Statistical properties of thermal neutron capture cross sections calculated with randomly generated resonance parameters

Furutachi, Naoya; Minato, Futoshi   ; Iwamoto, Osamu  

We investigated the probability distribution of thermal neutron capture cross sections () deduced stochastically with the resonance parameters randomly sampled from Wigner and Porter-Thomas distributions. We found that the typical probability distribution has an asymmetric shape. While there is a long tail on the large side due to a resonance happening to be close to the thermal energy, the multiresonance contribution considerably reduces the probability on the small side. We also found that the probability distributions have a similar shape if nuclei have an average resonance spacing sufficiently larger than an average radiation width. We compared the typical probability distribution with the distribution of the experimental values of 193 nuclei and found a good agreement between them.