Experimental results on antiproton–nuclei annihilation cross section at very low energies

¹ Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany
² Physics Department, CERN, 1211 Geneva 23, Switzerland
³ Wigner Institute for Particle and Nuclear Physics, H-1525 Budapest, Hungary
⁴ Department of Physics, University of Tokyo. Tokyo 113-0033, Japan
⁵ Dipartimento di Ingegneria dell’Informazione, Università di Brescia, I-25123 Brescia, Italy
⁶ Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Brescia, I-25123 Brescia, Italy
⁷ Università degli Studi dell’Insubria, I-22100 Como, Italy
⁸ Istituto Nazionale di Fisica Nucleare, Sezione di Milano Bicocca, I-20126 Milano, Italy
⁹ Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste, Italy

^a e-mail: valerio.mascagna@ing.unibs.it

Published online: 20 March 2014

Abstract

Investigating the antiproton cross section on nuclei at low energies (1 eV – 1 MeV) is of great interest for fundamental cosmology and nuclear physics as well. The process is of great relevance for the models which try to explain the matter/antimatter asymmetry in the universe assuming the existence of the so-called “island” where antinucleon-nucleon annihilations occur in the border region [1]. For the nuclear physics point of view, the annihilation process is considered a useful tool to evaluate the neutron/proton ratio probing the external region of the nucleus. Moreover, the cross section measured at LEAR in the 80s–90s showed an unexpected behaviour for energies below 1 MeV. The results showed a saturation with the atomic mass number against the A^2/3 trend which is known for higher energies.

The ASACUSA collaboration at CERN measured 5.3 MeV antiproton annihilation cross section on different nuclei whose results demonstrated to be consistent with the black-disk model with the Coulomb correction [2]. So far, experimental limits prevented the data acquisition for energies below 1 MeV. In 2012 the 100 keV region has been investigated for the first time [3].

We present here the results of the experiment.