An Improved Determination of $α_{S}$ From Neutrino-Nucleon Scattering

Abstract

We present an improved determination of the proton structure functions $F_{2}$ and $xF_{3}$ from the CCFR $ν$-Fe deep inelastic scattering (DIS) experiment. Comparisons to high-statistics charged-lepton scattering results for $F_{2}$ from the NMC, E665, SLAC, and BCDMS experiments, after correcting for quark-charge and heavy-target effects, indicate good agreement for $x>0.1$ but some discrepancy at lower x. The $Q^{2}$ evolution of the structure functions yields the quantum chromodynamics (QCD) scale parameter $Λ_{\bar{MS}}^{NLO,(4)}=337 \pm 28$(exp.) MeV. This corresponds to a value of the strong coupling constant at the scale of mass of the Z-boson of $α_{S}(M_{Z}^{2})=0.119 \pm 0.002 (exp.) \pm 0.004 (theory)$ and is one of the most precise measurements of this quantity.

Figures (2)

• Figure 1: The $F_{2}$ and $xF_{3}$ data (statistical errors) and the best QCD fit (solid line). Cuts of $Q^{2}>5\ GeV^{2}$, $W^{2}>10\ GeV^{2}$, and $x<0.7$ were applied for the NLO-QCD fit which include target mass corrections. The dashed line extrapolates the QCD fit into the data regions excluded by the cuts. Deviations of the data from the extrapolated fit are partly due to non-perturbative effects.
• Figure 2: $F_{2}$ from CCFR $\nu$-Fe DIS compared to $F_{2}$ from $e$D and $\mu$D DIS. Errors bars are the statistical and systematic errors added in quadrature. The charged-lepton data have been corrected to an isoscalar Fe target, and for quark-charge effects in the DIS scheme which is valid to all orders (see text). The NMC data plotted in the figure were extracted with the same $R$ as used in the CCFR analysis NMC.