Experimental proton-proton correlation function derived for the pp→ppη reaction

Abstract

Based on the high statistics data from the pp → ppX reaction measured by the COSY-11 collaboration [1] we have derived a two-proton correlation function for the production of the ppη and pp + pions systems. The measured correlation function normalized to the value simulated for a point-like source was compared with a theoretical prediction in order to estimate the size of the reaction volume.

Two-proton correlation function: a gentle introduction

“…In qualitative terms the curves are similar: all show a depression close to threshold and a prominent peak at about 20 MeV/c. The same behavior has been observed experimentally [1]. In our model the position of the peak does not seem to be dependent upon d whilst its height is very sensitive to the source radius.…”

“…The recent COSY-11 collaboration measurement of the two-proton correlation function in the pp → ppη reaction, reported at this meeting [1], arouse some interest in a simple theoretical description of the correlation function. In these notes we present a pedagogical introduction to the practical methods that can be used for calculating the correlation function.…”

“…The first distribution, D(r), is the effective source density function that is usually for convenience assumed to be a Gaussian D(r) = (4πd 2 ) −3/2 e −(r/2d) 2 (2) with a single parameter d reflecting the size of the source. The second factor entering the overlap integral (1), is a probability density involving the square of the wave function Φ k k k (r r r) describing two-particle system in the continuum. Actually, formula (1) is only a static approximation to the correlation function derived under the assumption that the final-state interaction between the two detected particles dominates, while all other interactions are negligible.…”

Study of the NN$\eta '$ Production with COSY-11

“…COSY-11 experiment [33,34] has provided already an important data for these studies [35][36][37][38], with the most precise direct measurement of the total width of the η ′ meson Γ η ′ [39,40], and the first rough estimation of the η ′ -N interaction from the excitation function of the cross section for the pp → ppη ′ reaction [41]. Here we describe an analysis of the data used earlier for Γ η ′ determination in view of the extraction of the production cross-section for the η ′ meson σ pp→ppη ′ in proton-proton collisions and an update of the σ pp→ppη ′ values presented previously [35][36][37].…”

Study of the $\eta $-Meson Production with Polarized Proton Beam

“…Up to now, measurements of the analyzing power for the pp → ppη reaction were performed by the COSY-11 and DISTO collaborations [48][49][50][51]. Due to the lack of statistics and small detector acceptance (in case of COSY-11 [52,53]) these first measurements did not allow for unambiguous conclusions about the production mechanisms. Therefore, a high statistics measurement was made with the large acceptance (∼ 4π) symmetric WASA detector [56].…”