arXiv subjects

Tetsuo Hyodo

Publications and source records attributed to Tetsuo Hyodo.

At least 55 records · Page 3Linked to original sources

arXiv2023

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.

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arXiv2023

Analysis of $Ξ(1620)$ resonance and $\bar{K}Λ$ scattering length with chiral unitary approach

We study the $Ξ(1620)$ resonance near the $\bar{K}Λ$ threshold in the light of the recent experimental constraints. The Belle collaboration have found a resonance peak of $Ξ(1620)$ slightly below the $\bar{K}^{0}Λ$ threshold in the $π^{+}Ξ^{-}$ invariant mass spectrum, and the ALICE collaboration have determined the $K^{-}Λ$ scattering length from the measurement of the momentum correlation functions in the heavy ion collisions. Using the effective range expansion, we classify the nature of the pole of the near-threshold eigenstate in terms of the scattering length, in the presence of the decay channel. It is shown that the quasibound state below the threshold can be described by only the scattering length, while the description of the resonance above the threshold requires the contribution from the effective range. Based on the chiral unitary approach, we construct a theoretical model which generates the pole of $Ξ(1620)$ below the $\bar{K}Λ$ threshold with relatively narrow width, as reported by the Belle collaboration. It is quantitatively demonstrated that the spectrum of the $Ξ(1620)$ quasibound state is distorted by the effect of the nearby $\bar{K}Λ$ threshold. We then construct another model which reproduces the $K^{-}Λ$ scattering length by the ALICE collaboration. In this case, the eigenstate pole does not appear in the physically relevant Riemann sheets, and the spectrum shows a cusp structure at the $\bar{K}Λ$ threshold. We finally examine the compatibility of the value of the $\bar{K}Λ$ scattering length and the subthreshold pole of $Ξ(1620)$ including the experimental uncertainties.

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arXiv2022

Nature of excited $Ξ$ baryons with threshold effects

Spectroscopy of excited baryons with strangeness $S=-2$ is stimulated by recent experimental developments. Here we focus on the $Ξ(1620)$ which locates close to the $\bar{K}Λ$ threshold. To take into account the threshold effects, we construct the coupled-channels meson-baryon scattering amplitude where the $Ξ(1620)$ appears as a resonance. We demonstrate that the $\bar{K}Λ$ threshold effects distort the peak of the $Ξ(1620)$ resonance from the simple Breit-Wigner distribution.

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arXiv2022

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.

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arXiv2022

Analysis of coupled-channel potentials with quark and hadron degrees of freedom

The quark-antiquark potentials are known to be confining in the absence of the $\bar{q}q$ pair creation. On the other hand, the inter-hadron potentials vanish at large distance, because the interaction range is limited by the inverse pion mass. When the $\bar{q}q$ pair creation and annihilation are switched on, the channel coupling occurs between the quark and hadron degrees of freedom, modifying the behavior of potentials. In this work, we investigate the properties of the effective potentials obtained by eliminating one of the channels. We show that the coupling to the eliminated channel induces a non-local and energy dependent effective potential, irrespective of the properties of the transition potential. In addition, when the hadron channel having continuous scattering eigenstates is eliminated, the resulting inter-quark potential contains an imaginary part above the threshold to describe the decay effect into the meson pair.

hep-ph↗

arXiv2022

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↗

arXiv2022

Femtoscopic study on $DD^$ and $D\bar{D}^$ interactions for $T_{cc}$ and $X(3872)$

We investigate $DD^*$ and $D\bar{D}^*$ momentum correlations in high-energy collisions to elucidate the nature of $T_{cc}$ and $X(3872)$ exotic hadrons. Single range Gaussian potentials with the channel couplings to the isospin partners are constructed based on the empirical data. The momentum correlation functions of the $D^0D^{*+}$, $D^+D^{*0}$, $D^0\bar{D}^{*0}$, and $D^+D^{*-}$ pairs are computed with including the coupled-channel effects. We discuss how the nature of the exotic states are reflected in the behaviors of the correlation results.

hep-ph↗

arXiv2022

Theory of kaon-nuclear systems

The strong interaction between an antikaon and a nucleon is at the origin of various interesting phenomena in kaon-nuclear systems. In particular, the interaction in the isospin $I=0$ channel is sufficiently attractive to generate a quasi-bound state, the $Λ(1405)$ resonance, below the $\bar{K}N$ threshold. Based on this picture, it may be expected that the $\bar{K}N$ interaction also generates quasi-bound states in kaon-nuclear systems, sometimes called kaonic nuclei. At the same time, the $\bar{K}N$ quasi-bound picture of the $Λ(1405)$ is also related to the discussion of hadronic molecules in hadron spectroscopy. Here an overview is presented of the theoretical studies developed for kaon-nucleon and kaon-nuclear systems. We start from the modern understanding of the $Λ(1405)$ resonance. We then discuss the $\bar{K}N$ interaction and various aspects of few-body kaonic nuclei. Heavier kaon-nuclear systems are examined from the viewpoint of nuclear many-body physics, with focus on the properties of antikaons in nuclear matter. Related topics, such as the $K^{-}p$ momentum correlation functions in high-energy collisions and the studies of kaonic atoms, are also discussed.

