The quark–antiquark asymmetry of the nucleon sea from Λ and fragmentation

Abstract

We present a general analysis of the spin transfer for Λ and Λ production in deepinelastic scattering of polarized charged leptons on the nucleon, and find that the pattern of different behaviors of Λ and Λ production observed by the E665 Collaboration suggests the possibility of quark-antiquark asymmetries either in the quark to Λ fragmentation functions and/or in the quark and antiquark distributions of the target proton. We also point out that the strange-antistrange asymmetry of the nucleon sea may produce an observable contribution to the different behaviors of Λ and * e-mail: mabq@phy.pku.edu.cn † e-mail: ischmidt@fis.utfsm.cl ‡ e-mail: Jacques.Soffer@cpt.univ-mrs.fr § e-mail: jjyang@fis.utfsm.cl ¶ Mailing address Λ production. We find that a softer s(x) than s(x) as predicted by the light-cone baryon-meson fluctuation model of intrinsic quark-antiquark pairs of the nucleon sea might lead to a reasonable picture. However, the magnitude is still too small to explain the E665 data and the conclusion has also strong model-dependence. This may suggest the importance of quark-antiquark asymmetry in the quark to Λ fragmentation functions, provided that the E665 data are confirmed.PACS numbers: 14.20. Jn, 12.38.Bx, 13.87.Fh, 13.88.+e 2 It is well known that the production of Λ and Λ in deep-inelastic scattering (DIS) of lepton on the nucleon may provide information on the quark content of the target nucleon [1,2], as well as on the quark to Λ fragmentation functions [3,4]. The idea that the fragmentation of the Λ hyperon in DIS of a charged lepton on a nucleon target can supply information concerning the strange content of the nucleon was originally proposed in Refs. there are still large uncertainties in the quark to Λ fragmentation function, and it is practically more urgent to measure the Λ fragmentation functions before using the Λ fragmentation to probe the quark content of the nucleon. Indeed, some symplifying assumptions about the quark to Λ fragmentation functions were found to be of little predictive power when applied to Λ production in e + e − annihilation process at the Z resonance [6,7], and to semi-inclusive Λ production of polarized charged lepton DIS process on the nucleon target [8].However, there have been recent progress [9,10,11] in order to understand the quark to Λ fragmentation functions by connecting them with the quark distributions inside the Λ by the Gribov-Lipatov relation (GLR) [12]:where D h q (z) is the fragmentation function for a quark q splitting into a hadron h with longitudinal momentum fraction z, and q h (x) is the quark distribution for finding the quark q inside the hadron h carrying a momentum fraction x. D h q and q h depend also on the energy scale Q 2 , and this relation holds, in principle, in a certain Q 2 range and in leading order approximation. It is shown recently [13] that the Gribov-Lipatov relation is also verified to hold in leading order for the space-and time-like splitting 3 functions of QCD. Moreover, although Eq. (1) is only valid at x → 1 and ...

Quark fragmentation functions in a diquark model forΛproduction

“…Much work has already been done to relate the flavor and spin structure of the Λ to various fragmentation processes [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Explicit calculations have been performed for the quark fragmentation functions in a quark-diquark model [11].…”