Iranian researchers open new path to studying particles containing top quarks

Iranian researchers at the University of Tehran have opened a new theoretical path for studying a largely unexplored class of particles that could contain the top quark, the heaviest known elementary particle.

A research team at the university’s Faculty of Physics has carried out a series of studies examining whether different types of hadrons, containing one, two or even three top quarks could exist.

A hadron is a particle made up of two or more quarks, such as the proton and neutron that make up the atomic nucleus.
The work has been published in international journals including the

European Physical Journal C, the International Journal of Theoretical Physics and Annals of Physics, with the studies also made available through the arXiv research repository.

The latest study focuses on hadrons containing a single top quark.
Using a theoretical method known as QCD Sum Rules, the researchers calculated the masses of a broad range of hypothetical particles, including different types of baryons and mesons.

Their earlier studies examined top-antitop systems, known as toponium, as well as hypothetical baryons containing three top quarks and particles containing two top quarks.

Together, the studies provide a systematic picture of what different top-containing hadrons might look like and how they could potentially be detected.

The top quark is particularly unusual because, despite being the heaviest of the six known quarks, it exists for an extraordinarily short time — about 5×10⁻²⁵ seconds.

This is shorter than the time generally associated with the process through which quarks become bound into hadrons.

As a result, scientists have long questioned whether a top quark could combine with other quarks before it decays.

The researchers’ calculations suggest that some top-containing hadrons could potentially exist as weakly bound states.

If confirmed experimentally, such particles could offer a new way to study the strong force under extreme conditions and test the limits of the Standard Model of particle physics.

“Because the top quark has an extremely short lifetime, whether it can form hadrons has always been a major challenge,” Kazem Azizi, a member of the research team said.

“However, recent theoretical and experimental developments show that these systems deserve closer study,” he added.

The researchers say their predictions could provide useful benchmarks for searches at the Large Hadron Collider (LHC) and future facilities such as the proposed Future Circular Collider (FCC).

LHC is the world’s largest and most powerful particle accelerator, used to smash particles together at extremely high energies so scientists can study their properties and search for new particles.

FCC is a proposed next-generation particle accelerator that would be much larger and more powerful than the LHC, designed to study fundamental particles and forces in even greater detail.

If such particles are eventually observed, they could provide valuable insight into how the strong interaction behaves at energy scales that have so far remained largely unexplored.

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