Pion Correlations and Resonance Effects in ppbar Annihilation to 4pi0 at Rest

TL;DR

This paper investigates pion correlations in proton-antiproton annihilation to four neutral pions at rest, revealing resonance effects and challenging the applicability of the HBT mechanism.

Contribution

It provides the first detailed analysis of pi0pi0 correlations in this reaction, highlighting resonance effects and contrasting them with stochastic models.

Findings

Dip at small invariant mass of pion pairs

Enhancement in double differential distribution for small invariant masses

Resonance models fit the data better than HBT mechanism

Abstract

We study pi0pi0 correlations in the exclusive reaction ppbar -> 4pi0 at rest with complete reconstruction of the kinematics for each event. The inclusive distribution shows a dip at small invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while the stochastic HBT mechanism is not supported by the present findings.