@article{OPUS4-22594, title = {Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in \({pp}\) collisions at root s=13 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {776}, journal = {Physics Letters B}, number = {1}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2017.11.049}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225947}, pages = {318-337}, year = {2018}, abstract = {A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton-proton collisions at root s = 13 TeV is presented. This search uses 36.1 fb(-1) of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67\% (39\%) at the 95\% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass m(H) = 125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models. (c) 2017 The Author(s). Published by Elsevier B.V.}, language = {en} } @article{OPUS4-22595, title = {Searches for heavy \({ZZ}\) and \({ZW}\) resonances in the \({llqq}\) and \({vvqq}\) final states in \({pp}\) collisions at root s=13 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {9}, journal = {Journal of High Energy Physics}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP03(2018)009}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225951}, pages = {1-52}, year = {2018}, abstract = {This paper reports searches for heavy resonances decaying into ZZ or ZW using data from proton-proton collisions at a centre-of-mass energy of root s - 13 TeV. The data, corresponding to an integrated luminosity of 36.1 fb(-1), were recorded with the ATLAS detector in 2015 and 2016 at the Large Hadron Collider. The searches are performed in final states in which one Z boson decays into either a pair of light charged leptons (electrons and muons) or a pair of neutrinos, and the associated W boson or the other Z boson decays hadronically. No evidence of the production of heavy resonances is observed. Upper bounds on the production cross sections of heavy resonances times their decay branching ratios to ZZ or ZW are derived in the mass range 300-5000 GeV within the context of Standard Model extensions with additional Higgs bosons, a heavy vector triplet or warped extra dimensions. Production through gluon-gluon fusion, Drell-Yan or vector-boson fusion are considered, depending on the assumed model.}, language = {en} } @article{OPUS4-22542, title = {Search for heavy \({ZZ}\) resonances in the l\(^+\)l\(^-\)l\(^+\)l\(^-\) and l\(^+\)l\(^-\) nu(nu)over-bar final states using proton-proton collisions at root s=13 TeV with the ATLAS detector}, series = {The European Physical Journal C}, volume = {78}, journal = {The European Physical Journal C}, number = {293}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-018-5686-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225421}, pages = {1-34}, year = {2018}, abstract = {A search for heavy resonances decaying into a pair of Z bosons leading to l(+) l(-) l(+) l(-) and l(+) l(-) nu(nu) over bar final states, where l stands for either an electron or a muon, is presented. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1) collected with the ATLAS detector during 2015 and 2016 at the Large Hadron Collider. Different mass ranges for the hypothetical resonances are considered, depending on the final state and model. The different ranges span between 200 and 2000 GeV. The results are interpreted as upper limits on the production cross section of a spin-0 or spin-2 resonance. The upper limits for the spin-0 resonance are translated to exclusion contours in the context of Type-I and Type-II two-Higgs-doublet models, while those for the spin-2 resonance are used to constrain the Randall-Sundrum model with an extra dimension giving rise to spin-2 graviton excitations.}, language = {en} } @article{OPUS4-22672, title = {Search for Low-Mass Dijet Resonances Using Trigger-Level Jets with the ATLAS Detector in \(pp\) Collisions at root \(s\)=13 TeV}, series = {Physical Review Letters}, volume = {121}, journal = {Physical Review Letters}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevLett.121.081801}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226725}, pages = {1-20}, year = {2018}, abstract = {Searches for dijet resonances with sub-TeV masses using the ATLAS detector at the Large Hadron Collider can be statistically limited by the bandwidth available to inclusive single-jet triggers, whose data-collection rates at low transverse momentum are much lower than the rate from standard model multijet production. This Letter describes a new search for dijet resonances where this limitation is overcome by recording only the event information calculated by the jet trigger algorithms, thereby allowing much higher event rates with reduced storage needs. The search targets low-mass dijet resonances in the range 450-1800 GeV. The analyzed data set has an integrated luminosity of up to 29.3 fb(-1) and was recorded at a center-of-mass energy of 13 TeV. No excesses are found; limits are set on Gaussian-shaped contributions to the dijet mass distribution from new particles and on a model of dark-matter particles with axial-vector couplings to quarks.}, language = {en} }