In nuclear and particle physics, inverse beta decay, commonly abbreviated to IBD,[1] is a nuclear reaction involving an electron antineutrino scattering off a proton, creating a positron and a neutron.
[3] Inverse beta decay proceeds as[2][3][4] where an electron antineutrino (νe) interacts with a proton (p) to produce a positron (e+) and a neutron (n).
Most of the antineutrino energy is distributed to the positron due to its small mass relative to the neutron.
The positron promptly[4] undergoes matter–antimatter annihilation after creation and yields a flash of light with energy calculated as[5]
[4] The timing of the delayed capture is 200–300 microseconds after IBD initiation (≈256 μs in the Borexino detector[4]).
The timing and spatial coincidence between the prompt positron annihilation and delayed neutron capture provides a clear IBD signature in neutrino detectors, allowing for discrimination from background.
[4] The IBD cross section is dependent on antineutrino energy and capturing element, although is generally on the order of 10−44 cm2 (~ attobarns).