arXiv subjects

Takumi Doi

Publications and source records attributed to Takumi Doi.

At least 19 recordsLinked to original sources

arXiv2026

$\bar{D}$-meson Nucleon Scattering from Lattice QCD at the Physical Point

We report the first lattice QCD study of the $s$-wave scattering of the $\bar{D}$-meson and the nucleon at the physical point, utilizing (2+1)-flavor configurations generated by the HAL QCD collaboration with a pion mass of $m_π\simeq 137$ MeV and a lattice spacing of $a\simeq0.084$ fm. By applying the HAL QCD method to the four-point correlation function of the $\bar{D}N$ system, we obtain a leading-order potential of the derivative expansion of the interaction kernel, which is then used to extract the $s$-wave phase shifts of low-energy $\bar{D}N$ scattering. Both the isospin $I=0$ and $I=1$ channels have a short-range repulsive core and a shallow attractive pocket in the intermediate to long-range region, though the $I=0$ channel is more attractive than the $I=1$ channel. We also observe that the $\bar{D}N$ potential exhibits more attraction than the $KN$ potential, which is its analog in the strange sector. In terms of the $s$-wave phase shifts, the $I=0$ channel shows a weak attractive behavior in the low-energy region with a positive scattering length of $0.246 \pm 0.105 (_{-0.051}^{+0.084})$ fm, whereas the $I=1$ channel shows repulsion with a negative scattering length of $-0.086 \pm 0.050 (_{-0.001}^{+0.037})$ fm. No bound states are found in both isospin channels, indicating the absence of a pentaquark state in the $s$-wave $\bar{D}N$ system.

hep-lat↗

arXiv2025

Probing Nucleon-$Ω_{\rm ccc}$Interaction via Lattice QCD at Physical Quark Masses

We study the S-wave interactions between the nucleon ($N$) and the triply charmed Omega baryon ($Ω_{\mathrm{ccc}}$) using (2+1)-flavor lattice QCD with a physical pion mass ($m_π\simeq 137.1$ MeV) on a lattice volume $\simeq (8.1~\mathrm{fm})^3$. The charm quark is implemented with a relativistic heavy-quark action at its physical mass. Employing the time-dependent HAL QCD method, the $N$-$Ω_{\mathrm{ccc}}$ potentials in the spin-1 ($^3\mathrm{S}_1$) and spin-2 ($^5\mathrm{S}_2$) channels are extracted. In both channels, overall attraction is found with the scattering parameters, $a_0 = 0.56(0.13)\left(^{+0.26}_{-0.03}\right)$ fm and $r_{\mathrm{eff}} = 1.60(0.05)\left(^{+0.04}_{-0.12}\right)$ fm for the $^3\mathrm{S}_1$ channel, and $a_0 = 0.38(0.12)\left(^{+0.25}_{-0.00}\right)$ fm and $r_{\mathrm{eff}} = 2.04(0.10)\left(^{+0.03}_{-0.22}\right)$ fm for the $^5\mathrm{S}_2$ channel, indicating the absence of a dibaryon bound state. The extracted potentials are further decomposed into spin-independent and spin-dependent components. The spin-independent potential is a dominant component and features a short-range attractive core and a long-range attractive tail, while the spin-dependent potential shows short-range attraction (repulsion) in the spin-1 (spin-2) channel. Qualitative comparisons with previous studies of the $N$-$J/ψ$ and $N$-$Ω_{\rm{sss}}$ systems at $m_π\simeq 146$ MeV are provided, emphasizing the role of heavy-hadron chromo-polarizability arising from soft-gluon exchange between the nucleon and flavor-singlet hadrons. The charm quark mass dependence of the $N$-$Ω_{\rm ccc}$ potential is investigated as well.

