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T: Fachverband Teilchenphysik

T 75: Suche nach Supersymmetrie III

T 75.2: Vortrag

Donnerstag, 22. März 2018, 16:45–17:00, Philo-HS3

Studies to increase the sensitivity of the search for top squarks in final states with one electron or muon at the ATLAS experiment — •David Handl, Jovan Mitrevski, and Jeannine Wagner-Kuhr — LMU München

Many theories favour a relatively light top squark (t₁), which is the supersymmetric partner of the top quark, with a mass that should be within the reach of the LHC.

The presented studies focus on events with multiple jets, missing transverse momentum and exactly one isolated electron or muon in the final state. A particular simplified model is considered where the mass difference between the top squark and the neutralino (χ₁⁰) is smaller than the top quark (Δ m ≡ m_t1 − m_χ1⁰ < m_t ), leading to a three-body decay. Such decay scenarios are very challenging because the kinematics are very similar to the production of top quark pairs.

Machine learning (ML) techniques, such as boosted decision trees and neural networks could provide a very helpful tool to isolate the signal from the standard model background. In this talk applications of multivariate algorithms to the current search are presented. The corresponding sensitivity reach is determined and compared to the current standard cut-based approach. Analyses conducted in extreme phase space regions generally face the issue of low statistics, which is a crucial aspect for the evaluation of systematic effects. To overcome this issue a ML-based reweighting procedure is applied on the high-statistic Monte-Carlo sample, which is used for the default prediction, to imitate systematic effects and the results are validated and discussed.