Cosmological birefringence constraints from the Planck 2015 CMB likelihood

The Planck 2015 cosmic microwave background (CMB) likelihood is employed to constrain the cosmological birefringence angle, i.e. the in vacuo rotation of the linear polarization that CMB photons would experience during propagation in case of parity violating coupling within the electromagnetic sector of the Standard Model of particle physics. We find alpha = 0.0 degrees +/- 1.3 degrees (stat)+/- 1 degrees. (sys) which is well compatible with no parity violation mechanism in action from recombination epoch to present.