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Première mesure des sections efficaces de courant chargé et neutre avec le faisceau de positrons polarisé à HERA II et analyses QCD-électrofaibles

Abstract : In 2003--2004 the HERA collider delivered $e^+p$ collisions with a longitudinally polarised positron beam. We present the measurement of inclusive Neutral and Charged Current DIS cross section using the H1 detector. The total Charged Current cross section for $Q^2>400$ GeV$^2$, $y<0,9$ is measured with a Right-handed ($P=0,33$) sample of 15,3 pb$^(-1)$ and a Left-handed ($P=-0,40$) sample of 21,7 pb$^(-1)$ yielding \begin(eqnarray) \sigma_(CC)(P=+0,33)&=& 34,67\mbox( pb )\pm 1,94\mbox( pb )\:(\mbox(stat))\pm 1,66\mbox( pb )\:(\mbox(sys)) \\ \sigma_(CC)(P=-0,40)&=& 13,80\mbox( pb )\pm 1,04\mbox( pb )\:(\mbox(stat))\pm 0,94\mbox( pb )\:(\mbox(sys)). \end(eqnarray) This result is consistent with the proportionality of the cross section with respect to the polarisation, in good agreement with the Standard Model expectations. The second part of this work is devoted to QCD analysis of the proton structure. The H1 data alone are used to extract flavor separated parton densities. This analysis is further used as a basis to extract various electroweak parameters, such as the $W$ boson mass and the quarks couplings to the $Z$. Then a global QCD analysis of DIS and Drell Yan data is realized, focusing on the strange sea asymmetry which is found to be small\,: $\int_0^1 x(s-\bar(s))\mathrm(d)x=(1,8\pm3,8)\times10^(-4)$. The impact of new E866 data on high $x$ partons densities is discussed and the extraction of the strong coupling is realized $\alpha_s=0,1197\pm0,0008 \mbox( (exp))\pm ()^(+0,0005)_(-0,0007)\mbox( (mod))\pm0,006 \mbox( (th))$.
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https://tel.archives-ouvertes.fr/tel-00009338
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Submitted on : Monday, May 30, 2005 - 2:42:10 PM
Last modification on : Wednesday, September 16, 2020 - 4:22:06 PM
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  • HAL Id : tel-00009338, version 1

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B. Portheault. Première mesure des sections efficaces de courant chargé et neutre avec le faisceau de positrons polarisé à HERA II et analyses QCD-électrofaibles. Physique des Hautes Energies - Expérience [hep-ex]. Université Paris Sud - Paris XI, 2005. Français. ⟨tel-00009338⟩

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