On the background in the ${\hat{I}}^{3}p\to \ddot{I}‰(\ddot{I}{€}^0{\hat{I}}^3)p$ reaction and mixed event simulation

Abstract

In this paper we evaluate sources of background for the ${\hat{I}}^{3}p\to \ddot{I}‰p$, with the $\ddot{I}‰$ detected through its $\ddot{I}{€}^0{\hat{I}}^3$ decay channel, to compare with the experiment carried out at ELSA. We find background from ${\hat{I}}^{3}p\to \ddot{I}{€}^0\ddot{I}{€}^{0}p$ followed by decay of a $\ddot{I}{€}^0$ into two ${\hat{I}}^3$, recombining one $\ddot{I}{€}^0$ and one ${\hat{I}}^3$, and from the ${\hat{I}}^{3}p\to \ddot{I}{€}^0\hat{I}\cdot p$ reaction with subsequent decay of the $\hat{I}\cdot$ into two photons. This background accounts for the data at $\ddot{I}{€}^0{\hat{I}}^3$ invariant masses beyond 700 MeV, but strength is missing at lower invariant masses which was attributed to photon misidentification events, which we simulate to get a good reproduction of the experimental background. Once this is done, we perform an event mixing simulation to reproduce the calculated background and we find that the method provides a good description of the background at low $\ddot{I}{€}^0{\hat{I}}^3$ invariant masses but fakes the background at high invariant masses, making background events at low invariant masses, which are due to ${\hat{I}}^3$ misidentification events, responsible for the background at high invariant masses which is due to the ${\hat{I}}^{3}p\to \ddot{I}{€}^0\ddot{I}{€}^{0}p$ and ${\hat{I}}^{3}p\to \ddot{I}{€}^0\hat{I}\cdot p$ reactions.

10 pages, 5 figures