Testing CPT Symmetry with CMB Measurements: Update after WMAP5

In this Letter we update our previous results on the test of CPT symmetry with cosmic microwave background (CMB) measurements. A CPT-violating interaction in the photon sector \mathstrutL} _{CS }∼ p_μ A_ν \tilde{F}^{μ ν} gives rise to a rotation of the polarization vectors of the propagating CMB photons. Recently the WMAP group used the newly released polarization data of WMAP5 to measure this rotation angle Δ α and obtained Δα = -1.7° ± 2.1° (1 σ). However, in their analysis the BOOMERANG 2003 data are not included. Here we revisit this issue by combining the full data of WMAP5 and BOOMERANG 2003 angular power spectra for the measurement of this rotation angle Δ α and find that Δα = -2.6° ± 1.9° at a 68% confidence level.