Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigma(L)/sigma(T)

TL;DR

This study provides precise measurements of the proton and deuteron structure functions, $F_2^p$ and $F_2^d$, and the ratio $R=\

Abstract

The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.

Figures (11)

• Figure 1: The sensitivity of the measured structure function $F_2^d$ to the assumed value of $R$. This is illustrated for five $x$ bins. The lines indicate the results of fits to $F_2^d$ computed assuming $R$ to be given by the $R_{1990}$ parametrisation of ref. rslac (dotted), twice that parametrisation (solid), or zero (dashed) for five $x$ bins, with $F_2$ scaled by the numbers in brackets.
• Figure 2: The standard NMC method for calculating $R$ (filled circles) compared to two alternative extractions described in the text, per $x$ bin (open squares) or per $(x,Q^2)$ bin (open triangles). Only statistical errors are shown. The three extractions are compared before any iteration is performed; in particular, the results shown for the standard method are not the final ones (these are shown in figs. 10 and 11).
• Figure 3: The structure function $F_2^p(x, Q^2)$ versus $Q^2$ in bins of $x$. The six data sets correspond to four different incident energies and two triggers. The new small angle trigger data are shown as filled symbols; bins of $x$ where no small angle data exist are not shown. The data in each $x$ bin have been scaled by the factors indicated in brackets. The error bars represent the quadratic sum of systematic and statistical errors. The normalisation uncertainties are not included.
• Figure 4: The structure function $F_2^d(x, Q^2)$ versus $Q^2$ in bins of $x$. The six data sets correspond to four different incident energies and two triggers. The new small angle trigger data are shown as filled symbols; bins of $x$ where no small angle data exist are not shown. The data in each $x$ bin have been scaled by the factors indicated in brackets. The error bars represent the quadratic sum of systematic and statistical errors. The normalisation uncertainties are not included.
• Figure 5: The structure function $F_2^p(x, Q^2)$ versus $Q^2$ in bins of $x$. The corresponding values are given in table 5. The six data sets of fig. 3 have been averaged. The data in each $x$ bin have been scaled by the factors indicated in brackets. The error bars represent the statistical errors; the total systematic uncertainties, apart from the 2.5% normalisation uncertainty, are indicated by the bands.