Z-peaked excess in goldstini scenarios

Abstract

We study a possible explanation of a 3.0 σ excess recently reported by the ATLAS Collaboration in events with Z-peaked same-flavour opposite-sign lepton pair, jets and large missing transverse momentum in the context of gauge-mediated SUSY breaking with more than one hidden sector, the so-called goldstini scenario. In a certain parameter space, the gluino two-body decay chaing → gχ 0 1,2 → gZG becomes dominant, whereχ 0 1,2 andG are the Higgsino-like neutralino and the massive pseudo-goldstino, respectively, and gluino pair production can contribute to the signal. We find that a mass spectrum such as mg ∼ 1000 GeV, mχ0 1,2 ∼ 800 GeV and mG ∼ 600 GeV demonstrates the rate and the distributions of the excess, without conflicting with the stringent constraints from jets plus missing energy analyses and with the CMS constraint on the identical final state.

ATLAS on-Z excess via gluino-Higgsino-singlino decay chains in the NMSSM

“…As we will discuss in the next section, these two regions have different dark matter properties. It should be noted that the NMSSM in the small λ region is almost the same with the MSSM plus an additional gauge singlet fermion whose couplings to the MSSM sector are suppressed as in the simplified goldstini model [16]. In this region, the analyses of ref.…”

“…After the report, many scenarios in the MSSM as well as in the NMSSM have been proposed to explain the ATLAS on-Z excess without conflicting with constraints from various SUSY searches including the CMS on-Z result [6,[8][9][10][11][12][13][14][15][16][17][18][19][20]. To have on-shell Z bosons in final states while escaping other SUSY search constraints, scenarios with a gravitino as the lightest SUSY particle (LSP) seems to be one of the simplest possibilities.…”

“…In ref. [16], it has been shown that this problem can be evaded by introducing a non-MSSM massive particle, a goldstiniG , into which the lightest neutralino mainly decays. Due to the massiveness of the goldstini, the Z bosons are emitted softly, and hence, the constraints from 0 lepton + multi jets + E miss T searches become weaker.…”

“…Motivated by the study about the goldstini [16], we consider the case of the singlino-like neutralino LSP. In this section, we quickly review the mass spectrum of the NMSSM by paying particular attention to the dependence on parameters.…”

“…In this region, the analyses of ref. [16] would be applied. In table 1, we show the two benchmark parameter sets in the two distinct parameter regions which exemplify the small λ and the large λ regions, respectively.…”