Eur. Phys. J. C (2006) 47: 805-814
https://doi.org/10.1140/epjc/s2006-02594-6

Theoretical Physics

The suppression of neutralino annihilation into Zh

¹ Centre de Physique Théorique, CNRS Luminy, case 907, 13288, Marseille Cedex 9, France
² Laboratoire de Physique Corpusculaire, IN2P3-CNRS, Université Blaise Pascal, 63177, Aubière Cedex, France
³ Service de Physique Théorique, Université Libre de Bruxelles, Campus de la Plaine CP225, Bruxelles, Belgium

^* e-mail: labonne@clermont.in2p3.fr

Received: 15 February 2006
Revised: 29 March 2006
Published online: 30 June 2006

Abstract

The indirect detection of neutralino dark matter is most promising through annihilation channels producing a hard energy spectrum for the detected particles, such as neutralino annihilation into Zh. A cancellation however makes this particular annihilation channel generically subdominant in the huge parameter space of supersymmetric models. This cancellation requires non-trivial relations between neutralino mixings and masses, which we derive from gauge independence and unitarity of the MSSM. To show how the cancellation overshoots leaving only a subdominant result, we use a perturbative expansion in powers of the electroweak/supersymmetry breaking ratio m_Z/m_χ.