Lambda Polarization in Deep-Inelastic Production

2002

We propose a model for the longitudinal polarization of Λ baryons produced in deep-inelastic lepton scattering at any xF , based on static SU(6) quark-diquark wave functions and polarized intrinsic strangeness in the nucleon associated with individual valence quarks. Free parameters of the model are fixed by fitting the NOMAD data on the longitudinal polarization of Λ hyperons in neutrino interactions. Our model correctly reproduces the observed dependences of Λ polarization on the kinematic variables. Within the context of our model, the NOMAD data imply that the intrinsic strangeness associated with a valence quark has anticorrelated polarization. We also compare our model predictions with results from the HERMES and E665 experiments using charged leptons. Predictions of our model for the COMPASS experiment are also presented.

2007

Abstract. We consider models for the spin transfers to Λ and ¯ Λ hyperons produced in lepton-nucleon deep-inelastic scattering. We make predictions for longitudinal Λ and ¯ Λ spin transfers for the COMPASS experiment and for HERA, and for the spin transfer to Λ hyperons produced at JLAB. We demonstrate that accurate measurements of the spin transfers to Λ and ¯ Λ hyperons with COMPASS kinematics have the potential to probe the intrinsic strangeness in the nucleon. We show that a measurement of ¯Λ polarization could provide a clean probe of the spin transfer from ¯s quarks and provides a new possibility to measure the antistrange quark distribution function. COMPASS data in a domain of x that has not been studied previously will provide valuable extra information to fix models for the nucleon spin structure. The spin transfer to ¯ Λ hyperons, which could be measured by the COMPASS experiment, would provide a new tool to distinguish between the SU(6) and Burkardt-Jaffe (BJ) models for...

The European Physical Journal C, 2007

We consider models for the spin transfer to Λ andΛ hyperons produced in lepton-nucleon deep-inelastic scattering. We make predictions for longitudinal Λ andΛ spin transfer for the COMPASS experiment and for HERA, and for the spin transfer to Λ hyperons produced at JLAB. We show that a measurement of Λ polarization in the COMPASS experiment in a region of x that has not previously been explored will sharpen the free parameters of our model, while a measurement ofΛ polarization will provide a new and clean tool to distinguish between SU(6) and Burkardt-Jaffe (BJ) models for the nucleon spin decomposition, as well as to probe the strange parton distributions in the nucleon. These may also be distinguished very cleanly by accurate measurements of Λ andΛ spin transfers in experiments at HERA, which have an unprecedented potential to separate hyperons produced in the fragmentation of the struck (anti-)quark and the remnant nucleon. Finally, we show that the spin transfer to Λ hyperons measured in a JLAB experiment would be dominated by the spin transfer of the intrinsic polarized strangeness in the remnant nucleon, providing an independent way to check our model predictions.

AIP Conference Proceedings, 2007

We consider models for the spin transfers to Λ andΛ hyperons produced in lepton-nucleon deep-inelastic scattering. We make predictions for longitudinal Λ andΛ spin transfers for the COMPASS experiment and for HERA, and for the spin transfer to Λ hyperons produced at JLAB. We demonstrate that accurate measurements of the spin transfers to Λ andΛ hyperons with COMPASS kinematics have the potential to probe the intrinsic strangeness in the nucleon. We show that a measurement ofΛ polarization could provide a clean probe of the spin transfer froms quarks and provides a new possibility to measure the antistrange quark distribution function. COMPASS data in a domain of x that has not been studied previously will provide valuable extra information to fix models for the nucleon spin structure. The spin transfer toΛ hyperons, which could be measured by the COMPASS experiment, would provide a new tool to distinguish between the SU(6) and Burkardt-Jaffe (BJ) models for baryon spin structure. In the case of the HERA electron-proton collider experiments with longitudinally-polarized electrons, the separation between the target and current fragmentation mechanisms is more clear. It provides a complementary probe of the strange quark distribution and helps distinguish between the SU(6) and BJ models for the Λ andΛ spin structure. Finally, we show that the spin transfer to Λ hyperons measured in a JLAB experiment would be dominated by the spin transfer of the intrinsic polarized strangeness in the remnant nucleon, providing an independent way to check our model predictions.

2000

The flavor and helicity distributions of the Λ and Λ hyperons for both valence and sea quarks are calculated in a perturbative QCD (pQCD) based model. We relate these quark distributions to the fragmentation functions of the Λ and Λ, and calculate the z-dependence of the longitudinal spin transfer to the Λ and Λ in lepton deepinelastic scattering (DIS). It is shown that the spin transfer to the Λ is compatible with the first HERMES results at DESY and further tests are suggested. We also make predictions for the z-dependence of the Λ and Λ longitudinal polarizations in e-mail: mabq@th.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 neutrino (antineutrino) DIS processes. We investigate the sea contribution to the fragmentation functions, and we test a possible scenario where sea quarks in Λ (or sea antiquarks in Λ) are negatively polarized, whereas sea antiquarks in the Λ (or sea quarks in Λ ) are positiv...