hep-lat↗

arXiv2025

$S$-wave kaon-nucleon interactions from lattice QCD at the physical point

We investigate S-wave kaon-nucleon ($KN$) interactions with strangeness $S=+1$ in lattice QCD using the time-dependent HAL QCD method. Employing the $(2+1)$-flavor gauge configuration with $m_{\pi}\approx 137~\textrm{MeV}$ and $m_{K}\approx 502~\textrm{MeV}$, we calculate the $KN$ potentials at the leading order in the derivative expansion. The potentials in both isospin channels ($I=1$ and $I=0$) exhibit repulsion at short distances, while only the $I=0$ potential has a small attractive pocket at intermediate distances. From these potentials, we compute the phase shifts as well as the low-energy scattering parameters. The obtained phase shifts show no signals corresponding to resonances or bound states in both isospin channels, suggesting the absence of the $\Theta^{+}(1540)$ pentaquark in the S-wave $KN$ systems. The results for $I=0$ suggest that the scattering amplitudes in this channel are dominated by P-wave components rather than S-wave.

hep-lat↗

arXiv2025

Decoding Two-Particle States in QCD with Spatial Wavefunctions

A systematic framework for constructing optimized interpolating operators strongly coupled to QCD two-particle states is developed, which is achieved by incorporating inter-hadron spatial wavefunctions. To efficiently implement these operators in lattice QCD, a novel quark smearing technique utilizing noise vectors is proposed. Applied to the $\Omega_{ccc}\Omega_{ccc}$ system, these optimized operators prove superior to combinations of limited plane-wave operators, enabling the resolution of distinct eigenstates separated by only $\sim 5$ MeV near the threshold $2m_{\Omega_{ccc}} \simeq 9700$ MeV. This exceptional resolving power opens new possibilities for studies of a wide range of hadronic systems in QCD.

hep-lat↗

arXiv2025

Wavefunction-based operator optimization for two-hadron systems in lattice QCD

A systematic way to constructing optimized interpolating operators for two-hadron systems is developed by incorporating inter-hadron spatial wavefunctions. The wavefunctions can be obtained from an iterative process with an appropriate initial guess. To implement these operators, a novel quark smearing technique utilizing $Z_3$ noise vectors is proposed, which allows for effectively incorporating inter-hadron spatial wavefunctions at the source without using all-to-all quark propagators. Proof-of-principle application to the $\Omega_{ccc}\Omega_{ccc}$ system using physical-point lattice configurations with a large size $La\simeq8.1$~fm demonstrates that optimized operators outperform combinations of limited plane-wave operators in the variational analysis, enabling clear identification of states around $2m_{\Omega_{ccc}}\simeq 9700$ MeV with the energy gap as narrow as $\sim 5$ MeV. A comparison on correlation functions, effective energies, and HAL QCD potentials between unoptimized operators and optimized operators is given, with a special emphasis on the effects from nearby elastic scattering states. Potential applicability of the optimized operator to various two-hadron systems and its relation to the variational method are also discussed.

hep-lat↗

arXiv2025

Lattice gauge ensembles and data management

We summarize the status of lattice QCD ensemble generation efforts and their data management characteristics. Namely, these proceedings combine the contributions to a dedicated parallel session during the 41st International Symposium on Lattice Field Theory (Lattice 2024), during which representatives of 16 lattice QCD collaborations provided details on their simulation program, with focus on plans for publication, data management, and storage requirements. The parallel session was organized by the International Lattice Data Grid (ILDG), following an open call to the lattice QCD community for participation in the session.

