While searching for new Higgs bosons the CMS experiment at the Large Hadron Collider (LHC) may have just found a surprise. They have observed an excess of events that look to be a new particle, and are reporting high statistical evidence for their claim. The only question is what exactly is this new particle?

The search was initially designed to look for new, heavier, versions of the Higgs boson decaying to a top quark and an anti-top quark. Its well known that the Higgs boson of the Standard Model, discovered jointly by ATLAS and CMS in 2012, underlies the mechanism which gives all fundamental particles their masses. The Higgs boson itself interacts with particles in proportion to their mass, preferring heavier particles over lighter ones. It therefore interacts the most strongly with the heaviest known fundamental particle, the top quark, which has a mass of ~173 GeV. The Higgs boson itself only has a bass of 125 GeV, meaning conservation of energy dictates it can’t decay into a top quark-antiquark pair.

However many theories of physics beyond the the Standard Model predict additional Higgs bosons, heavier cousins of the current one. If these new heavy Higgs bosons had a mass larger than 350 GeV, they would likely decay to a top quark-antiquark pair quite often. CMS therefore was analyzed its data searching for this signature, hoping to find signs of a new Higgs boson. To do so, they had scrutinize very carefully the known production of top quark-antiquark pairs, which are produced copiously at the LHC from other processes. If a new particle was being produced and decaying to top quarks, the mass of the new particle would give the top quarks a characteristic energy. One key sign of a new particle would therefore be an excess of top quark-antiquark events at a particular energy, corresponding to the mass of the new particle. 

When CMS scrutinized their data looking for such an excess they found one. But curiously right ~350 GeV, the minimum energy required to produce the top quark-antiquark pair. It would be quite the coincidence for a new particle to show up right at this minimum threshold, which made CMS consider alternative possibilities.

 

 One unorthodox explanation that seems to fit the bill is ‘toponium’, a short lived bound state of the top quark-antiquark pair is being formed. Toponium would be the heaviest version of ‘quarkonia’ we have seen, bound states of quark antiquark pairs that form bound states similar to atoms. We have observed and measured quarkonia states of the other quarks for decades, however it was long thought that the top quark, whose large mass causes it to decay in just 10^(-25) seconds, would decay too quickly to create observable bound state effects at a hadron collider. Toponium production would happen most often if the top quarks were produced just at the energy threshold, such that they don’t any extra energy. These low energy top quarks would spend more time close to each other than normal, rather than immediately flying away, so they could have time to briefly form a toponium state before decaying. However, once small hints of intriguing excesses started appearing in LHC analyses, updated calculations in the last few years suggested that perhaps such an effect could be observable.

These calculations are approximate, and more work is still being done to refine them. But the preliminary predictions they give for the properties of toponium seem to match well with what CMS is seeing, both in terms of the rate of toponium production and the quantum properties of the toponium state (spin and parity).

Still CMS is being cautious before claiming a discovery of toponium. They claim observation of an ‘excess at the top quark pair production threshold’ which is consistent with toponium. However given the limited present data and incomplete theoretical models of toponium, they cannot rule out that the excess they are seeing is coming from a new Higgs-like particle.

Further work will be needed to develop improved theoretical models of toponium, and detailed studies from CMS assessing the properties of their observed excess. The excess will also need confirmation from CMS’s rival LHC experiment, ATLAS, to ensure it has not merely made a mistake in its analysis.

However, the smart money would say this very likely looks like toponium. Which, while not signaling the long sought overthrow of the standard model, would be an unexpected and cool surprise from the LHC. Understanding the properties of this previously-thought-impossible quasiparticle will spawn much fruitful research in the years to come. Physicists love a surprise!

Paper:

“Observation of a pseudoscalar excess at the top quark pair production threshold” https://arxiv.org/abs/2503.22382

Additional CMS Paper considering Heavy-Higgs interpretation “Search for heavy pseudoscalar and scalar bosons decaying to top quark pairs in proton-proton collisions”

Read more

CERN Courier “CMS observes top–antitop excess“

Symmetry Magazine “Don’t call it toponium“

Discloure: The author is a member of the CMS collaboration but did not directly work on this analysis

Erratum 4/15/2025 : The article was updated to clarify that in the theory literature prior to the LHC toponium was thought possible to form, just that it was thought to be too small an effect to be observable. The article previously incorrectly stated it had been previously thought impossible to form

Recent satellite data indicate that the South Atlantic Anomaly in Earth's magnetic field is potentially splitting into two anomalies. This phenomenon, attributed to disturbances in the outer core, threatens the planet's magnetic shielding. This supports a young Earth perspective based on evidence of total energy decay from the magnetic field.

Researchers at a field station in Panama observed a katydid with striking hot-pink coloration in the rainforest. Rather than assuming the coloration was simply a genetic anomaly, they monitored the insect to document what would occur over time. Eleven days later, it was completely green.

The findings, published in Ecology, center on Arota festae, a leaf-mimicking katydid found in Panama, Colombia, and Suriname. This observation is shifting researchers’ understanding of dynamic camouflage in relation to the changing colors of rainforest leaves.

More Than a Mutation

The discovery happened on March 27, 2025, at the Smithsonian Tropical Research Institute’s field station on Barro Colorado Island. Dr. Benito Wainwright, the lead author from the University of St Andrews, observed an adult female A. festae with a bright, hot pink color under a research station light. Since this color is so rare, the team kept the insect in natural conditions and checked on its appearance every day.

The katydid retained its pink coloration for four days, which then faded to a lighter shade. By the eleventh day, it had matched the typical green coloration of the species. The insect survived long enough to mate and died naturally the following month.

“Finding this individual was a genuine surprise,” Wainwright said. “Rather than a bizarre genetic quirk, this may actually be a finely tuned survival strategy that tracks the life cycle of the rainforest leaves this insect is trying to resemble.”

Camouflage That Changes With the Forest

This color change is connected to a process called delayed greening. In many tropical plants, new leaves start out pink or red and turn green as they grow. On Barro Colorado Island, about a third of plant species show this color pattern year-round, so pink leaves are always present in the forest.

A katydid that changes color in step with this pattern can stay hidden in its environment. The research team suggests that A. festae may have evolved to match its color transition to the leaf color cycle, allowing it to blend in at each stage rather than maintaining a single color.

A First in the Scientific Record

Pink katydids have been documented in scientific literature since 1878, but have generally been regarded as rare and disadvantageous mutations. This new observation challenges that interpretation. There are no previous records of a katydid completing a full color transition within a single adult stage; therefore, this appears to be the first documented case.

Dr. Matt Greenwell from the University of Reading, who co-authored the study, explained the finding as an example of how exactly the rainforest can influence the animals that live there.

“You would think that a bright pink insect in a mostly green forest would stand out to predators like a worker in a high-vis jacket,” Greenwell said. “The idea that an insect might gradually shift color to keep pace with the leaves it mimics shows how dynamic the rainforest can be, and is a remarkable example of camouflage in action.”

More Questions Than Answers

The researchers point out that their findings are based on a single observed individual, which limits the study. They still do not know whether this color shift occurs across the species, what biological mechanisms drive it, or whether environmental or internal factors trigger it.

Still, this finding offers a new way to think about insect camouflage. Rather than seeing color as fixed, A. festae shows that some species may have evolved to adjust their color as the environment changes, staying hidden by following ongoing changes instead of matching just one background.

Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.