Eur. Phys. J. C (2009) 62: 547-572
https://doi.org/10.1140/epjc/s10052-009-1042-y

Regular Article - Theoretical Physics

Mass bounds on a very light neutralino

¹ Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn, Bonn, Germany
² Instituto de Física de Cantabria (CSIC-UC), Santander, Spain
³ Departamento de Física Teórica y del Cosmos and CAFPE, Universidad de Granada, 18071, Granada, Spain
⁴ DESY Zeuthen, Zeuthen, Germany
⁵ Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805, Munich, Germany
⁶ IPPP, University of Durham, Durham, DH1 3LE, UK

^* e-mail: kittel@th.physik.uni-bonn.de

Received: 12 February 2009
Revised: 17 April 2009
Published online: 27 May 2009

Abstract

Within the Minimal Supersymmetric Standard Model (MSSM) we systematically investigate the bounds on the mass of the lightest neutralino. We allow for non-universal gaugino masses and thus even consider massless neutralinos, while assuming in general that R-parity is conserved. Our main focus is on laboratory constraints. We consider collider data, precision observables, and also rare meson decays to very light neutralinos. We then discuss the astrophysical and cosmological implications. We find that a massless neutralino is allowed by all existing experimental data and astrophysical and cosmological observations.