In the standard model of particle physics, the Higgs boson has the largest known rest mass. The Higgs boson was discovered in 2012 at the Large Hadron Collider (LHC), and it plays a crucial role in the mechanism of electroweak symmetry breaking, which gives mass to elementary particles.
The rest mass of the Higgs boson is approximately 125 giga-electron volts (GeV) or about 2.2 x 10^-25 kilograms. This makes it significantly heavier than other particles in the standard model, such as electrons, quarks, and neutrinos, which have masses on the order of a few mega-electron volts (MeV) or less.
The reason for the relatively large mass of the Higgs boson lies in its interaction with the Higgs field. According to the standard model, all elementary particles acquire their mass through interactions with this field. The Higgs field permeates all of space, and particles moving through it experience resistance or "drag," similar to how objects moving through a medium experience resistance. This resistance, known as the Higgs mechanism, imparts mass to the particles.
The energy associated with the Higgs field is proportional to the mass of the Higgs boson. Therefore, the Higgs boson's mass represents the scale at which the electroweak symmetry breaking occurs and is related to the strength of the Higgs field. Since the Higgs boson interacts with itself, its mass is subject to quantum corrections from these self-interactions, making it sensitive to the energy scale of the underlying theory.
It's important to note that the Higgs boson is not the heaviest particle in the universe. Other particles, such as certain types of hypothetical dark matter particles, could potentially have even larger masses, but their existence and properties are still unknown and the subject of ongoing research.