Neutral decay modes of the η0 particle

Search for the radiative decay η→π0γγ in the SND experiment at VEPP-2M

“…The best combination was selected for each event during the fit. χ 2 of the fit (χ πγγ ) is small for desired events from (12), while background (13) has wider distribution. Fig.6 shows χ πγγ distribution for 170 experimental events left after the above described cuts with one more condition χ πγγ < 40.…”

“…Signal and background composition of our data sample was estimated by using binned maximum likelihood method incorporating the finiteness of the Monte Carlo statistics [56]. Using HMCMLL routine from the HBOOK package [57], the experimental histogram was fitted by the sum of two Monte Carlo histograms for the signal (12) and background (13). As a result of this fit, the signal events fraction in the experimental data, depicted in Fig.6, was found to be (4.1±7.6)%.…”

“…High γ detection efficiency provided by heavy liquid bubble chamber techniques was also used in η → π 0 γγ decay studies. For example, for a xenon bubble chamber an average γ detection efficiency was as high as 94% [12]. In this experiment, the chamber was irradiated by a 2.34 GeV/c π + beam and η mesons were produced on quasi-free neutrons in the xenon nuclei through the reaction π + + n → η + p. Experiment [13] also used a xenon bubble chamber but π − + n → π − + n + η reaction to produce η-s by an incident 3.5 GeV/c π − beam.…”

“…SND detector, section along the beams: (1) beam pipe, (2) drift chambers, (3) scintillation counter, (4) light guides, (5) PMTs, (6) NaI(Tl) crystals, (7) vacuum phototriodes, (8) iron absorber, (9) streamer tubes, (10) 1 cm iron plates, (11) scintillation counters,(12) and(13)elements of collider magnetic system.…”

“…Points with error bars -experiment. Shaded histogram -expected η → π 0 γγ signal according to simulation of the process(12).…”