Neutral-meson production in pp collisions at RHIC and QCD test of z scaling
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ELEMENTARY PARTICLES AND FIELDS Theory
Neutral-Meson Production in pp Collisions at RHIC and QCD Test of z Scaling* M. V. Tokarev** Joint Institute for Nuclear Research, Dubna, Russia Received March 21, 2008; in final form, August 15, 2008
Abstract—New experimental data on inclusive cross section of neutral-vector-meson (ω 0 , φ, KS0 ) pro√ duction in proton–proton collisions at s = 200 GeV obtained at RHIC are analyzed in the framework of z scaling. Properties of z-presentation√are used to predict hadron yields over a wide range of transverse momentum pT and collisions energy s. The next-to-leading-order perturbative QCD calculations of √ inclusive cross sections of π 0 mesons produced in pp and p¯p collisions over a wide range of s and pT are compared with ISR, S¯ ppS, RHIC data and predictions of z scaling. The dependence of the spectra in pT and z presentations for different parton distribution and fragmentation functions is studied. The sensitivity of the obtained results to the choice of the renormalization (µR ), initial-state factorization (µF ), and finalstate factorization (fragmentation) (µH ) scales is verified. It is shown that self-similar features of particle production dictated by the z scaling give strong restriction on the asymptotic behavior of the inclusive spectra in high-pT region. PACS numbers: 13.85.Ni, 13.87.Fh, 12.38.-t, 11.30.Ly DOI: 10.1134/S106377880903020X
1. INTRODUCTION Different approaches to description of particle production are used to search for regularities (Bjorken, Feynman, and KNO scalings, quark-counting rules, etc.) reflecting general principles in lepton, hadron, and nucleus interactions at high energies. One of the most basic principles is self-similarity of hadron production valid both in soft and hard constituent interactions. Other general principles are locality and fractality which can be applied to hard processes at small scales. These investigations have shown that the interactions of hadrons and nuclei can be described in terms of interactions of their constituents. Fractality in hard processes is a specific feature connected with substructure of the constituents. This includes self-similarity over a wide scale range. One of the scalings in high-energy inclusive reactions is z scaling observed in high-pT particle production (see [1] and references therein). It is based on principles of locality, self-similarity, and fractality of hadronic interactions. The scaling function ψ(z) and scaling variable z used for data presentation are expressed via experimental quantities such as the inclusive cross section Ed3 σ/dp3 and the multiplicity density dN/dη. The z presentation of data reveals ∗ **
The text was submitted by the author in English. E-mail: [email protected]
properties of energy and angular independence with power law, ψ(z) ∼ z −β , at high z. In the paper results of analysis of new data on high-pT spectra of ω 0 , φ, KS0 , and π 0 mesons produced in pp collisions at the Relativistic Heavy Ion Collider (RHIC) in the framework of z scaling are presented. Proper
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