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Register a new userRunning coupling constant of ten-flavor QCD with the Schrodinger functional method
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Walking technicolor theory attempts to realize electroweak symmetry breaking as the spontaneous chiral symmetry breakdown caused by the gauge dynamics with slowly varying gauge coupling constant and large mass anomalous dimension. Many-flavor QCD is one of the candidates owning these features. We focus on the SU(3) gauge theory with ten flavors of massless fermions in the fundamental representation, and compute the gauge coupling constant in the Schrodinger functional scheme. Numerical simulation is performed with $O(a)$-unimproved lattice action, and the continuum limit is taken in linear in lattice spacing. We observe evidence that this theory possesses an infrared fixed point.
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The electroweak gauge symmetry is allowed to be spontaneously broken by the strongly interacting vector-like gauge dynamics. When the gauge coupling of a theory runs slowly in a wide range of energy scale, the theory is a candidate for walking technicolor. This may open up the possibility that the origin of all masses may be traced back to the gauge theory. We use the SF method to see whether the gauge coupling of 10-flavor QCD walks or not. Preliminary result is reported.
The electroweak gauge symmetry is allowed to be spontaneously broken by the strongly interacting vector-like gauge dynamics. When the gauge coupling of a theory runs slowly in a wide range of energy scale, the theory is extremely interesting. This may open up the possibility that the origin of all masses may be traced back to the gauge theory. We use the SF method to determine the scale dependence of the gauge coupling of 10-flavor QCD. Preliminary results are reported.
In the exploration of viable models of dynamical electroweak symmetry breaking, it is essential to locate the lower end of the conformal window and know the mass anomalous dimensions there for a variety of gauge theories. We calculate, with the Schrodinger functional scheme, the running coupling constant and the mass anomalous dimension of SU(2) gauge theory with six massless Dirac fermions in the fundamental representation. The calculations are performed on $6^4$ - $24^4$ lattices over a wide range of lattice bare couplings to take the continuum limit. The discretization errors for both quantities are removed perturbatively. We find that the running slows down and comes to a stop at $0.06 lesssim 1/g^2 lesssim 0.15$ where the mass anomalous dimension is estimated to be $0.26 lesssim gamma^*_m lesssim 0.74$.
We present a determination of the strange, charm and bottom quark masses as well as the strong coupling constant in 2+1 flavor lattice QCD simulations using highly improved staggered quark action. The ratios of the charm quark mass to the strange quark mass and the bottom quark mass to the charm quark mass are obtained from the meson masses calculated on the lattice and found to be $m_c/m_s=11.871(91)$ and $m_b/m_c=4.528(57)$ in the continuum limit. We also determine the strong coupling constant and the charm quark mass using the moments of pseudoscalar charmonium correlators: $alpha_s(mu=m_c)=0.3697(85)$ and $m_c(mu=m_c)=1.267(12)$ GeV. Our result for $alpha_s$ corresponds to the determination of the strong coupling constant at the lowest energy scale so far and is translated to the value $alpha_s(mu=M_Z,n_f=5)=0.11622(84)$.
In this Letter, we provide a determination of the coupling constant in three-flavor quantum chromodynamics (QCD), $alpha^{overline{mathrm{MS}}}_s(mu)$, for $overline{mathrm{MS}}$ renormalization scales $mu in (1,,2)$ GeV. The computation uses gauge field configuration ensembles with $mathcal{O}(a)$-improved Wilson-clover fermions generated by the Coordinated Lattice Simulations (CLS) consortium. Our approach is based on current-current correlation functions and has never been applied before in this context. We convert the results perturbatively to the QCD $Lambda$-parameter and obtain $Lambda_{overline{mathrm{MS}}}^{N_f=3} = 342 pm 17$ MeV, which agrees with the world average published by the Particle Data Group and has competing precision. The latter was made possible by a unique combination of state-of-the-art CLS ensembles with very fine lattice spacings, further reduction of discretization effects from a dedicated numerical stochastic perturbation theory simulation, combining data from vector and axial-vector channels and matching to high-order perturbation theory.
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