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T: Fachverband Teilchenphysik

T 31: Methods in particle physics 3 (lepton reconstruction)

T 31.7: Vortrag

Dienstag, 5. März 2024, 17:30–17:45, Geb. 20.30: 2.066

Development of the Prompt Lepton Improved Veto — Arnulf Quadt, Baptiste Ravina, and •Tim Schlömer — I. Physikalisches Institut, Georg-August-Universität Göttingen

Prompt leptons originate from decays of heavy bosons like the W- and Z-boson, produced in the hard scattering process. These leptons originate from the primary vertex, due to the short lifetime of the bosons. In contrast, non-prompt, or fake leptons are mostly produced in semileptonic decays of c- or b-hadrons, which are characterised by a longer lifetime and therefore of a distinct secondary vertex.

The selection is mostly based on isolation observables like the measured energy activity around the lepton candidates. It is very important to select the prompt leptons, and fake leptons are important backgrounds in many multi-lepton analyses. In multi-lepton analyses, like ttH, ttW or tttt, fake leptons are the dominant background, even with the tightest isolation criteria.

One of the algorithms used in the ATLAS Collaboration that identify prompt leptons and veto fake leptons is the "Prompt Lepton Improved Veto" (PLIV), using several isolation, and additionally lifetime observables to distinguish between prompt and fake leptons. The most important input is a lifetime observable constructed from track information. Other important inputs are isolation observables such as Δ R between lepton and track jet, and the transverse momentum in a cone around the lepton.

For the improvement of PLIV, studies on new Neural Network architectures and calibration are performed.

Keywords: Fake lepton rejection; PLIV; Multi-lepton analyses