Outside the nucleus, free neutrons are unstable and have a mean lifetime of 879.6±0.8 s (about 14 minutes, 39.6 seconds). Therefore, the half-life for this process (which differs from the mean lifetime by a factor of ln(2) ≈ 0.693) is 611±1 s (about 10 minutes, 11 seconds). The beta decay of the neutron, described above, can be denoted as follows: n0 → p+ + e− + νe n0 → p+ + W− → p+ + e− + νeudd → uud + W− → uud + e− + νe A small fraction (about one in 1000) of free neutrons decay with the same products, but add an extra particle in the form of an emitted gamma ray: n0 → p+ + e− + νe + γ