[Paper Review] Study of multiparticle production by gluon dominance model (Part II)

P. Ermolov, Е. С. Кокоулина+6 more|ArXiv.org|Mar 24, 2005

High-Energy Particle Collisions Research1 references3 citations

TL;DR

This paper extends the gluon dominance model (GDM) to describe multiparticle production in proton-proton and proton-antiproton collisions, incorporating quark topology and soft photon emission to explain experimental data. It successfully reproduces charged and neutral multiplicity distributions, explains excess soft photons via blackbody-like emission, and estimates emission region sizes from photon momentum spectra, achieving good agreement with RHIC and fixed-target data across a wide energy range.

ABSTRACT

The gluon dominance model presents a description of multiparticle production in proton-proton collisions and proton-antiproton annihilation. The collective behavior of secondary particles in $pp$-interactions at 70 GeV/c and higher is studied in the project {\bf "Thermalization"}. The obtained neutral and charged multiplicity distribution parameters explain some RHIC-data. The gluon dominance model is modified by the inclusion of intermediate quark topology for the multiplicity distribution description in the pure $p\bar p$-annihilation at few tens GeV/c and explains behavior of the second correlative moment. This article proposes a mechanism of the soft photon production as a sign of hadronization. Excess of soft photons allows one to estimate the emission region size.

Motivation & Objective

• To develop a unified phenomenological model based on QCD and hadronization for describing multiparticle production in high-energy hadronic collisions.
• To explain the observed excess of soft photons in pp and p-pbar annihilation beyond QED predictions.
• To estimate the spatial size of the emission region for soft photons using thermal emission models.
• To improve the gluon dominance model by including intermediate quark topology for better description of multiplicity distributions in p-pbar annihilation at a few tens GeV/c.
• To achieve quantitative agreement between theoretical predictions and experimental data on multiplicity distributions and second-order correlation moments.

Proposed method

• Uses a two-stage model: first, gluon emission from initial hadrons (Poisson-distributed with mean m̄), followed by hadronization of gluons into quark-antiquark pairs.
• Applies binomial distribution to model neutral meson (π⁰) production from hadronized gluons, with probabilities p₀ and p_c for neutral and charged mesons.
• Modifies the GDM by introducing intermediate quark topologies (0, 2, 4 charged pions) in p-pbar annihilation, using convolution of gluon and hadron components.
• Employs a blackbody-like emission spectrum to model soft photons (p_T ≤ 0.1 GeV/c), estimating photon density and emission region size via n_γ(T) ∝ T³.
• Fits the model to experimental data using parameters: m̄ = 3.36 ± 0.18, N = 4.01 ± 0.61, n̄^h = 1.74 ± 0.26, and topology ratios c₀:c₂:c₄ = 15:40:0.05 at χ²/ndf = 5.77/4.
• Uses the relation L ∝ 1/p_T to estimate emission region size from soft photon momentum, yielding L ≈ 11 fm at p_T = 10 MeV/c.

Experimental results

Research questions

• RQ1 How can the gluon dominance model be extended to describe multiplicity distributions in p-pbar annihilation at a few tens GeV/c?
• RQ2 What role does intermediate quark topology play in explaining the second-order correlation moment of particle multiplicities?
• RQ3 Why is there an excess of soft photons in high-energy hadronic collisions beyond QED predictions?
• RQ4 Can soft photon emission be modeled as thermal radiation, and what does this imply for the size of the emission region?
• RQ5 How well does the modified GDM reproduce experimental multiplicity distributions across a wide energy range?

Key findings

• The mean multiplicity of π⁰ mesons in pp collisions at 69 GeV/c is found to be 1.036 ± 0.041, consistent with the gluon dominance model.
• The model predicts a maximum total multiplicity of 42 particles in pp interactions, with 26 charged and 16 neutral mesons, consistent with TSTM.
• By restricting the upper limit of neutral mesons to 2n_ch at low charged multiplicities (n_ch ≤ 10), the model improves agreement with experimental data, excluding Anti-Centauro events.
• The probability of charged meson production is 1.46 times higher than for neutral mesons, as inferred from p_c/p_0 ≈ 1.46 in the binomial model.
• For p-pbar annihilation at 14.75 GeV/c, the model fits data with m̄ = 3.36 ± 0.18, N = 4.01 ± 0.61, and n̄^h = 1.74 ± 0.26, with topology ratios c₀:c₂:c₄ = 15:40:0.05.
• Estimates of the emission region size for soft photons range from 11 fm (p_T = 10 MeV/c) to 2.0 fm (p_T = 50 MeV/c), derived from blackbody-like photon density and momentum spectra.