Parton distributions: a new global analysis

Abstract

We present a new analysis of parton distributions of the proton. This incorporates a wide range of new data, an improved treatment of heavy flavours and a re-examination of prompt photon production. The new set (MRST) shows systematic differences from previous sets of partons which can be identified with particular features of the new data and with improvements in the analysis. We also investigate the sensitivities of the results to (i) the uncertainty in the determination of the gluon at large x, (ii) the value of alpha_S(M_Z^2) and (iii) the minimum Q^2 cut on the data that are included in the global fit.

Figures (44)

• Figure 1: The gluon distributions at $Q^2$ = 2, 5, 20 and 100 GeV$^2$ corresponding to the MRST, MRST(${g\uparrow}$) and MRST(${g\downarrow}$) sets of partons with, respectively, the central, larger and smaller gluon at large $x$. We take MRST as the default set of partons throughout the paper.
• Figure 2: The ratios of the ${g\uparrow}$ and ${g\downarrow}$ gluons to the 'central' gluon (MRST) at $Q^2$ = 10 and 10$^4$ GeV$^2$. For comparison the ratio of the CTEQ4M CTEQ4M gluon to our central gluon is also shown.
• Figure 3: MRST partons at $Q^2 = 20$ GeV$^2$.
• Figure 4: MRST partons at $Q^2 = 10^4$ GeV$^2$.
• Figure 5: Comparison of the MRST partons with those of the previous MRS(R2) set at $Q^2 = 20$ GeV$^2$ (upper plot) and $Q^2 = 10^4$ GeV$^2$ (lower plot).