@article{OPUS4-22689, title = {Observation of Light-by-Light Scattering in Ultraperipheral Pb + Pb Collisions with the ATLAS Detector}, series = {Physical Review Letters}, volume = {123}, journal = {Physical Review Letters}, organization = {The ATLAS Collaboration}, doi = {10.1103/PhysRevLett.123.052001}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226892}, pages = {1-21}, year = {2019}, abstract = {This Letter describes the observation of the light-by-light scattering process, gamma gamma -> gamma gamma, in Pb + Pb collisions at root S-NN = 5.02 TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73 nb(-1), collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy E-T(gamma) > 3 GeV and pseudorapidity vertical bar eta(gamma)vertical bar < 2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12 +/- 3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78 +/- 13(stat) +/- 7(syst) +/- 3(lumi) nb.}, language = {en} } @article{OPUS4-22681, title = {Identification of boosted Higgs bosons decaying into \(b\)-quark pairs with the ATLAS detector at 13 TeV}, series = {European Physical Journal C}, volume = {79}, journal = {European Physical Journal C}, number = {836}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-019-7335-x}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226812}, pages = {1-38}, year = {2019}, abstract = {This paper describes a study of techniques for identifying Higgs bosons at high transverse momenta decaying into bottom-quark pairs, H -> b (b) over bar, for proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy root s = 13 TeV. These decays are reconstructed from calorimeter jets found with the anti-k(t) R = 1.0 jet algorithm. To tag Higgs bosons, a combination of requirements is used: b-tagging of R = 0.2 track-jets matched to the large-R calorimeter jet, and requirements on the jet mass and other jet substructure variables. The Higgs boson tagging efficiency and corresponding multijet and hadronic top-quark background rejections are evaluated using Monte Carlo simulation. Several benchmark tagging selections are defined for different signal efficiency targets. The modelling of the relevant input distributions used to tag Higgs bosons is studied in 36 fb(-1) of data collected in 2015 and 2016 using g -> b (b) over bar and Z(-> b (b) over bar)gamma event selections in data. Both processes are found to be well modelled within the statistical and systematic uncertainties.}, language = {en} } @article{OPUS4-22682, title = {Measurement of the inclusive cross-section for the production of jets in association with a \(Z\) boson in proton-proton collisions at 8 TeV using the ATLAS detector}, series = {European Physical Journal C}, volume = {79}, journal = {European Physical Journal C}, number = {847}, organization = {The ATLAS Collaboration}, doi = {10.1140/epjc/s10052-019-7321-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226821}, pages = {1-47}, year = {2019}, abstract = {The inclusive cross-section for jet production in association with a Z boson decaying into an electronpositron pair is measured as a function of the transverse momentum and the absolute rapidity of jets using 19.9 fb(-1) of root s = 8 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The measured Z + jets cross-section is unfolded to the particle level. The cross-section is compared with state-of-the-art Standard Model calculations, including the next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations, corrected for non-perturbative and QED radiation effects. The results of the measurements cover final-state jets with transverse momenta up to 1 TeV, and show good agreement with fixed-order calculations.}, language = {en} } @article{OPUS4-22690, title = {Search for diboson resonances in hadronic final states in 139 fb\(^{-1}\) of \(pp\) collisions at √\(s\)=13 TeV with the ATLAS detector}, series = {Journal of High Energy Physics}, volume = {09}, journal = {Journal of High Energy Physics}, number = {91}, organization = {The ATLAS Collaboration}, doi = {10.1007/JHEP09(2019)091}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226905}, pages = {1-42}, year = {2019}, abstract = {Narrow resonances decaying into WW, WZ or ZZ boson pairs are searched for in 139 fb(-1) of proton-proton collision data at a centre-of-mass energy of root s = 13TeV recorded with the ATLAS detector at the Large Hadron Collider from 2015 to 2018. The diboson system is reconstructed using pairs of high transverse momentum, large-radius jets. These jets are built from a combination of calorimeter- and tracker-inputs compatible with the hadronic decay of a boosted W or Z boson, using jet mass and substructure properties. The search is performed for diboson resonances with masses greater than 1.3TeV. No significant deviations from the background expectations are observed. Exclusion limits at the 95\% confidence level are set on the production cross-section times branching ratio into dibosons for resonances in a range of theories beyond the Standard Model, with the highest excluded mass of a new gauge boson at 3.8TeV in the context of mass-degenerate resonances that couple predominantly to gauge bosons.