## Publicly Accessible Penn Dissertations

2015

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Physics & Astronomy

Evelyn J. Thomson

#### Abstract

A search for weakly-produced Chargino1, Neutralino2 supersymmetric particles

decaying to two final state electrons or muons with the same electric

charge is presented. The analysis is performed on 20.3\ifb~of

integrated luminosity collected in 2012 with the Atlas Detector at the

Large Hadron Collider, running at $\sqrt{s} = 8$ TeV. Pairs of

like-sign leptons are collected and discriminated against background

using Boosted Decision Trees trained on compressed supersymmetric

simplified models. No significant excesses above background

expectations are observed. The 95% confidence limits are placed on

Chargino1 Neutralino2 pairs decaying via W and Z bosons and via intermediate

sleptons with two different assumptions on the relative slepton mass.

In the most optimistic scenarios considered, Chargino1 below 410 GeV are

excluded assuming a massless LSP. In the compressed scenario,

Chargino1 $< 180$ GeV are excluded, with $\Delta$M Chargino1, LSP $>20$

GeV. Results from this analysis are also combined with those from a

complementary search in the three lepton final state.

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