Beyond leading twist: ρ meson decay constants and distribution amplitudes in a self-consistent light-front quark model

초록

In this study, we present a comprehensive analysis of decay constants and chiral-even and chiral-odd distribution amplitudes (DAs) up to twist 4 for the rho meson in the standard light-front quark model (LFQM) based on the Bakamjian-Thomas (BT) construction. For the rho meson, which possesses both longitudinal (h = 0) and transverse (h = +1) polarizations, two types of decay constants, f rho i and f rho perpendicular to, arises accordingly. We demonstrate that these decay constants can be self-consistently extracted from both local (z mu = 0) and nonlocal (z mu not equal 0) matrix elements (0 q<overline>(z)Gamma q(-z) rho(P' h)), with Gamma = (gamma mu' sigma mu nu' gamma mu gamma 5' 1), in a manner independent of current components, polarizations, and reference frames. In particular, we emphasize the role of nonlocal matrix elements involving axial-vector and scalar currents, where mixing between f rho i and f rho perpendicular to occurs. We show that this mixing is consistently resolved through the BT construction, ensuring the proper extraction of these decay constants. Additionally, we investigate the structure of chiraleven DAs (phi i2;V' phi i3;V' psi perpendicular to 3;A' phi i 4;V) and chiral-odd DAs (phi perpendicular to 2;T' phi perpendicular to 3;T' psi i3;S' phi perpendicular to 4;T) beyond leading twists, and present their corresponding xi-moments and Gegenbauer moments. These results provide deeper insight into the nonperturbative structure of vector mesons and demonstrate the robustness and self-consistency of the LFQM based on the BT framework.

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