Abstract
The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERN's Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.
Highlights
Experimental setupEmulsion detectors were used to study the antiproton annihilation products generated in different materials
MC (CHIPS) MC (FTFP) MC (FLUKA)2 3 4 5 6 7 8 Total multiplicity Copper SilverGold assessed in terms of signal density (S.D.) along the reconstructed tracks, usingS.D. = ∑ Sxyz/L. x,y,z∈C S.D. # of tracksAverage multiplicity for minimally ionizing particles (MIPs)Average multiplicity for heavily ionizing particles (HIPs)
The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles
Summary
Emulsion detectors were used to study the antiproton annihilation products generated in different materials. The 5.3 MeV antiprotons from the AD (3 × 107 p/shot every 100 s) were slowed down using several different titanium and aluminium foils with variable thicknesses. The emulsion detector was situated at the downstream end of the vacuum chamber (∼1 m in length), where it could be reached by a defocused beam of low-energy antiprotons (∼100 keV). This distance from the degrading layer was necessary to reduce the background due to annihilations taking place at the moderator. Silver and gold, each having a thickness of 10 μm, were placed as targets at the end of the vacuum chamber, in front of the emulsion detectors. We collected approximately 1500 antiprotons per cm in about 10 AD shots
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