Clear["Global`*"]
n=40;
b=2*Pi;
\[Lambda]=3;
d=0.5;
g=30*Pi;
\[Gamma]L=6*Pi;
B=2;
z=D[phiout[t]^2,t];
phiout[t_]=(2 Sqrt[2/5] Sqrt[36 B^6 d+49 B^4 d^3+14 B^2 d^5+d^7])/(3 B^3)*Sin[B t]^3*Exp[-d*t];
\[Gamma]=10;
f[t_]=1/2*\[Gamma]*\[Lambda]*Exp[-\[Lambda]*t];
gg[t_]=Simplify[(D[phiout[t],t]+\[Lambda]*phiout[t])/\[Lambda]/Sqrt[\[Gamma]]];
xx[t_]=Simplify[-D[gg[t],t]-Integrate[f[t-\[Tau]]*gg[\[Tau]],{\[Tau],0,t}]]/(g*Sqrt[n]);
pe[t_]=1-xx[t]^2+Integrate[2*g*Sqrt[n]*gg[\[Tau]]*xx[\[Tau]]-2*\[Gamma]L*xx[\[Tau]]^2,{\[Tau],0,t}];
dd=Integrate[xx[\[Tau]]^2/pe[\[Tau]],{\[Tau],0,t},Assumptions->t\[Element]Reals]

试了下，我觉得基本没戏