Rankin-Selberg integrals for $\mathrm{GSpin}$ groups with application to the global Gan-Gross-Prasad conjecture

We construct Rankin-Selberg integrals using Bessel models for a product of tensor product partial $L$-functions \begin{equation*} L^S(s,\pi\times\tau_1) L^S(s,\pi\times\tau_2)\cdots L^S(s,\pi\times\tau_r) \end{equation*} where $\pi$ is an irreducible cuspidal automorphic representation of a quasi-split $\mathrm{GSpin}$ group, and $\tau_1, \cdots, \tau_r$ are irreducible unitary cuspidal automorphic representations of $\mathrm{GL}_{k_1}, \cdots, \mathrm{GL}_{k_r}$ respectively. As an application, we prove one direction of the global Gan-Gross-Prasad conjecture for generic representations of quasi-split $\mathrm{GSpin}$ groups.