Centered vertical dashed line in article

How to draw centered vertical dashed lines in article?

Also, is there a better alignment solution without using a lot of qquad?

documentclass[a4paper,20pt]{article}

usepackage[centering,
           top=2.5cm,bottom=2.5cm,right=2.3cm,left=2.3cm,
           headsep=25pt,headheight=20pt]{geometry}
usepackage{ctex}
usepackage{xeCJK}
usepackage{enumitem}
usepackage{multirow}
usepackage{amsmath,amsthm,amsfonts,amssymb}
usepackage{cases}
usepackage{graphicx}
usepackage{color,xcolor}
usepackage{mathtools}
usepackage{eso-pic}

AddToShipoutPicture{%
parbox[b]{paperwidth}{%
hfillcolor{red}rule{1pt}{paperheight}hfillmbox{}%
}}



begin{document}

begin{flalign*}
1. 
&&  &qquadqquadint_{0}^{+infty}frac{xsqrt{x}}{left(a+xright)^{2}left(a^{2}+x^{2}right)^{2}},mathrm{d}x quad(a>0)&& 
&&  &color{red!80}{qquadqquadqquadquadfrac{sqrt{2}left(sqrt{2}-1right)pi}{16a^{3}sqrt{a}}}&&
end{flalign*}
begin{flalign*}
2. 
&&  &int_{0}^{pi}sinleft(xright)arctanleft[frac{1}{2sinleft(xright)}right]mathrm{d}x && 
&&  &color{red!80}{qquadqquad,,frac{3-sqrt{5}}{2}pi}&&
end{flalign*}
begin{flalign*}
3. 
&&  &quadint_0^{+infty}!dfrac{x^2ln(x)}{1+x^4},mathrm{d}x && 
&&  &color{red!80}{qquad,,,,,frac{pi^2}{8sqrt{2}},}&&
end{flalign*}
begin{flalign*}
4. 
&&  &int_0^pifrac{sinleft[x+expBig(frac{pi}{2tan,!x}Big)right]}{sin x},mathrm{d}x&& 
&&  &color{red!80}{qquadqquadquad,,,,dfrac{pi}{e}}&&
end{flalign*}
begin{flalign*}
5. 
&&  &mathrm{P.V.}int_{-infty}^{+infty}!dfrac{sinleft(frac{x^2}{pi,}right)}{sinh(x+a)}mathrm{d}xqquad,,&& 
&&  &color{red!80}{quaddfrac{1-cosleft(frac{a^2}{pi}right)cosh(a)}{sinh(a)},pi,}&&
end{flalign*}
begin{flalign*}
6. 
&&  &int_{-infty}^{+infty}int_{-infty}^{+infty}int_{-infty}^{+infty}frac{cosleft(xi xright)cosleft(eta yright)cosleft(zeta zright)}{expleft(lambdasqrt{x^{2}+y^{2}+z^{2}}right)},mathrm{d}xmathrm{d}ymathrm{d}z&& 
&&  &color{red!80}{qquadqquadqquad,,frac{8pilambda}{left(lambda^{2}+xi^{2}+eta^{2}+zeta^{2}right)^{2}},}&&
end{flalign*}
begin{flalign*}
7. 
&&  &int_0^{+infty}frac{sinleft(xright)sinhleft(xright)}{xleft[cos(x)+cosh(x)right]},mathrm{d}x&& 
&&  &color{red!80}{qquadqquadquad,,,dfrac{pi}{4}}&&
end{flalign*}
begin{flalign*}
8. 
&&  &qquadqquadqquadqquad,,,int_0^{pi}frac{cos^{2}left(mxright)}{alpha+cos^{2}x},mathrm{d}x&& 
&&  &color{red!80}{qquadqquadqquadqquadquaddfrac{2pibeta^{2}left(1-beta^{2m}right)}{1+beta^{4}}quad(beta=sqrt{alpha+1}-sqrt{alpha})}&&
end{flalign*}
begin{flalign*}
9. 
&&  &int_{0}^{+infty}frac{xlnleft(x^{2}+1right)}{left(x+1right)left(x^{2}+1right)},mathrm{d}x&& 
&&  &color{red!80}{qquad,frac{pi}{16}left(pi+8ln2right),}&&
end{flalign*}
begin{flalign*}
10. 
&&  &qquadquadint_0^{+infty}dfrac{sin^2(atan,!x)}{x^2},mathrm{d}xquad(a>0)&& 
&&  &color{red!80}{qquadqquadqquadquad,,frac{pi}{2},}&&
end{flalign*}



end{document}