Dresden 2013 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 35: Top-Quarks 3

T 35.4: Vortrag

Montag, 4. März 2013, 17:30–17:45, HSZ-02

Reconstruction of the tt system in the dilepton channel using Neutrino Weighting — Kevin Kröninger, Arnulf Quadt, Elizaveta Shabalina, and •Tamara Vázquez Schröder — Georg- August-Universität, Göttingen, Germany

Top-quark pairs can decay in three different modes: 4/9th fully hadronic, 4/9th semileptonic and 1/9th dileptonic. The dilepton decay channel has two charged leptons and two neutrinos in the final state. It has a low branching fraction, but few background processes. Neutrinos escape direct detection but their presence can be inferred via an excess of missing transverse energy in the event. Due to the presence of two neutrinos in the final state, there is not enough information in the event to define kinematics and fully reconstruct the event. Kinematics are underconstrained by one degree of freedom. The neutrino weighting approach is used to reconstruct top events in the dilepton channel by assuming a neutrino rapidity distribution from Standard Model expectations and a top quark mass a priori. Event weights are then derived per event from comparing calculated and reconstructed missing transverse momentum for each top quark mass hypothesis, taking into account the detector resolution of the missing transverse energy. The neutrino weighting algorithm is now implemented in the KLFitter framework, having the option of choosing the best permutation of jets and so being able to reconstruct the top quark kinematics. This talk will focus on the neutrino weighting approach inside KLFitter and the possible implementation of this reconstruction code in a top mass measurement in the dilepton channel.