Scheme dependence, leading order and higher twist studies of MRST partons

Abstract

We extend a recent global analysis of nucleon parton distributions carried out at next-to-leading order (NLO) in the MSbar scheme to provide distributions in the so-called DIS scheme. We pay particular attention to the translation of the heavy quark distributions in going from the MSbar to the DIS scheme. We repeat the global analysis at leading order (LO) and comment on the major effects produced when going from LO to NLO. Finally we include in the global analysis a freely parameterised form of possible higher twist contributions to make an exploratory study of the size of these effects as a function of x.

Figures (3)

• Figure 1: Comparison of large $x$ data from BCDMS, NMC and SLAC with LO and NLO fits of MRST.
• Figure 2: Comparison of very large $x$ data from BCDMS and SLAC with the standard NLO fit of MRST and the higher twist fit MRST(HT).
• Figure 3: Ratios of $u$ and $d$ partons in the two sets MRST(HT) and MRST.