Same-flavour Opposite-sign Dilepton Pair Research Articles

Search for top squarks in events with a Higgs or Z boson using 139\xa0fb^{-1} of pp collision data at sqrt{s}=13\xa0TeV with the ATLAS detector

This paper presents a search for direct top squark pair production in events with missing transverse momentum plus either a pair of jets consistent with Standard Model Higgs boson decay into b-quarks or a same-flavour opposite-sign dilepton pair with an invariant mass consistent with a Z boson. The analysis is performed using the proton–proton collision data at sqrt{s}=13 TeV collected with the ATLAS detector during the LHC Run-2, corresponding to an integrated luminosity of 139 fb^{-1}. No excess is observed in the data above the Standard Model predictions. The results are interpreted in simplified models featuring direct production of pairs of either the lighter top squark (tilde{t}_1) or the heavier top squark (tilde{t}_2), excluding at 95% confidence level tilde{t}_1 and tilde{t}_2 masses up to about 1220 and 875 GeV, respectively.

Search for direct top squark pair production in events with a Higgs or Z boson, and missing transverse momentum in sqrt{s}=13 TeV pp collisions with the ATLAS detector

A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at sqrt{s}=13 TeV collected with the ATLAS detector at the LHC in 2015–2016, corresponding to an integrated luminosity of 36.1 fb−1. No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks ( {tilde{t}}_1 ) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs ( {tilde{t}}_2 ) decaying via {tilde{t}}_2to Z{tilde{t}}_1 or {tilde{t}}_2to h{tilde{t}}_1 . The results exclude at 95% confidence level {tilde{t}}_2 and {tilde{t}}_1 masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.

Erratum to: Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in $$\sqrt{s}=8$$ s = 8 TeV pp collisions with the ATLAS detector

It has been found that one of the signal models in Figs. 5 and 9 was incorrectly labelled in the legend. The label has been fixed, while none of the results or exclusions have changed.

Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in [Formula: see text]TeV pp collisions with the ATLAS detector.

Two searches for supersymmetric particles in final states containing a same-flavour opposite-sign lepton pair, jets and large missing transverse momentum are presented. The proton–proton collision data used in these searches were collected at a centre-of-mass energy sqrt{s}=8 TeV by the ATLAS detector at the Large Hadron Collider and corresponds to an integrated luminosity of 20.3 fb^{-1}. Two leptonic production mechanisms are considered: decays of squarks and gluinos with Z bosons in the final state, resulting in a peak in the dilepton invariant mass distribution around the Z-boson mass; and decays of neutralinos (e.g. tilde{chi }^{0}_{2} rightarrow ell ^{+}ell ^{-}tilde{chi }^{0}_{1}), resulting in a kinematic endpoint in the dilepton invariant mass distribution. For the former, an excess of events above the expected Standard Model background is observed, with a significance of three standard deviations. In the latter case, the data are well-described by the expected Standard Model background. The results from each channel are interpreted in the context of several supersymmetric models involving the production of squarks and gluinos.