Münster 2002 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 23: Theory III
HK 23.6: Vortrag
Mittwoch, 13. März 2002, 12:30–12:45, A
The case for a large polarized antiquark flavor asymmetry Δ ū(x) − Δ d(x) — •C. Weiss1, R.J. Fries1, K. Goeke2, M. Polyakov2, and A. Schäfer1 — 1Institut für Theoretische Physik, Universität Regensburg, D–93053 Regensburg, Germany — 2Institut für Theoretische Physik II, Ruhr–Universität Bochum, D–44780 Bochum, Germany
The flavor asymmetry of the polarized antiquark distributions in the proton, Δ ū(x) − Δ d(x), is measured in semi-inclusive DIS at HERMES and in future polarized Drell–Yan / W± production experiments at RHIC. Standard explanations for the origin of the antiquark flavor asymmetries are i) the Pauli blocking effect in a constituent quark picture of the nucleon, or ii) “meson cloud” contributions to the DIS process. Estimates of Δ ū(x) − Δ d(x) from rho meson contributions have resulted in very small values [1]. We show that a sizable polarized flavor asymmetry is obtained in the meson cloud picture from the interference of π N and σ N contributions to the DIS process [2]. The value of Δ ū(x) − Δ d(x) expected from this effect is compatible with the Pauli blocking model of Glück and Reya [3], as well as with the prediction of the chiral quark–soliton model based on the Nc → ∞ limit of QCD [4]. We comment on the experimental consequences of a large polarized flavor asymmetry.
[1] R.J. Fries and A. Schäfer, Phys. Lett. B 443, 40 (1998)
[2] B. Dressler, K. Goeke, M. V. Polyakov and C. Weiss, Eur. Phys. J. C 14, 147 (2000)
[3] M. Glück and E. Reya, Mod. Phys. Lett. A 15, 883 (2000)
[4] D.I. Diakonov et al. Nucl. Phys. B 480, 341 (1996)