13 research outputs found
Parity Doubling and the S Parameter Below the Conformal Window
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 SU(3) gauge theory with and 6 fermions in the fundamental
representation. The spectrum becomes more parity doubled and the S parameter
per electroweak doublet decreases when is increased from 2 to 6,
motivating study of these trends as is increased further, toward the
critical value for transition from confinement to infrared conformality.Comment: 4 pages, 5 figures; to be submitted to PR
Light Scalar Meson and Decay Constant in SU(3) Gauge Theory with Eight Dynamical Flavors
The SU(3) gauge theory with nearly massless Dirac fermions has long
been of theoretical and phenomenological interest due to the near-conformality
arising from its proximity to the conformal window. One particularly
interesting feature is the emergence of a relatively light, stable
flavor-singlet scalar meson in contrast to the
theory QCD. In this work, we study the finite-volume dependence of the
meson correlation function computed in lattice gauge theory and
determine the meson mass and decay constant extrapolated to the
infinite-volume limit. We also determine the infinite volume mass and decay
constant of the flavor-nonsinglet scalar meson .Comment: 36 pages, 11 figures, supplementary data in zenodo
https://dx.doi.org/10.5281/zenodo.800795
Strongly interacting dynamics and the search for new physics at the LHC
We present results for the spectrum of a strongly interacting SU(3) gauge
theory with light fermions in the fundamental representation.
Carrying out non-perturbative lattice calculations at the lightest masses and
largest volumes considered to date, we confirm the existence of a remarkably
light singlet scalar particle. We explore the rich resonance spectrum of the
8-flavor theory in the context of the search for new physics beyond the
standard model at the Large Hadron Collider (LHC). Connecting our results to
models of dynamical electroweak symmetry breaking, we estimate the vector
resonance mass to be about 2 TeV with a width of roughly 450 GeV, and predict
additional resonances with masses below ~3 TeV.Comment: 6 pages, 6 figures. Added report number. Version submitted to journa
Linear sigma EFT for nearly conformal gauge theories
We construct a generalized linear sigma model as an effective field theory (EFT) to describe nearly conformal gauge theories at low energies. The work is motivated by recent lattice studies of gauge theories near the conformal window, which have shown that the lightest flavor-singlet scalar state in the spectrum (σ) can be much lighter than the vector state (ρ) and nearly degenerate with the PNGBs (π) over a large range of quark masses. The EFT incorporates this feature. We highlight the crucial role played by the terms in the potential that explicitly break chiral symmetry. The explicit breaking can be large enough so that a limited set of additional terms in the potential can no longer be neglected, with the EFT still weakly coupled in this new range. The additional terms contribute importantly to the scalar and pion masses. In particular, they relax the inequality M2σ ≥ 3M2π, allowing for consistency with current lattice data
Nonperturbative investigations of SU(3) gauge theory with eight dynamical flavors
We present our lattice studies of SU(3) gauge theory with = 8
degenerate fermions in the fundamental representation. Using nHYP-smeared
staggered fermions we study finite-temperature transitions on lattice volumes
as large as , and the zero-temperature
composite spectrum on lattice volumes up to . The spectrum
indirectly indicates spontaneous chiral symmetry breaking, but
finite-temperature transitions with fixed enter a strongly
coupled lattice phase as the fermion mass decreases, which prevents a direct
confirmation of spontaneous chiral symmetry breaking in the chiral limit. In
addition to the connected spectrum we focus on the lightest flavor-singlet
scalar particle. We find it to be degenerate with the pseudo-Goldstone states
down to the lightest masses reached so far by non-perturbative lattice
calculations. Using the same lattice approach, we study the behavior of the
composite spectrum when the number of light fermions is changed from eight to
four. A heavy flavor-singlet scalar in the 4-flavor theory affirms the contrast
between QCD-like dynamics and the low-energy behavior of the 8-flavor theory.Comment: 31 pages, 36 figures, 8 tables. v2: update to published versio
Light Scalar Meson and Decay Constant in SU(3) Gauge Theory with Eight Dynamical Flavors
The SU(3) gauge theory with nearly massless Dirac fermions has long
been of theoretical and phenomenological interest due to the near-conformality
arising from its proximity to the conformal window. One particularly
interesting feature is the emergence of a relatively light, stable
flavor-singlet scalar meson in contrast to the
theory QCD. In this work, we study the finite-volume dependence of the
meson correlation function computed in lattice gauge theory and
determine the meson mass and decay constant extrapolated to the
infinite-volume limit. We also determine the infinite volume mass and decay
constant of the flavor-nonsinglet scalar meson