We performed ultracold neutron storage measurements to search for additional losses due to neutron ($n$) to mirror-neutron ($n^{\prime }$) oscillations as a function of an applied magnetic field $B$. In the presence of a mirror magnetic field $B^{\prime }$, ultracold neutron losses would be maximal for $B\approx B^{\prime }$. We did not observe any indication for $n{n}^{\prime }$ oscillations and placed a lower limit on the oscillation time of ${\tau }_{n{n}^{\prime }}>12.0\mathrm{s}$ at 95% C.L. for any $B^{\prime }$ between 0 and $12.5\mu \mathrm{T}$.

• Received 26 May 2009

DOI:https://doi.org/10.1103/PhysRevD.80.032003