TY  - JOUR
T1  - 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
JF  - Journal of High Energy Physics
N2  - 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 \(\tilde{t}_2\) → \(Z\tilde{t}_1\) or \(\tilde{t}_2\) → \(h\tilde{t}_1\). 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.
KW  - High energy physics
KW  - Beyond Standard Model
KW  - Hadron-Hadron scattering (experiments)
KW  - Higgs physics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-173210
VL  - 2017
IS  - 08
ER  - 
TY  - JOUR
T1  - Search for new phenomena with large jet multiplicities and missing transverse momentum using large-radius jets and flavour-tagging at ATLAS in 13 TeV \(pp\) collisions
JF  - Journal of High Energy Physics
N2  - A search is presented for particles that decay producing a large jet multiplicity and invisible particles. The event selection applies a veto on the presence of isolated electrons or muons and additional requirements on the number of \(b\)-tagged jets and the scalar sum of masses of large-radius jets. Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton collisions at \(\sqrt{s}\) = 13 TeV, which corresponds to 36.1 fb\(^{−1}\) of integrated luminosity, no evidence is found for physics beyond the Standard Model. The results are interpreted in the context of simplified models inspired by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are pair-produced. More generic models within the phenomenological minimal supersymmetric Standard Model are also considered.
KW  - High energy physics
KW  - Beyond Standard Model
KW  - Hadron-Hadron scattering (experiments)
KW  - Supersymmetry
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172302
VL  - 34
ER  - 
TY  - JOUR
T1  - Measurement of inclusive and differential cross sections in the \(H\) → \({ZZ}^*\) → \(4{ℓ}\) decay channel in \({pp}\) collisions at \(\sqrt{s} = 13\) TeV with the ATLAS detector
JF  - Journal of High Energy Physics
N2  - Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the \(H\) → \({ZZ^*}\) → \(4{ℓ}\) decay channel. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb\(^{−1}\). The inclusive fiducial cross section in the \(H\) → \({ZZ^*}\) → \(4{ℓ}\) decay channel is measured to be 3.62 ± 0.50(stat)\(^{+0.25}_{− 0.20}\) (sys) fb, in agreement with the Standard Model prediction of 2.91 ± 0.13 fb. The cross section is also extrapolated to the total phase space including all Standard Model Higgs boson decays. Several differential fiducial cross sections are measured for observables sensitive to the Higgs boson production and decay, including kinematic distributions of jets produced in association with the Higgs boson. Good agreement is found between data and Standard Model predictions. The results are used to put constraints on anomalous Higgs boson interactions with Standard Model particles, using the pseudo-observable extension to the kappa-framework.
KW  - High energy physics
KW  - Hadron-Hadron scattering (experiments)
KW  - Higgs physics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172724
VL  - 2017
IS  - 10
ER  - 
TY  - JOUR
T1  - Search for top quark decays \(t → qH\), with \(H → γγ\), in \(\sqrt{s} = 13\) TeV \(pp\) collisions using the ATLAS detector
JF  - Journal of High Energy Physics
N2  - This article presents a search for flavour-changing neutral currents in the decay of a top quark into an up-type (\({q = c, u}\)) quark and a Higgs boson, where the Higgs boson decays into two photons. The proton-proton collision data set analysed amounts to 36.1 fb\(^{−1}\) at \(\sqrt{s} = 13\) TeV collected by the ATLAS experiment at the LHC. Top quark pair events are searched for, where one top quark decays into \(qH\) and the other decays into \(bW\). Both the hadronic and leptonic decay modes of the \(W\) boson are used. No significant excess is observed and an upper limit is set on the \({t → cH}\) branching ratio of 2.2 × 10\(^{−3}\) at the 95% confidence level, while the expected limit in the absence of signal is 1.6 × 10\(^{−3}\). The corresponding limit on the \(tcH\) coupling is 0.090 at the 95% confidence level. The observed upper limit on the \({t → uH}\) branching ratio is 2.4 × 10\(^{−3}\).
KW  - High energy physics
KW  - Flavour changing neutral currents
KW  - Hadron-Hadron scattering (experiments)
KW  - Higgs physics
KW  - Top physics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172568
VL  - 2017
IS  - 10
ER  - 
TY  - JOUR
T1  - Search for supersymmetry in events with \(b\)-tagged jets and missing transverse momentum in \(pp\) collisions at \(\sqrt{s}\) = 13 TeV with the ATLAS detector
JF  - Journal of High Energy Physics
N2  - A search for the supersymmetric partners of the Standard Model bottom and top quarks is presented. The search uses 36.1 fb\(^{−1}\) of \(pp\) collision data at \(\sqrt{s}\) = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Direct production of pairs of bottom and top squarks (\(\overline{b}_1\) and \(\overline{t}_1\)) is searched for in final states with \(b\)-tagged jets and missing transverse momentum. Distinctive selections are defined with either no charged leptons (electrons or muons) in the final state, or one charged lepton. The zero-lepton selection targets models in which the \(\overline{b}_1\) is the lightest squark and decays via \(\overline{b}_1\) → \(b\overline{χ}^0_1\), where \(\overline{χ}^0_1\) is the lightest neutralino. The one-lepton final state targets models where bottom or top squarks are produced and can decay into multiple channels, \(\overline{b}_1\) → \(b\overline{χ}^0_1\) and \(\overline{b}_1\) → \(t\overline{χ}^±_1\), or \(\overline{t}_1\) → \(t\overline{χ}^0_1\) and \(\overline{t}_1\) → \(b\overline{χ}^±_1\), where \(\overline{χ}^±_1\) is the lightest chargino and the mass difference \(m_{\overline{χ}^±_1}\) − \(m_{\overline{χ}^0_1}\) is set to 1 GeV. No excess above the expected Standard Model background is observed. Exclusion limits at 95% confidence level on the mass of third-generation squarks are derived in various supersymmetry-inspired simplified models.
KW  - High energy physics
KW  - Hadron-Hadron scattering (experiments)
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172320
VL  - 2017
IS  - 195
ER  - 
TY  - JOUR
T1  - Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using \(\sqrt{s}=13\) TeV proton-proton collision data
JF  - Journal of High Energy Physics
N2  - A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three \(b\)-tagged jets is presented. The search uses 36.1 fb\(^{−1}\) of \(\sqrt{s}=13\) TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the \(b\)-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of \(R\)-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model \(t\overline{t}t\overline{t}\) production of 60 fb (6.5 × the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields.
KW  - High energy physics
KW  - Beyond Standard Model
KW  - Hadron-Hadron scattering (experiments)
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172802
VL  - 2017
IS  - 09
ER  -