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Phys. Rev. D 79, 054502 (2009) [37 pages]

Light hadron spectroscopy using domain wall valence quarks on an asqtad sea

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A. Walker-Loud
Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA

H.-W. Lin, D. G. Richards, and R. G. Edwards
Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

M. Engelhardt
Physics Department, New Mexico State University, Las Cruces, New Mexico 88003-8001, USA

G. T. Fleming
Sloane Physics Laboratory, Yale University, New Haven, Connecticut 06520, USA

Ph. Hägler and B. Musch
Institut fur Theoretische Physik T39, Physik-Department der TU München, James-Franck-Strasse, D-85747 Garching, Germany

M. F. Lin, H. Meyer, J. W. Negele, A. V. Pochinsky, M. Procura, and S. Syritsyn
Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

C. J. Morningstar
Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

K. Orginos
Department of Physics, College of William and Mary, Williamsburg Virginia 23187-8795, USA and Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

D. B. Renner
DESY Zeuthen, Theory Group, Platanenallee 6, D-15738 Zeuthen, Germany

W. Schroers
Department of Physics, Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan

Received 21 July 2008; revised 12 January 2009; published 6 March 2009

We calculate the light hadron spectrum in full QCD using two plus one flavor asqtad sea quarks and domain wall valence quarks. Meson and baryon masses are calculated on a lattice of spatial size L≈2.5  fm, and a lattice spacing of a≈0.124  fm, for pion masses as light as mπ≈300  MeV, and compared with the results by the MILC Collaboration with asqtad valence quarks at the same lattice spacing. Two- and three-flavor chiral extrapolations of the baryon masses are performed using both continuum and mixed action heavy baryon chiral perturbation theory. Both the three-flavor and two-flavor functional forms describe our lattice results, although the low-energy constants from the next-to-leading order SU(3) fits are inconsistent with their phenomenological values. Next-to-next-to-leading order SU(2) continuum formulae provide a good fit to the data and yield an extrapolated nucleon mass consistent with experiment, but the convergence pattern indicates that even our lightest pion mass may be at the upper end of the chiral regime. Surprisingly, our nucleon masses are essentially linear in mπ over our full range of pion masses, and we show this feature is common to all recent dynamical calculations of the nucleon mass. The origin of this linearity is not presently understood, and lighter pion masses and increased control of systematic errors will be needed to resolve this puzzling behavior.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevD.79.054502
DOI:
10.1103/PhysRevD.79.054502
PACS:
11.15.Ha, 12.38.Gc, 12.38.Lg, 14.40.−n
 
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