Search for pair and single production of new heavy quarks that decay to a Z boson and a third-generation quark in pp collisions at s√=8 TeV with the ATLAS detector

TY - JOUR

T1 - Search for pair and single production of new heavy quarks that decay to a Z boson and a third-generation quark in pp collisions at s√=8 TeV with the ATLAS detector

AU - Aad, G.

AU - Abbott, B.

AU - Abdallah, J.

AU - Dam, Mogens

AU - Hansen, Peter Henrik

AU - Hansen, Jørgen Beck

AU - Hansen, Jørn Dines

AU - Xella, Stefania

AU - Petersen, Troels Christian

AU - Thomsen, Lotte Ansgaard

AU - Mehlhase, Sascha

AU - Jørgensen, Morten Dam

AU - Løvschall-Jensen, Ask Emil

AU - Monk, James William

AU - Pedersen, Lars Egholm

AU - Wiglesworth, Graig

AU - Alonso Diaz, Alejandro

AU - Galster, Gorm Aske Gram Krohn

AU - Pingel, Almut Maria

PY - 2014/9/18

Y1 - 2014/9/18

N2 - Abstract: A search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark (T ), the decay targeted is T → Zt, while the decay targeted for a new charge −1/3 quark (B) is B → Zb. The search is performed with a dataset corresponding to 20.3 fb−1 of pp collisions at (Formula presented.) TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Selected events contain a high transverse momentum Z boson candidate reconstructed from a pair of oppositely charged same-flavor leptons (electrons or muons), and are analyzed in two channels defined by the absence or presence of a third lepton. Hadronic jets, in particular those with properties consistent with the decay of a b-hadron, are also required to be present in selected events. Different requirements are made on the jet activity in the event in order to enhance the sensitivity to either heavy quark pair production mediated by the strong interaction, or single production mediated by the electroweak interaction. No significant excess of events above the Standard Model expectation is observed, and lower limits are derived on the mass of vector-like T and B quarks under various branching ratio hypotheses, as well as upper limits on the magnitude of electroweak coupling parameters.

AB - Abstract: A search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark (T ), the decay targeted is T → Zt, while the decay targeted for a new charge −1/3 quark (B) is B → Zb. The search is performed with a dataset corresponding to 20.3 fb−1 of pp collisions at (Formula presented.) TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Selected events contain a high transverse momentum Z boson candidate reconstructed from a pair of oppositely charged same-flavor leptons (electrons or muons), and are analyzed in two channels defined by the absence or presence of a third lepton. Hadronic jets, in particular those with properties consistent with the decay of a b-hadron, are also required to be present in selected events. Different requirements are made on the jet activity in the event in order to enhance the sensitivity to either heavy quark pair production mediated by the strong interaction, or single production mediated by the electroweak interaction. No significant excess of events above the Standard Model expectation is observed, and lower limits are derived on the mass of vector-like T and B quarks under various branching ratio hypotheses, as well as upper limits on the magnitude of electroweak coupling parameters.

U2 - 10.1007/JHEP11(2014)104

DO - 10.1007/JHEP11(2014)104

M3 - Journal article

SN - 1126-6708

VL - 2014

JO - Journal of High Energy Physics (Online)

JF - Journal of High Energy Physics (Online)

M1 - 104

ER -