Isospin Dependence of Power Corrections in Deep Inelastic Scattering

TL;DR

This work analyzes deep inelastic scattering on proton and deuteron targets to extract the isospin dependence of power (higher-twist) corrections while carefully accounting for nuclear effects in the deuteron. The authors perform a QCD analysis including leading-twist contributions with target-mass corrections, plus dynamical HT terms, and fit PDFs and αs to a broad DIS data set, incorporating nuclear smearing and off-shell effects. They find the isospin asymmetry in HT terms to be negligible for HT^T but negative for HT^2 at high x, with HT predictions from infrared renormalon models not aligning with the data. The results provide improved constraints on neutron structure functions and HT contributions, with important implications for neutrino experiments and resonance-region extrapolations, and they highlight the need for more precise high-x data.

Abstract

We present results of a perturbative QCD analysis of deep inelastic measurements of both the deuteron and proton structure functions. We evaluate the theoretical uncertainty associated to nuclear effects in the deuteron, and we extract simultaneously the isospin depedendence of: i)the higher twists terms; ii) the ratio of the longitudinal to transverse cross sections; iii) the ratio of the neutron to proton structure functions. The extraction of the latter, in particular, has been at the center of an intense debate. Its accurate determination is crucial both theoretically and for the interpretation of the more precise neutrino experiments including the newly planned high intensity 50 GeV proton synchrotron.

Figures (16)

• Figure 1: Deuteron Compton scattering amplitude in incoherent scattering approximation.
• Figure 2: The ratio $R_2^D$ calculated in different approximations. In the upper panel this ratio is presented as a function of $x$ for fixed $Q^2$: Fermi motion and binding effects (dotted line), Fermi motion and binding effects combined with target mass corrections (dashed line); the full calculation including Fermi motion, binding, target mass and off-shell corrections is given by the solid line. The shaded area in the upper panel corresponds to the prediction of the nuclear density model of Ref.Gomez. In the lower panel the ratio $R_2^D$ is shown as a function of $W$ for a few different $Q^2$.
• Figure 3: Average nucleon kinetic and separation energy and off-shellness $\Delta$ as functions of the nuclear mass number $A$.
• Figure 4: Kinematic region of the data used in analysis. The curves correspond to constant values of the invariant mass $W$ whose values in units of GeV are indicated in the plot.
• Figure 5: Isospin asymmetries of the HT terms obtained using different treatments of Fermi motion and binding corrections: Eqs.(\ref{['D-SF']}) (delimited by solid lines, see text); Atwood--West West74 (dash--dotted line); Eqs.(\ref{['D-SF']}) in the Bjorken limit, i.e. if all $1/Q^2$ terms were disregarded (short dashes). The curve with long dashes shows the result without Fermi motion and binding corrections.