Measurement of the neutron lifetime with ultra-cold neutrons stored in a magneto-gravitational trap

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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.