So what else is there... the letter Phi stands for the Higgs field. The letter Psi stands for all the fermions, i.e. electron, muon, tauon, the quarks and the neutrinos. The expression in the middle which has two Psi and a Phi in it describes how the fermions get their mass from the Higgs field.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition