Analysis of the neutralino system in two-body decays of neutralinos

Abstract

In the minimal supersymmetric standard model ͑MSSM͒, the neutralinos, the spin-1/2 Majorana superpartners of the neutral gauge and Higgs bosons, are expected to be among the light supersymmetric particles that can be produced copiously at future high-energy colliders. We analyze two-body neutralino decays into a neutralino plus a Z boson or the lightest neutral Higgs boson h, allowing the relevant parameters to have complex phases. We show that the two-body tree-level decays of neutralinos are kinematically allowed in a large region of the MSSM parameter space and they can provide us with a powerful probe of the Majorana nature and CP properties of the neutralinos through the Z-boson polarization measured from Z-boson leptonic decays.

CP-sensitive observables in $e^ + e^-\to\tilde\chi^0_i \tilde\chi^0_j$ and neutralino decay into the Z boson

“…Note that also the diagonal elements, being CP even quantities, are changed for ϕ M 1 = 0 and ϕ µ = 0. This fact has been exploited in [10] as a possibility to determine the CP violating phases.…”

“…with the subsequent two-body decay of one neutralino into the Z boson (for recent studies see [9,10])…”

Correlated decays of pair-produced scalar taus

“…Many studies of the Majorana nature of neutralinos have been performed [8,9,10,11]. Reference [9] observed that the CP and CP T properties of the final state determine the Majorana nature of neutralinos in the process e + e − →χ 0 1χ 0 i → ℓ + ℓ −χ0 1χ 0 1 (i = 2, 3, 4).…”

“…Selectron pair production in e − e − scattering, e − e − →ẽ −ẽ− , would also be of great utility, as it could proceed only on account of t-channel Majorana neutralino exchange [10]. In addition, Majorana effects in two-or three-body decays of neutralinos are known to exist [11].…”

Analysis of the neutralino system in three–body leptonic decays of neutralinos

“…For that purpose, it will be crucial to measure their quantum numbers and to confirm that they are indeed Majorana fermions [4,5,6,7]. Moreover, masses, mixings, couplings and CP violating phases must be measured in a model-independent way [8,9,10] to reconstruct the fundamental SUSY parameters and to verify the SUSY relations at the electroweak scale, leading to a reliable extrapolation to the grand unification scale or the Planck scale [11].…”