Subthreshold antiproton production in <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="normal">Si</mi></mrow><mprescripts></mprescripts><mrow></mrow><mrow><mn>28</mn></mrow><mrow></mrow><mrow></mrow></mmultiscripts></mrow></math></span> collisions at 2.1 GeV/nucleon

J. B. Carroll; S. Carlson; J. Gordon; T. Hallman; G. Igo; P. Kirk; G. F. Krebs; P. Lindstrom; M. A. McMahan; V. Perez-Mendez; A. Shor; S. Trentalange; Z. F. Wang

doi:10.1103/PhysRevLett.62.1829

Subthreshold antiproton production in ${}^{28}{Si}$ collisions at 2.1 GeV/nucleon

J. B. Carroll, S. Carlson, J. Gordon, T. Hallman, G. Igo, P. Kirk, G. F. Krebs, P. Lindstrom, M. A. McMahan, V. Perez-Mendez, A. Shor, S. Trentalange, and Z. F. Wang

Phys. Rev. Lett. 62, 1829 – Published 17 April 1989

Abstract

We report on the first observation of subthreshold antiproton production in nucleus-nucleus collisions. This measurement was made for the system ${}^{28}{Si}$ at a bombarding energy of 2.1 GeV/nucleon (kinetic energy per NN pair in the c.m. frame ∼850 MeV). A differential cross section $d^{2}$ σ/dP d Ω of 80±40 nb/sr (GeV/c) was measured for p¯ production at 1.9 GeV/c and 0°. This result is 3 orders of magnitude larger than that predicted by a calculation incorporating internal motion of the nucleons in the colliding nuclei.