On the background in the $\gamma p\to \omega ({\pi }^0\gamma )p$ reaction and mixed event simulation

Abstract

In this paper we evaluate sources of background for the $\gamma p\to \omega p$, with the $\omega$ detected through its ${\pi }^0\gamma$ decay channel, to compare with the experiment carried out at ELSA. We find background from $\gamma p\to {\pi }^0{\pi }^{0}p$ followed by decay of a ${\pi }^0$ into two $\gamma$, recombining one ${\pi }^0$ and one $\gamma$, and from the $\gamma p\to {\pi }^0\eta p$ reaction with subsequent decay of the $\eta$ into two photons. This background accounts for the data at ${\pi }^0\gamma$ 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 ${\pi }^0\gamma$ invariant masses but fakes the background at high invariant masses, making background events at low invariant masses, which are due to $\gamma$ misidentification events, responsible for the background at high invariant masses which is due to the $\gamma p\to {\pi }^0{\pi }^{0}p$ and $\gamma p\to {\pi }^0\eta p$ reactions.

arXiv comment10 pages, 5 figures

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Cited by in corpus (3)

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• The width of the omega meson in the nuclear medium
• An iterative method to estimate the combinatorial background