Spiral structure and logarithmic evolution of deuteron form factors: evidence for a transitional regime in QCD

We present a consistent analysis of elastic electron–deuteron scattering combining perturbative quantum chromodynamics (pQCD) scaling, helicity amplitudes, and phenomenological parameterizations of deuteron form factors. Particular attention is paid to logarithmic corrections governed by anomalous dimensions of six-quark operators and to two-photon exchange (TPE). Three classes of parameterizations corresponding to different dynamical regimes are considered: pre-asymptotic valence-quark dominance, effective higher-twist contributions, and modified logarithmic evolution. A global fit to the world data for the structure functions $A(Q^2)$ and $B(Q^2)$, differential cross sections, and tensor polarization observables is performed using a combined strategy of global and local minimization. The best description of the complete data set is achieved within the $f_1$ parameterization, which incorporates pre-asymptotic logarithmic behavior and correlated valence-quark dynamics. Among the considered models, $f_1$ gives the smallest value of ${\chi }^2\mathrm{/}\mathrm{d}\mathrm{o}\mathrm{f}$. The obtained results indicate that the presently accessible momentum-transfer region corresponds to a transitional regime between hadronic and quark–gluon descriptions. Helicity-conserving amplitudes dominate, whereas the asymptotic pQCD regime has not yet been fully realized. This may indicate nontrivial multiquark correlations related to hidden-color configurations in the short-distance deuteron structure. The tensor polarization observable $t_{21}$ is especially sensitive to the asymptotic behavior of the helicity amplitudes. Future measurements at larger $Q^2$ may provide a decisive test for distinguishing between the considered dynamical scenarios.