The mechanism by which the Higgs field gives particles mass, known as the Higgs mechanism, differs from the way other fields give particles mass. Let's compare the Higgs mechanism to the mechanism of mass generation in other fields, such as the electromagnetic field (photon) and the strong nuclear force field (gluon).
- Spontaneous symmetry breaking: The Higgs mechanism involves the phenomenon of spontaneous symmetry breaking. The Higgs field exists in a symmetric state initially, but as the universe cools down after the Big Bang, it undergoes a phase transition to a lower energy state. This phase transition breaks the symmetry, and the Higgs field acquires a non-zero vacuum expectation value (VEV). The particles that interact with the Higgs field gain mass through their interactions with the Higgs boson, which is an excitation of the Higgs field.
In contrast, the other force fields, such as the electromagnetic and strong nuclear force fields, do not exhibit spontaneous symmetry breaking. The particles associated with these fields, like the photon and gluon, remain massless.
- Gauge invariance: The Higgs mechanism breaks the local gauge symmetry of the electroweak force, which unifies the electromagnetic and weak nuclear forces. In this process, three out of the four initially massless gauge bosons (W+, W-, and Z) acquire mass through interactions with the Higgs boson, while the remaining gauge boson, the photon, remains massless.
In other fields, such as the electromagnetic and strong nuclear forces, the gauge symmetry remains unbroken, and the associated gauge bosons (photon and gluon) remain massless.
- Yukawa coupling: In the Higgs mechanism, the Higgs field interacts with fermions (such as quarks and leptons) through a Yukawa coupling term. This coupling generates mass for the fermions proportional to the strength of their interaction with the Higgs field.
On the other hand, the massless particles associated with other force fields, like the photon and gluon, do not have direct interactions with the corresponding fields. Their masses are zero by virtue of the symmetries and properties of those fields.
In summary, the Higgs mechanism is distinct from the mass generation mechanism in other fields. It involves spontaneous symmetry breaking, the acquisition of mass by gauge bosons, and the Yukawa coupling with fermions. Other force fields, such as the electromagnetic and strong nuclear forces, do not involve spontaneous symmetry breaking and their associated particles (photon and gluon) remain massless.