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Radiation
Division

New Experiment
on 4pi-Symmetry of the Neutron wave Function


A half-integral spin particle should achieve a sign reversal of the wave function produced by the operator for rotation through 2pi radians:

R(alpha) = exp(-ialpha · sigma/2) = 1 · cos(alpha/2) - isigma · sin(alpha/2)   .

In our neutron interferometry experiment the spin evolution is due to adiabatically rotating magnetic fields and manifests geometric rotation, in contrast to experiments of the 70's, where the neutron precessed in a homogeneous magnetic field, so that the rotation is a calculated quantity.

Fig. 1

Fig. 1: A complex magnetic field setup built around a skew symmetric LLL-interferometer.



Fig. 2

Fig.2: Magnetic field magnitudes along the beam axis.



Fig. 3

Fig. 3: The two effective magnetic field vectors were rotated through angles of pi opposite senses, i.e., through a relative angle of 2pi. The reverse of the currents through the coils changes the sense of rotation keeping the magnitude of the relative angle.

The experimental result shows a very good agreement with theoretical expectations.

experimental results vs. theoretical expectations

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  Online: November 1998