No Arabic abstract
On the twentieth anniversary of the observation of the top quark, we trace our understanding of this heaviest of all known particles from the prediction of its existence, through the searches and discovery, to the current knowledge of its production mechanisms and properties. We also discuss the central role of the top quark in the Standard Model and the windows that it opens for seeking new physics beyond the Standard Model.
The top quark, the heaviest known elementary particle discovered at the Fermilab Tevatron more than twenty years ago, has taken a central role in the study of fundamental interactions. Due to its large mass, the top quark provides a unique environment for tests of the standard model. With a cumulative luminosity of more than 100~fb$^{-1}$ collected at $sqrt{s}=7,8,13$ TeV by each of the ATLAS and CMS experiments at the Large Hadron Collider in the first ten years of operation, top quark physics is probing uncharted territories in precision and rare measurements with sensitivity to New Physics processes. This document summarizes the latest experimental measurements and studies of top quark properties.
Recent top quark event modeling studies done using LHC proton-proton collision data collected with the CMS detector at centre of mass energies of 8 and 13 TeV and state-of-the-art theoretical predictions are summarized. A new factorized approach for parton shower uncertainties is presented. A top quark specific PYTHIA8 CMS tune, along with tunes using new color reconnection models, is discussed. The possibility of having a consistent choice of parton distribution function in the matrix element and the parton shower is demonstrated with tunes constructed with leading, next-to-leading, and next-to-next-to-leading ord
The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies: 380 GeV, 1.5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the search for rare flavour-changing neutral current (FCNC) top-quark decays. It also includes a top-quark pair production threshold scan around 350 GeV which provides a precise measurement of the top-quark mass in a well-defined theoretical framework. At the higher-energy stages, studies are made of top-quark pairs produced in association with other particles. A study of ttH production including the extraction of the top Yukawa coupling is presented as well as a study of vector boson fusion (VBF) production, which gives direct access to high-energy electroweak interactions. Operation above 1 TeV leads to more highly collimated jet environments where dedicated methods are used to analyse the jet constituents. These techniques enable studies of the top-quark pair production, and hence the sensitivity to BSM physics, to be extended to higher energies. This paper also includes phenomenological interpretations that may be performed using the results from the extensive top-quark physics programme at CLIC.
A search for dark matter produced in association with a top quark pair is presented. The search is performed using 19.7 $mathrm{fb^{-1}}$ of proton-proton collisions recorded at a center of mass energy of 8 TeV with the CMS detector at the LHC. The signature investigated is top quark pairs in the semi-leptonic final state plus missing transverse energy. This work focuses in particular on dark matter production through scalar interaction where a proportionality to the quark mass is expected.
The top quark physics has entered the precision era. The CDF and D0 collaborations are finalizing their legacy results of the properties of the top quark after the shutdown of the Fermilab Tevatron three years ago. The ATLAS and CMS collaborations have been publishing results from the LHC Run I with 7 TeV and 8 TeV proton-proton collisions, with many more forthcoming. We present a selection of recent results produced by the Tevatron and LHC experiments.