The electrodynamics modified by the Chern–Simons termLcs～pμAνF?μνwith a non-vanishingpμviolates theCharge-Parity-Time Reversalsymmetry (CPT) and rotates the linear polarizations of the propagatingCosmic Microwave Background(CMB) photons. In this Letter we measure the rotation angle Δαby performing a global analysis on the current CMB polarization measurements from thefive-year Wilkinson Microwave Anisotropy Probe(WMAP5),BOOMERanG 2003(B03), BICEP and QUaD using a Markov Chain Monte Carlo method. Neglecting the systematic errors of these experiments, we find that the results from WMAP5, B03 and BICEP all are consistent and their combination givesΔα=?2.62±0.87deg(68%C.L.), indicating a 3σdetection of the CPT violation. The QUaD data alone givesΔα=0.59±0.42deg(68%C.L.) which has an opposite sign for the central value and smaller error bar compared to that obtained from WMAP5, B03 and BICEP. When combining all the polarization data together, we findΔα=0.09±0.36deg(68%C.L.) which significantly improves the previous constraint on Δαand test the validity of the fundamental CPT symmetry at a higher level.
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