Yes the rudder is the primary control to maintain tracking during a loop and the most common off tracking occurs during the pull up and normally to the left is propellor (P) factor (most conventionally configured airplanes will yaw to the left during the initial pull (yaw not roll).

P factor is the production of more thrust on the right side of the propellor disc than the left when ever the propellor disc is being pulled to a high angle of attack to the relative wind. It is not torque. Torque reacts in roll not yaw.

This can be minimized somewhat with a small amount of right thrust.

John