• T (or Time) invariance is a theory predicting that if a process is governed by a physical theory, then the same physical thoery applies in the reverse direction of time. C (or charge) invariance is the same principle when matter is replace by it's anit-matter counterpart. Lastly, there is P (or parity) invarianve which applies to a spacial inversion (i.e. the 3-D cartestion vector {x,y,z} becomes {-x,-y,-z}). When the three operations are all utilized on a system, then the TCP theorem indicates the system remains invariant.

    However, with the discoveries of parity and CP violation in nuetral kaon decay (weak interaction), it became a question as whether time may not be invariant for other processes. T non-Invariance has been observed only in the weak decay of neutral kaons.

  • The study of this effect in the beta decay of nuetrons thus helps to give an insight as to the nature of symmetry breaking in physics. To date, a null value has been given to the D term, from the generalized beta decay formula derived by Jackson, Treiman, and Wyld in 1957, to the order of 10^(-3). This experiment proposes to improve measurement accuracy to one order greater via improvements in the techniques of polarization, detection and other areas.

    The generalized formula for neutron beta decay is:

    The D term is a triple product of the neutron spin, electron and antineutrino momentum. This is a T odd, P even term, thus resulting in a possible T non-Invariance effect if it is non-trivial. Else, if this term is zero, then neutron beta decay is T-Invariant.

    Other techniques have been investigated to determine the value of the D term. One such technique is to mease whether or not the nuetron contains an Electric Dipole Moment (EDM). If the neutron had a permanent EDM, then upon different polarizations, the value of D would have different signs. Thus, by applying various magnetic pulses, this EDM would exhibit a precession and thus creating a measureable field of its own.