Vector meson fragmentation using a model with broken SU(3) at the next-to-leading order

Abstract

A detailed study of fragmentation of vector mesons at the next-to-leading order (NLO) is given for e + e − scattering. A model with broken SU (3) symmetry uses three input fragmentation functions α(x, Q 2 ), β(x, Q 2 ) and γ(x, Q 2 ) and a strangeness suppression parameter λ to describe all the light quark fragmentation functions for the entire vector meson octet. At a starting low energy scale of Q 2 0 = 1.5 (GeV) 2 for three light quarks (u, d, s) along with initial parameterization, the fragmentation functions are evolved through DGLAP evolution equations at NLO and the crosssection is calculated. The heavy quarks contribution are added in appropriate thresholds during evolution. The results obtained are fitted at the momentum scale of √ s = 91.2GeV for LEP and SLD data. Good-quality fits are obtained for ρ, K * , ω and φ mesons, implying the consistency and efficiency of this model that explains the fragmentation functions of vector mesons both at the leading and the next to leading order in QCD.

Fragmentation of ω and ϕ mesons in e+e− and pp collisions at NLO

“…The details regarding the model were discussed in detail in Refs. [2], [14] and [15] in which the e + e − data were fitted to the NLO cross sections using this model. In Ref.…”

“…The fragmentation functions of all octet vector mesons can be written in terms of three universal functions that are named valence (V ), sea (γ), and gluon (D g ) fragmentation functions [15] (see Table I). The model defines the fragmentation functions at an initial scale of Q 2 0 , taken to be Q 2 0 = 1.5 GeV 2 , for three light quarks u, d and s, where the charm and bottom flavour contributions are kept zero.…”

“…This requires a good understanding of φ hadroproduction in p p collisions, which will serve as a baseline for nucleus-nucleus studies. With this motivation, analyses had been done for vector meson fragmentation in e + e − scattering at Leading Order (LO) [14] and Next-to-Leading Order (NLO) [15] and in p p collisions at LO [14] as well. In this paper, for the first time, this has been extended to a combined investigation for the fragmentation of the entire vector meson nonet in e + e − and for ω and φ meson production in p p collisions at NLO using the LEP [16][17][18] and SLD [19] data for e + e − and RHIC PHENIX [20] data for p p hadroproduction.…”

“…A key feature of the analysis (described earlier in Refs. [14] and [15] and applied to the present study) is the ability to use the entire nonet vector meson hadroproduction data by defining SU(3)-symmetric fragmentation functions common to the entire set of octet mesons. This drastically reduces the number of independent fragmentation functions (from three quark-and one gluon fragmentation function for each member of the octet) to two universal quark-and one gluon fragmentation function.…”

“…Some additional parameters are subsequently introduced to account for SU(3) symmetry breaking and singlet-octet mixing to allow the study of the entire vector meson nonet. The definition of input fragmentation functions and other parameters relevant to the model [15] remain the same in this study and have been briefly reviewed here for completeness; some differences in the choice of fragmentation functions for analyses are also mentioned below. The hadroproduction in p p collisions at NLO presented here is particularly important in view of the fact that gluons contribute at higher order in e + e − collisions but contribute at the same order as quarks in p p processes.…”