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Tomona Kinugawa

Publications and source records attributed to Tomona Kinugawa.

16 recordsLinked to original sources

Properties of the $D_{s0}^*(2317)^\pm$ in hot and dense nuclear matter

We investigate the properties of the $D_{s0}^\ast(2317)^\pm$ in hot and dense nuclear matter using a coupled-channel molecular model built on next-to-leading-order heavy meson chiral perturbation theory. In-medium modifications to the $D_{s0}^\ast(2317)^+$ stem from changes to the $DK$ channel within the coupled $DK$-$D_s \eta$ system. As nuclear density increases, the $D_{s0}^\ast(2317)^+$ quasiparticle peak shifts toward lower energies and broadens, tracking the behavior of the $D$-meson spectral function. As for temperature effects, those are milder, with the thermal smearing of the Fermi surface and the melting of $\Sigma_c N^{-1}$ excitations in the $D$-meson spectral function shifting the $D_{s0}^\ast(2317)^+$ peak back toward its free-space mass while narrowing it. Conversely, the behavior of the $D_{s0}^\ast(2317)^-$ is governed by the $\bar D \bar K$ channel and its medium behavior is driven by the $\bar K$ spectral function. With increasing temperature, the $D_{s0}^\ast(2317)^-$ also approaches its free-space mass, but its width broadens before saturating at high temperatures. Incorporating explicit medium dependencies into the interaction kernel, driven by density and/or temperature variations in the pion decay constant, further shifts the $D_{s0}^\ast(2317)^+$ mass lower and narrows its width with temperature. As for $D_{s0}^\ast(2317)^-$, its mass also drops with temperature but its width increases. These contrasting medium behaviors offer a promising pathway to constrain the internal structure of these exotic states.

hep-ph

Compositeness of near-threshold eigenstates with Coulomb plus short-range interactions

We investigate the internal structure of near-threshold $s$-wave eigenstates in a two-body system with Coulomb plus short-range interactions. Using a nonrelativistic effective field theory, we derive the expression for the compositeness in terms of the energy derivative of the self-energy, which is applicable to the present system with the non-separable Coulomb interaction. For near-threshold states, the compositeness can be written solely in terms of the Coulomb scattering length, the Coulomb effective range, and the Bohr radius, providing the weak-binding relation in the presence of the Coulomb interaction. We numerically study the pole trajectories and the compositeness and find that the Coulomb interaction qualitatively modifies the threshold behavior of the poles and the internal structure of the eigenstates. We show that when the Coulomb interaction is relatively strong, the enhancement of the compositeness near the threshold is absent, in contrast to purely short-range interactions. On the other hand, for a weak Coulomb interaction, a remnant of short-range universality survives, and near-threshold bound states tend to be composite dominant. Furthermore, even resonances are dominated by the composite component in the presence of the Coulomb interaction, owing to their continuous connection to the bound-state regime. We apply the formalism to realistic systems with near-threshold eigenstates, including exotic hadrons and nuclei.

hep-ph

Structure of near-threshold states in systems with Coulomb and short-range interactions

We study the nature of near-threshold eigenstates in systems with the attractive Coulomb plus short-range interactions. Using a model providing the Coulomb-modified effective range expansion, we analyze pole trajectories and the internal structure of near-threshold states characterized by the compositeness. We find that bound state and resonance poles are disconnected in the presence of the attractive Coulomb interaction, in contrast to the repulsive Coulomb force. Near the threshold, bound states become almost purely composite, while the behavior of the compositeness near unityis controlled by the competition between the Coulomb and short-range interactions, characterized by the Bohr radius and the Coulomb effective range.

hep-ph

Internal structure of near-threshold states using compositeness

Understanding the internal structure of near-threshold states is essential for revealing the nature of exotic hadrons. Motivated by this challenge, we discuss the clustering structures of near-threshold $s$-wave eigenstates using the compositeness, which characterizes the clustering nature of the states. We show that shallow bound states usually possess cluster-dominant structures, while near-threshold narrow resonances are non-cluster-dominant. Through this study, we establish a theoretical foundation for the threshold energy rule, which has been known empirically.

