2/8/2010 Colloquium - Mariola Lesiak-Bzdak
Title: Cross section and tensor analyzing power of the d+d ->4He+eta reaction near threshold
Date: Feb 8, 2010
Location: 3105 Etcheverry Hall
The eta meson interaction with nucleons and nuclei has attracted much attention in recent years. The reason for that is the possibility of the formation of eta-nucleus bound states. While no such a state has been directly observed, studies of the eta-nucleus interaction near threshold can be used to determine the eta-nucleus scattering length, and then, in principle, would permit conclusions on the existence of such eta-nucleus bound system. Some estimations suggest that the eta-4He system is the lightest possible candidate.
In this talk the study of the near threshold eta meson production in the d+d -> 4He+eta reaction will be presented. The angular distributions of the unpolarized differential cross section and tensor analyzing power of the d+d -> 4He+eta reaction have been measured at an excess energy of 16.6 MeV. Using these results the partial wave decomposition of the scattering amplitude was performed. Extraction of the magnitude of the s-wave scattering amplitude allowed to obtain firmer bounds on the scattering length of the eta-4He system. The results do not, however, unambiguously prove the existence of the quasi-bound eta-4He state.
Mariola Lesiak-Bzdak earned her Ph.D. and M.S., both in Physics, from Jagiellonian University in Krakow, Poland in 2008, and 2003, respectively. During her MS studies she was attracted to the experimental study of meson physics and joined the GEM Collaboration investigating that subject on the cooler synchrotron COSY in Forschungszentrum Julich, Germany. During her PhD studies she continued investigation of the production of pion and eta mesons in proton-proton, proton-deuteron collisions. The main focus of her research was the near threshold eta meson production in deuteron-deuteron interactions in the context of a possible formation of a bound state of eta meson and a nucleus. In 2004 she received a PhD scholarship for 2-year stay at the Institute of Nuclear Physics in Forschungszentrum Julich, Germany.