Walking signals in Nf=8 QCD on the lattice

Yasumichi Aoki, Tatsumi Aoyama, Masafumi Kurachi, Toshihide Maskawa, Kei-ichi Nagai, Hiroshi Ohki, Akihiro Shibata, Koichi Yamawaki, and Takeshi Yamazaki (LatKMI Collaboration)
Phys. Rev. D 87, 094511 – Published 20 May 2013

Abstract

We investigate chiral and conformal properties of the lattice QCD with eight flavors (Nf=8) through meson spectrum using the highly improved staggered quark (HISQ) action. We also compare our results with those of Nf=12 and Nf=4 which we study on the same systematics. We find that the decay constant Fπ of the pseudoscalar meson “pion” π is nonzero, with its mass Mπ consistent with zero, both in the chiral limit extrapolation of the chiral perturbation theory. We also measure other quantities which we find are in accord with the π data results: The ρ meson mass is consistent with nonzero in the chiral limit, and so is the chiral condensate, with its value neatly coinciding with that from the Gell-Mann-Oakes-Renner relation in the chiral limit. Thus, our data for the Nf=8 QCD are consistent with the spontaneously broken chiral symmetry. Remarkably enough, while the Nf=8 data near the chiral limit are well described by the chiral perturbation theory, those for the relatively large fermion bare mass mf away from the chiral limit actually exhibit a finite-size hyperscaling relation, suggesting a large anomalous dimension γm1. This implies that there exists a remnant of the infrared conformality, and suggests that a typical technicolor (“one-family model”) as modeled by the Nf=8 QCD can be a walking technicolor theory having an approximate scale invariance with large anomalous dimension γm1.

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  • Received 27 February 2013

DOI:https://doi.org/10.1103/PhysRevD.87.094511

© 2013 American Physical Society

Authors & Affiliations

Yasumichi Aoki1, Tatsumi Aoyama1, Masafumi Kurachi1, Toshihide Maskawa1, Kei-ichi Nagai1, Hiroshi Ohki1, Akihiro Shibata2, Koichi Yamawaki1, and Takeshi Yamazaki1 (LatKMI Collaboration)

  • 1Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602, Japan
  • 2Computing Research Center, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan

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Issue

Vol. 87, Iss. 9 — 1 May 2013

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