Abstract
We study to which extent SUSY extensions of the Standard Model can describe the excess of events of 3.0 standard deviations observed by ATLAS in the on-Z signal region, respecting constraints by CMS on similar signal channels as well as constraints from searches for jets and E^mathrm{miss}_text {T}. GMSB-like scenarios are typically in conflict with these constraints, and do not reproduce well the shape of the E^mathrm{miss}_text {T} distribution of the data. An alternative scenario with two massive neutralinos can improve fits to the total number of events as well as to the H_text {T} and E^mathrm{miss}_text {T} distributions. Such a scenario can be realised within the NMSSM.
Highlights
After the first run of the LHC at a center of mass (c.m.) energy of mostly 8 TeV, no significant excesses have been observed in searches for physics beyond the standard model [1,2]
In [3], an excess of 3.0 standard deviations was reported by ATLAS in [4] in the on-Z signal region: summing electron and muon pairs, 29 events passing the cuts were observed versus 10.6 ± 3.2 background events expected
One can make the somewhat optimistic assumption that these contributions do not exceed 50 % of the contributions of the g → q + q + χ10 → q + q + Z + Gdecay chain. This point remains within the constraints from [17], but contributes about 10 events to the ATLAS on-Z signal region
Summary
After the first run of the LHC at a center of mass (c.m.) energy of mostly 8 TeV, no significant excesses have been observed in searches for physics beyond the standard model [1,2]. Jets from both steps of the gluino decay cascade (including the jets from the Z boson) are relatively soft, and constraints from searches for jets and ETmiss are easier to satisfy unless the mass splitting mg − mχ is too large. Such a scenario has been considered recently in [9].
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