Yoichi Ikeda

Chiral SU(3) theory of antikaon-nucleon interactions with improved threshold constraints

K-nucleon interactions are investigated in the framework of coupled-channels dynamics based on the next-to-leading order chiral SU(3) meson-baryon effective Lagrangian. A recent determination of the 1s shift and width of kaonic hydrogen enables us to set accurate constraints on the coupled-channels meson-baryon amplitudes in the strangeness S = 1 sector. Theoretical uncertainties in the subthreshold extrapolation of the coupled-channels amplitudes are discussed. Using this framework, we give predictions for K neutron interactions and for the spectrum of the (1405) resonance. A simplied, eective three-channel model using leading order chiral SU(3) meson-baryon interactions is also constructed for convenient application in K-nuclear few-body calculations.

Improved constraints on chiral SU(3) dynamics from kaonic hydrogen

A new improved study of K -proton interactions near threshold is performed using coupledchannels dynamics based on the next-to-leading order chiral SU(3) meson-baryon eective Lagrangian. Accurate constraints are now provided by new high-precision kaonic hydrogen measurements. Together with threshold branching ratios and scattering data, these constraints permit an updated analysis of the complex KN and coupled-channels amplitudes and an improved determination of the K p scattering length, including uncertainty estimates.

Hadron–hadron interactions from imaginary-time Nambu–Bethe–Salpeter wave function on the lattice

Abstract Imaginary-time Nambu–Bethe–Salpeter (NBS) wave function is introduced to extend our previous approach for hadron–hadron interactions on the lattice. Scattering states of hadrons with different energies encoded in the NBS wave function are utilized to extract non-local hadron–hadron potential. “The ground state saturation”, which is commonly used in lattice QCD but is hard to be achieved for multi-baryons, is not required. We demonstrate that the present method works efficiently for the nucleon–nucleon interaction (the potential and the phase shift) in the S 0 1 channel.

Two-baryon potentials and H-dibaryon from 3-flavor lattice QCD simulations

Abstract Baryon–baryon potentials are obtained from 3-flavor QCD simulations with the lattice volume L ≃ 4 fm , the lattice spacing a ≃ 0.12 fm , and the pseudo-scalar-meson mass M ps = 469 – 1171 MeV . The NN scattering phase-shifts and the mass of H-dibaryon in the flavor SU ( 3 ) limit are extracted from the resultant potentials by solving the Schrodinger equation. The NN phase-shifts in the SU ( 3 ) limit is shown to have qualitatively similar behavior as the experimental data. A bound H-dibaryon in the SU ( 3 ) limit is found to exist in the flavor-singlet J P = 0 + channel with the binding energy of about 26 MeV for the lightest quark mass M ps = 469 MeV . Effect of flavor SU ( 3 ) symmetry breaking on the H-dibaryon is estimated by solving the coupled-channel Schrodinger equation for Λ Λ – N Ξ – Σ Σ with the physical baryon masses and the potential matrix obtained in the SU ( 3 ) limit: a resonant H-dibaryon is found between ΛΛ and NΞ thresholds in this treatment.

Exploring Three-Nucleon Forces in Lattice QCD

Three-nucleon forces (3NF) are investigated from two-flavor lattice QCD simulations. We utilize the Nambu-Bethe-Salpeter (NBS) wave function to determine two-nucleon forces (2NF) and 3NF in the same framework. As a first exploratory study, we extract 3NF in which three nucleons are aligned linearly with an equal spacing. This is the simplest geometrical configuration which reduces the huge computational cost of calculating the NBS wave function. Quantum numbers of the three-nucleon system are chosen to be (I, J^P)=(1/2,1/2^+) (the triton channel). Lattice QCD simulations are performed using N_f=2 dynamical clover fermion configurations at the lattice spacing of a = 0.156 fm on a 16^3 x 32 lattice with a large quark mass corresponding to m_pi= 1.13 GeV. We find repulsive 3NF at short distance in the triton channel. Several sources of systematic errors are also discussed.

