Δm(π⁰)_d

u

d

u

d

u

(u, u)^R

(u, d)^V

(u, u)^V = 0

(u, d)^B

d

(d, u)^V

(d, d)^R

(d, u)^B

(d, d)^V

u

(u, u)^V = 0

(u, d)^B

(u, u)^R

(u, d)^V

d

(d, u)^B

(d, d)^V

(d, u)^V

(d, d)^R