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OnderzoekVan Swinderen InstituteFundamental Interactions and Symmetries (TRIµP)PhysicsTime-Reversal Violation

Time Reversal Violation

Introduction

The current understanding of the mechanism leading to time-reversal violation (TRV) in particles physics is one of the great achievements of the Standard Model (SM). At the same time there is a strong push to move theory beyond the SM, both to relate the parameters of the SM to an underlying larger framework and to address questions raised by cosmological observations. The search for TRV can play an important role in this respect. Theoretical models that try to provide a new framework nearly always predict additional sources of TRV that are not in the SM. Therefore, establishing new limits for non-SM TRV will constrain these new models. In this work we will discuss two approaches involving searches at low energy for TRV beyond the SM. At KVI we pursue two different searches that are complementary. The first one concerns searches for a permanent electric dipole moment and the second concerns correlations in β- decay.

 

Below is a pictorial display of these two processes:
Time Reversal Violation
A pictorial display of the two time reversal violation processes studied at the Trimp group.

The direction of an object is given by its spin a spinning object seen in a mirror keeps the rotates in the same direction, i.e. it is invariant under Parity. If the object has a dipole moment (the earth object) than the + and – part of the dipole exchange position, i.e. it is odd under Parity. The opposite is true when time is reversed, the dipole is not affected but the spin direction changes sign. Thus a permanent dipole violates both time reversal and parity. In contrast to β- decay the momentum vectors of the emitted β and  v do change with respect to the mirror plane however all three changes sign when time is reversed. The product

Product of the momentum vectors
 
is therefore odd under time reversal and even under parity and consequently different physics beyond the SM is probed by searches for an electric dipole moment and time forbidden correlations in β-decay.
Last modified:20 June 2014 10.19 a.m.