Light-Front Spin-1 Model: Parameters Dependence

Abstract

We study the structure of the ρ-meson within a light-front model with constituent quark degrees of freedom. We calculate electroweak static observables: magnetic and quadrupole moments, decay constant and charge radius. The prescription used to compute the electroweak quantities is free of zero modes, which makes the calculation implicitly covariant. We compare the results of our model with other ones found in the literature. Our model parameters give a decay constant close to the experimental one.

Poincaré-invariant constituent quark model for light mesons: capabilities and constraints

“…3, the ρ-meson lepton decay constant f ρ as a function of the only free parameter of the model, b ρ , is presented. The interval on the vertical axis representing the experimental values of f ρ , that is f exp ρ = (152 ± 8) MeV [4,5], is shown. It corresponds to the interval of the values of b ρ which give, through our calculation, the correct experimental values of the decay constant.…”

“…One of the interesting related prediction was introduced as a consequence of the so-called Wu-Yang hypothesis [38] (see also [12]; the wave function (19) with n = 3 is used. This work 152±8 0.56±0.04 (fixed) [4] 154 0.268 [33] 146 0.54 [34] 130 0.312 [35] -0.67 [36] -0.67 [37] 134 0.296…”

“…In this connection such particles are in the focus of experiments on up-to-day accelerators. The most important results here are the following: measurement of the pion form factor at large momentum transfers in JLab (see, e.g., [2,3]), the obtaining of the ρ-meson decay constant from the reaction τ → ρ ν τ [4,5], the magnetic moment measurement of the radiation transition ρ → πγ * . The interesting result obtained by BABAR collaboration concerning the deviation of the behavior of the transition form factor F π→γγ * (Q 2 ) for large momentum transfer from that predicted by perturbative QCD [6] remains unexplained.…”

Electroweak properties ofρ-meson in the instant form of relativistic quantum mechanics

“…In recent years there has been significant progress in the experimental study of ρ-meson: measurement of the lepton decay constant from the process τ → ρν τ [1,2], extraction of the ρ-meson magnetic moment from processes γ * → 4π [3], measurement of the magnetic moment of decay ρ → πγ * [4], the expected measurement of the electromagnetic form factors of the ρ-meson from the reaction e + + e − → ρ + + ρ − [5]. To the moment, there are a large number of calculations of the rho meson electroweak properties in different approaches (see, e.g., [6][7][8][9][10][11]).…”

“…So, by analogy with pion calculations from [14] we use the following set of parameters: M=0.22 GeV for the constituent quark mass; the quark anomalous magnetic moments enter our expressions through the sum (κ u + κd) and we take κ u + κd = 0.0268 in natural units; for the quark MSR we use the relation r 2 q 0.3/M 2 . The parameters of the wave functions b in (13), (14) were fixed from the requirements of the description of experimental values of ρ-meson lepton decay constants 152 ± 8 MeV [1]. The ρ-meson mass in our calculations is taken from [2] …”