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Contribution du quark étrange à la structure électromagnétique du nucléon : Les résultats de l'expérience PVA4 à Q² = 0.23 (GeV/c)²

Abstract : Quantum Chromodynamics describes the proton as three valence quarks surrounded by a sea of quark – antiquark pairs and gluons. The purpose of an international program, which the PVA4 experiment takes part, is to quantify the contribution of the strange quark to the charge and current distributions in the nucleon. Experimentally, to determine theses distributions measurements of elastic scattering of longitudinally polarized electrons on a hydrogen target are performed. Two types of interaction intervene in these experiments: the electromagnetic interaction (virtual photon exchange) which dominates, and the weak interaction (neutral boson Z0 exchange). The non-conservation of parity in the weak interaction induces an asymmetry in the counting rate according to the helicity of the electron beam. The difficulty of these experiments is that they require to control the systematic errors and to record high statistics due to the low asymmetry (about 10-5 and 10-6 according to the transferred momentum). This document presents the first Rosenbluth separation specific to the PVA4 at Q² = 0.23 (GeV/c)². A formalism related to the violation of parity to separate the strange form factors is developed. The PVA4 experimental setup dedicated to the measurement is given, as well as the Monte Carlo technique used to extract the strange quark contribution is detailed. The results of the analysis are presented, and show that while the strange electric component is compatible with a null value, a nonzero contribution of the magnetic part is possible.
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https://tel.archives-ouvertes.fr/tel-00151260
Contributor : Marouan Abdelbaste El Yakoubi <>
Submitted on : Wednesday, June 13, 2007 - 7:23:31 PM
Last modification on : Wednesday, September 16, 2020 - 4:08:14 PM
Long-term archiving on: : Thursday, April 8, 2010 - 6:46:52 PM

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  • HAL Id : tel-00151260, version 1

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Marouan Abdelbaste El Yakoubi. Contribution du quark étrange à la structure électromagnétique du nucléon : Les résultats de l'expérience PVA4 à Q² = 0.23 (GeV/c)². Physique Nucléaire Théorique [nucl-th]. Université Paris Sud - Paris XI, 2007. Français. ⟨tel-00151260⟩

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