Extraction of twist-four matrix elements of the nucleon

✍ Scribed by W. Melnitchouk

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 217 KB
• Volume: 654
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/s0375-9474(00)88505-x

✦ Synopsis

With all the experimental and theoretical activity in recent years surrounding deepinelastic spin sum rules, such as the Bjorken and Ellis-Jaffe sum rules, an intriguing issue which has not received sufficient attention is higher-twist effects. In this talk, we report on the extraction [1] of the twist-four matrix elements from recent data taken by the E143 Collaboration at SLAC [2] on the proton and deuteron gl structure functions at low Q2 in the resonance region.

According to the phenomenon of parton-hadron duality, the low Q2 data have a direct bearing on the size of the higher-twist matrix elements. From the successful phenomenology of QCD sum rules [3], power corrections in an operator product expansion (OPE) have direct control over the structure of the low-lying resonances, and resonances (including the nucleon elastic contribution) fix the higher-twist matrix elements. (ln the case of unpolarized deep-inelastic scattering, a similar analysis was performed in Ref. [4].) According to the OPE, in the limit of large Q2 >> A~ci ) the first moment, F N, of the gl structure function of the nucleon can be calculated via the twist expansion: rN(Q ~) -fo 1 dx glN(X, Q2) "r=2,4,...