hep-lat↗

arXiv2025

$NJ/ψ$ and $Nη_c$ interactions from lattice QCD

The interaction between nucleon and charmonia ($J/ψ$ and $η_c$) is expected to deepen our understanding of various aspects in nonperturbative QCD ranging from the origin of nucleon mass to $J/ψ$ mass modification in nuclear medium and properties of hidden-charm pentaquark states. Here, we present the low-energy $NJ/ψ$ and $Nη_c$ interactions based on ($2+1$) flavor lattice QCD simulations with nearly physical pion mass $m_π=146$ MeV. The interactions, extracted from the spacetime correlations of the nucleon and charmonium system by using the HAL QCD method, are found to be attractive in all distances and manifest a characteristic long-range tail consistent with the two-pion exchange interaction. The resulting scattering lengths are around $0.3$ fm, $0.4$ fm and $0.2$ fm for $NJ/ψ$ with spin $3/2$, with spin $1/2$, and $Nη_c$, respectively. Our results are orders of magnitude larger than those from the photoproduction experiments assuming the vector meson dominance.

hep-lat↗

arXiv2025

Left-hand cut and the HAL QCD method

We investigate how the left-hand cut (LHC) problem is treated in the HAL QCD method. For this purpose, we first consider the effect of the LHC to the scattering problem in non-relativistic quantum mechanics with potentials. We show that the $S$-matrix or the scattering phase shift obtained from the potential including the Yukawa term ($e^{- m_πr}/r$) with the infra-red (IR) cutoff $R$ is well-defined even for the complex momentum $k$ as long as $R$ is finite, and they are compared with those obtained by the analytic continuation without the IR cutoff. In the $R\to\infty$ limit, the phase shift approaches the result from the analytic continuation at ${\rm Im}\, k < m_π/2$, while they differ at ${\rm Im}\, k > m_π/2$, except $k= k_b$, where $k_b$ is the binding momentum. We also observe that $k_b$ can be correctly obtained even at finite but large $R$. Using knowledge obtained in the non-relativistic quantum mechanics, we present how we should treat the LHC in the HAL QCD potential method.

hep-lat↗

arXiv2024

Nucleon-charmonium interactions from lattice QCD

We present a realistic lattice QCD study on low-energy $N$-$J/ψ$ and $N$-$η_c$ interactions based on (2+1) flavor configurations with nearly physical pion mass $m_π=146$ MeV. The interactions, extracted from the spacetime correlations of nucleon and charmonium system by using the HAL QCD method, are found to be attractive in all distances and possess a characteristic long-range tail consistent with the two-pion exchange potential. The resulting $S$-wave scattering lengths are $0.30(2)\left(^{+0}_{-2}\right)$ fm, $0.38(4)\left(^{+0}_{-3}\right)$ fm, and $0.21(2)\left(^{+0}_{-1}\right)$ fm for spin-$3/2$ $N$-$J/ψ$, spin-$1/2$ $N$-$J/ψ$, and spin-$1/2$ $N$-$η_c$, respectively. Our results are orders of magnitude larger than those from the photoproduction experiments assuming the vector meson dominance. Our findings may provide deeper understanding of the nonperturbative QCD phenomena ranging from the origin of nucleon mass to the in-medium $J/ψ$ mass modification as well as the properties of hidden-charm pentaquark states.

hep-lat↗

arXiv2024

Scale setting and hadronic properties in light quark sector with $(2+1)$-flavor Wilson fermions at the physical point

We report scale setting and hadronic properties for our new lattice QCD gauge configuration set (HAL-conf-2023). We employ $(2+1)$-flavor nonperturbatively improved Wilson fermions with stout smearing and the Iwasaki gauge action on a $96^4$ lattice, and generate configurations of 8,000 trajectories at the physical point. We show the basic properties of the configurations such as the plaquette value, topological charge distribution and their auto-correlation times. The scale setting is performed by detailed analyses of the $Ω$ baryon mass. We calculate the physical results of quark masses, decay constants of pseudoscalar mesons and single hadron spectra in light quark sector. The masses of the stable hadrons are found to agree with the experimental values within a sub-percent level.

