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T: Teilchenphysik
T 308: QCD I
T 308.4: Talk
Tuesday, March 11, 2003, 16:45–17:00, SFO11
Estimating power corrections to the Bjorken sum rule for the neutrino structure function F1ν n − F1ν p — •C. Weiss2 and Nam–Young Lee1 — 1Institut für Theoretische Physik II, Ruhr–Universität Bochum — 2Institut für Theoretische Physik, Universität Regensburg
Direct measurements of the the structure functions F1ν p and F1ν n at a neutrino factory would allow for an accurate determination of αs from QCD fits of the Q2–dependence of the Bjorken sum rule, complementing that based on the Gross–Llewellyn-Smith sum rule for F3 [1]. The theoretical error of the extracted αs is dominated by the uncertainty about the twist–4 (1/Q2–) correction caused by non-perturbative quark–gluon correlations in the nucleon [2]. We estimate this correction in an approach based on the instanton model of the QCD vacuum [3]. For the reduced matrix element of the flavor–nonsinglet twist–4 operator ū g Gµν γνγ5 u − (u → d) at a scale of ∼ 0.6 GeV we obtain a value of 0.18 GeV2, in good agreement with QCD sum rule estimates [4]. Our result allows to reduce the theoretical error in the determination of αs.
[1] M. L. Mangano et al.: “Physics at the front-end of a neutrino factory: A quantitative appraisal,” Report of the nuDIS Working Group for the ECFA–CERN Neutrino Factory Study, hep-ph/0105155.
[2] S. I. Alekhin and A. L. Kataev, hep-ph/0209165
[3] C. Weiss, hep-ph/0210132; Nam–Young Lee and C. Weiss, to be published
[4] V. M. Braun and A. V. Kolesnichenko, Nucl. Phys. B283 (1987) 723