Wave function of the Roper from lattice QCD
Date
2013
Authors
Roberts, D.
Kamleh, W.
Leinweber, D.
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Physics Letters B: Nuclear Physics and Particle Physics, 2013; 725(1):164-169
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Dale S. Roberts, Waseem Kamleh, Derek B. Leinweber
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Abstract
We apply the eigenvectors from a variational analysis in lattice QCD to successfully extract the wave function of the Roper state, and a higher mass P<inf>11</inf> state of the nucleon. We use the 2+1 flavour 32<sup>3</sup>×64 PACS-CS configurations at a near-physical pion mass of 156 MeV. We find that both states exhibit a structure consistent with a constituent quark model. The Roper d-quark wave function contains a single node consistent with a 2S state, and the third state wave function contains two, consistent with a 3S state. A detailed comparison with constituent quark model wave functions is carried out, obtained from a Coulomb plus ramp potential. These results validate the approach of accessing these states by constructing a variational basis composed of different levels of fermion source and sink smearing. Furthermore, significant finite volume effects are apparent for these excited states which mix with multi-particle states, driving their masses away from physical values and enabling the extraction of resonance parameters from lattice QCD simulations. © 2013 .
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© 2013 Published by Elsevier B.V.