A new study suggests that protons contain intrinsic charm quarks

A subatomic particle is made up of three lighter particles called quarks, two of which are up quarks and one down quark. It has been speculated for decades that protons may also contain more massive quarks, known as 'intrinsic' charm quarks. In Nature, physicists report on an analysis that supports this theory.

The charm quark is much heavier than the up or down quark. In fact, theoretical physicist Juan Rojo of the Vrije Universiteit Amsterdam says the proton can have a component heavier than the proton itself.

It was Rojo's and colleagues' goal to reveal the proton's hypothetical charm by combining a variety of experimental results and theoretical calculations. It is important to measure this feature in order to fully understand one of the universe's most important particles.

It is known to physicists that a proon appears more complicated the deeper it is probed. It has been observed that protons contain a motley crew of transient quarks and antiquarks when observed at very high energies, for example.

in collisions at particle accelerators like the Large Hadron Collider, or LHC, near Geneva. When gluons split into quark-antiquark pairs inside protons, they create 'extrinsic' quarks.

The identity of the proton isn't determined by intrinsic quarks. These are simply the results of how gluons behave at high energies. There might be deep-seated charm quarks inside protons even at low energies.

A particle in quantum physics does not take on a definite state until it is measured - instead, it takes on probabilities to describe its state. It's possible to find a charm quark and an antiquark inside a proton if protons contain intrinsic charm.

A proton's mass isn't a simple sum of its parts because protons aren't well-defined particles. A proton may contain particles heavier than itself due to the small probability that the charm quarks and antiquarks aren't added to its mass.