Measurement of the neutron lifetime with ultra-cold neutrons stored in a   magneto-gravitational trap
  We report a new measurement of the neutron lifetime using ultra-cold neutrons stored in a magneto-gravitational trap made of permanent magnets. Neutrons surviving in the trap after fixed storage times have been counted and the trap losses have continuously been monitored during storage by detecting neutrons leaking from the trap. The value of the neutron lifetime resulting from this measurement is $\tau_n=(878.3\pm1.9)$s. It is the most precise measurement of the neutron lifetime obtained with magnetically stored neutrons. 
V.F. Ezhov, A.Z. Andreev, G. Ban, B.A. Bazarov, P. Geltenbort, A.G.   Glushkov, V.A. Knyazkov, N.A. Kovrizhnykh, G.B. Krygin...
nucl-ex physics.ins-det