An extended model for nonet pseudo-scalar meson fragmentation

Abstract

An SU(3) symmetric model with high predictivity for octet meson (\pi, K) quark fragmentation functions with a simple approach to SU(3) symmetry breaking (due to the relatively heavy strange quarks) is extended to the singlet sector, with some reasonable assumptions, in order to study \eta and \eta' fragmentation. Due to the presence of SU(3) symmetry, fits to the \pi and K data help to constrain the fragmentation functions for \eta and \eta' mesons. The use of 2-jet and 3-jet (especially the gluon jet) inclusive meson production in e^+e^- collisions and \pi, \eta inclusive production in p p collisions enable the extraction of the gluon fragmentation functions as well. While sea quarks in strange mesons (K^{+-},K^0,Kbar^0) and the heavier \eta, \eta' mesons are suppressed by a factor of lambda_H = m_\pi^2/m_H^2 < 0.1 for H=K,\eta,\eta', the gluons are not as severely suppressed: f_g^H=0.3--0.35. A detailed parametrisation of the three independent fragmentation functions V(x, Q2), \gamma(x, Q2), and D_g(x, Q2) are given in LO QCD; all nonet meson gluon fragmentation functions and quark fragmentation functions of all flavours can be expressed in terms of these functions with a few model parameters including \lambda_H and f_g. The data prefer a nonet mixing angle -24deg<=\theta_P<=-16deg and rule out no-mixing.