)$ and $\ensuremath{\eta}(2225)$ as the bound states of $\ensuremath{\Lambda}\overline{\ensuremath{\Lambda}}(^{3}S_{1})$ and $\ensuremath{\Lambda}\overline{\ensuremath{\Lambda}}(^{1}S_{0})$, respectively.

D¯Ninteraction in a color-confining chiral quark model

We investigate the low-energy elastic DbarN interaction using a quark model that confines color and realizes dynamical chiral symmetry breaking. The model is defined by a microscopic Hamiltonian inspired in the QCD Hamiltonian in Coulomb gauge. Constituent quark masses are obtained by solving a gap equation and baryon and meson bound-state wave functions are obtained using a variational method. We derive a low energy meson-nucleon potential from a quark-interchange mechanism whose ingredients are the quark-quark and quark-antiquark interactions and baryon and meson wave functions, all derived from the same microscopic Hamiltonian. The model is supplemented with (sigma,rho,omega,a0) single-meson exchanges to describe the long-range part of the interaction. Cross-sections and phase shifts are obtained by iterating the quark-interchange plus meson-exchange potentials in a Lippmann-Schwinger equation. Once model parameters in meson exchange potential are fixed to describe the low-energy experimental phase shifts of the K+N and K0N reactions, predictions for Dbar0N and D-N reactions are obtained without introducing new parameters.

Deuteron Breakup Differential Cross Sections and Analyzing Powers of $${\overrightarrow{d} + p}$$ Scattering at E d = 16 and 130 MeV

Deuteron breakup differential cross sections and analyzing powers for \({\overrightarrow{d} + p}\) scattering at E d = 16 and 130 MeV are examined using the energy-independent quark-model nucleon–nucleon interaction fss2. The Coulomb effect is incorporated by the sharp cut-off Coulomb force, acting between quarks, without the phase-shift renormalization for the breakup amplitudes. Our results are very similar to those by the meson-exchange potentials, including disagreement for some specific kinematical configurations. The accurate and systematic KVI data at E d = 130 MeV are reasonably reproduced by taking the Coulomb cut-off radius ρ ≥ 16 fm.

Off-shell Effect of the Quark-model NN Interaction in the Nd Scattering

Low- and medium-energy nucleon–deuteron (Nd) scattering less than the incident energy 65 MeV per nucleon is examined by using the quark-model nucleon–nucleon (NN) interaction fss2. The off-shell effect of this non-local interaction yields a part of the attractive effect given by the three-nucleon force in the standard description by the meson-exchange potentials. The triton binding energy and the spin-doublet scattering length are well described by fss2 without introducing the three-nucleon force. The nucleon analyzing power is slightly improved from the results by the AV18 potential, but the so-called Ay puzzle in the low-energy region is not essentially solved nor is the similar deficiency of the peak heights seen in the vector analyzing power of the deuteron, iT11(θ). Other observables are rather similar to the predictions by meson-exchange potentials, including disagreements of the deuteron breakup differential cross sections with experiment for some particular kinematical configurations. The space-star anomaly of the nd and pd scattering at EN = 13 MeV is not improved. The accurate and systematic KVI data of the \({^{1}H(\overrightarrow{d}, 2p)n}\) scattering at Ed = 130 MeV are compared with the predictions by fss2 for the breakup differential cross sections and the deuteron analyzing powers.

Exotic mesons with hidden bottom near thresholds

We study heavy hadron spectroscopy near open bottom thresholds. We employ $\mathrm{B}$ and ${\mathrm{B}}^{*}$ mesons as effective degrees of freedom near the thresholds, and consider meson exchange potentials between them. All possible composite states which can be constructed from the $\mathrm{B}$ and ${\mathrm{B}}^{*}$ mesons are studied up to the total angular momentum $J\ensuremath{\le}2$. We consider, as exotic states, isosinglet states with exotic ${J}^{PC}$ quantum numbers and isotriplet states. We solve numerically the Schr\"odinger equation with channel couplings for each state. The masses of twin resonances ${\mathrm{Z}}_{\mathrm{b}}(10\text{ }610)$ and ${\mathrm{Z}}_{\mathrm{b}}(10\text{ }650)$ recently found by Belle are reproduced. We predict several possible bound and/or resonant states in other channels for future experiments.

Nucleon–Deuteron Breakup Differential Cross Sections Derived from the Quark-Model NN Interaction

The nd and pd breakup differential cross sections for E N ≤ 65 MeV are examined using the energy- independent quark-model nucleon-nucleon interaction fss2. The Coulomb effect is incorporated by the sharp cut-off Coulomb force, acting between quarks, without the phase-shift renormalization for the breakup ampli- tudes. Our model yields the results very similar to the meson-exchange potentials, including disagreement for some specific kinematical configurations. This includes the notorious space star anomaly of the nd and pd scattering at E N = 13 MeV. The KVI data for the breakup differential cross sections of Ed = 130 MeV dp scattering are reasonably reproduced by taking the Coulomb cut-off radius ρ = 16 fm.

Quark-Model Baryon-Baryon Interaction Applied to Neutron-Deuteron Scattering. III

The low-energy breakup differential cross sections of the neutron-deuteron (nd) scattering are studied by employing the energy-independent version of the quark-model baryon-baryon interaction fss2. This interaction reproduces almost all the breakup differential cross sections predicted by the meson-exchange potentials for the neutron incident energies $E_n \leq$ 65 MeV. The space star anomaly of 13 MeV nd scattering is not improved even in our model. Some overestimation of the breakup differential cross sections at $E_n$=22.7 - 65 MeV implies that systematic studies of various breakup configurations are necessary both experimentally and theoretically.