In the framework of the Standard Model of particle physics, which describes the known particles and their interactions, every particle is associated with an antiparticle that has the same mass but opposite charge and other quantum numbers. This is known as the concept of particle-antiparticle symmetry.
However, it is important to note that not all particles in the Standard Model have been directly observed or discovered yet. For example, the Higgs boson was theorized long before its discovery in 2012 at the Large Hadron Collider (LHC). So, it is possible that there are particles predicted by theoretical models that have not been experimentally confirmed or whose antiparticles have not been observed yet.
Furthermore, there are some theoretical concepts that suggest the existence of particles that are their own antiparticles. These particles are called Majorana particles. In particle physics, neutrinos are considered potential Majorana particles, but their true nature is still an open question and subject to ongoing research and experimental investigation.
It's also worth mentioning that beyond the Standard Model, various extensions and theories, such as supersymmetry, propose the existence of additional particles and interactions that go beyond the particle-antiparticle symmetry. These extensions often introduce new types of particles, some of which may not have a corresponding antiparticle or may have more complex relationships with their antiparticles.
In summary, within the framework of the Standard Model, every particle has an associated antiparticle. However, there may be particles or hypothetical particles that have not yet been observed or whose properties, including their relationship with antiparticles, are not fully understood. The nature of particles and their antiparticles is an active area of research and exploration in particle physics.