The t quantity is known as the square of the 4-momentum transfer
[math]\displaystyle{ t \equiv \left({\mathbf P_1^*}- {\mathbf P_1^{'*}}\right)^2=\left({\mathbf P_2^{*}}- {\mathbf P_2^{'*}}\right)^2 }[/math]
In the CM Frame
[math]\displaystyle{ {\mathbf P_1^{*}}=-{\mathbf P_2^{*}} }[/math]
[math]\displaystyle{ {\mathbf P_1^{'*}}=-{\mathbf P_2^{'*}} }[/math]
In the Lab Frame
[math]\displaystyle{ {\mathbf P_1^{2}}+ {\mathbf P_1^{'2}}-2 {\mathbf P_1} {\mathbf P_1^{'}} }[/math]
[math]\displaystyle{ =2m^2-2E_1E_1^'+2 p_1 p_1^'=2m^2-2E_2E_2^'+2 p_2 p_2^' }[/math]
with [math]\displaystyle{ p_2=0 }[/math]
and [math]\displaystyle{ E_2=m }[/math]
[math]\displaystyle{ t=2m^2-2mE_2^'=2(m^2-E_2^'m) }[/math]
[math]\displaystyle{ \textbf{\underline{Navigation}} }[/math]
[math]\displaystyle{ \vartriangleleft }[/math]
[math]\displaystyle{ \triangle }[/math]
[math]\displaystyle{ \vartriangleright }[/math]