22 research outputs found
Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
We present new data for angular distributions and on the cross section ratio
of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q =
59.8 MeV. The data have been obtained at the WASA-at-COSY experiment
(Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target.
While the shape of obtained angular distributions show only a slow variation
with the energy, the new results indicate a distinct and unexpected total cross
section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the
variation of the production mechanism within this energy interval.Comment: 9 pages, 9 figure
Search for the eta-mesic 4He with WASA-at-COSY detector
An exclusive measurement of the excitation function for the dd->3Heppi-
reaction was performed at the Cooler Synchrotron COSY-Juelich with the
WASA-at-COSY detection system. The data were taken during a slow acceleration
of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematic threshold
for the eta meson production in the dd->4He-eta reaction at 2.336 GeV/c. The
corresponding excess energy with respect to the 4He-eta system varied from
-51.4MeV to 22MeV. The integrated luminosity in the experiment was determined
using the dd->3Hen reaction. The shape of the excitation function for the
dd->3Heppi- was examined. No signal of the 4He-eta bound state was observed. An
upper limit for the cross-section for the bound state formation and decay in
the process dd->(4He-eta)bound->3Heppi- was determined on the 90% confidence
level and it varies from 20nb to 27nb for the bound state width ranging from
5MeV to 35MeV, respectively.Comment: 8 pages, 9 figure
ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?
We report on a high-statistics measurement of the basic double pionic fusion
reaction over the energy region of the so-called ABC
effect, a pronounced low-mass enhancement in the -invariant mass
spectrum. The measurements were performed with the WASA detector setup at COSY.
The data reveal the ABC effect to be associated with a Lorentzian shaped energy
dependence in the integral cross section. The observables are consistent with a
resonance with in both and systems.
Necessary further tests of the resonance interpretation are discussed