TY  - JOUR
T1  - Search for s-channel single top-quark production in proton–proton collisions at \(\sqrt{s}\)=8 TeV with the ATLAS detector
JF  - Physics Letters B
N2  - This Letter presents a search at the LHC for s-channel single top-quark production in proton–proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb\(^{−1}\). Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of σs=5.0±4.3 pb, consistent with the Standard Model expectation.
KW  - s-Channel
KW  - electroweak production
KW  - top-quark
KW  - ATLAS
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-139869
VL  - 740
ER  - 
TY  - JOUR
T1  - Measurement of the top-quark mass in the fully hadronic decay channel from ATLAS data at \(\sqrt {s}\)=7TeV
JF  - European Physical Journal C: Particles and Fields
N2  - The mass of the top quark is measured in a data set corresponding to 4.6  fb\(^{-1}\) of proton–proton collisions with centre-of-mass energy \(\sqrt {s}\)=7 TeV collected by the ATLAS detector at the LHC. Events consistent with hadronic decays of top–antitop quark pairs with at least six jets in the final state are selected. The substantial background from multijet production is modelled with data-driven methods that utilise the number of identified b-quark jets and the transverse momentum of the sixth leading jet, which have minimal correlation. The top-quark mass is obtained from template fits to the ratio of three-jet to dijet mass. The three-jet mass is calculated from the three jets produced in a top-quark decay. Using these three jets the dijet mass is obtained from the two jets produced in the W boson decay. The top-quark mass obtained from this fit is thus less sensitive to the uncertainty in the energy measurement of the jets. A binned likelihood fit yields a top-quark mass of m\(_{t}\)= 175.1 ± 1.4 (stat.) ± 1.2 (syst.) GeV.
KW  - ATLAS
KW  - proton–proton collisions
KW  - top-quark mass
KW  - fully hadronic
KW  - LHC
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149905
VL  - 75
IS  - 4
ER  - 
TY  - JOUR
T1  - Search for a CP-odd Higgs boson decaying to Zh in pp   collisions at \(\sqrt{s}\)=8 TeV with the ATLAS detector
JF  - Physics Letters B
N2  - A search for a heavy, CP-odd Higgs boson, A, decaying into a Z boson and a 125 GeV Higgs boson, h, with the ATLAS detector at the LHC is presented. The search uses proton–proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb\(^{-1}\). Decays of CP-even h bosons to ττ or bb pairs with the Z   boson decaying to electron or muon pairs are considered, as well as h→bb decays with the Z boson decaying to neutrinos. No evidence for the production of an A   boson in these channels is found and the 95% confidence level upper limits derived for σ(gg→A)×BR(A→Zh)×BR(h→f\(\bar{f}\)) are 0.098–0.013 pb for f=τ and 0.57–0.014 pb for f=b in a range of m\(_{A}\)=220–1000 GeVmA=220–1000 GeV. The results are combined and interpreted in the context of two-Higgs-doublet models.
KW  - BSM Higgs boson
KW  - ATLAS
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143050
VL  - 744
ER  -