arXiv subjects
Publications and source records attributed to Valeriu Zetocha.
In this thesis we study two processes in which instantons may play an important role: the decays of charmonium states $η_c$, $χ_c$ and glueball and the OZI violation in channels relevant to the proton spin decomposition puzzle. We also present an algorithm for computation of integrals over compact groups and exemplify it on integrals over SU(N) fundamental and adjoint representations.
We study instanton contributions to hadronic decays of the scalar glueball, the pseudoscalar charmonium state $η_c$, and the scalar charmonium state $χ_c$. Hadronic decays of the $η_c$ are of particular interest. The three main decay channels are $K\bar{K}π$, $ηππ$ and $η'ππ$, each with an unusually large branching ratio $\sim 5%$. On the quark level, all three decays correspond to an instanton type vertex $(\bar{c}c)(\bar{s}s)(\bar{d}d)(\bar{u}u)$. We show that the total decay rate into three pseudoscalar mesons can be reproduced using an instanton size distribution consistent with phenomenology and lattice results. Instantons correctly reproduce the ratio $B(ππη)/B(ππη')$ but over-predict the ratio $B(K\bar{K}π)/B(ππη(η'))$. We consider the role of scalar resonances and suggest that the decay mechanism can be studied by measuring the angular distribution of decay products.