Newton polygons of L -functions of polynomials xd+axd−1xd+axd−1 with p ≡ −1 mod d

For prime p≡−1modd and q a power of p, we obtain the slopes of the q-adic Newton polygons of L  -functions of xd+axd−1∈Fq[x]xd+axd−1∈Fq[x] with respect to finite characters χ when p is larger than an explicit bound depending only on d   and logp⁡qlogp⁡q. The main tools are Dwork's trace formula and Zhu's rigid transform theorem.