COMPASS results on proton longitudinal spin structure function $g_1$ and quark fragmentation functions

Abstract : We present a few recent highlights from the COMPASS experiment at CERN, related to the nucleon spin and structure: the proton spin structure function $\text{g}_{1} ^{p}(x)$ measured using 200 GeV polarized muons, together with a QCD fit of $\text{g}_{1}$ world data; pion and kaon multiplicities in DIS in view of constraining quark fragmentation functions.The statistical precision on $\text{g}_{1} ^{p}$ is improved by a factor of $\sim 2$ at low $x$. A reevaluation of the Bjorken sum rule based on COMPASS data alone confirms its validation within 9% accuracy. An NLO QCD fit to $\text{g}_{1}$ world data leads to a value of the quark spin contribution to the nucleon spin $\Delta \Sigma$, between 0.26 and 0.36 at $Q^{2} = 3$ (GeV/c)$^{2}$, the size of the uncertainty being driven by the unknown shape of the polarized parton distributions. The results on pion and kaon multiplicities produced in DIS of muons off an isoscalar target constitute an impressive data set of more than 400 points in $\pi$ and 400 in K, covering a large kinematical domain in ($x, z, Q^{2}$), which will be used in future NLO QCD fits to extract quark fragmentation functions into $\pi$ and K. A LO fit is performed to extract the favoured and unfavoured quark fragmentation functions into pions.
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Communication dans un congrès
5th International Conference on New Frontiers in Physics, Jul 2016, Kolymbari, Greece. EPJ Web Conf., 164, pp.01007, 2017, 〈10.1051/epjconf/201716401007〉
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https://hal.archives-ouvertes.fr/hal-01669609
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Soumis le : mercredi 20 décembre 2017 - 23:42:48
Dernière modification le : mercredi 12 décembre 2018 - 04:31:24

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Fabienne Kunne. COMPASS results on proton longitudinal spin structure function $g_1$ and quark fragmentation functions. 5th International Conference on New Frontiers in Physics, Jul 2016, Kolymbari, Greece. EPJ Web Conf., 164, pp.01007, 2017, 〈10.1051/epjconf/201716401007〉. 〈hal-01669609〉

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