Boosted top quarks and jet structure

Sebastian Schätzel

doi:10.1140/epjc/s10052-015-3636-x

Abstract

The Large Hadron Collider (LHC) is the first machine that provides high enough energy to produce large numbers of boosted top quarks. The decay products of these top quarks are confined to a cone in the top quark flight direction and can be clustered to a single jet. Top quark reconstruction then amounts to analysing the structure of the jet and looking for subjets that are kinematically compatible with top quark decay. Many techniques have been developed recently to best use these topologies to identify top quarks in a large background of non-top jets. This article reviews the results obtained using LHC data recorded in the years 2010-2012 by the experiments ATLAS and CMS. Studies of Standard Model top quark production and searches for new massive particles that decay to top quarks are presented.

Highlights

The Large Hadron Collider (LHC) at the European particle physics research centre CERN in Geneva, Switzerland, is a discovery machine at the energy frontier
This review focuses on the boosted decay topology in which the decay particles are confined to a cone in the top quark flight direction, the opening angle of which depends inversely on the top quark Lorentz factor γ = E/m
The b-tagging algorithm MV1 used for the results presented in this article is based on a neural net that combines information from significances of impact parameters and decay length, the total invariant mass of the tracks at the vertex, the fraction of the total jet energy carried by tracks that is associated with tracks from the vertex, the multiplicity of two track vertices, and the direction of the b-hadron determined from the subsequent decay vertex of the charmed hadron

Summary

Introduction

The Large Hadron Collider (LHC) at the European particle physics research centre CERN in Geneva, Switzerland, is a discovery machine at the energy frontier. A primary goal, the observation of the Higgs boson, has already been achieved [1,2] and major emphasis is being placed on the determination of the properties of the observed particle. Another important research topic is the search for deviations from predictions of the Standard Model of particle physics (SM). The top quark decays before it hadronises and is reconstructed via its decay products. This review focuses on the boosted decay topology in which the decay particles are confined to a cone in the top quark flight direction, the opening angle of which depends inversely on the top quark Lorentz factor γ = E/m.1. The first paper on this topic was published by Seymour [3]

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Results

Conclusion