Nuclear Physics & RIKEN Theory Seminar

"Physical Predictions with Mixed Action Lattice QCD"

Presented by Andre Walker-Loud, University of Maryland

Friday, March 30, 2007, 2:00 pm — Small Seminar Room, Bldg. 510

There has recently been a rapid growth in the use of mixed action or hybrid lattice QCD simulations for the computation of hadronic matrix elements. Mixed action simulations allow one to construct hadronic source and sink operators with chirally symmetric discretization methods for the valence fermions (which are numerically expensive) in the background of gauge configurations which are generated with (numerically cheaper) discretization methods for the sea fermions that violate chiral symmetry. Using effective field theory methods, I will show that the chiral symmetry of the valence fermions is strong enough to suppress sources of chiral symmetry breaking associated with the lattice spacing artifacts which generally plague lattice simulations. This leads to a nearly universal form for the extrapolation formulae of hadronic observables, independent of the discretization method used for the sea fermions. For quantities protected by chiral symmetry, the counterterm structure is identical to the physical counterterm structure, which arises in chiral perturbation theory.

These realizations are only apparent when one uses an on-shell renormalization scheme, which I will explicitly demonstrate. I will also discuss the general implications this has for extrapolation formulae both on and off the lattice. I will then make use of these observations to discuss several hadronic observables with an emphasis on two-hadron systems. Finally I will use this understanding and existing lattice results to make predictions of quantities not directly measured in lattice simulations. In particular, I make an explicit prediction for the I=1 KK scattering length.

Hosted by: Agnes Mocsy

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