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arXiv2022

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↗

arXiv2021

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↗

arXiv2021

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↗

arXiv2021

QCD and the Strange Baryon Spectrum

The strange quark plays a unique role in QCD, reflecting its intermediate mass between the light and heavy quarks. In recent years, remarkable progress has been made in the spectroscopy of baryons with strangeness. Many new features of the strange baryon spectrum have been revealed by accurate experimental data with novel techniques, as well as systematic developments of theoretical framework to describe hadron resonances. The basic properties of strange baryons, namely, the pole positions, spin and parity, and decay branching ratios, are being determined accurately. As a consequence, the Particle Data Group have added new entries in the particle listings, such as the $Λ(1380)$ and the $Ω(2012)$. The developments of the spectroscopy stimulate intensive discussion on the exotic internal structure of strange baryons beyond the ordinary three-quark configuration. In this review, we introduce the basics of QCD, the scattering theory, and the exotic internal structure of hadrons, emphasizing the importance of the pole positions of the scattering amplitude for the characterization of hadron resonances. We then summarize the current status of selected strange baryon resonances; $Λ(1405)$, $Λ(1670)$, $Ξ(1620)$, $Ξ(1690)$, and $Ω(2012)$, from theoretical and experimental viewpoints.

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arXiv2020

$K^-p$ Correlation Function from High-Energy Nuclear Collisions and Chiral SU(3) Dynamics

The two-particle momentum correlation function of a K^-p pair from high-energy nuclear collisions is evaluated in the KbarN-piSigma-piLambda coupled-channels framework. The effects of all coupled channels together with the Coulomb potential and the threshold energy difference between K^-p and Kbar0 n are treated completely for the first time. Realistic potentials based on the chiral SU(3) dynamics are used which fit the available scattering data. The recently measured correlation function is found to be well reproduced by allowing variations of the source size and the relative weight of the source function of piSigma with respect to that of KbarN. The predicted K^-p correlation function from larger systems, which is less affected by the piSigma source function, indicates that the investigation of its source size dependence is useful in providing further constraints in the study of the KbarN interaction.

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arXiv2020

Dynamically generated hadron resonances

Recent developments in hadron spectroscopy triggers the discussion on various exotic configurations beyond the simple three-quark state for baryons and quark-anti-quark pair for mesons. In particular, the states observed near a two-hadron threshold are often regarded as candidates of hadronic molecules, which are made of constituent hadrons and dynamically generated by the hadronic interactions. However, identification of the hadronic molecules involves several subtle difficulties which are often overlooked or underestimated. Here we summarize these subtleties and present a promising approach to distinguish the dynamically generated states from others using observable quantities.

hep-ph↗

arXiv2019

Probing $ΩΩ$ and $pΩ$ dibaryons with femtoscopic correlations in relativistic heavy-ion collisions

The momentum correlation functions of baryon pairs, which reflects the baryon-baryon interaction at low energies, are investigated for multi-strangeness pairs ($ΩΩ$ and $NΩ$) produced in relativistic heavy-ion collisions. We calculate the correlation functions based on an expanding source model constrained by single-particle distributions. The interaction potentials are taken from those obtained from recent lattice QCD calculations at nearly physical quark masses. Experimental measurements of these correlation functions for different system sizes will help to disentangle the strong interaction between baryons and to unravel the possible existence of strange dibaryons.

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arXiv2019

Nature of the D_0 meson in the D pi scattering with chiral symmetry

We study the nature of the scalar D_0 meson from the viewpoint of chiral symmetry. With the linear representation of chiral symmetry, we construct the D pi scattering amplitude satisfying the chiral low-energy theorem, in which the D_0 meson appears as an s-wave resonance. We show that the properties of the D_0 meson can be successfully reproduced as the chiral partner of the D meson coupled with the D pi scattering states. At the same time, we find that the spectral function and the pole position of D_0 are not very sensitive to the reduction of the chiral condensate, indicating the importance of the dressing of the bare state by the D pi molecular component.

hep-ph↗

arXiv2018

Local meson-baryon coupled-channels potential for the Lambda(1405)

A local coupled-channels Kbar N-pi Sigma-pi Lambda potential is constructed, equivalently reproducing the scattering amplitude in chiral SU(3) dynamics. By analyzing the wave function of the Lambda(1405), we show the Kbar N dominance of the upper pole within the two-pole structure of the Lambda(1405). The resulting potential will be useful for investigating Kbar few-nucleon systems including their coupled channels.

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arXiv2018

Strangeness $S=-2$ baryon-baryon interactions in relativistic chiral effective field theory

We study the strangeness $S=-2$ baryon-baryon interactions in relativistic chiral effective field theory at leading order. Among the 15 relevant low energy constants, eight of them are determined by fitting to the state of the art lattice QCD data of the HAL QCD Collaboration (with $m_π=146$ MeV), and the rest are either taken from the study of the $S=-1$ hyperon-nucleon systems, assuming strict SU(3) flavor symmetry, or temporarily set equal to zero. Using the so-obtained low energy constants, we extrapolate the results to the physical point, and show that they are consistent with the available experimental scattering data. Furthermore, we demonstrate that the $ΛΛ$ and $ΞN$ phase shifts near the $ΞN$ threshold are very sensitive to the lattice QCD data fitted, to the pion mass, and to isospin symmetry breaking effects. As a result, any conclusion drawn from lattice QCD data at unphysical pion masses (even close to the physical point) should be taken with caution. Our results at the physical point, similar to the lattice QCD data, show that a resonance/quasi-bound state may appear in the $I=0$ $ΛΛ$/$ΞN$ channel.

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