Antiproton-nucleus electromagnetic annihilation as a way to access the proton timelike form factors

H. Fonvieille; V. A. Karmanov

doi:10.1140/epja/i2009-10884-4

EPJ

Antiproton-nucleus electromagnetic annihilation as a way to access the proton timelike form factors

H. Fonvieille¹^* and V. A. Karmanov²

¹ Laboratoire de Physique Corpusculaire, Université Blaise Pascal, IN2P3, 63177, Aubière Cedex, France
² Lebedev Physical Institute, Leninsky Prospekt 53, 119991, Moscow, Russia

Received: 1 September 2009
Accepted: 1 October 2009
Published online: 20 October 2009

Abstract

Contrary to the reaction

e ⁺ e ^- with a high-momentum incident antiproton on a free target proton at rest, in which the invariant mass M of the e ⁺ e ^- pair is necessarily much larger than the

p mass 2m , in the reaction

e ⁺ e ^- n the value of M can take values near or below the

p mass. In the antiproton-deuteron electromagnetic annihilation, this allows to access the proton electromagnetic form factors in the timelike region of q² near the

p threshold. We estimate the cross-section

for an antiproton beam momentum of 1.5GeV/c. We find that near the

p threshold this cross-section is about 1pb/MeV. The case of heavy-nuclei target is also discussed. Elements of experimental feasibility are presented for the process

e ⁺ e ^- n in the context of the

ANDA project.

PACS: 25.43.+t Antiproton-induced reactions – / 14.20.Dh Protons and neutrons – / 13.40.Gp Electromagnetic form factors –

Joint Annual Meeting of the Swiss and Austrian Physical Societies
26-30 August 2019
Zurich, Switzerland

EPJ

Antiproton-nucleus electromagnetic annihilation as a way to access the proton timelike form factors

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