hep-lat↗

arXiv2024

Building Hadron Potentials from Lattice QCD with Deep Neural Networks

In this study, we develop a deep learning method to learn hadronic interactions unsupervisedly from the correlation functions calculated in lattice QCD simulations. We present our approach of using deep neural networks to model the inter-hadron potentials that are learned from Nambu-Bethe-Salpeter (NBS) wave functions. This enables the incorporation of most general forms of potentials into the Schrödinger-type equation for detailed analysis of hadronic interactions. Our results include validations with separable potentials, as well as the local and non-local potentials for the $Ω_{ccc}-Ω_{ccc}$ system. The neural networks accurately capture the essential features of these interactions, providing a reliable tool for predicting and analyzing hadron scattering properties, potentially bridging the experimental observables and lattice QCD data.

hep-lat↗

arXiv2024

Lattice QCD and Baryon-Baryon Interactions

In this chapter, the current status on baryon-baryon interactions such as nuclear forces in lattice Quantum ChromoDynamics (QCD) is reviewed. In studies of baryon-baryon interactions in lattice QCD, the most reliable method so far is the potential method, proposed by the Hadrons to Atomic nuclei from Lattice QCD (HAL QCD) collaboration, whose formulation, properties and extensions are explained in detail. Using the HAL QCD potential method, potentials between nucleons (proton and neutron, denoted by $N$) in the derivative expansion have been extracted in various cases. The lattice QCD results shown in this chapter include a Leading Order (LO) central potential in the parity-even $NN(^1S_0)$ channel, LO central and tensor potentials in the parity-even $NN(^3S_1$-$^3D_1)$ channel, and a Next-to-Leading Order (NLO) spin-orbit potential as well as LO potentials in the parity-odd channels. Preliminary results at the almost physical pion and kaon masses, in addition to exploratory studies on three-nucleon potentials, are presented. Interactions between generic baryons including hyperons, made of one or more strange quarks as well as up and down quarks, have also been investigated. Universal properties of potentials between baryons become manifest in the flavor SU(3) symmetric limit, where masses of three quarks, up, down and strange, are all equal. In particular, it is observed that one bound state, traditionally called the $H$-dibaryon, appears in the flavor singlet representation of SU(3). A fate of the $H$ dibaryon is also discussed with flavor SU(3) breaking taken into account at the almost physical point. Finally, various kinds of dibaryons, bound or resonate states of two baryons, including charmed dibaryons, have been predicted by lattice QCD simulations at the almost physical point.

hep-lat↗

arXiv2024

Toward nuclear physics from lattice QCD on quantum computers

One of the ultimate missions of lattice QCD is to simulate atomic nuclei from the first principle of the strong interaction. This is an extremely hard task for the current computational technology, but might be reachable in coming quantum computing era. In this paper, we discuss the computational complexities of classical and quantum simulations of lattice QCD. It is shown that the quantum simulation scales better as a function of a nucleon number and thus will outperform for large nuclei.

hep-lat↗

arXiv2024

Doubly charmed tetraquark $T_{cc}^+$ in (2+1)-flavor QCD near physical point

We study the doubly charmed tetraquark state $T_{cc}^+$ by the HAL QCD method applied to the $D^*D$ system in $(2+1)$ flavor lattice QCD at nearly physical pion mass, $m_π= 146$ MeV. We obtain the attractive potential at all distances in the $S$-wave of the isoscalar $D^* D$ system, whose long distance behavior is well described by the two-pion exchange (TPE), and it generates a virtual pole near $D^* D$ threshold with a pole position $E_{\rm pole} = -59 (^{+53}_{-99}) (^{+2}_{-67})$ keV and an inverse scattering length $1/a_0=0.05(5)(^{+2}_{-2})$ fm$^{-1}$. The virtual pole turns into a loosely bound state pole if the pion mass in the TPE potential is extrapolated to the physical value, $m_π=135$ MeV. The potential at the physical pion mass is shown to give a semi-quantitative description of the $D^0 D^0π^+$ mass spectrum at the LHCb.

hep-lat↗

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.

