The size of the pion from full lattice QCD with physical u, d, s and c quarks

Koponen, J., Davies, C. T. H. , Dowdall, R. J. and Lepage, G. P. (2016) The size of the pion from full lattice QCD with physical u, d, s and c quarks. Physical Review D, 93, 054503. (doi: 10.1103/PhysRevD.93.054503)

Abstract

We present the first calculation of the electromagnetic form factor of the π meson at physical light quark masses. We use configurations generated by the MILC collaboration including the effect of u, d, s and c sea quarks with the Highly Improved Staggered Quark formalism. We work at three values of the lattice spacing on large volumes and with u/d quark masses going down to the physical value. We study scalar and vector form factors for a range in space-like q2 from 0.0 to -0.13 GeV2 and from their shape we extract mean square radii. Our vector form factor agrees well with experiment and we find hr2iV = 0:403(18)(6) fm2. For the scalar form factor we include quark-line disconnected contributions which have a significant impact on the radius. We give the first results for SU(3) flavour-singlet and octet scalar mean square radii, obtaining: hr2isinglet S = 0:506(38)(53)fm2 and hr2ioctet S = 0:431(38)(46)fm2. We discuss the comparison with expectations from chiral perturbation theory.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Davies, Professor Christine and Koponen, Dr Jonna and Dowdall, Dr Rachel
• Authors: Koponen, J., Davies, C. T. H., Dowdall, R. J., and Lepage, G. P.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review D
• Publisher: American Physical Society
• ISSN: 1550-7998
• ISSN (Online): 1550-2368
• First Published: First published in Physical Review D 93:054503
• Publisher Policy: Reproduced under a Creative Commons License