hep-ph

Compositeness of hadrons, nuclei, and atomic systems

Recent observations of exotic hadrons have stimulated the theoretical investigation of the internal structure of hadrons. While all hadrons are ultimately composed of quarks and gluons bound by the strong interaction, quark clustering phenomena can generate hadronic molecules -- weakly bound systems of hadrons -- which are expected to emerge near two-hadron thresholds. However, it should be noted that a pure hadronic molecule is not realized, as the strong interaction induces mixing with other possible configurations. The compositeness of hadrons has been developed as a promising concept to quantitatively characterize the fraction of the hadronic molecular component. Here we summarize the modern understanding of the compositeness to study the internal structure of hadrons and review the application of the compositeness to various quantum systems in different energy scales, such as nuclei and atomic systems, in addition to hadrons.

hep-ph

Compositeness of near-threshold states with repulsive Coulomb interaction combined with short-range potential

We investigate the internal structure of near-threshold states in a system with a repulsive Coulomb interaction combined with a short-range potential, using the compositeness. We construct a model in which the eigenmomentum is expressed in terms of three observables: the Coulomb scattering length, the Coulomb effective range, and the Bohr radius. In the presence of the Coulomb interaction, a bound state directly goes into a resonance as parameters are varied, bypassing a virtual state, in contrast to the case with only the short-range interaction. We show that the compositeness of near-threshold states can be expressed solely in terms of these observables. When the magnitude of the Coulomb effective range is much smaller than that of the Bohr radius, both shallow bound states and near-threshold resonances exhibit common structures with large compositeness, reflecting the remnant of the low-energy universality.

hep-ph

Internal structure of $T_{cc}$ and $X(3872)$ by using compositeness

The internal structure of the near-threshold exotic hadrons, $T_{cc}$ and $X(3872)$, are studied by respecting the decay and coupled-channel contributions. The effective field theory model is introduced to calculate the compositeness, the probability of finding the hadronic molecular component. Applying the new interpretation scheme for the complex compositeness of unstable states and using the bare energies of the compact component estimated by the constituent quark model, we find that approximately 50 % of the $T_{cc}$ wavefunction is occupied by the $D^{0}D^{*+}$ molecular component. This indicates that the structure of $T_{cc}$ is primarily dominated by the $D^0D^{*+}$ component, having the nearest threshold. However, other components, such as the isospin partner $D^{*0}D^{+}$ channels, also provide non-negligible contributions. On the other hand, about 90 % of $X(3872)$ is composed of the $D^{0}\bar{D}^{0*}$ molecular component. This is because the non-composite bare state and the charged $D\bar{D}^{*}$ threshold are located relatively far from the $X(3872)$ and contribute very little to its internal structure.

hep-ph

Structure of near-threshold resonances with new interpretation scheme of complex compositeness

The nature of near-threshold resonances is quantitatively studied with a new interpretation scheme using the complex compositeness. A difficulty was known in the understanding of the internal structure of unstable resonances because their complex compositeness is not an interpretable measure. To overcome this problem, we develop a new interpretation scheme respecting the ambiguous aspects of the identification of the internal structure of resonances. We then apply the interpretation scheme to the near-threshold resonances slightly above the threshold, described by the effective range expansion. With the new interpretation scheme, we show that near-threshold resonances are dominated by the non-molecular component. Namely, even in the near-threshold region, the nature of resonances is sharply contrasted with bound states whose internal structure is usually molecular dominant.

hep-ph

Compositeness of $T_{cc}$ and $X(3872)$ by considering decay and coupled-channels effects

The compositeness of weakly bound states is discussed using the effective field theory from the viewpoint of the low-energy universality. We introduce a model with coupling of the single-channel scattering to the bare state, and study the compositeness of the bound state by varying the bare state energy. In contrast to the naive expectation that the near-threshold states are dominated by the molecular structure, we demonstrate that a non-composite state can always be realized even with a small binding energy. At the same time, however, it is shown that a fine tuning is necessary to obtain the non-composite weakly bound state. In other words, the probability of finding a model with the composite dominant state becomes larger with the decrease of the binding energy in accordance with the low-energy universality. For the application to exotic hadrons, we then discuss the modification of the compositeness due to the decay and coupled-channels effects. We quantitatively show that these contributions suppress the compositeness, because of the increase of the fraction of other components. Finally, as examples of near-threshold exotic hadrons, the structures of $T_{cc}$ and $X(3872)$ are studied by evaluating the compositeness. We find the importance of the coupled-channels and decay contributions for the structures of $T_{cc}$ and $X(3872)$, respectively.

