Parity Nonconservation in Cesium

The PNC transition 6si/2 — 7si/2 has been observed in atomic cesium in Paris [14] and Boulder et al. [5]. Cesium is a 55 electron atom with a nucleus consisting of 78 neutrons and 55 protons which has spin 7/2. (The experiment is insensitive to other isotopes.) The total spin of atomic s-states is then F=3 or F=4. The transition frequency between these states. 

The physics that leads to this PNC transition is the exchange of a virtual Z either between a quark in the nucleus and an electron, or between two electrons. The latter effect, considered in section 4.5.4, is extremely small. PNC arises when the Z matrix element is vector on the nucleus and axial on the electron or vice versa (AjvPe)- The dominant PNC 

Here Z is the number of protons, N the number of neutrons, and CiuA the vector part of the Z-quark vertex for the up and down quarks. Putting in the tree level values of C u and Cu gives 

When radiative corrections are included in an analysis that uses the very precise measurement of the Z mass, a standard model prediction for Qw results [37] that has a weak dependence on the Higgs mass Mj. The formula is 

If Qw can be extracted from experiment with sufficient precision, the constant S, and therefore the Higgs mass, can be determined. Unfortunately, if the Higgs mass is less than 200 GeV, as is indicated by other weak interaction tests, the contribution to Qw even at the upper end of that mass 

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