Search for eta mesic 3He with the WASA-at-COSY facility in the pd-> 3He 2gamma and pd-> 3He 6gamma reactions

Abstract

We report on the experimental search for the bound state of an $\eta$ meson and $^{3}\hspace{-0.03cm}\mbox{He}$ nucleus performed using the WASA-at-COSY detector setup. In order to search for the $\eta$-mesic nucleus decay, the $pd\to$ $^{3}\hspace{-0.03cm}\mbox{He} 2γ$ and $pd\to$ $^{3}\hspace{-0.03cm}\mbox{He} 6γ$ channels have been analysed. These reactions manifest the direct decay of $\eta$ meson bound in $^{3}\hspace{-0.03cm}\mbox{He}$ nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to an ${}^3$He-$\eta$ nucleus width $\Gamma$ above 20 MeV and binding energy $B_s$ between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the $\eta$-mesic $^{3}\hspace{-0.03cm}\mbox{He}$ nucleus formation followed by the $\eta$ meson decay which varies between $2$ nb and $15$ nb depending on possible bound state parameters.

arXiv commentArticle accepted to be published in PLB

References in corpus (28)

• Photoproduction of eta-mesic 3He
• Precision study of the eta-3He system using the d+p->3He+eta reaction
• The WASA Detector Facility at CELSIUS
• Meson-nucleus potentials and the search for meson-nucleus bound states
• Eta bound states in nuclei: a probe of flavour-singlet dynamics
• Coherent photoproduction of eta-mesons off 3He - search for eta-mesic nuclei
• Transparency ratio in γA -> η' A' and the in-medium η' width
• Measurement of the $pn\to pp{\pi }^0{\pi }^{-}$ Reaction in Search for the Recently Observed Resonance Structure in $d{\pi }^0{\pi }^0$ and $d{\pi }^{+}{\pi }^{-}$ systems
• Determination of the η'-nucleus optical potential
• Etaprime and Eta Mesons with Connection to Anomalous Glue
• Determination of the eta'-proton scattering length in free space
• Measurement of excitation spectra in the ${}^{12}$C$(p,d)$ reaction near the ${\eta }^{\prime }$ emission threshold
• Interaction of eta mesons with nuclei
• Search for $\eta$-mesic nuclei in recoil-free transfer reaction
• Exclusive Measurement of the eta --> pi+ pi- gamma Decay
• Quantum reflection and dwell times of metastable states
• Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
• Determination of the ${\mathbf{\eta }}^3\mathrm{He}$ threshold structure from the low energy $\mathbf{pd}\to {\mathbf{\eta }}^3\mathrm{He}$ reaction
• QCD symmetries in eta and etaprime mesic nuclei
• Precision study of the d+p->3He+eta reaction for excess energies between 20 and 60 MeV
• Onset of $\eta$-meson binding in the He isotopes
• Proton-${\eta }^{\prime }$ interactions at threshold
• Studies of mesic nuclei via decay reactions
• Constraining the optical potential in the search for eta-mesic 4He
• $\eta$-nucleus interaction from the $d+d$ reaction around the $\eta$ production threshold
• Solution of the eta-4He problem with quasi-particle formalism
• Total and differential cross sections of $\eta$-production in proton-deuteron fusion for excess energies between $Q_{\eta }=13\text{MeV}$ and $Q_{\eta }=81\text{MeV}$
• Luminosity determination for the quasi-free nuclear reactions

Cited by in corpus (4)

• Resonance-like structure near the $\eta d$ threshold in the $\gamma d${$\to$}${\pi }^0\eta d$ reaction
• Search for the $\eta$ mesic ${}^3$He in the $pd\to dp{\pi }^0$ reaction with the WASA-at-COSY facility
• Status of the search for $\eta$-mesic nuclei with particular focus on $\eta$-Helium bound states
• Probing the existence of η^3He mesic nucleus with a few-body approach