Hamburg 2016 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 77: Top Quark IV (single top, FCNC)

T 77.8: Vortrag

Mittwoch, 2. März 2016, 18:30–18:45, VMP9 HS

Single top production in association with a Z boson at ATLAS — Ian C. Brock and •Irina Cioară — Physikalisches Institut, University of Bonn

An interesting channel to be investigated with the new 13 TeV data at ATLAS is the electroweak process in which a Z boson is radiated in the t-channel single top production (tZ channel). The lepton + jets decay topology of this channel produces one b-jet, one charged lepton with high transverse momentum, three light-quark jets plus one in the forward direction and one neutrino. Almost four times less frequent, the dilepton channel is investigated as well by searching for events with two leptons coming from the Z boson decay, three jets from the hadronic top-quark decay and one jet in the forward region.

Because of the low production rate and many background processes with much higher cross section, multivariate analysis techniques are used for separating signal and background.

Besides the potential to constrain the top-Z boson coupling, this channel is also interesting because it is, until now, an unconsidered irreducible background for flavour changing neutral current decays of the top quark in tt production and will also constitute one of the main sources of background for a single-top + Higgs(H→ bb) analysis. Some BSM models also predict a final state in which a top-quark and a Z boson are produced.