nucl-ex↗

arXiv2023

Doubly Charmed Tetraquark $T^+_{cc}$ from Lattice QCD near Physical Point

The doubly charmed tetraquark $T^+_{cc}$ recently discovered by the LHCb Collaboration is studied on the basis of $(2+1)$-flavor lattice QCD simulations of the $D^*D$ system with nearly physical pion mass $m_π=146$ MeV. The interaction of $D^*D$ in the isoscalar and $S$-wave channel, derived from the hadronic spacetime correlation by the HAL QCD method, is attractive for all distances and leads to a near-threshold virtual state with a pole position $E_\text{pole}=-59\left(^{+53}_{-99}\right)\left(^{+2}_{-67}\right)$ keV and a large scattering length $1/a_0=0.05(5)\left(^{+2}_{-2}\right)~\text{fm}^{-1}$. The virtual state is shown to evolve into a loosely bound state as $m_π$ decreases to its physical value by using a potential modified to $m_π=135$ MeV based on the pion-exchange interaction. Such a potential is found to give a semiquantitative description of the LHCb data on the $D^0D^0π^+$ mass spectrum. Future study is necessary to perform physical-point simulations with the isospin-breaking and open three-body-channel effects taken into account.

hep-lat↗

arXiv2023

Lattice QCD studies on decuplet baryons as meson-baryon bound states in the HAL QCD method

We study decuplet baryons from meson-baryon interactions in lattice QCD, in particular, $Δ$ and $Ω$ baryons from P-wave $I=3/2$ $Nπ$ and $I=0$ $Ξ\bar{K}$ interactions, respectively. Interaction potentials are calculated in the HAL QCD method using 3-quark-type source operators at $m_π \approx 410~\textrm{MeV}$ and $m_{K} \approx 635~\textrm{MeV}$, where $Δ$ as well as $Ω$ baryons are stable. We use the conventional stochastic estimate of all-to-all propagators combined with the all-mode averaging to reduce statistical fluctuations. We have found that the $Ξ\bar K$ system has a weaker attraction than the $Nπ$ system while the binding energy from the threshold is larger for $Ω$ than $Δ$. This suggests that an inequality $m_{N}+m_π-m_Δ<m_Ξ+m_{\bar K}-m_Ω$ comes mainly from a smaller spatial size of a $Ξ\bar K$ bound state due to a larger reduced mass, rather than its interaction. Root-mean-square distances of bound states in both systems are small, indicating that $Δ$ and $Ω$ are tightly bound states and thus can be regarded qualitatively as composite states of 3 quarks. Results of binding energies agree with those obtained from temporal 2-point functions within large systematic errors, which arise dominantly from the lattice artifact at short distances.

hep-lat↗

arXiv2022

Attractive $N$-$ϕ$ Interaction and Two-Pion Tail from Lattice QCD near Physical Point

First results on the interaction between the $ϕ$-meson and the nucleon ($N$) are presented based on the ($2+1$)-flavor lattice QCD simulations with nearly physical quark masses. Using the HAL QCD method, the spacetime correlation of the $N$-$ϕ$ system in the spin 3/2 channel is converted into the $N$-$ϕ$ scattering phase shift through the interaction potential. The $N$-$ϕ$ potential appears to be a combination of a short-range attractive core and a long-range attractive tail. The latter is found to be consistent with the two-pion exchange (TPE) obtained from the interaction between a color-dipole and the nucleon. The resultant scattering length and effective range for $m_π=$ 146.4 MeV are $ a^{(3/2)}_0=-1.43(23)_{\rm stat.}\left(^{+36}_{-06}\right)_{\rm syst.} {\rm fm}$ and $ r^{(3/2)}_{\rm eff}=2.36(10)_{\rm stat.}\left(^{+02}_{-48}\right)_{\rm syst.} {\rm fm}$, respectively. The magnitude of the scattering length is shown to have nontrivial dependence of $m_π$ and is sensitive to the existence of the long-range tail from TPE.

hep-lat↗