Charge-parity violation

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 prediction of a heavy boson has received preliminary empirical support [92,96] from an anomaly in Z decay widths that points toward the existence of Z bosons with a mass of 812 GeV 1 33j [92,96] within the SO(l) grand unified field model, and a Higgs mechanism of 145 GeV4gj3. This suggests that a new massive neutral boson has been detected. Analysis of the hadronic peak cross sections obtained at LEP [96] implies a small amount of missing invisible width in Z decays. The effective number of massless neutrinos is 2.985 0.008, which is below the prediction of 3 by the standard model of electroweak interactions. The weak charge Qw in atomic parity violation can be interpreted as a measurement of the S parameter. This indicates a new Qw = 72.06 0.44, which is found to be above the standard model pre-... 

Hadronic modes, including Charge conjugation x Parity violating (CPV) modes ... 

Here j is the electromagnetic four-current, and j are weak charged currents and finally j° is the weak neutral current that couples to the Z° boson. This neutral current deserves our particular attention when we are interested in molecular parity violating effects. 

After the discovery of parity violation the CP symmetry, i.e., the invariance of the physical laws against the simultaneous transformation of charge and space reflection, was still assumed to be exact. However, in 1964 Cronin and Fitch (Nobel Prize 1980) discovered (Christenson et al. 1964) that the weak interaction violates that as well, although this violation is tiny, not maximal, like that of the P invariance. CP violation makes it possible to differentiate between a world and an antiworld and may be related to the matter - antimatter asymmetry. 

For HERA physics we must replace dcross-section which includes both 7 and Z exchange. In this case there is an important new feature. Because of the parity-violating... 

The demise of the parity principle brought down another symmetry principle that goes by the awkward name of charge conjugation. This principle, C symmetry, simply means that the same laws that describe a process involving matter will also describe the same process involving antimatter. In fact, however, the violation... 

P4 is again a Stokes parameter for unpolarised electrons. P5 and Pe must be zero if Px = 0. This can be seen by taking a mirror reflection in the scattering plane. Nonzero values of P5 and Pe would violate parity conservation if Px = 0, since the electron beam geometry would remain unchanged unless there is an x-component of Pe. Similarly the tilt (e) in the charge-cloud distribution out of the scattering plane indicated in fig. 9.7 must vanish unless Px 0. 

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