Introduction

This is the summary of our current understanding of Monte Carlo (MC) data used to analyse possible sources of hadronic background in the Radphi experiment. MC data were generated and simulated, with the help of Gradphi, according to the list of 79 reactions of interest [1]. These reactions were chosen from the compilation of known photo-production reactions in Ref.[2] which we thought might contribute to the background either through false reconstruction of charged particles or miss-reconstruction of correct photon multiplicity. In the list are included $3\gamma$ reactions with decays $\omega \rightarrow \pi^0\gamma$ and $\phi \rightarrow \eta\gamma$ that serve to calibrate detector. In the case of $5\gamma$ reactions we wanted to study the background itself so that $\phi \rightarrow a_0\gamma$ and $\phi \rightarrow f_0\gamma$ reactions are not generated. The reactions are organized in 8 groups (channels) depending on the primary meson produced in the $\gamma N \rightarrow X N$ reaction (where X represents a meson while N stands for the proton or neutron): $\omega, \rho, \eta, \eta', \phi, b_1, a_1, a_2$. Total number of generated events corresponds to $10^6$ events/$\mu b$ photo-production cross section, taking into account the decay branching ratios. This gave us statistics $\approx$ 100/125 times less than we have from the summer 2000 run (for proton/neutron reactions respectively). The goal of this study is to understand the background well enough that we can identify a handful of background reactions to simulate with the full statistics of the experimental data. The analysis of the invariant mass of events reconstructed in the LGD after simulation will be shown. It gives us information about dominant background reactions. Additionally, analysis of data from the CPV and BGV will be presented. This can give us a handle for eliminating background in the event sample we are interested in. At this stage we are mainly focused on $3\gamma$ events since they have to be understand before we attack the more interesting $5\gamma$ events.