  The review of experimental measurements of neutron lifetime is presented.
Latest measurements with gravitational trap (PNPI NRC KI) and magnetic trap
(LANL, USA) confirmed the result obtained by PNPI group in 2005. The results of
measurements performed using UCN storing method are in good agreement; however,
there is a significant discrepancy at 3.6{\sigma} (1% of decay probability)
level with beam method experiment. The latest most accurate measurements of the
neutron decay asymmetry and neutron lifetime measurements by storage method are
in agreement within the Standard Model. This article discusses the possible
causes of discrepancy in the measurements of the neutron lifetime. The most
probable cause, apparently, is the loss of protons in beam method experiment
during storage in a magnetic trap due to charge exchange collisions of protons
with the residual gas. The proton becomes neutral and leaves the trap, which
leads to a decrease in the number of registered protons, i.e. to a decrease in
the probability of neutron decay or to an increase in the measured neutron
lifetime.
