“…After the observation of the D * s0 (2317) and D s1 (2460), the HHχPT has been extended to discuss the mass corrections of the excited heavy mesons with spin-parity 0 + and 1 + [577, 620,621,635,30,636,637,638,639,622]. In these works, the two even-parity states [D * s0 (2317), D s1 (2460)] and their non-strange partner states [D * 0 (2300), D 1 (2430)] were treated as the spin doublets (0 + , 1 + ) with j P = 1 2 + (L = 1), which were described by the superfield S. As mentioned in Sec.1.1, one mystery of the excited charmed mesons is their surprising mass degeneracy,…”