arXiv subjects

Yuki Kamiya

Publications and source records attributed to Yuki Kamiya.

At least 19 recordsLinked to original sources

arXiv2024

Theoretical study on $\Lambda\alpha$ and $\Xi\alpha$ correlation functions

We examine the $\Lambda$-${}^4\mathrm{He}$ ($\alpha$) and $\Xi \alpha$ momentum correlation in high-energy collisions to further elucidate the properties of the hyperon-nucleon interactions. For the $\Lambda\alpha$ system, we compare $\Lambda\alpha$ potential models with different strengths at short range. We find that the difference among the models is visible in the momentum correlation from a small-size source. This indicates that the $\Lambda\alpha$ momentum correlation can constrain the property of the $\Lambda N$ interaction at short range, which plays an essential role in dense nuclear matter. For the $\Xi\alpha$ system, we employ the folding $\Xi \alpha$ potential based on the lattice QCD $\Xi N$ interactions. The $\Xi \alpha$ potential supports a Coulomb assisted bound state of ${}^5_{\Xi}\mathrm{H}$ in the $\Xi^-\alpha$ channel, while the $\Xi^0\alpha$ channel is unbound. To examine the sensitivity of the correlation function to the nature of the $\Xi \alpha$ potential, we vary the potential strength simulating stronger and weaker interactions. The result of the correlation function clearly reflects the bound state nature in the $\Xi^-\alpha$ correlation.

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arXiv2024

Theoretical study of the $\Xi\alpha$ correlation function

We study $\Xi$-$^4{\mathrm{He}}$ ($\alpha$) momentum correlation functions in the high-energy nuclear collisions to investigate the nature of the $\Xi N$ interactions. We employ the folding $\Xi \alpha$ potential based on the lattice QCD $\Xi N$ interactions to compute the correlation function. The $\Xi \alpha$ potential supports a Coulomb-assisted bound state ${}^5_{\Xi}\mathrm{H}$ in the $\Xi^-\alpha$ channel, while the $\Xi^0\alpha$ channel is unbound. To examine the sensitivity of the correlation function to the nature of the $\Xi \alpha$ interaction, we vary the potential strength simulating stronger and weaker interactions. The result of the correlation function is sensitive to the existence of the bound state in the $\Xi^0 \alpha$ channel, and the characteristic behavior of the bound state remains also in the $\Xi^-\alpha$ correlation with the Coulomb interaction. The effect of the repulsive core of the $\Xi\alpha$ potential can be found in the correlation from the small source as the distinctive dip in the intermediate momentum region.

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arXiv2024

Femtoscopic study of the $\Lambda\alpha$ interaction

We examine the $\Lambda$-${}^4\mathrm{He}$ ($\alpha$) momentum correlation in high-energy collisions to elucidate the interaction between Lambdas ($\Lambda$) and nucleons ($N$). We compare phenomenological $\Lambda\alpha$ potentials with different strengths at short range. In addition to the conventional Gaussian-type potentials, we construct the $\Lambda\alpha$ potentials by substituting the nucleon density distribution in $\alpha$ into the Skyrme-type $\Lambda$ potentials. We find that the dependence on the employed potential models is visible in the correlation functions from a small-size source. This indicates that the $\Lambda\alpha$ momentum correlation could constrain the property of the $\Lambda N$ interaction at high densities, which is expected to play an essential role in dense nuclear matter. Also, we verify that the Lednicky-Lyuboshits formula can yield erroneous results for a small-size source with a potential which has a large interaction range, like the $\Lambda\alpha$ system.

