Charge parity reversal

After discovery of the combined charge and space parity violation, or CP-violation, in iT°-meson decay [7], the search for the electric dipole moments (EDMs) of elementary particles has become one of the most fundamental problems in physics [6, 8, 9, 10, 1]. A permanent EDM is induced by the weak interaction that breaks both the space symmetry inversion and time-reversal invariance [11]. Considerable experimental effort has been invested in probing for atomic EDMs induced by EDMs of the proton, neutron and electron, and by P,T-odd interactions between them. The best available restriction for the electron EDM, de, was obtained in the atomic T1 experiment [12], which established an upper limit of de < 1.6 X 10 e-cm, where e is the charge of the electron. The benchmark upper limit on a nuclear EDM is obtained in atomic experiment on i99Hg [13], ]dHgl < 2.1 X 10 e-cm, from which the best restriction on the proton EDM, dp < 5.4 x 10 " e-cm, was also recently obtained by Dmitriev Sen kov [14] (the previous upper limit on the proton EDM was obtained in the TIE experiment, see below). 

The weak interactions that cause atomic PNC violate not only the symmetry of parity, P, but also the symmetry of charge conjugation, C. However, the product of these, CP, is conserved. Because any quantum field theory conserves CPT, where T is time reversal this is equivalent to saying that T is conserved. However, even this symmetry is known to be violated. To date, this incompletely understood phenomenon has been seen in only two systems, the neutral kaon system, and, quite recently, the neutral B meson system. However, as noted already in the 1950 s by Ramsey and Purcell [62], an elementary particle possessing an intrinsic electric dipole moment also violates T invariance, so that detection of such a moment would be a third way of seeing T noninvariance. 

CP invariance The symmetry generated by the combined operation of changing charge conjugation (Q and parity (P). CP violation occurs in weak interactions in kaon decay and in B-mesons. See also CPT theorem time reversal. 

The conclusion of these works is that the parity (P) invariance and, separately, the charge conjugation (C) invariance are violated in P decay, while the time reversal (T) or combined CP invariance is not. The parity non-invariance (i.e., non-invariance of the Hamiltonian of the weak interaction under space reflection) can be expressed alternativelyby saying that the parity is not conserved. This formulation is a consequence of the fact that the parity P is an observable quantity. The presence of two-pion decay mode in the K° kaon decay implies, however, that even the CP invariance is violated in the weak interaction (Christenson et al. 1964). 

Optical transitions within the shell arise due to interaction of the electric and magnetic components of the electromagnetic radiation with the/electrons and are therefore either electric or magnetic dipole transitions (ED or MD), respectively. The electric dipole transition can be considered a linear displacement of charge and its direction is reversed through inversion, meaning it has odd parity. The magnetic dipole transition, on the other... 

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