Search for η\eta-mesic 3He^{3}He in non-mesonic final states

2018
91 pages
Thesis: Other
  • Jagiellonian U. (main)
(2018)
  • Published: Apr 17, 2019
    and
  • Published: 2019
e-Print:

Citations per year

20192020202112
Abstract: (arXiv)
In May-June 2014, the experiment devoted to the search for the bound state of the η\eta meson and 3^3HeHe nucleus has been performed at COSY accelerator in Research Center J\"ulich in Germany with WASA-at-COSY facility. The excitation functions for pd3pd\rightarrow^3He2γHe2\gamma, pd3pd\rightarrow^3He6γHe6\gamma, pdpppπpd\rightarrow ppp\pi^{-}, pdppnπ0pd\rightarrow ppn\pi^{0}, pddnπpd\rightarrow dn\pi^{-}, pddpπ0pd\rightarrow dp\pi^{0}, pdpdpd\rightarrow pd, and pdppnpd\rightarrow ppn reactions have been measured in the vicinity of the η\eta meson production threshold. The experiment was carried out using COSY ramped proton beam and deuterium pellet target. The beam momentum varied continuously in the range of 1.4261.635 GeV/c1.426-1.635~GeV/c corresponding to 3^3HeηHe-\eta excess energy range from 70-70 to +30 MeV+30~MeV. The analysis of the obtained excitation functions for the pd3pd\rightarrow^3HeηHe\eta indicate slightly the signal from the bound state for Γ>20 MeV\Gamma>20~MeV and B[0;15] MeVB\in[0;15]~MeV. However, the observed indication is in the range of the systematic error. Therefore the final conclusion of this thesis is that no narrow structure that could be interpreted as η\eta-mesic nucleus was observed in both excitation curves. Thus, the upper limit for the total cross section of the bound state formation was estimated assuming that the η\eta decay branching ratios in the bound state is the same as in free space. The upper limit at the 90%90\% confidence level varies from 22 to 15 nb15~nb within the binding energy range from 00 to 60 MeV60~MeV and the width from 2.52.5 to 40 MeV40~MeV.
  • mezon $\eta$
  • jądra mezonowe
  • detektor WASA-at-COSY
  • atom: mesic atom
  • bound state: formation
  • bound state: width
  • excited state
  • threshold: production
  • eta: mesic atom
  • beam: momentum