https://ippog-static.web.cern.ch/ippog-static/resources/2012/cms-hep-tutorial.html
Particle physics investigates the fundamental building blocks of matter and the interactions between particles. The top quark was discovered at Fermilab's Tevatron in 1995. It is the heaviest known elementary particle to date. Due to its large mass, the production of top quarks requires particle collisions at very high energies. The Large Hadron Collider (LHC) at CERN provides higher energy and collision rates compared to the Tevatron, making it a top quark factory. The multitude of top quark events recorded by LHC experiments enables unprecedented precision in determining the properties and interactions of top quarks. The measured mass of the top quark at the Tevatron and LHC is a fundamental parameter of the Standard Model of particle physics. Since the discovery of the Higgs boson at the LHC in 2012, the precise knowledge of the top quark mass allows for investigating the internal consistency of the Standard Model. Various methods are used to measure the top quark mass. Generally, they all require a sophisticated understanding of the experiment, often involving the detection of decay products of the unstable top quark. Each potential decay mode of the top quark presents its own challenges for top quark reconstruction.
The measurement presented in this study examines the process where two top quarks decay through t → bW, with one W boson decaying to a quark-antiquark pair and the other decaying to a charged lepton and the corresponding neutrino. (At least four jets, two bottom jets, and two light jets from the top quark decay, and an undetected neutrino.)
The lepton+jets channel combines the ability to fully reconstruct the event kinematics with a good rejection of background processes. The analysis utilizes the kinematic compatibility of the decay products with a correctly reconstructed 𝑡𝑡𝑡𝑡 hypothesis. The aim of this study is to calculate the kinematic distributions of the top quark mass and other particles within the ROOT data analysis framework. The "CMS HEP Tutorial" using real data from the CMS experiment in 2011 has been followed.
C++ and ROOT are used in this study.