Scientists at CERN’s Large Hadron Collider (LHC) have revealed unexpected anomalies in the data, suggesting the presence of the smallest composite particles ever observed.
The findings of CMS Collaboration highlight the potential for detection of “toponium.” This is a fleeting bond between the top quark and the antimatter counterpart.
Top quark, the heaviest of all basic particles, has the shortest lifespan, and its interaction makes studying difficult.
Although toponium formation has long been thought to be undetectable in LHC, this latest finding suggests that this is not the case.
However, alternative explanations continue to be possible, particularly from CERN’s Atlas experiment, and further analysis is required.
The role of top quarks in particle physics.
LHC frequently generates upper Quark-Antiquark pairs (TT-BARs) through high-energy proton collisions.
Measuring the frequency of these events is important for testing standard models of particle physics. This has governed understanding of basic particles for over 50 years.
In addition to confirming known theories, studying top quarks also helps scientists search for still wavy particles. Some physicists speculate that dark matter and other unknown phenomena may be associated with undiscovered heavy particles.
The surplus of TT-BAR pairs in experimental data often suggests the presence of additional Higgs bosons, but the most recent observations suggest that they may differ.
Abnormal data can cause excitement
Between 2016 and 2018, CMS researchers analyzed enormous amounts of TT-BAR production data, searching for indications of additional Higgs-like particles.
The upper quark, 184 times heavier than the proton, is expected to interact strongly with such particles. If the undiscovered Higgs boson is large enough, it should collapse into the TT-BAR pair and produce a “jet” that can detect the “jet” of particles within the CMS detector.
However, CMS found an excess of upper anti-angle pairs that were formed accurately at the minimum energy threshold required to generate them. This anomaly has led researchers to revisit long-standing hypotheses: upper Quark-Antiquark binding states, or toponium formation.
The elusive nature of toponium
Unlike other Quark-Antiquark boundary states and Quarkonia, TT-Bar pairs are not expected to form stable bonds.
However, quantum chromodynamics – the theory that explains how powerful nuclear forces couple to quarks – predicts possible boundary state reinforcement at TT-BAR production thresholds.
Alternative explanations such as the presence of basic Higgs-like bosons cannot be excluded, but CMS calculations support the toponium hypothesis.
The cross section, which is a measure of the likelihood of particle interaction, was found to be 8.8 picobalun with approximately 15% uncertainty.
This exceeds the five-sigma threshold required for confirmed discoveries in particle physics, reducing the likelihood that the anomaly is a statistical fluke to nearly zero.
A new frontier in particle physics?
If verified, toponium completes the Quarkonium family, including Carm-Anticharm and Bottomonium (Bottom-Antibottom).
The former was discovered in 1974 during the November Revolution in particle physics, and the latter was identified in 1977.
Currently, the bottomium, which measures approximately 0.4 femtometers, holds the title of the smallest known hadron. However, due to its high mass, the toponium is expected to be even smaller, making it the smallest composite particle ever detected.
Detecting toponium in high-energy collisions was thought to be unlikely as the top quarks decay in less than a trillion second before forming a stable bond state.
Unlike other Quarkonias, where attenuation is caused by the disappearance of its constituent particles, the toponium collapses on its own due to the rapid collapse of one of its quarks.
The scientific community remains cautious, as alternative theories can still explain the observed data. Both CMS and Atlas work together to further investigate anomalies and analyze additional data sets to see if the toponium is indeed present.
If proven, this discovery can reconstruct an understanding of the top quark interactions and opens new doors to exploration to unlock the mystery of the most basic building blocks of the universe.
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