Abstract
The production of vector mesons in the fragmentation process of polarized quarks is studied within the recursive String+${}^3P_0$ model, improving a previous version of the model in which the production of pseudoscalar mesons only was considered. Two types of couplings of the vector meson to quarks are introduced, their coupling constants being the additional free parameters of the model. The angular distribution of the decay products of the polarized vector meson is deduced from the spin density matrix of the meson and the spin information is propagated along the fragmentation chain taking into account the entanglement of spin states. The new model is implemented in a stand alone Monte Carlo program utilized to investigate in detail kinematic distributions and transverse spin asymmetries. The sensitivity of these observables to the new free parameters is discussed and the Monte Carlo results are compared with experimental data on transverse spin asymmetries.
Highlights
The quark fragmentation process is one of the most intriguing and interesting phenomenon of quantum chromodynamics
The production of vector mesons in the fragmentation process of polarized quarks is studied within the recursive string þ 3P0 model, improving a previous version of the model in which the production of pseudoscalar mesons only was considered
The angular distribution of the decay products of the polarized vector meson is deduced from the spin density matrix of the meson and the spin information is propagated along the fragmentation chain taking into account the entanglement of spin states
Summary
The quark (and gluon) fragmentation process is one of the most intriguing and interesting phenomenon of quantum chromodynamics. Interesting is the spin-dependent fragmentation function Hh1q⊥ðz; pTÞ which describes the Collins effect in the fragmentation of a transversely polarized quark q in a not analyzed hadron [2]. In this paper we present the new string þ 3P0 model (M20), extending M19, in which the production of VMs in the polarized quark fragmentation chain is taken into account. The fragmentation process qAq B → h1h2...hr...hN, where qA is a quark, q B either an antiquark in eþe− annihilation or the target remnant in SIDIS and h1h2...hr...hN the primary produced hadrons, is phenomenologically described as the decay of a relativistic string, stretched between qA and q B [23,31]. One cannot simulate separately the decay of h and the fragmentation of the leftover quark q0
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