Steven Weinberg (1933 - 2021)
Sheldon Glashow (1932 - )
Abdus Salam (1926 - 1996)
| Steven Weinberg (1933 - 2021) |
Sheldon Glashow (1932 - ) |
Abdus Salam (1926 - 1996) |
 |
 |
 |
 |
 |
 |
In a landmark 1967 paper, “A Model
of Leptons,” often considered the first paper about the Standard
Model, Weinberg noted that any theory of weak interactions must
involve only leptons (and quarks) with left-handed
chirality. The equal number of right-handed leptons and
quarks must be projected out. The coupling to weak charge
requires defining weak isospin and weak hypercharge. The
left-handed leptons form doublets, while the right handed ones
are singlets, and the same applies to quarks. In the same
paper Weinberg indicated a way to to unify electromagnetic and
weak interactions for leptons and introduced the concept of
spontaneous symmetry breaking with gauge fields to generate the
masses of the weak bosons.
 |
 |
Note that before SSB there
are two independent coupling constants, g′ and g. One
way to relate them to parameters after SSB is to think
of the coupling constant g vanishing, but a new
parameter, the Weinberg angle θW
appearing to determine what linear combination of the
neutral vector bosons W0 and B0
turns into the massive Z boson and what combination
turns into the massless γ. Because the Weinberg
angle is a form of coupling constant, its value "runs"
with momentum transfer. |
Helicity states can be described with the same formalism used for intrinsic spin-1/2, namely two-entry column vectors and 2 x 2 matrix operators. |
 |
 |
 |
 |
 |
 |
The quest for further unifications beyond the electroweak sent physics, beginning in the 1970s, down a rabbit hole from which it has never quite emerged, despite the total and complete failure of ALL such efforts. Where do we go next?