The KOALA Experiment for (anti)proton-proton Elastic Scattering

TL;DR

The KOALA experiment measures proton-proton elastic scattering over a wide momentum transfer range using a recoil detector and forward scintillators, providing precise data for scattering parameters and luminosity at COSY.

Contribution

This work introduces a novel experimental setup combining recoil and forward detectors to accurately measure elastic scattering over a broad |t| range.

Findings

Successful installation and commissioning at COSY.

High energy resolution of the recoil detector (<30 keV).

Effective background suppression and elastic event identification.

Abstract

The KOALA experiment measures the differential cross section of (anti)proton-proton elastic scattering over a wide range of four-momentum transfer squared 0.0008 < |t| < 0.1 (GeV/c)$^2$ . The forward scattering parameters and the absolute luminosity can be deduced by analyzing the characteristic shape of the differential cross-section spectrum. The experiment is based on fixed target kinematics and uses an internal hydrogen cluster jet target. The wide range of |t| is achieved by measuring the total kinetic energy of the recoil protons near 90{\deg} with a recoil detector, which consists of silicon and germanium single-sided strip sensors. The energy resolution of the recoil detector is better than 30 keV (FWHM). A forward detector consisting of two layers of plastic scintillators measures the elastically scattered beam particles in the forward direction close to the beam axis. It helps suppress the large background at small recoil angles and improves the identification of elastic scattering events in the low |t| range. The KOALA setup has been installed and commissioned at COSY in order to validate the detector by measuring the proton-proton elastic scattering. The results from this commissioning are presented here.