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

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 $sigma_{gammagamma}$ = 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: $M_{pi^0pi^0}$ = 359.2 pm 1.9 MeV, {Gamma} = 48.9 pm 4.9 MeV; the ratio of Br(Rrightarrow{gamma}{gamma}) / Br(Rrightarrow$pi^0pi^0$) = (1.8 {div} 3.7)cdot10^-3.

Resonance Structure in the $gammagamma$ Invariant Mass Spectrum in $p$C- and $d$C-Interactions

Along with $pi^0$ and $eta$ mesons, a resonance structure in the invariant mass spectrum of two photons at $M_{gammagamma}= 360 pm 7 pm 9$ MeV is observed in the reaction $d Ctogamma + gamma +X$ at momentum 2.75 GeV/c per nucleon. Estimates of its width and production cross section are $Gamma = 63.7 pm 17.8$ MeV and $sigma_{gammagamma}=98pm24^{+93}_{-67} {rm mu b}$, respectively. The collected statistics amount to $2339 pm 340$ events of $1.5cdot 10^6$ triggered interactions of a total number $sim 10^{12}$ of $d$C-interactions. This resonance structure is not observed in $p$C collisions at the beam momentum 5.5 GeV/c. Possible mechanisms of this ABC-like effect are discussed.