The K + K + scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the MILC asqtad-improved gauge configurations with rooted staggered sea quarks. Three-flavor mixed-action chiral perturbation theory at next-to-leading order, which includes the leading effects of the finite lattice spacing, is used to extrapolate the results of the lattice calculation to the physical value of m K + /f K + . We find m K + a K + K + = −0.352 ± 0.016, where the statistical and systematic errors have been combined in quadrature.

We present evidence for the existence of a bound H-dibaryon, an I = 0, J = 0, s = −2 state with valence quark structure uuddss, at a pion mass of mπ ∼ 389 MeV. Using the results of Lattice QCD calculations performed on four ensembles of anisotropic clover gauge-field configurations, with spatial extents of L ∼ 2.0, 2.5, 3.0 and 3.9 fm at a spatial lattice spacing of bs ∼ 0.123 fm, we find an H-dibaryon bound by B H ∞ = 16.6 ± 2.1 ± 4.6 MeV at a pion mass of mπ ∼ 389 MeV.It is now well established that quantum chromodynamics (QCD), the theory describing the dynamics of quarks and gluons, and the electroweak interactions, underlie all of nuclear physics, from the hadronic mass spectrum to the synthesis of heavy elements in stars. To date, there have been few quantitative connections between nuclear physics and QCD, but fortunately, Lattice QCD is entering an era in which precise predictions for hadronic quantities with quantifiable errors are being made. This development is particularly important for processes which are difficult to explore in the laboratory, such as hyperon-hyperon and hyperon-nucleon interactions for which knowledge is scarce, primarily due to the short lifetimes of the hyperons, but which may impact the late-stages of supernovae evolution. In this letter we report strong evidence for a bound H-dibaryon, a six-quark hadron with valence structure uuddss, from n f = 2 + 1 Lattice QCD calculations at light-quark masses that give the pion a mass of m π ∼ 389 MeV.The prediction of a relatively deeply bound system with the quantum numbers of ΛΛ (called the H-dibaryon) by Jaffe [1] in the late 1970s, based upon a bag-model calculation, started a vigorous search for such a system, both experimentally and also with alternate theoretical tools. Experimental constraints on, and phenomenological models of, the H-dibaryon can be found in Refs. [2,3,4]. While experimental studies of doublystrange hypernuclei restrict the H-dibaryon to be unbound or to have a small binding energy, the most recent constraints on the existence of the H-dibaryon come from heavy-ion collisions at RHIC, from which it is concluded that the H-dibaryon does not exist in the mass region 2.136 < M H < 2.231 GeV [5], effectively eliminating the possibility of a loosely-bound H-dibaryon at the physical light-quark masses. Recent experiments at KEK suggest there is a resonance near threshold in the H-dibaryon channel [6].The first study of baryon-baryon interactions with Lattice QCD was performed more than a decade ago [7,8]. This calculation was quenched and with m π > ∼ 550 MeV. The NPLQCD collaboration performed the first n f = 2+ 1 QCD calculations of baryon-baryon interactions [9,10] at low-energies but at unphysical pion masses. Quenched and dynamical calculations were subsequently performed by the HALQCD collaboration [11,12]. A number of quenched Lattice QCD calculations [13,14,15,16,17,18] have searched for the H-dibaryon, but to date no definitive results have been reported. Earlier work concluded that the H-dibaryon does not exi...

Results of a high-statistics, multi-volume Lattice QCD exploration of the deuteron, the di-neutron, the H-dibaryon, and the Ξ − Ξ − system at a pion mass of m π ∼ 390 MeV are presented. Calculations were performed with an anisotropic n f = 2+1 Clover discretization in four lattice volumes of spatial extent L ∼ 2.0, 2.5, 2.9 and 3.9 fm, with a lattice spacing of b s ∼ 0.123 fm in the spatial-direction, and b t ∼ b s /3.5 in the time-direction. Using the results obtained in the largest two volumes, the Ξ − Ξ − is found to be bound by B Ξ − Ξ − = 14.0(1.4)(6.7) MeV, consistent with expectations based upon phenomenological models and low-energy effective field theories constrained by nucleonnucleon and hyperon-nucleon scattering data at the physical light-quark masses. Further, we find that the deuteron and the di-neutron have binding energies of B d = 11(05)(12) MeV and B nn = 7.1(5.2)(7.3) MeV, respectively. With an increased number of measurements and a refined analysis, the binding energy of the H-dibaryon is B H = 13.2(1.8)(4.0) MeV at this pion mass, updating our previous result.2

The scattering lengths and effective ranges that describe low-energy nucleon-nucleon scattering are calculated in the limit of SU(3)-flavor symmetry at the physical strange-quark mass with Lattice Quantum Chromodynamics. The calculations are performed with an isotropic clover discretization of the quark action in three volumes with spatial extents of L ∼ 3.4 fm, 4.5 fm and 6.7 fm, and with a lattice spacing of b ∼ 0.145 fm. With determinations of the energies of the two-nucleon systems (both of which contain bound states at these up and down quark masses) at rest and moving in the lattice volume, Lüscher's method is used to determine the low-energy phase shifts in each channel, from which the scattering length and effective range are obtained. The scattering parameters, in the 1 S 0 channel are found to be m π a ( 1 S 0 ) = 9.50 . These values are consistent with the two-nucleon system exhibiting Wigner's supermultiplet symmetry, which becomes exact in the limit of large-N c . In both spin channels, the phase shifts change sign at higher momentum, near the start of the t-channel cut, indicating that the nuclear interactions have a repulsive core even at the SU(3)-symmetric point.

We present an update of the one-meson-exchange ͑OME͒ results for the weak decay of s-and p-shell hypernuclei ͓A. Parreño, A. Ramos, and C. Bennhold, Phys. Rev. C 56, 339 ͑1997͔͒, paying special attention to the role played by final state interactions between the emitted nucleons. The present study also corrects for a mistake in the inclusion of the K and K* exchange mechanisms, which substantially increases the ratio of neutron-induced to proton-induced transitions ⌫ n /⌫ p . With the most up-to-date model ingredients, we find that the OME approach is able to describe very satisfactorily most of the measured observables, including the ratio ⌫ n /⌫ p .