Parity Doubling and the $S$ Parameter below the Conformal Window

T. Appelquist, R. Babich, R. C. Brower, M. Cheng, M. A. Clark, S. D. Cohen, G. T. Fleming, J. Kiskis, M. F. Lin, E. T. Neil, J. C. Osborn, C. Rebbi, D. Schaich, and P. M. Vranas (Lattice Strong Dynamics (LSD) Collaboration)

Phys. Rev. Lett. 106, 231601 – Published 6 June 2011

Abstract

We describe a lattice simulation of the masses and decay constants of the lowest-lying vector and axial resonances, and the electroweak $S$ parameter, in an $S U (3)$ gauge theory with $N_{f} = 2$ and 6 fermions in the fundamental representation. The spectrum becomes more parity doubled and the $S$ parameter per electroweak doublet decreases when $N_{f}$ is increased from 2 to 6, motivating study of these trends as $N_{f}$ is increased further, toward the critical value for transition from confinement to infrared conformality.

Received 8 October 2010

DOI:https://doi.org/10.1103/PhysRevLett.106.231601

Authors & Affiliations

T. Appelquist¹, R. Babich², R. C. Brower², M. Cheng³, M. A. Clark⁴, S. D. Cohen², G. T. Fleming¹, J. Kiskis⁵, M. F. Lin¹, E. T. Neil¹, J. C. Osborn⁶, C. Rebbi², D. Schaich², and P. M. Vranas³ (Lattice Strong Dynamics (LSD) Collaboration)

¹Department of Physics, Sloane Laboratory, Yale University, New Haven, Connecticut 06520, USA
²Department of Physics, Boston University, Boston, Massachusetts 02215, USA
³Physical Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
⁴Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
⁵Department of Physics, University of California, Davis, California 95616, USA
⁶Argonne Leadership Computing Facility, Argonne, Illinois 60439, USA