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Register a new userSome continuum physics results from the lattice V-A correlator
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We present preliminary results on extractions of the chiral LECs L_10 and C_87 and constraints on the excited pseudoscalar state pi(1300) and pi(1800) decay constants obtained from an analysis of lattice data for the flavor ud light quark V-A correlator. A comparison of the results for the correlator to the corresponding mildly-model-dependent continuum results (based primarily on experimental hadronic tau decay data) is also given
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A combination of lattice and continuum data for the light-quark V-A correlator, supplemented by results from a chiral sum-rule analysis of the flavor-breaking flavor $ud$-$us$ V-A correlator difference, is shown to make possible a high-precision NNLO determination of the renormalized NLO chiral low-energy constant $L_{10}^r$. Key to this determination is the ability to simultaneously fix the two combinations of NNLO low-energy constants also entering the analysis. With curre
Including the meson-baryon (5 quark) intermediate states in a lattice simulation is challenging. However, it is important in order to obtain the correct energy eigenstates and to relate them to scattering phase shifts. Recent results for the negative parity nucleon channel and the problem of baryonic resonances in lattice calculations are discussed.
We review recent lattice QCD activities with emphasis on the impact on nuclear physics. In particular, the progress toward the determination of nuclear and baryonic forces (potentials) using Nambu-Bethe-Salpeter (NBS) wave functions is presented. We discuss major challenges for multi-baryon systems on the lattice: (i) signal to noise issue and (ii) computational cost issue. We argue that the former issue can be avoided by extracting energy-independent (non-local) potentials from time-dependent NBS wave functions without relying on the ground state saturation, and the latter cost is drastically reduced by developing a novel unified contraction algorithm. The lattice QCD results for nuclear forces, hyperon forces and three-nucleon forces are presented, and physical insights are discussed. Comparison to results from the traditional Lueschers method is given, and open issues to be resolved are addressed as well.
We present physical results obtained from simulations using 2+1 flavors of domain wall quarks and the Iwasaki gauge action at two values of the lattice spacing $a$, ($a^{-1}$=,1.73,(3),GeV and $a^{-1}$=,2.28,(3),GeV). On the coarser lattice, with $24^3times 64times 16$ points, the analysis of ref.[1] is extended to approximately twice the number of configurations. The ensembles on the finer $32^3times 64times 16$ lattice are new. We explain how we use lattice data obtained at several values of the lattice spacing and for a range of quark masses in combined continuum-chiral fits in order to obtain results in the continuum limit and at physical quark masses. We implement this procedure at two lattice spacings, with unitary pion masses in the approximate range 290--420,MeV (225--420,MeV for partially quenched pions). We use the masses of the $pi$ and $K$ mesons and the $Omega$ baryon to determine the physical quark masses and the values of the lattice spacing. While our data are consistent with the predictions of NLO SU(2) chiral perturbation theory, they are also consistent with a simple analytic ansatz leading to an inherent uncertainty in how best to perform the chiral extrapolation that we are reluctant to reduce with model-dependent assumptions about higher order corrections. Our main results include $f_pi=124(2)_{rm stat}(5)_{rm syst}$,MeV, $f_K/f_pi=1.204(7)(25)$ where $f_K$ is the kaon decay constant, $m_s^{bar{textrm{MS}}}(2,textrm{GeV})=(96.2pm 2.7)$,MeV and $m_{ud}^{bar{textrm{MS}}}(2,textrm{GeV})=(3.59pm 0.21)$,MeV, ($m_s/m_{ud}=26.8pm 1.4$) where $m_s$ and $m_{ud}$ are the mass of the strange-quark and the average of the up and down quark masses respectively, $[Sigma^{msbar}(2 {rm GeV})]^{1/3} = 256(6); {rm MeV}$, where $Sigma$ is the chiral condensate, the Sommer scale $r_0=0.487(9)$,fm and $r_1=0.333(9)$,fm.
The exact decomposition of the proton spin has been a much debated topic, on the experimental as well as the theoretical side. In this talk we would like to report on recent non-perturbative results and ongoing efforts to explore the proton spin from lattice QCD. We present results for the relevant generalized form factors from gauge field ensembles that feature a physical value of the pion mass. These generalized form factors can be used to determine the total spin and angular momentum carried by the quarks. In addition we present first results for our ongoing effort to compute the angular momentum of the gluons in the proton.
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