Suppression of neutral pion production in deep-inelastic scattering off nuclei with the CLAS detector

TL;DR

This paper reports the first detailed measurement of neutral pion production ratios in deep-inelastic scattering off various nuclei, revealing suppression at high energy fractions and enhancement at low z, influenced by nuclear size and scattering processes.

Contribution

It provides the first three-fold differential measurement of neutral pion ratios in electron-nucleus scattering, highlighting nuclear effects on hadronization.

Findings

Suppression of neutral pions increases with nuclear size.

Enhancement observed at low z and high pT, especially in heavier nuclei.

Evidence of competing effects from partonic scattering and hadronic interactions.

Abstract

We present the first three-fold differential measurement for neutral pion multiplicity ratios produced in semi-inclusive deep-inelastic electron scattering on carbon, iron and lead nuclei normalized to deuterium from CLAS at Jefferson Lab. We found that the neutral pion multiplicity ratio is maximally suppressed for the leading hadrons (energy fraction z approaching unity), suppression varying from 25% in carbon up to 75% in lead. An enhancement of the multiplicity ratio at low z and high p2T is observed, suggesting an interconnection between these two variables. This behavior is qualitatively similar to the previous two-fold differential measurement of charged pions by the HERMES Collaboration and recently - by CLAS Collaboration. The largest enhancement was observed at high pT2 for heavier nuclei, namely iron and lead, while the smallest enhancement was observed for the lightest nucleus, carbon. This behavior suggests a competition between partonic multiple scattering, which causes enhancement, and hadronic inelastic scattering, which causes suppression.