# LIMIT ON ${{\boldsymbol n}}{{\boldsymbol n}^{\,'}}$ OSCILLATIONS INSPIRE search

Lee and Yang (LEE 1956 ) proposed the existence of mirror world in an attempt to restore global parity symmetry. A possible candidate for dark matter. Limits depend on assumptions about fields ${{\mathit B}}$ and ${{\mathit B}^{\,'}}$. See the papers for details. See BEREZHIANI 2018 for a recent discussion.
VALUE (s) CL% DOCUMENT ID TECN  COMMENT
$\bf{> 448}$ 90
 2009 A
CNTR Assumes ${{\mathit B}^{\,'}}$ $<$ 100 nT
• • • We do not use the following data for averages, fits, limits, etc. • • •
$>17$ 95 1
 2018
CNTR UCN, scan of ${{\mathit B}}$ field
$> 12$ 95 2
 2009 A
CNTR UCN, scan 0${}\leq{}{{\mathit B}}{}\leq{}$12.5 $\mu$T
$> 414$ 90
 2008
CNTR UCN, ${{\mathit B}}$ field on $\&$ off
$> 103$ 95
 2007
CNTR UCN, ${{\mathit B}}$ field on $\&$ off
1  The ${{\mathit B}}$ field was set to (0.09, 0.12, 0.21) G. Limits on oscillation time are valid for any mirror field ${{\mathit B}^{\,'}}$ in ($0.08 - 0.17$) G, and for aligned fields ${{\mathit B}}$ and ${{\mathit B}^{\,'}}$. For larger values of ${{\mathit B}^{\,'}}$, the limits are significantly reduced.
2  Losses of neutrons due to oscillations to mirror neutrons would be maximal when the magnetic fields ${{\mathit B}}$ and ${{\mathit B}^{\,'}}$ in the two worlds were equal. Hence the scan over ${{\mathit B}}$ by ALTAREV 2009A: the limit applies for any ${{\mathit B}^{\,'}}$ over the given range. At ${{\mathit B}^{\,'}}$ = 0, the limit is 141 s (95$\%$ CL).
References:
 BEREZHIANI 2018
EPJ C78 717 New experimental limits on neutron - mirror neutron oscillations in the presence of mirror magnetic field
 ALTAREV 2009A
PR D80 032003 Neutron to Mirror-Neutron Oscillations in the Presence of Mirror Magnetic Fields
 SEREBROV 2009A
NIM A611 137 Search for neutronmirror neutron oscillations in a laboratory experiment with ultracold neutrons
 SEREBROV 2008
PL B663 181 Experimental Search for Neutron$−$Mirror Neutron Oscillations using Storage of Ultracold Neutrons
 BAN 2007
PRL 99 161603 Direct Experimental Limit on Neutron$−$Mirror-Neutron Oscillations