Application of dilaton chiral perturbation theory to Nf=8 , SU(3) spectral data

Abstract

We extend dilaton chiral perturbation theory (dChPT) to include the taste splittings in the Nambu-Goldstone sector observed in lattice simulations of near-conformal theories with staggered fermions. We then apply dChPT to a recent simulation by the LSD Collaboration of the SU(3) gauge theory with 8 fermions in the fundamental representation, which is believed to exhibit near-conformal behavior in the infrared, and in which a light singlet scalar state, nearly degenerate with the pions, has been found. We find that the mesonic sector of this theory can be successfully described by dChPT, including, in particular, the mesonic taste splittings found in the simulation. We confirm that current simulations of this theory are in the "large-mass" regime.

Goldstone Boson Scattering with a Light Composite Scalar

“…1, 5 and 6. The values we get lie close to the allowed ranges found in earlier dilaton studies of the N f = 8 theory [33,58] which reported good agreement between the tree level EFT and the available lattice data, but did not consider scattering observables. The estimated uncertainties of the fit parameters are obtained by calculating the inverse Hessian of the chi-squared function at its minimum, to extract the standard errors.…”

Dilaton chiral perturbation theory and applications

“…Here we review some of the fits performed in Ref. [11] of the tree-level predictions to data for the pion mass and decay constant, as well as the dilaton mass, as a function of the fermion mass. 1 The ensembles of Ref.…”

“…2 we show results of one of the fits of Ref. [11], using data for M 2 ⇡ /F 2 ⇡ , aF ⇡ and M 2 ⌧ /F 2 ⇡ at the lowest four am values. The fit has a p-value of 0.89.…”

Gliding Down the QCD Transition Line, from Nf = 2 till the Onset of Conformality

“…We emphasise that at T = 0, it is very hard to distinguish a chirally broken theory from a mass-deformed conformal theory, see, for instance, Refs. [76][77][78].…”