5 research outputs found
Determination of from Gross-Llewellyn Smith sum rule by accounting for infrared renormalon
We recapitulate the method which resums the truncated perturbation series of
a physical observable in a way which takes into account the structure of the
leading infrared renormalon. We apply the method to the Gross-Llewellyn Smith
(GLS) sum rule. By confronting the obtained result with the experimentally
extracted GLS value, we determine the value of the QCD coupling parameter which
turns out to agree with the present world average.Comment: invited talk by G.C. in WG3 of NuFact02, July 1-6, 2002, London; 4
pages, revte
Modeling power corrections to the Bjorken sum rule for the neutrino structure function F_1
Direct measurements of the the structure functions F_1^{nu p} and F_1^{nu n}
at a neutrino factory would allow for an accurate extraction of alpha_s from
the Q^2-dependence of the Bjorken sum rule, complementing that based on the
Gross-Llewellyn-Smith sum rule for F_3. We estimate the power (1/Q^2-)
corrections to the Bjorken sum rule in the instanton vacuum model. For the
reduced matrix element of the flavor-nonsinglet twist-4 operator
ubar_g_Gdual_gamma_gamma5_u - (u -> d) we obtain a value of 0.18 GeV^2, in good
agreement with the QCD sum rule calculations of Braun and Kolesnichenko. Our
result allows to reduce the theoretical error in the determination of alpha_s.Comment: 3 pages, 1 figure, uses iopart.cls. Proceedings of the 4th NuFact'02
Workshop "Neutrino Factories based on Muon Storage Rings", Imperial College,
London, July 1-6, 200
Resolved Photon Processes
We review the present level of knowledge of the hadronic structure of the
photon, as revealed in interactions involving quarks and gluons ``in" the
photon. The concept of photon structure functions is introduced in the
description of deep--inelastic scattering, and existing
parametrizations of the parton densities in the photon are reviewed. We then
turn to hard \gamp\ and \gaga\ collisions, where we treat the production of
jets, heavy quarks, hard (direct) photons, \jpsi\ mesons, and lepton pairs. We
also comment on issues that go beyond perturbation theory, including recent
attempts at a comprehensive description of both hard and soft \gamp\ and \gaga\
interactions. We conclude with a list of open problems.Comment: LaTeX with equation.sty, 85 pages, 29 figures (not included). A
complete PS file of the paper, including figures, can be obtained via
anonymous ftp from
ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-898.ps.