$U(1)_A$ Topological Susceptibility and its Slope, Pseudoscalar Gluonium and the Spin of the Proton

S. Narison (1)

1 LPTA - Laboratoire de Physique Théorique et Astroparticules

We review the determinations of the pseudoscalar glueball and eventual radial excitation of the \eta' masses and decay constants from QCD spectral sum rules (QSSR). The glueball mass is (2.05+-0.19) which one can compare with the eventual experimental candidate X(1835), while the \eta(1400) is likely a radial excitation of the \eta'-meson. Their effects on the estimates of U(1)_A topological susceptibility and its slope as well as the impact of the latter in the estimate of the spin of the proton is discussed. We predict the singlet polarized parton distributions to be a^0(Q^2=4 GeV^2)=0.32+-0.02, which is about a factor two smaller than the OZI value, but comparable with the COMPASS measurement of 0.24+-0.02.

Domaines: Physique des Hautes Energies - Réseau [hep-lat]; Physique des Hautes Energies - Phénoménologie [hep-ph]; Physique des Hautes Energies - Théorie [hep-th]; Physique Nucléaire Théorique [nucl-th]

S. Narison. $U(1)_A$ Topological Susceptibility and its Slope, Pseudoscalar Gluonium and the Spin of the Proton. Adrianofest, Jan 2006, Pisa, Italy. ⟨in2p3-00104573⟩