arXiv subjects
Publications and source records attributed to Kazuhiro Tanaka.
We review the nucleon's twist-3 polarized structure functions from the viewpoint of gauge invariant, nonlocal light-cone operators in QCD. We discuss a systematic treatment of the polarized structure functions and the corresponding parton distribution functions. We emphasize unique features of higher twist distributions, and the role of the QCD equations of motion to derive their anomalous dimensions for Q^2-evolution.
We present a systematic study of twist-3 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion. A complete set of distribution amplitudes is constructed for ρ, ω, K^* and ϕmesons, which satisfies all (exact) equations of motion and constraints from conformal expansion.
Hadron spin physics is now one of the most active fields of physics. Especially in the last ten years, great progress has been made both theoretically and experimentally that has considerably improved our knowledge of the spin structure of nucleons. We review the nucleon's polarized structure functions from the viewpoint of factorization theorems and the gauge invariant, nonlocal light-cone operators in QCD. We discuss a systematic treatment of the polarized structure functions and the corresponding parton distribution functions, which are relevant to inclusive lepto- and hadro-production. We give a detailed analysis of these spin-dependent distribution functions at the twist-2 and twist-3 level, and present various properties and relations satisfied by the parton distributions, which can be derived directly from QCD. We emphasize unique features of higher twist distributions, and the role of the QCD equations of motion to derive their sensitivity to the quark-gluon correlation and their anomalous dimensions for Q^2-evolution.
We investigate the nucleon's transverse spin-dependent structure function g_2(x, Q^{2}) in the framework of the operator product expansion and the renormalization group. We construct the complete set of the twist-3 operators for the flavor singlet channel, and give the relations among them. We develop an efficient, covariant approach to derive the anomalous dimension matrix of the twist-3 singlet operators by computing the off-shell Green's functions. As an application, we investigate the renormalization mixing for the lowest moment case, including the operators proportional to the equations of motion as well as the ``alien'' operators which are not gauge-invariant.
We investigate the nucleon's transverse spin-dependent structure function g_2(x, Q^2) in the framework of the operator product expansion and the renormalization group. We construct the complete set of the twist-3 operators for the flavor singlet channel, and give the relations among them. We develop an efficient, covariant approach to derive the anomalous dimension matrix of the twist-3 singlet operators by computing the off-shell Green's functions. As an application, we investigate the Q^2-evolution of g_2(x, Q^{2}) for the lowest moment case, and discuss its experimental implication.
We investigate the renormalization of the twist-3 operators which are relevant for the spin-dependent structure function $g_{2}(x, Q^{2})$. We derive the anomalous dimension for the non-singlet part by calculating the off-shell Green's functions of the twist-3 operators including the operators which are proportional to the equation of motion.
The energy spectrum of nucleons in high-density nuclear matter is investigated in the framework of relativistic meson-nucleon many-body theory, employing the $1/N$ expansion method. The coupling of the nucleon with the particle-hole excitations in the medium flattens the spectra in the vicinity of the Fermi surface. The effect grows logarithmically for increasing density and eventually leads to instability of the normal state. The validity of the mean-field theory at high density is criticized.