By Amit Malewar 17 Oct, 2024
Collected at: https://www.techexplorist.com/atlas-experiment-reveals-pairs-top-quarks-produced/91258/
In collisions between protons at the Large Hadron Collider (LHC), pairs of top quarks—hefty particles—are often produced alongside other heavy quarks like bottom and charm quarks. Studying these collisions helps physicists understand the strong force described by quantum chromodynamics (QCD). Researchers can also distinguish between common and rare events by measuring how often these particles are produced.
Recently, the ATLAS collaboration analyzed data from LHC Run 2 (2015–2018) to see how often top quark pairs appear with bottom or charm quarks. One study focused on top quark pairs created with “b-jets” (particles from bottom quarks). They used flavor-tagging algorithms to identify these b-jets accurately by looking for specific patterns.
Examining events with electron-muon pairs and multiple b-jets, they measured how often these top quark pairs are produced. Their results were more accurate than current theoretical predictions, especially for events with many b-jets.
They also examined the motion of the b-jets and total jet energy to determine how well simulations matched accurate data, revealing areas where models need improvement to better understand the production of additional b-jets.
In a second ATLAS study presented at the 17th International Workshop on Top Quark Physics, researchers significantly improved by measuring how often top-quark pairs are produced alongside jets from charm quarks (c-jets) for the first time.
They analyzed events with one or two leptons (electrons and muons) using a special flavor-tagging algorithm designed to identify c-jets, which are harder to detect than b-jets due to their shorter lifetimes and less clear signatures in the ATLAS detector.
The study found that while most theoretical models matched the data reasonably well, they typically underestimated the production rates of c-jets. This research, which separately measured the production rates of single and multiple charm quarks in top-quark-pair events, emphasizes the need for improved simulations to enhance future measurements.
These studies enhance our understanding of how top quarks interact with bottom and charm quarks within the framework of quantum chromodynamics (QCD). They also open up opportunities to investigate rarer processes involving top quarks, such as the simultaneous production of four top quarks, which could expand our knowledge of physics beyond what is currently known.
Journal References:
- Atlas Collaboration. Measurement of tt¯ production associated with additional b-jets in the eμ final state in proton-proton collisions at s√=13 TeV with the ATLAS detector. DOI: 10.48550/arXiv.2407.13473
- The ATLAS detector measures top-quark pair production in association with charm quarks in proton-proton collisions at 13 TeV. DOI: 10.48550/arXiv.2409.11305
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