DOI: 10.1140/epjc/s2003-01196-2
Uncertainties of predictions from parton distributions I: Experimental errors
A.D. Martin1, R.G. Roberts2, W.J. Stirling1 and R.S. Thorne31 Institute for Particle Physics Phenomenology, University of Durham, DH1 3LE, UK
2 Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK
3 Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge, CB3 0HE, UK
(Received: 13 November 2002 / Published online: 5 May 2003 )
Abstract
We determine the uncertainties on observables arising from the
errors on the experimental data that are fitted in the global
MRST2001 parton analysis. By diagonalizing the error matrix we
produce sets of partons suitable for use within the framework of
linear propagation of errors, which is the most convenient method
for calculating the uncertainties. Despite the potential
limitations of this approach we find that it can be made to work
well in practice. This is confirmed by our alternative approach of
using the more rigorous Lagrange multiplier method to determine
the errors on physical quantities directly. As particular examples
we determine the uncertainties on the predictions of the
charged-current deep-inelastic structure functions, on the
cross-sections for
W production and for Higgs boson production
via gluon-gluon fusion at the Tevatron and the LHC, on the ratio
of
W- to
W+ production at the LHC and on the moments of the
non-singlet quark distributions. We discuss the corresponding
uncertainties on the parton distributions in the relevant
x,Q2
domains. Finally, we briefly look at uncertainties related to the
fit procedure, stressing their importance and using
,
and extractions of
as examples. As a
by-product of this last point we present a slightly updated set of
parton distributions, MRST2002.
© Società Italiana di Fisica, Springer-Verlag 2003
