%0 Journal Article
%T Quark Condensate from Renormalization Group Optimized Spectral Density
%+ Laboratoire Charles Coulomb (L2C)
%A Kneur, Jean-Loïc
%A Neveu, Andre
%Z 5 pages, talk given at 18th International Conference in Quantum Chromodynamics (QCD 15) Montpellier, published in the proceedings
%< avec comité de lecture
%Z L2C:15-245
%@ 0920-5632
%J Nuclear Physics B - Proceedings Supplements
%I Elsevier
%V 270
%P 98-102
%8 2016
%D 2016
%Z 1512.03406
%R 10.1016/j.nuclphysbps.2016.02.021
%K renormalization group
%K optimized perturbation
%K spectral density
%K Chiral quark condensate
%Z Physics [physics]/High Energy Physics - Phenomenology [hep-ph]
%Z Physics [physics]/High Energy Physics - Lattice [hep-lat]
%Z Physics [physics]/High Energy Physics - Theory [hep-th]Journal articles
%X Our renormalization group consistent variant of optimized perturbation, RGOPT, is used to calculate the nonperturbative QCD spectral density of the Dirac operator and the related chiral quark condensate $\langle \bar q q \rangle$, for $n_f=2$ and $n_f=3$ massless quarks. Sequences of approximations at two-, three-, and four-loop orders are very stable and give $\langle \bar q q \rangle^{1/3}_{n_f=2}(2\, {\rm GeV}) = -(0.833-0.845) \bar\Lambda_2 $, and $ \langle \bar q q \rangle^{1/3}_{n_f=3}(2\, {\rm GeV}) = -(0.814-0.838) \bar\Lambda_3 $ where the range is our estimated theoretical error and $\bar\Lambda_{n_f}$ the basic QCD scale in the $\rm \bar{MS}$-scheme. We compare those results with other recent determinations (from lattice calculations and spectral sum rules).
%G English
%L hal-01264155
%U https://hal.science/hal-01264155
%~ CNRS
%~ L2C
%~ MIPS
%~ UNIV-MONTPELLIER
%~ UM-2015-2021