}, language = {en} } @article{OPUS4-22691, title = {FCC-hh: The Hadron Collider: Future Circular Collider Conceptual Design Report Volume 3}, series = {European Physical Journal - Special Topics}, volume = {228}, journal = {European Physical Journal - Special Topics}, organization = {The FCC Collaboration}, doi = {10.1140/epjst/e2019-900087-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226917}, pages = {755-1107}, year = {2019}, abstract = {In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100TeV. Its unprecedented centre of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.}, language = {en} } @article{OPUS4-22692, title = {HE-LHC: The High-Energy Large Hadron Collider : Future Circular Collider Conceptual Design Report Volume 4}, series = {European Physical Journal - Special Topics}, volume = {228}, journal = {European Physical Journal - Special Topics}, number = {5}, organization = {The FCC Collaboration}, doi = {10.1140/epjst/e2019-900088-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226928}, pages = {1109-1382}, year = {2019}, abstract = {In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.}, language = {en} } @article{OPUS4-22693, title = {FCC Physics Opportunities: Future Circular Collider Conceptual Design Report Volume 1}, series = {European Physical Journal C}, volume = {79}, journal = {European Physical Journal C}, number = {474}, organization = {The FCC Collaboration}, doi = {10.1140/epjc/s10052-019-6904-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226938}, pages = {1-161}, year = {2019}, abstract = {We review the physics opportunities of the Future Circular Collider, covering its e(+)e(-), pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the synergy and complementarity of the different colliders, which will contribute to a uniquely coherent and ambitious research programme, providing an unmatchable combination of precision and sensitivity to new physics.}, language = {en} } @article{OPUS4-22694, title = {FCC-ee: The Lepton Collider: Future Circular Collider Conceptual Design Report Volume 2}, series = {European Physical Journal - Special Topics}, volume = {228}, journal = {European Physical Journal - Special Topics}, number = {2}, organization = {The FCC Collaboration}, doi = {10.1140/epjst/e2019-900045-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226947}, pages = {261-623}, year = {2019}, abstract = {In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today's technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.}, language = {en} } @article{OPUS4-22609, title = {Search for a heavy Higgs boson decaying into a \(Z\) boson and another heavy Higgs boson in the \({llbb}\) final state in \({pp}\) collisions at root \(s\)=13 TeV with the ATLAS detector}, series = {Physics Letters B}, volume = {783}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.07.006}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226098}, pages = {392-414}, year = {2018}, abstract = {A search for a heavy neutral Higgs boson, A, decaying into a Z boson and another heavy Higgs boson, H, is performed using a data sample corresponding to an integrated luminosity of 36.1 fb(-1) from proton-proton collisions at root s = 13 TeV recorded in 2015 and 2016 by the ATLAS detector at the Large Hadron Collider. The search considers the Z boson decaying to electrons or muons and the H boson into a pair of b-quarks. No evidence for the production of an A boson is found. Considering each production process separately, the 95\% confidence-level upper limits on the pp -> A -> ZH production cross-section times the branching ratio H -> bb are in the range of 14-830 fb for the gluon-gluon fusion process and 26-570 fb for the b-associated process for the mass ranges 130-700 GeV of the H boson and 230-800 GeV of the A boson. The results are interpreted in the context of two-Higgs-doublet models. (C) 2018 Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).}, language = {en} } @article{OPUS4-22606, title = {Measurement of the Higgs boson mass in the \(H\) -> \({ZZ}\)* -> 4l and \(H\) -> \({γγ}\) channels with root \(s\)=13 TeV \({pp}\) collisions using the ATLAS detector}, series = {Physics Letters B}, volume = {784}, journal = {Physics Letters B}, organization = {The ATLAS Collaboration}, doi = {10.1016/j.physletb.2018.07.050}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226065}, pages = {345-366}, year = {2018}, abstract = {The mass of the Higgs boson is measured in the H -> ZZ* -> 4l and in the H -> gamma gamma decay channels with 36.1 fb(-1) of proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The measured value in the H -> ZZ* -> 4l channel is m(H)(ZZ*) = 124.79 +/- 0.37 GeV, while the measured value in the H -> gamma gamma channel is m(H)(gamma gamma) = 124.93 +/- 0.40 GeV. Combining these results with the ATLAS measurement based on 7 and 8 TeV proton-proton collision data yields a Higgs boson mass of m(H) = 124.97 +/- 0.24 GeV. (c) 2018 The Author. Published by Elsevier B.V.}, language = {en} }