Extraction of Hadron Interactions above Inelastic Threshold in Lattice QCD

We propose a new method to extract hadron interactions above inelastic threshold from the Nambu–Bethe–Salpeter amplitude in lattice QCD. We consider the scattering such as A + B → C + D, where A, B, C, D are names of different 1-particle states. An extension to cases where particle productions occur during scatterings is also discussed.

Mirage in Temporal Correlation functions for Baryon-Baryon Interactions in Lattice QCD

A bstractSingle state saturation of the temporal correlation function is a key condition to extract physical observables such as energies and matrix elements of hadrons from lattice QCD simulations. A method commonly employed to check the saturation is to seek for a plateau of the observables for large Euclidean time. Identifying the plateau in the cases having nearby states, however, is non-trivial and one may even be misled by a fake plateau. Such a situation takes place typically for a system with two or more baryons. In this study, we demonstrate explicitly the danger from a possible fake plateau in the temporal correlation functions mainly for two baryons (ΞΞ and N N ), and three and four baryons (3He and 4He) as well, employing (2+1)-flavor lattice QCD at mπ = 0.51GeV on four lattice volumes with L = 2.9, 3.6, 4.3 and 5.8 fm. Caution is required when drawing conclusions about the bound N N , 3N and 4N systems based only on the standard plateau fitting of the temporal correlation functions.n

Quark-Anti-Quark Potentials from Nambu-Bethe-Salpeter Amplitudes on Lattice

Quark--anti-quark (anti-q-q) potentials with finite quark masses are studied from the anti-q-q Nambu-Bethe-Salpeter (NBS) wave functions in quenched lattice QCD. With the use of a method which has been recently developed in the derivation of nuclear forces from lattice QCD, we derive the anti-q-q potentials from the NBS wave functions. We calculate the anti-q-q NBS wave functions in pseudo-scalar and vector channels for several quark masses. The derived potentials at each quark mass in both channels show linear plus Coulomb form. We also discuss the quark-mass and channel dependence of the anti-q-q potentials.

ΛcN interaction from lattice QCD and its application to Λc hypernuclei

Abstract The interaction between Λ c and a nucleon (N) is investigated by employing the HAL QCD method in the ( 2 + 1 ) -flavor lattice QCD on a ( 2.9 fm ) 3 volume at m π ≃ 410 , 570 , 700 MeV. We study the central potential in S 0 1 channel as well as central and tensor potentials in S 1 3 − 3 D 1 channel, and find that the tensor potential for Λ c N is negligibly weak and central potentials in both S 0 1 and S 1 3 − 3 D 1 channels are almost identical with each other except at short distances. Phase shifts and scattering lengths calculated with these potentials show that the interaction of Λ c N system is attractive and has a similar strength in S 0 1 and S 1 3 channels at low energies (i.e. the kinetic energy less than about 40 MeV). While the attractions are not strong enough to form two-body bound states, our results lead to a possibility to form Λ c hypernuclei for sufficiently large atomic numbers (A). To demonstrate this, we derive a single-folding potential for Λ c hypernuclei from the Λ c -nucleon potential obtained in lattice QCD, and find that Λ c hypernuclei can exist for A ≥ 12 with the binding energies of a few MeV. We also estimate the Coulomb effect for the Λ c hypernuclei.

Baryon interactions from lattice QCD with physical quark masses – Nuclear forces and ΞΞ forces –

We present the latest lattice QCD results for baryon interactions obtained at nearly physical quark masses. Nf = 2 + 1 nonperturbatively O(a) -improved Wilson quark action with stout smearing and Iwasaki gauge action are employed on the lattice of (96a)4 ≃(8.1fm)4 with a-1 ≃2.3 GeV, where mπ ≃146 MeV and mK ≃525 MeV. In this report, we study the two-nucleon systems and two-Ξ systems in 1 S0 channel and 3 S 1 -3 D 1 coupled channel, and extract central and tensor interactions by the HAL QCD method. We also present the results for the NΩ interaction in 5 S2 channel which is relevant to the NΩ pair-momentum correlation in heavy-ion collision experiments.