The Effect of Vector Meson Decays on Dihadron Fragmentation Functions

Abstract

Abstract. Dihadron Fragmentation Functions (DFF) provide a vast amount of information on the intricate details of the parton hadronization process. Moreover, they provide a unique access to the "clean" extraction of nucleon transversity parton distribution functions in semi inclusive deep inelastic two hadron production process with a transversely polarised target. On the example of the u → π + π − , we analyse the properties of unpolarised DFFs using their probabilistic interpretation. We use both the NJL-jet hadronization model and PYTHIA 8.1 event generator to explore the effect of the strong decays of the vector mesons produced in the quark hadronization process on the pseudoscalar DFFs. Our study shows that, even though it is less probable to produce vector mesons in the hadronization process than pseudo scalar mesons of the same charge, the products of their strong decays drastically affect the DFFs for pions because of the large combinatorial factors. Thus, an accurate description of both vector meson production and decays are crucial for theoretical understanding of DFFs.

Dihadron fragmentation functions in the quark-jet model: Transversely polarized quarks

“…[19,21,[24][25][26]28,29]. We calculate various number densities by averaging over a large number of MC simulation events of quark hadronization.…”

“…Over the past several years it has been developed to include the production of kaons and other hadrons [17][18][19][20], as well as the transverse momentum dependence [21] by utilizing MC simulations of the hadronization process and the Nambu-Jona-Lasinio (NJL) quark model [22,23] for calculating the input elementary fragmentation functions. We also studied DiFFs [24][25][26] within the framework, with a simplistic treatment of the quark polarization to access the so-called single-hadron Collins fragmentation function and the IFF. A self-consistent treatment of the quark polarization within the quark-jet picture was recently developed in Ref.…”

Monte Carlo implementation of polarized hadronization

“…The original model of Field and Feynman [2,3] has been significantly extended in recent years to describe various phenomena in hadronization in the so-called NJL-jet model, which uses the NJL effective quark model [9,10] to calculate the input elementary hadron emission probabilities. The extensions include the calculations of the collinear FFs for various hadrons [8,[21][22][23], transverse-momentumdependent FFs [24], dihadron FFs [25][26][27][28] and spindependent effects [29][30][31]. The latter have proven especially challenging, as the naive interpretations of the polarization transfer dynamics lead to higher-order Collins modulations [32] that are nonphysical, while the probabilities of hadron emission should only depend linearly on the polarization of the initial quark.…”

Dihadron fragmentation functions in the quark-jet model: Longitudinally polarized quarks

“…The DiFFs have been already studied in the quarkjet model, both for the case of an unpolarized [16,17] and transversely polarized quark [18]. In the first studies the simplistic treatment of the polarization transfer during the quark hadronization nevertheless created unphysical modulations that had to be circumvented using additional assumptions.…”