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 nextto-leading order (NLO) in the MS 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 MS 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.

A QCD analysis of HERA and fixed target structure function data

“…This correction is negative for x < 0.5 and becomes large and positive at high x. The same trend is observed in the analysis of MRST [31] (asterisks). We refer to Section 5 for further investigations of higher twist effects.…”

“…The dashed curve shows H(x) obtained from an alternative fit described in Section 5. Also plotted are the results from an analysis of MRST [31] (asterisks). In the inset H(x) from this analysis is compared to the result from the QCD fit of [24] to the SLAC and BCDMS data.…”

Detecting heavy charged Higgs bosons at the LHC with triple b-tagging

“…The resulting signal cross-sections shall be obtained by convoluting these partonic cross-sections with the MRS-LO(05A) parton densities [12]. We have also checked that essentially identical results are obtained with the CTEQ4L parton densities [13].…”

“…iv) Besides we shall be using current estimates of the b-tagging efficiency and rapidity coverage for the LHC [11] along with more recent structure functions [12,13].…”

xF 3 ( x,Q 2 ) Structure Function and Gross-Llewellyn Smith Sum Rule with Nuclear Effect and Higher Twist Correction

“…The usual approach in analyses whose main aim is the extraction of leading twist PDFs is either to parametrize the higher twist contributions by a phenomenological form and fit the parameters to the experimental data [56,57], or to extract the Q 2 dependence by fitting it in individual bins in x [44,46,47,58,59].…”