Abstract
A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton has been performed using 3.2 fb^{-1} of proton–proton collision data at sqrt{s}=13{mathrm { TeV}} recorded by the ATLAS detector at the Large Hadron Collider in 2015. Two exclusive final states are considered, with either exactly one or at least two tau leptons. No excess over the Standard Model prediction is observed in the data. Results are interpreted in the context of gauge-mediated supersymmetry breaking and a simplified model of gluino pair production with tau-rich cascade decays, substantially improving on previous limits. In the GMSB model considered, supersymmetry-breaking scale (Lambda ) values below 92 {mathrm { TeV}} are excluded at the 95% confidence level, corresponding to gluino masses below 2000 {mathrm { GeV}}. For large values of tan beta , values of Lambda up to 107 {mathrm { TeV}} and gluino masses up to 2300 {mathrm { GeV}} are excluded. In the simplified model, gluino masses are excluded up to 1570 {mathrm { GeV}} for neutralino masses around 100 {mathrm { GeV}}. Neutralino masses below 700 {mathrm { GeV}} are excluded for all gluino masses between 800 and 1500 {mathrm { GeV}}, while the strongest exclusion of 750 {mathrm { GeV}} is achieved for gluino masses around 1450 {mathrm { GeV}}.
Highlights
Supersymmetry (SUSY) [1,2,3,4,5,6] introduces a symmetry between fermions and bosons, resulting in a SUSY partner for each Standard Model (SM) particle, with identical mass and quantum numbers, and a difference of half a unit of spin
The multi-jet background contributes to the selection when two conditions are simultaneously fulfilled: jets have to be mis-identified as tau leptons, and large missing transverse momentum must arise from jet energy mis-measurement
These regions are defined by the same set of selection criteria as for the SRs, except that the criterion corresponding to the plotted variable is not applied
Summary
Supersymmetry (SUSY) [1,2,3,4,5,6] introduces a symmetry between fermions and bosons, resulting in a SUSY partner (sparticle) for each Standard Model (SM) particle, with identical mass and quantum numbers, and a difference of half a unit of spin. The Mmes scale is required to be larger than Λ, to avoid tachyonic messengers and charge- and colour-breaking vacua, and lower than the Planck mass to suppress flavour violation The latter condition implies that the lightest supersymmetric particle is a very light gravitino. As in previous ATLAS searches [13, 14], the GMSB model is probed as a function of Λ and tan β, and the other parameters are set to Mmes = 250 TeV, N5 = 3, sign(μ) = 1 and Cgrav = 1 For this choice of parameters, the NLSP is the lightest scalar tau (τ1) for large values of tan β, while for lower tan β values, the τ1 and the superpartners of the right-handed electron and muon (eR, μR) are almost degenerate in mass. The sparticle decay widths are assumed to be small compared to sparticle masses, such that they play no role in the kinematics
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