Method for cross-talk determination in 4-neutron coincidence experiments

In this contribution, a new method derived by M. Petrascu et al, allowing to determine quantitatively the cross-talk (c-t) in 4-neutron coincidences, is described. Implicitly, this method gives the P4-n probability characterizing the validity of the 4-n event as a true coincidence one. In a previously work it was observed that t = t2 - t1 distribution of c-t ( t1 being the arrival time of the first neutron in detector 1 and t2 the arrival time of the neutron in detector 2) presents at low t values, a window in which c-t is very low. This window has been denoted by TC. An example is given corresponding to the second order coincidence between detectors 76 and 23 (denoted in the following a, b respectively), the probability for c-t is very low indeed 10-3. It follows that the probability for the experimental point, to be a true coincidence one, is Pab = 0.999. Also, as another example, the coincidence between detectors 8 (denoted c) and 70 (denoted d) which appears to be a 4th order coincidence (detectors, separated by 3 detectors). One can see that the probability Pcd = 0.994. It follows that the probability 1P4-n = 0.999 x 0.994 = 0.993. The other combinations are 2P4-n = Pad x Pbc = 0.989 and 3P4-n = Pac x Pbd = 0.991. The total probability P4-n = 1/3(1P4-n + 2P4-n + 3P4-n) = 0.991. The c-t points were generated by MENATE code. The obtained data confirm also the validity of an analysis given earlier by M. Petrascu et al. (authors)