Neutralino and chargino production in U(1)′ at the LHC

Abstract

We examine the production and decay modes of neutralinos and charginos in a softly-broken supersymmetric model with an extra Abelian symmetry U(1)′. We perform the study in a U(1)′ model with a secluded sector, where the tension between the electroweak scale and developing a large enough mass for Z′ is resolved by incorporating three additional SU(2) singlet fields into the model. Although the chargino sector is the same as in the MSSM, the neutralino sector of the model is very rich: five new fermion fields are added to the neutral sector bring the total neutralino states to nine. We implement the model into standard packages and perform a detailed and systematic analysis of production and decay modes at the LHC, for three different scenarios, consistent with the Higgs data and relic density constraints. We concentrate on final signals (1) $1\ell+\mathit{jets}+\not\! \! E_{T}$, (2) $2\ell+\mathit{jets}+\not\! \! E_{T}$ and (3) $3\ell+0\mathit{jets}+\not\! \! E_{T}$, and comment on the case with $0\ell+\mathit{jets}+\not\! \! E_{T}$. We discuss backgrounds and indicate how these signals can be observed, and how the model can be distinguished from other supersymmetric model scenarios.

Appendix: Feynman diagrams for decays channels

We list the main decay channels of chargino and neutralinos in Scenario A, (Fig. 7), Scenario B, (Fig. 8) and Scenario C (Fig. 9).

Fig. 7

Generic Feynman diagrams for the decays of the chargino ${\tilde{\chi}}_{1}^{\pm}$ and neutralinos ${\tilde{\chi}}_{2}^{0}, {\tilde{\chi}}_{4}^{0}$, and ${\tilde{\chi}}_{6}^{0}$ in Scenario A of the secluded U(1)′ model. Here $\tilde{l}$ are scalar leptons, H _i ,A _j are scalar and pseudoscalar Higgs bosons, and W and Z are gauge bosons

Fig. 8

Generic Feynman diagrams for the decays of the chargino ${\tilde{\chi}}_{1}^{\pm}$ and neutralinos ${\tilde{\chi}}_{i}^{0}, i=2, \ldots,6$ in Scenario B of the secluded U(1)′ model. Intermediate particle notation is the same as in Fig. 7

Fig. 9

Generic Feynman diagrams for the decays of the chargino ${\tilde{\chi}}_{1}^{\pm}$ and neutralino ${\tilde{\chi}}_{2}^{0}$ in Scenario C of the secluded U(1)′ model. Intermediate particle notation is the same as in Fig. 7, and $\tilde{\nu}_{l}$ is the scalar neutrino