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arXiv2023

Indication of a p-$ϕ$ bound state from a correlation function analysis

The existence of a nucleon-$ϕ$ (N-$ϕ$) bound state has been subject of theoretical and experimental investigations for decades. In this letter, indication of a \pphi bound state is found, using for the first time two-particle correlation functions as alternative to invariant mass spectra. Newly available lattice calculations for the spin 3/2 \Nphi interaction by the HAL QCD collaboration are used to constrain the spin 1/2 counterpart from the fit of the experimental \pphi correlation function measured by ALICE. The corresponding scattering length and effective range are $f_0^{(1/2)}=\left(-1.54^{+0.53}_{-0.53}(\mathrm{stat.})^{+0.16}_{-0.09}(\mathrm{syst.})+i\cdot0.00^{+0.35}_{-0.00}(\mathrm{stat.})^{+0.16}_{-0.00}(\mathrm{syst.})\right)$~fm and $d_0^{(1/2)}=\left(0.39^{+0.09}_{-0.09}(\mathrm{stat.})^{+0.02}_{-0.03}(\mathrm{syst.})+i\cdot0.00^{+0.00}_{-0.04}(\mathrm{stat.})^{+0.00}_{-0.02}(\mathrm{syst.})\right)$~fm, respectively. The results imply the appearance of a \pphi bound state with an estimated binding energy in the range of $12.8-56.1$ MeV.

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arXiv2023

Can the two-pole structure of the $D_0^*(2300)$ be understood from recent lattice data?

It was demonstrated in a series of papers employing unitarized chiral perturbation theory that the phenomenology of the scalar open-charm state, the $D_0^*(2300)$, can be understood as the interplay of two poles, corresponding to two scalar-isospin doublet states with different SU(3) flavor content. Within this formalism the lightest open charm positive parity states emerge as being dynamically generated from the scattering of the Goldstone-boson octet off $D$ mesons, a picture that at the same time solves various problems that the experimental observations posed. However, in recent lattice studies of $Dπ$ scattering at different pion masses only one pole was reported in the $D_0^*$ channel, while it was not possible to extract reliable parameters of a second pole from the lattice data. In this paper we demonstrate how this seeming contradiction can be understood and that imposing SU(3) constraints on the fitting amplitudes allows one to extract information on the second pole from the lattice data with minimal bias. The results may also be regarded as a showcase how approximate symmetries can be imposed in the $K$-matrix formalism to reduce the number of parameters.

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arXiv2023

New insights into the nature of the $\Lambda(1380)$ and $\Lambda(1405)$ resonances away from the SU(3) limit

Starting from the SU(3) limit, we consider the nature of the dynamically generated resonances $\Lambda(1380)$, $\Lambda(1405)$ and $\Lambda(1680)$ as the pion and kaon masses are tuned to their physical values. We show that the accidental symmetry of the two octets due to the leading order Weinberg-Tomozawa term is broken by the next-to-leading order terms. Most interestingly, we observe an interchange of the two trajectories of the $\Lambda(1380)$ and the $\Lambda(1405)$ away from the SU(3) limit at next-to-leading order. This remarkable phenomenon can be investigated using lattice QCD calculations that start from the SU(3) limit.

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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.

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arXiv2021

Coupled-channel effects of the $Σ_c^{()}\bar{D}^{()}$-$Λ_c(2595)\bar{D}$ system and molecular nature of the $P_c$ pentaquark states from one-boson exchange model

The effects of the $Σ_c\bar{D}^*$-$Λ_{c}(2595)\bar{D}$ coupled-channel dynamics and various one-boson-exchange (OBE) forces for the LHCb pentaquark states, $P_c(4440)$ and $P_c(4457)$, are reinvestigated. Both the pion and $ρ$-meson exchanges are considered for the $Σ_c\bar{D}^*$-$Λ_{c}(2595)\bar{D}$ coupled-channel dynamics. It is found that the role of the $Λ_{c}(2595)\bar{D}$ channel in the descriptions of the $P_c(4440)$ and $P_c(4457)$ states is not significant with the OBE parameters constrained by other experimental sources. The naive OBE models with the short-distance $δ(\vec{r})$ term of the one-pion exchange (OPE) keep failing to reproduce the $P_c(4440)$ and $P_c(4457)$ states simultaneously. The OPE potential with the full $δ(\vec{r})$ term results in a too large mass splitting for the $J^P=1/2^-$ and $3/2^-$ $Σ_c\bar{D}^*$ bound states with total isospin $I=1/2$. The OBE model with only the OPE $δ(\vec{r})$ term dropped may fit the splitting much better but somewhat underestimates the splitting. Since the $δ(\vec r)$ potential is from short-distance physics, which also contains contributions from the exchange of mesons heavier than those considered explicitly, we vary the strength of the $δ(\vec r)$ potential and find that the masses of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ can be reproduced simultaneously with the $δ(\vec r)$ term in the OBE model reduced by about 80\%. While two different spin assignments are possible to produce their masses, in the preferred description, the spin parities of the $P_c(4440)$ and $P_c(4457)$ are $3/2^-$ and $1/2^-$, respectively.

