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

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 $dC\to \gamma +\gamma +X$ 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 ${\sigma }_{\gamma \gamma }=98\pm 24_{-67}^{+93}\mu \mathrm{b}$, respectively. The collected statistics amount to $2339\pm 340$ events of $1.5\cdot 10^6$ 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.

References in corpus (4)

• Dilepton production and off-shell transport dynamics at SIS energies
• Study of dielectron production in C+C collisions at 1 AGeV
• Level crossing of particle-hole and mesonic modes in eta mesic nuclei
• Observation of New Resonance Structure in the Invariant Mass Spectrum of Two gamma-Quanta in dC-Interactions at Momentum 2.75 GeV/c per Nucleon