Strange quark-antiquark asymmetry of nucleon sea from $\Lambda /\bar{\Lambda }$ polarization

Abstract

Distinctions between quark to $\Lambda$ and $\bar{\Lambda }$ longitudinal spin transfers in the semi-inclusive deep inelastic scattering process were observed by the E665 and COMPASS Collaborations. There are suggestions that the difference between $\Lambda$ and $\bar{\Lambda }$ production is related to the asymmetric strange-antistrange distribution inside the nucleon. However, previous calculations are still too small to explain the experimental data. From a realistic consideration of quark to $\Lambda$ fragmentation due to different flavors, we investigate the strange quark contribution for $\Lambda$ production and polarization. We find that the strange quark-antiquark asymmetry of the nucleon sea can be amplified into an observable quantity from the difference between $\Lambda$ and $\bar{\Lambda }$ polarizations after taking into account the larger probability of the $\Lambda$ produced from the $s$ quark fragmentation process compared to that from the $u$ or $d$ quark. The qualitative agreement between our calculation and the experimental data supports the existence of the intrinsic strange sea and the strange-antistrange asymmetry. Thus the polarization of $\Lambda /\bar{\Lambda }$ does open a new window to probe the nucleon sea properties, especially the strange content and its quark-antiquark asymmetry.

Comments: 6 latex pages, 6 figures, final version for publication