Dresden 2000 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 2: Theorie I

HK 2.5: Talk

Monday, March 20, 2000, 15:15–15:30, B 81

Polarized antiquark flavor asymmetry Δ ū(x) − Δ d (x) in semi-inclusive DIS and Drell–Yan pair production — •B. Dressler¹, K. Goeke¹, M.V. Polyakov^1,2, P. Schweitzer¹, M. Strikman^3,2, and C. Weiss¹ — ¹Institut f. Theoretische Physik II, Ruhr–Universität Bochum — ²Petersburg Nuclear Physics Institute, Russia — ³Pennsylvania State University, U.S.A.

An open issue in the spin structure of the nucleon are the flavor asymmetries of the polarized antiquark distributions, Δ ū(x) − Δ d (x) and Δ ū(x) + Δ d (x) − 2 Δ s, which cannot be extracted from inclusive DIS alone. The 1/N_c expansion of QCD suggests that the polarized flavor asymmetries may be larger than the corresponding unpolarized ones. This is confirmed by model calculations of the polarized antiquark distributions at a low normalization point in the chiral quark–soliton model of the nucleon, which give sizable flavor asymmetries [1]. We discuss the prospects for measuring the flavor asymmetries in two types of semi-inclusive experiments: i) Hadron production in semi-inclusive polarized eN scattering (e.g. at HERMES) [2]; ii) Drell–Yan lepton pair production in polarized NN scattering at HERA or RHIC energies [3]. In particular, the spin asymmetries in the latter process are shown to be remarkably sensitive to Δ ū(x) − Δ d (x).

[1] D.I. Diakonov et al., Nucl. Phys. B 480, 341 (1996).

[2] B. Dressler et al. Bochum Report RUB-TPII-12/99, hep-ph/9909541.

[3] B. Dressler et al., Bochum Report RUB-TPII-13/99, hep-ph/9910464.