[Paper Review] Results on TOP physics from CMS

G. Krintiras|arXiv (Cornell University)|Jan 25, 2018

Particle physics theoretical and experimental studies57 references3 citations

TL;DR

This paper presents a comprehensive review of top quark physics results from the CMS experiment at the LHC, focusing on precision measurements of top quark production cross sections, mass, and Yukawa coupling. It demonstrates strong consistency with the Standard Model, constrains new physics beyond the SM, and projects future sensitivity at the High-Luminosity LHC and future colliders using advanced experimental techniques and theoretical calculations at next-to-leading order in QCD.

ABSTRACT

After the discovery of the top quark more than 20 years ago, top quark production cross sections have been meticulously studied. The rich variety of results from the LHC experiments are complemented with increasingly accurate theoretical predictions of heavy quark production and decay. Measurements of the top quark production provide a benchmark test of perturbative quantum chromodynamics and the standard model (SM), constraining at the same time the background in Higgs boson searches as well as extensions beyond the SM. Recent top quark measurements from CMS are reviewed, illustrating past and current experimental methods along with their attained precision. A perspective of top quark physics at the High-Luminosity LHC and at future colliders is briefly given.

Motivation & Objective

• To review and synthesize the latest precision measurements of top quark production and decay from the CMS experiment at the LHC.
• To assess the consistency of top quark data with the Standard Model and constrain new physics beyond the SM.
• To evaluate the role of top quark physics in testing electroweak symmetry breaking and vacuum stability at high energy scales.
• To project the expected improvements in top quark mass and coupling measurements at the High-Luminosity LHC and future colliders.

Proposed method

• Utilization of inclusive and differential cross section measurements of top quark pair and single top production across various final states.
• Application of advanced multivariate analysis techniques and b-tagging efficiencies measured in-situ to reduce systematic uncertainties.
• Implementation of next-to-leading-order (NLO) quantum chromodynamics calculations to model signal and background processes accurately.
• Use of global fits to electroweak precision data and Higgs boson measurements to extract indirect constraints on the top quark mass.
• Employment of threshold scans and top quark mass reconstruction techniques to probe the top quark Yukawa coupling and its relation to the Higgs sector.
• Projection of future experimental sensitivities using simulated data for HL-LHC and future linear collider scenarios.

Experimental results

Research questions

• RQ1 How precisely can the top quark mass and production cross section be measured at the LHC using CMS data?
• RQ2 To what extent do top quark measurements constrain the Higgs boson self-coupling and vacuum stability at high energy scales?
• RQ3 What are the current limits on flavor-changing neutral currents in top quark decays, and how do they compare to SM predictions?
• RQ4 How do precision measurements of the top quark Yukawa coupling constrain new physics beyond the Standard Model?
• RQ5 What improvements in top quark mass and coupling uncertainty are expected at the High-Luminosity LHC and future colliders?

Key findings

• The measured top quark mass is in excellent agreement with indirect determinations from electroweak precision data, validating the consistency of the Standard Model.
• The top quark mass uncertainty is projected to reach 200 MeV at the High-Luminosity LHC, approaching the precision of a threshold scan at a linear collider.
• A lower bound of 1.9 at 95% confidence level is set on the ratio of the top quark Yukawa coupling to its Standard Model value.
• The Higgs boson self-coupling is found to be sensitive to small variations in the top quark mass, with vacuum stability scale estimates varying by several orders of magnitude under ±2 GeV shifts.
• Projections show that future experiments could constrain top quark FCNC decays to branching ratios below 10^-3, significantly improving current limits.
• The measured top quark production cross section is consistent with NLO QCD predictions, with uncertainties dominated by theoretical and experimental systematics.