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arXiv2021

Effect of deuteron breakup on the deuteron-$Ξ$ correlation function

The hadron-deuteron correlation function has attracted many interests as a potential method to access the three-hadron interactions. However, the weakly-bound nature of deuteron has not been considered in the preceding studies. In this study, the breakup effect of deuteron on the deuteron-$Ξ^-$ ($d$-$Ξ^-$) correlation function $C_{dΞ^-}$ is investigated. The $d$-$Ξ^-$ scattering is described by a nucleon-nucleon-$Ξ$ three-body reaction model. The continuum-discretized coupled-channels method, which is a fully quantum-mechanical and non-perturbative reaction model, is adopted. $C_{dΞ^-}$ turns out to be sensitive to the strong interaction and enhanced by the deuteron breakup effect by 6--8 % for the $d$-$Ξ^-$ relative momentum below about 70 MeV/$c$. Low-lying neutron-neutron continuum states are responsible for this enhancement. Within the adopted model, the deuteron breakup effect on $C_{dΞ^-}$ is found to be appreciable but not very significant. Except for the enhancement by several percent, studies on $C_{dΞ^-}$ without the deuteron breakup effect can be justified.

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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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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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arXiv2018

Universal physics of the few-body system of two neutrons and one flavored meson

We investigate the $s$-wave three-body system of two neutrons and one flavored meson with total spin-isospin $J=0,I=3/2$. The meson-neutron scattering length can become infinitely large in an unphysical region of the quark mass when extrapolated from strangeness to charm in the so-called zero coupling limit. Using a low-energy cluster effective field theory, we demonstrate that the Efimov effect is manifest in the three-body system when the meson-neutron scattering length is extrapolated to the unitary limit of the two-body interaction. We thereby discuss the consequence of universal physics in the physical $K^{-}nn$ and $D^{0}nn$ systems.

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arXiv2018

$N Ω$ interaction: meson exchanges, inelastic channels, and quasibound state

Based on a baryon-baryon interaction model with meson exchanges, we investigate the origin of the strong attraction in the $N Ω( {}^{5}S_{2} )$ interaction, which was indicated by recent lattice QCD simulations. The long range part of the potential is constructed by the conventional mechanisms, the exchanges of the $η$ meson and of the correlated two mesons in the scalar-isoscalar channel, denoted by "$σ$" in the literature. The short range part is represented by the contact interaction. We find that the meson exchanges do not provide sufficient attraction. This means that most of the attraction is attributed to the short range contact interaction. We then evaluate the effect of the coupled channels to the $N Ω( {}^{5}S_{2} )$ interaction. We find that, while the $D$-wave mixing of the $N Ω$ channel is negligible, the inelastic $ΛΞ$, $ΣΞ$, and $ΛΞ(1530)$ channels via the $K$ meson exchange give the attraction of the $N Ω( {}^{5}S_{2} )$ interaction to the same level with the elastic meson exchanges. Although the elimination of these channels induces the energy dependence of the single-channel $N Ω$ interaction, this effect is not significant. With the present model parameters fitted to reproduce the scattering length of the HAL QCD result of the nearly physical quark masses, we obtain the $N Ω( {}^{5}S_{2} )$ quasibound state with its eigenenergy $2611.3 - 0.7 i$ MeV, which corresponds to the binding energy $0.1$ MeV and width $1.5$ MeV for the decay to the $ΛΞ$ and $ΣΞ$ channels. From the analysis of the spatial structure and the compositeness, the quasibound state is shown to be the molecular state of $NΩ$. We also construct an equivalent local potential for the $N Ω( {}^{5}S_{2} )$ system which is useful for various applications.

