Resonance structure in the {\gamma}{\gamma} and $\pi^0\pi^0$ systems in dC interactions

TL;DR

This paper reports the observation of a resonance structure at approximately 360 MeV in the invariant mass spectra of two photons and two neutral pions in d+C interactions at 2.75 GeV/c per nucleon, providing estimates of its properties.

Contribution

It provides experimental evidence of a resonance at ~360 MeV in photon and pion systems in d+C collisions, with detailed measurements of its mass, width, and production cross section.

Findings

Resonance at Mγγ ≈ 360 MeV observed with width ~64 MeV.

Resonance confirmed in π0π0 invariant mass spectrum.

Measured ratio of decay channels: (1.8–3.7)×10^-3.

Abstract

Along with $\pi^0$ and {\eta} mesons, a resonance structure in the invariant mass spectrum of two photons at M{\gamma}{\gamma} = 360 \pm 7 \pm 9 MeV is observed in the reaction d + C \rightarrow {\gamma} + {\gamma} + X at momentum 2.75 GeV/c per nucleon. Estimates of its width and production cross section are {\Gamma} = 64 \pm 18 MeV and $\sigma_{\gamma\gamma}$ = 98 \pm 24 {\mu}b, respectively. The collected statistics amount to 2339 \pm 340 events of 1.5 \cdot 10^6 triggered interactions of a total number ~ 10^12 of dC-interactions. The results on observation of the resonance in the invariant mass spectra of two $\pi^0$ mesons are presented: the data obtained in the d + C \rightarrow {\gamma} + {\gamma} reaction is confirmed by the d + C \rightarrow $\pi^0$ + $\pi^0$ reaction: $M_{\pi^0\pi^0}$ = 359.2 \pm 1.9 MeV, {\Gamma} = 48.9 \pm 4.9 MeV; the ratio of Br(R\rightarrow{\gamma}{\gamma}) / Br(R\rightarrow$\pi^0\pi^0$) = (1.8 {\div} 3.7)\cdot10^-3.