Göttingen 1997 – scientific programme

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HK: Hadronen und Kerne

HK 8: Struktur von Baryonen und Mesonen I

HK 8.5: Talk

Monday, March 24, 1997, 15:15–15:30, HS I

Nucleon matrix elements of higher–twist operators from the instanton vacuum — •J. Balla¹, M. Polyakov^2,1, and C. Weiss¹ — ¹Institut f. Theoretische Physik II, Ruhr–Univ. Bochum — ²Petersburg Nuclear Physics Institute, St. Petersburg

Power corrections to the sum rules for polarized structure functions (Bjorken, Ellis–Jaffe) are governed by nucleon matrix elements of QCD operators of twist 3 and 4. We evaluate these matrix elements in the instanton vacuum, using the 1/N_c–expansion in which the nucleon is described as a chiral soliton. We employ a method by which QCD gluon operators are replaced by effective “constituent quark” operators, which can be evaluated in the effective chiral theory derived from instantons [1]. We compare our results to calculations using QCD sum rules.

[1] D. Diakonov, M. Polyakov and C. Weiss, Nucl. Phys. B 461 (1996) 539