Particle physics has seen a week of new discoveries, having found evidence of two theoretical particles – the “Weyl Fermion” and pentaquarks. Two independent research teams – one at Princeton University in New Jersey and the other at the Massachusetts Institute of Technology (MIT) – uncovered evidence of the Weyl fermion, both teams publishing in the research journal Science. Meanwhile, experiments at the Large Hadron Collider (LHC) revealed their new and unusual exotic form of matter. The discoveries might herald a new era of electronics.
The existence of Weyl fermions was first predicted in 1929 by a German mathematician/physicist Hermann Weyl. The particle was suggested to be one of the building blocks of subatomic particles and possess the unique property of being without any mass as well as behaving as both matter and antimatter. (Antimatter has equal mass to matter, however possesses an opposite charge). All other types of fermion appear to have mass, making the Weyl fermion a unique family member.
“The physics of the Weyl fermion are so strange, there [might] be many things that arise from this particle that we’re just [incapable] of imagining now,” explained co-author Zahid Hasan, a professor of physics at Princeton who led the research.
A Heavy Flavour Tracker that may track particles made of “charm” and “beauty” quarks. Credit@Brookhaven National Laboratory/Flickr
Around 6,000 km away, teams at the LHC seem to have been analysing collision data (pre-upgrade) with a fine-tooth comb and recently identified a new, exotic particle – pentaquarks, initially theorised back in 1979. At school, students learn how atoms are made of electrons orbiting a nucleus of protons on neutrons. However, since the 1960s, physicists have known that the basic neutrons and protons are themselves made up of even smaller particles – “quarks” – bound together by one of the four fundamental energies of the universe, the “strong force”. Any particle made of quarks held together in this way is known as a hadron.
Hadrons typically comprise different combinations of two to three quarks and until now it was questionable if pentaquarks may actually exist.
Pentaquarks are particularly challenging to observe due to their rarity and instability, so their existence tends to be very transient. Researchers on the LHCb experiment made the discovery by looking deeply into other exotic hadrons, in this case the Lambdab particle, created by collisions, and found it decays into three other hadrons: a Kaon, a J/psi (made of two quarks), and a proton (made of three quarks).
Another suggested layout of the quarks in a pentaquark particle. Alternatively, the five quarks might be tightly bound together. Credit@Daniel Dominguez/CERN
The Weyl fermion’s unique properties might revolutionise electronics in the future. Most importantly, the particle may be used to develop quantum computing – computers that use quantum-mechanical phenomena (such as superposition and quantum entanglement) to work with data. Many national governments and military bodies are currently funding quantum-computing research with the aim of eventually being able to solve certain challenges much more quickly than even the best digital computers. Weyl fermions in particular may create electrons without mass allowing them to flow more easily and reduce the amount of heat escaping. “It’s like they have their own GPS and steer themselves without scattering,” Hasan added.
Both discoveries answer questions in physics that are decades-old and are a testament to the power of mathematics. Observing particles such as pentaquarks and Weyl fermions tell physicists something new about the universe and offer a more whole understanding of what may lie in the great unknown. It potentially allows scientists to confront some of the more pressing questions in physics – what is dark matter? Why do protons and neutrons make up everyday matter rather than pentaquarks? What happened following the Big Bang?
What other productive, practical benefits might these particles offer?