Side Ridge in Ar + KCl Collisions at 1.8 GeV/nucleon with Reaction-Plane Deblurring

TL;DR

This study applies reaction-plane deblurring to analyze particle distributions in Ar + KCl collisions at 1.8 GeV/nucleon, revealing a side ridge indicative of in-plane particle motion, with results supported by transport model calculations.

Contribution

It introduces reaction-plane deblurring to improve the analysis of particle distributions and identifies a side ridge phenomenon in collision data not previously characterized.

Findings

Observation of a side ridge away from the beam axis for protons and deuterons.

Distributions peak away from the beam direction, indicating in-plane transverse velocity.

Transport pBUU calculations semi-quantitatively agree with experimental results.

Abstract

Reaction-plane deblurring is applied to the triple-differential distributions of protons, deuterons and negatively charged pions from central Ar + KCl collisions at 1.8 GeV/nucleon, measured with the LBL-GSI Streamer Chamber, to yield distributions relative to the true reaction plane of the collisions. Within the reaction plane and in the forward cm rapidity region a side ridge away from the beam axis is observed: the distributions peak away from the beam direction for protons and deuterons but not for pions. These findings are consistent with a source of particles moving at an in-plane transverse velocity of ~0.1 c. Transport pBUU calculations yield results in semi-quantitative agreement with those from the data.