Big vert in LaTeX: Analyzing Angular Distribution

[malawi_glenn]

Hi! I would like to have larger verts, representating abs, you can see for yourself how ugly this looks:
$$\dfrac{d\sigma }{d\Omega } (\pi ^+ \text{p}) = \dfrac{1}{k^2}\left[ \vert a^{\tfrac{3}{2}}_{0,\tfrac{1}{2}} + \left( 2a^{\tfrac{3}{2}}_{1,\tfrac{3}{2}} + a^{\tfrac{3}{2}}_{1,\tfrac{1}{2}} \right) \cos (\theta ) \vert ^2 + \vert \left( a^{\tfrac{3}{2}}_{1,\tfrac{3}{2}} - a^{\tfrac{3}{2}}_{1,\tfrac{1}{2}} \right) \sin (\theta )\vert ^2 \right]$$

I have searched in short AMS guide, but could not find it :(

 

[morphism]

Try \left| and \right|.

 

[malawi_glenn]

$$\dfrac{d\sigma }{d\Omega } (\pi ^+ \text{p}) = \dfrac{1}{k^2}\left[ \left| a^{\tfrac{3}{2}}_{0,\tfrac{1}{2}} + \left( 2a^{\tfrac{3}{2}}_{1,\tfrac{3}{2}} + a^{\tfrac{3}{2}}_{1,\tfrac{1}{2}} \right) \cos (\theta ) \right| ^2 + \vert \left( a^{\tfrac{3}{2}}_{1,\tfrac{3}{2}} - a^{\tfrac{3}{2}}_{1,\tfrac{1}{2}} \right) \sin (\theta )\vert ^2 \right]$$

 

[malawi_glenn]

great =) thanx

 

[malawi_glenn]

what?

 

[jaeger2000]

-Sometimes you don't want left and right just by itself.
-The following works instead:

\big\vert
\bigg\vert
\Bigg\vert

kind regards,
Ian Gregory, Sydney.