The time spectra in the neutron radiative decay experiment
To measure the main characteristics of radiative neutron decay, namely its relative intensity BR (branching ratio), it is necessary to measure the spectra of double coincidences between beta-electron and proton as well as the spectra of triple coincidences of electron, proton and radiative gamma-quantum. Analysis of double coincidences spectra requires one to distinguish events of ordinary neutron beta decay from the background; analysis of triple coincidences relies on distinguishing radiative neutron decay from background events. As demonstrated in our first experiment, these spectra presented a heterogeneous background that included response peaks related to the registration of electrons and protons by our electronic detection system. The NIST experimental group (emiT group) observed an analogous pattern on the spectrum of double coincidences. The current report is dedicated to the analysis of this heterogeneous background. In particular, this report demonstrates that the use of response function methodology allows to clearly identify radiative neutron decay events and to distinguish them from the background. This methodology enabled us to become the first team to measure the relative intensity of radiative neutron decay B.R.= (3.2+-1.6)*10-3 (where C.L.=99.7% and gamma quanta energy exceeds 35 kev). In addition, the review emphasizes that the background events on the spectrum of double coincidences are caused by ion registration, and demonstrates that one cannot ignore the ionic background, which is why experiment registered the ions and not recoil protons.