Question: selection from a list; how to ?

When I solve a certain equation I get a list of solutions t as below. I want to select some of the solutions and assign them to variables. In the program I am writing the number of items in the list of solutions will vary and so I cannot really select the list item by using t[3].t[4] etc. for example. 

I want to be able to select only the list items with say a square root sign or another term such as Pi, beta etc that appears in the list of solutions. So from t below for exampe if I want only those solutions with beta in the expression how do I select these terms bearing in mind that the number of solutions in the list will vary. 

t := I, -I, I, -I, I, -I, ((-4*Pi^2-beta^2+4*beta^2*Q^2*Pi^2+8*I*Pi^2*beta*Q)/(4*Pi^2+beta^2-4*beta^2*Q*Pi+4*beta^2*Q^2*Pi^2))^(1/2), -((-4*Pi^2-beta^2+4*beta^2*Q^2*Pi^2+8*I*Pi^2*beta*Q)/(4*Pi^2+beta^2-4*beta^2*Q*Pi+4*beta^2*Q^2*Pi^2))^(1/2), ((-4*Pi^2-beta^2+4*beta^2*Q^2*Pi^2-8*I*Pi^2*beta*Q)/(4*Pi^2+beta^2-4*beta^2*Q*Pi+4*beta^2*Q^2*Pi^2))^(1/2), -((-4*Pi^2-beta^2+4*beta^2*Q^2*Pi^2-8*I*Pi^2*beta*Q)/(4*Pi^2+beta^2-4*beta^2*Q*Pi+4*beta^2*Q^2*Pi^2))^(1/2)

How do I extract/select terms in beta from the list t ?