The String+${}^3P_0$ Model of Hadronization

TL;DR

The paper introduces an extension of the Lund string fragmentation model that incorporates quark spin effects using the string+${}^3P_0$ mechanism, successfully reproducing various transverse and longitudinal spin asymmetries in hadronization.

Contribution

It develops a spin-aware extension of the Lund model based on the ${}^3P_0$ mechanism, including vector mesons and spin correlations, to better describe polarized quark fragmentation.

Findings

Reproduces transverse spin effects like the Collins effect.

Accounts for longitudinal spin effects such as jet handedness.

Includes vector mesons and spin correlations in the model.

Abstract

We present the main theoretical aspects of the quantum mechanical string+${}^3P_0$ model of polarized quark fragmentation for pseudoscalar and vector meson production. The model is an extension of the Lund string fragmentation model that systematically includes the quark spin degree of freedom assuming the ${}^3P_0$ mechanism of quark pair production at string breaking. The recently achieved introduction of vector mesons accounts for the spin correlations between the latter and the quark of the fragmentation chain. The string+${}^3P_0$ model reproduces transverse spin effects such as the Collins effect and the dihadron asymmetry, and longitudinal spin effects such as the jet handedness.