The recent measurements of the Cosmic Microwave Background anisotropies at arcminute angular scales performed by the ACT and SPT experiments are probing the damping regime of CMB fluctuations .
The analysis of these datasets unexpectedly suggests that the effective number of relativistic degrees of freedom is larger than the standard value of N _ { eff } = 3.04 , and inconsistent with it at more than two standard deviations .
In this paper we study the role of a mechanism that could affect the shape of the CMB angular fluctuations at those scales , namely a change in the recombination process through variations in the fine structure constant .
We show that the new CMB data significantly improve the previous constraints on variations of \alpha , with \alpha / \alpha _ { 0 } = 0.984 \pm 0.005 , i.e .
hinting also to a more than two standard deviation from the current , local , value \alpha _ { 0 } .
A significant degeneracy is present between \alpha and N _ { eff } , and when variations in the latter are allowed the constraints on \alpha are relaxed and again consistent with the standard value .
Deviations of either parameter from their standard values would imply the presence of new , currently unknown physics .