Correlations between pions of low relative momenta

Two-particle pion correlations in exclusive πp and pp interactions at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$\sqrt s = 2.9 - 4$$ \end{document} GeV are studied in the region of low relative 4-momenta. Relevant correlation functions are obtained with allowance for the results of calculations based on the model of quark-gluon strings and the FRITIOF model. Positive correlations that make it possible to estimate the spatial size of the pion source are observed for pairs of identical pions. No correlations are observed for pairs featuring one charged and one neutral pion.