The question of whether quarks are fundamental particles or composed of even smaller entities is an ongoing topic of research in particle physics. Quarks are elementary particles that are considered to be the fundamental building blocks of matter, according to the current understanding of the Standard Model of particle physics.
Quarks are believed to be point-like particles, meaning they have no size or internal structure according to our current understanding. However, it's important to note that the term "size" can be a tricky concept when it comes to elementary particles, as they are described by quantum field theories that do not necessarily have a classical notion of size.
While quarks are indeed much larger than the Planck length (the scale at which some theories suggest spacetime could be fundamentally discrete or undergo quantum fluctuations), it doesn't necessarily mean they are composed of smaller entities. The scale at which quantum effects become significant, such as the Planck length, is related to the energy involved in the interaction, and it doesn't directly imply the existence of smaller constituents within a quark.
However, it's worth mentioning that there are various speculative theories beyond the Standard Model, such as string theory, which propose that particles like quarks and electrons could be made up of more fundamental entities. These theories suggest that quarks might have substructure at much smaller length scales, possibly involving extended objects like strings or higher-dimensional entities. However, such ideas are still highly speculative and not yet supported by experimental evidence.
In summary, quarks are currently considered fundamental particles in the framework of the Standard Model of particle physics. While they are larger than the Planck length, it doesn't necessarily imply that they are composed of smaller entities. The exploration of the fundamental nature of particles is an active area of research, and future discoveries may shed more light on this question.