pile-up

in radioanalytical chemistry
The processing by a radiation spectrometer of pulses resulting from the simultaneous adsorption of independent particles or photons in a radiation detector. As a result they are counted as one single particle or photon with energy between the individual energies and the sum of these energies.
Source:
PAC, 1994, 66, 2513 (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)) on page 2523
Orange Book, p. 235