hep-ph↗

arXiv2018

Structure of hadron resonances with a nearby zero of the amplitude

We discuss the relation between the analytic structure of the scattering amplitude and the origin of an eigenstate represented by a pole of the amplitude.If the eigenstate is not dynamically generated by the interaction in the channel of interest, the residue of the pole vanishes in the zero coupling limit. Based on the topological nature of the phase of the scattering amplitude, we show that the pole must encounter with the Castillejo-Dalitz-Dyson (CDD) zero in this limit. It is concluded that the dynamical component of the eigenstate is small if a CDD zero exists near the eigenstate pole. We show that the line shape of the resonance is distorted from the Breit-Wigner form as an observable consequence of the nearby CDD zero. Finally, studying the positions of poles and CDD zeros of the KbarN-piSigma amplitude, we discuss the origin of the eigenstates in the Lambda(1405) region.

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arXiv2017

Generalized weak-binding relations of compositeness in effective field theory

We study the compositeness of near-threshold states to investigate the internal structure of exotic hadron candidates. Within the framework of effective field theory, Weinberg's weak-binding relation is extended to more general cases by easing several preconditions. First, by evaluating the contribution from the decay channel, we obtain the generalized relation for unstable quasibound states. Next, we generalize the relation to include the nearby CDD (Castillejo-Dalitz-Dyson) pole contribution with the help of the Pade approximant. The validity of the estimation with the generalized weak-binding relations is examined by numerical calculations. The method to systematically evaluate the error in the weak-binding relation is presented. Finally, by applying the extended relation to Lambda(1405), f0(980) and a0(980), we discuss their internal structure, in comparison with other approaches.

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arXiv2017

Compositeness Of Quasibound States from Effective Field Theory

The internal structure of exotic hadron candidates are studied from the viewpoint of the compositeness of near-threshold states. We focus on the Weinberg's weak-binding relation between the experimental observables and the compositeness of the state. First we extend the relation for quasibound states within the framework of the effective field theory. Next, considering the correction term, we develop a systematic method to estimate the uncertainty of compositeness in the weak-binding relation. Finally, applying the extended relation and the error evaluation method, we conclude that the structure of Lambda(1405) is dominated by the Kbar N component.

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arXiv2016

Model-independent determination of the compositeness of near-threshold quasibound states

We study the compositeness of near-threshold states to clarify the internal structure of exotic hadron candidates. Within the framework of effective field theory, we extend the Weinberg's weak-binding relation to include the nearby CDD (Castillejo-Dalitz-Dyson) pole contribution with the help of the Pade approximant. Finally, using the extended relation, we conclude that the CDD pole contribution to the Lambda(1405) baryon in the Kbar N amplitude is negligible.

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arXiv2016

Structure of near-threshold quasi-bound states

We study the compositeness of near-threshold quasi-bound states in the framework of effective field theory. From the viewpoint of the low-energy universality, we revisit the model-independent relations between the structure of the bound state and the observables in the weak binding limit. The effective field theory is utilized to generalize the weak-binding relation of the stable bound states to unstable quasi-bound states with decay modes. We present the interpretation of the complex values of the compositeness for the unstable states. Combining the model-independent relation and the threshold observables extracted from the experimental data, we show that Lambda(1405) is dominated by the Kbar N molecular structure and that a_0(980) is dominated by the non-Kbar K component.

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