hep-ph

Compositeness of near-threshold $s$-wave resonances

The near-threshold clustering phenomenon is well understood by the low-energy universality, for shallow bound states below the threshold. Nevertheless, the characteristics of resonances slightly above the threshold still lack thorough elucidation. We introduce a novel probabilistic interpretation scheme for complex compositeness of resonances, in which resonances with large decay widths fall outside the domain where their internal structure can be interpreted probabilistically. Employing this scheme to analyze resonances via the effective range expansion, we demonstrate that near-threshold resonances have a small composite fraction, in sharp contrast to shallow bound states below the threshold.

hep-ph

Compositeness of near-threshold exotic hadrons with decay and coupled-channel effects

The near-threshold exotic hadrons such as $T_{cc}$ and $X(3872)$ are naively considered as the hadronic molecular state from the viewpoint of the low-energy universality. However, it is also known that the elementary dominant state is not completely excluded as the internal structure of the near-threshold states. Furthermore, the dominance of molecules is expected to be modified by the decay or coupled channels. We discuss these features of the near-threshold bound states by calculating the compositeness with the effective field theory.

hep-ph

Estimation of compositeness with correction terms

The compositeness $X$ is defined as the probability to observe the composite structure such as the hadronic molecule component in a bound state. One of the model-independent approaches to calculate $X$ is the weak-binding relation. However, when the scattering length $a_{0}$ is larger than the radius of the bound state $R$, the central value of the compositeness $X$ becomes larger than unity, which cannot be interpreted as a probability. For the systems with $a_{0}>R$, we need to estimate the compositeness with the correction terms. For the reasonable determination of the compositeness, we first present the quantitative estimation of the correction terms. Because the exact value of the compositeness should be contained in its definition domain $0\leq X\leq 1$, we propose the reasonable estimation method with the uncertainty band by excluding the region outside of the definition domain of the compositeness. We finally estimate the compositeness of physical systems, and obtain the result which we can interpret as the fraction of the composite component.

hep-ph

Structure of exotic hadrons by a weak-binding relation with finite-range correction

The composite nature of a shallow bound state is studied by using the weak-binding relation, which connects the compositeness of the bound state with observables. We first show that the previous weak-binding relation cannot be applied to the system with a large effective range. To overcome this difficulty, we introduce the finite-range correction by redefining the typical length scale in the weak-binding relation. A method to estimate the uncertainty of the compositeness is proposed. It is numerically demonstrated that the range correction enlarges the applicable region of the weak-binding relation. Finally, we apply the improved weak-binding relation to the actual hadrons, nuclei, and atomic systems [deuteron, $X(3872)$, $D^{*}_{s0}(2317)$, $D_{s1}(2460)$, $NΩ$ dibaryon, $ΩΩ$ dibaryon, ${}^{3}_Λ{\rm H}$, and ${}^{4}{\rm He}$ dimer] to discuss their internal structure from the compositeness. We present a reasonable estimation of the compositeness of the deuteron by properly taking into account the uncertainty. The results of $X(3872)$ and the $NΩ$ dibaryon show that the range correction is important to estimate the compositeness of physical states.

hep-ph

Application of the weak-binding relation with range correction

The weak-binding relation is a useful tool to study the internal structure of hadrons from the observable quantities. We introduce the range correction in the weak-binding relation for the system having a sizable magnitude of the effective range, and show that the applicability of the weak-binding relation can be enlarged by the range correction. Thanks to the low-energy universality, the weak-binding relation can be used to study the structure of shallow bound states in any systems with different length scales. We apply the weak-binding relation to actual systems, including hadrons, hypernuclei, and atoms and show the importance of the range correction.

hep-ph

Role of the effective range in the weak-binding relation

We study the range correction in the weak-binding relation, which relates the internal structure of hadrons with the scattering length and the binding energy. Utilizing the effective field theories, we show that the effective range originates from the derivative coupling interaction as well as from the channel coupling to the bare state, and that the different contributions are not distinguishable. By examining the compositeness in the effective field theories, it is demonstrated that the effective range induces the finite range correction for the weak-binding relation in addition to the previously known contributions. We thus propose to include the range correction in the uncertainty terms of the weak-binding relation.

hep-ph

Range correction in the weak-binding relation for unstable states

The compositeness is defined as the weight of the hadronic molecule in the hadron wave function. We can determine the internal structure of the weak-binding system without any specific models from the compositeness. In order to estimate the compositeness of the system with a large effective range, we introduce the range correction to Weinberg's weak-binding relation by modifying the correction terms. We study the applicability of the weak-binding relations by the numerical calculation and show that the improved relation can be applied to a larger parameter region compared with the previous one.

hep-ph