Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNon-perturbative renormalization of O(a) improved tensor currents
135
0
0.0
(
0
)
Authors
Leonardo Chimirri
Ask ChatGPT about the research
No Arabic abstract
We present our progress in the non-perturbative O(a) improvement and renormalization of tensor currents in three-flavor lattice QCD with Wilson-clover fermions and tree-level Symanzik improved gauge action. The mass-independent O(a) improvement factor of tensor currents is determined via a Ward identity approach, and their renormalization group running is calculated via recursive finite-size scaling techniques, both implemented within the Schrodinger functional framework. We also address the matching factor between bare and renormalization group invariant currents for a range of lattice spacings < 0.1 fm, relevant for phenomenological large-volume lattice QCD applications.
rate research
Read More
Renormalization constants of vector ($Z_V$) and axial-vector ($Z_A$) currents are determined non-perturbatively in quenched QCD for a renormalization group improved gauge action and a tadpole improved clover quark action using the Schrodinger functional method. Non-perturbative values of $Z_V$ and $Z_A$ turn out to be smaller than the one-loop perturbative values by $O(10%)$ at $a^{-1}approx 1$ GeV. A sizable scaling violation of meson decay constants $f_pi$ and $f_rho$ observed with the one-loop renormalization factors remains even with non-perturbative renormalization.
We apply non-perturbative renormalization to bilinears composed of improved staggered fermions. We explain how to generalize the method to staggered fermions in a way which is consistent with the lattice symmetries, and introduce a new type of lattice bilinear which transforms covariantly and avoids mixing. We derive the consequences of lattice symmetries for the propagator and vertices. We implement the method numerically for hypercubic-smeared (HYP) and asqtad valence fermion actions, using lattices with asqtad sea quarks generated by the MILC collaboration. We compare the non-perturbative results so obtained to those from perturbation theory, using both scale-independent ratios of bilinears (of which we calculate 26), and the scale-dependent bilinears themselves. Overall, we find that one-loop perturbation theory provides a successful description of the results for HYP-fermions if we allow for a truncation error of roughly the size of the square of the one-loop term (for ratios) or of size O(1) times alpha^2 (for the bilinears themselves). Perturbation theory is, however, less successful at describing the non-perturbative asqtad results.
The use of Heavy Quark Effective Theory (HQET) on the lattice as an approach to B-physics phenomenology is based on a non-perturbative matching of HQET to QCD in finite volume. As a first step to apply the underlying strategy in the three-flavor ($N_f = 2+1$) theory, we determine the renormalization constant and improvement coefficients relating the renormalized current and subtracted quark mass of (quenched) valence quarks in $mathcal{O}(a)$ improved $N_f=3$ lattice QCD. We present our strategy and first results for the relevant parameter region towards weak couplings along a line of constant physics, which corresponds to lattice resolutions $aleq 0.02,$fm and fixes the physical extent of the matching volume to $Lapprox 0.5,$fm.
Renormalization constants ($Z$-factors) of vector and axial-vector currents are determined non-perturbatively in quenched QCD for a renormalization group improved gauge action and a tadpole improved clover quark action using the Schrodinger functional method. Non-perturbative values of $Z$-factors turn out to be smaller than one-loop perturbative values by $O(15%)$ at lattice spacing of $a^{-1}approx$ 1 GeV. The pseudoscalar and vector meson decay constants calculated with the non-perturbative $Z$-factors show a much better scaling behavior compared to previous results obtained with tadpole improved one-loop $Z$-factors. In particular, the non-perturbative $Z$-factors normalized at infinite physical volume show that scaling violation of the decay constants are within about 10% up to the lattice spacing $a^{-1}sim 1$ GeV. The continuum estimates obtained from data in the range $a^{-1}=$ 1 -- 2 GeV agree with those determined from finer lattices ($a^{-1}sim 2-4$ GeV) with the standard action.
We propose a new strategy for the determination of the QCD coupling. It relies on a coupling computed in QCD with $N_{rm f} geq 3$ degenerate heavy quarks at a low energy scale $mu_{rm dec}$, together with a non-perturbative determination of the ratio $Lambda/mu_{rm dec}$ in the pure gauge theory. We explore this idea using a finite volume renormalization scheme for the case of $N_{rm f} = 3$ QCD, demonstrating that a precise value of the strong coupling $alpha_s$ can be obtained. The idea is quite general and can be applied to solve other renormalization problems, using finite or infinite volume intermediate renormalization schemes.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
