Spin asymmetries for events with high pT hadrons in DIS and an evaluation of the gluon polarization

Le résumé fourni par la source

We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the photon-gluon fusion process to above 30%. The most effective one, based on a neural network approach, provides the asymmetries ${A}_{p}^{\mathcal{l}\stackrel{\ensuremath{\rightarrow}}{N}\mathcal{l}\mathrm{hhX}}=0.030\ifmmode\pm\else\textpm\fi{}0.057(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.010(\mathrm{syst})$ and ${A}_{d}^{\mathcal{l}\stackrel{\ensuremath{\rightarrow}}{N}\mathcal{l}\mathrm{hhX}}=0.070\ifmmode\pm\else\textpm\fi{}0.076(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.010(\mathrm{syst}).$ From these values we derive an averaged gluon polarization $\ensuremath{\Delta}G/G=\ensuremath{-}0.20\ifmmode\pm\else\textpm\fi{}0.28(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.10(\mathrm{syst})$ at an average fraction of nucleon momentum carried by gluons $〈\ensuremath{\eta}〉=0.07.$

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