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Yes, nothing changes about the general rules if $m_u=m_d=0$. The CKM matrix is still the $SU(3)$ matrix transforming the up-type quark mass eigenstate to the up-electroweak-partners of the down-type quark mass eigenstates. The general CKM matrix distinguishes the phase. However, the CKM matrix becomes ambiguous and the number of generations is effectively ...


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In the Standard Model, the baryon and lepton number are accidental global symmetries. However, they are conserved only at the classical level: quantum corrections do not respect them, i.e., they are anomalous. The interesting thing is that they are violated by exactly the same amount. In terms of currents we write: $$\partial_\mu J_B^\mu=\partial_\mu ...


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A basic postulate in elementary particle theories is CPT invariance. Also the weak interaction is the only fundamental interaction that breaks parity-symmetry, and similarly, the only one to break CP-symmetry. ...... The laws of nature were long thought to remain the same under mirror reflection, the reversal of one spatial axis. The results of an ...



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