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Register a new userPion form factor from all-to-all propagators of overlap quarks
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We report on our calculation of the pion electromagnetic form factor with two-flavors of dynamical overlap quarks. Gauge configurations are generated using the Iwasaki gauge action on a 16^3 times 32 lattice at the lattice spacing of 0.12fm with sea quark masses down to m_s/6, where m_s is the physical strange quark mass. We describe our setup to measure the form factor through all-to-all quark propagators and present preliminary results.
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We measure the ground and excited states for B mesons in the static limit using maximally variance reduced estimators for light quark propagators. Because of the large number of propagators we are able to measure accurately also orbitally excited P, D and F states. We also present some results for Lambda_b.
In this paper, we report recent developments of the HAL QCD method for two hadron systems which contain quark annihilation processes using all-to-all quark propagators. We employ the hybrid method for all-to-all propagators, which combines a low-mode spectral decomposition of the quark propagator and stochastic estimators for remaining high modes, to evaluate the HAL QCD potentials for the first time. Using this method, we investigate the $I= 1,2$ $pi pi$ scatterings at $m_{pi} approx 870$ MeV. In the $I=2$ study, we study how statistical fluctuations of the HAL QCD potentials are increased due to stochastic estimators in the hybrid method, compared with the conventional one without them. We find that we can reduce statistical fluctuations by dilutions of stochastic noises in order to obtain sufficiently precise results, which turn out to be consistent with conventional results without all-to-all propagators. In the $I=1$ $pi pi$ case, which contains quark annihilation processes, we find that statistical fluctuations are further enhanced due to noise contaminations in annihilation processes. We, however, confirm that we can also reduce such statistical fluctuations to obtain the potential with a reasonable precision as long as we further increase a degree of dilutions at a price of large numerical costs and take an appropriate scheme for the potential.
We present a study of gauge invariant density-density correlators. Density-density correlators probe hadron wave functions and thus can be used to study hadron deformation. Their zero momentum projection requires the computation of all-to-all propagators, which are evaluated with the standard stochastic technique, the dilution method and the stochastic sequential technique. We compare the results to a previous analysis that did not employ the zero momentum projection.
Hadron spectroscopy on dynamical configurations are faced with the difficulties of dealing with the mixing of single particle states and multi-hadron states (for large spatial volumes and light dynamical quarks masses). It is conceivable that explicit multi-hadron interpolating operators will be necessary for obtaining sufficiently good overlap onto multi-hadron states in order to extract the low-lying excitation spectrum. We explore here the feasibility of using four noise diluted all-to-all quark propagators in the construction of explicit two-hadron operators on quenched, anisotropic lattices. Our longer term goal is to use these operators on large anisotropic, dynamical configurations for hadron spectroscopy.
We calculate the pion vector and scalar form factors in two-flavor QCD. Gauge configurations are generated with dynamical overlap quarks on a 16^3 x 32 lattice at a lattice spacing of 0.12 fm with sea quark masses down to a sixth of the physical strange quark mass. Contributions of disconnected diagrams to the scalar form factor is calculated employing the all-to-all quark propagators. We present a detailed comparison of the vector and scalar radii with chiral perturbation theory to two loops.
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