3 research outputs found
Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
The search for 4He-eta bound states was performed with the WASA-at-COSY
facility via the measurement of the excitation function for the dd->3He n pi0
and dd->3He p pi- processes. The beam momentum was varied continuously between
2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the dd->4He
eta reaction ranging from Q=-70 MeV to Q=30 MeV. The luminosity was determined
based on the dd->3He n reaction and quasi-free proton-proton scattering via
dd->pp n_spectator n_spectator reactions. The excitation functions determined
independently for the measured reactions do not reveal a structure which could
be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the
total cross sections for the bound state production and decay in
dd->(4He-eta)_bound->3He n pi0 and dd->(4He-eta)_bound->3He p pi- processes
were determined taking into account the isospin relation between both the
channels considered. The results of the analysis depend on the assumptions of
the N* momentum distribution in the anticipated mesic-4He. Assuming as in the
previous works, that this is identical with the distribution of nucleons bound
with 20 MeV in 4He, we determined that (for the mesic bound state width in the
range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about
3 nb and about 6 nb for npi0 and ppi- channels, respectively. However, based on
the recent theoretical findings of the N*(1535) momentum distribution in the
N*-3He nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector
acceptance decreases and hence the corresponding upper limits are 5 nb and 10
nb for npi0 and ppi- channels respectively.Comment: This article will be submitted to JHE
Spin polarizabilities of the proton by measurement of Compton double-polarization observables
The Compton double-polarization observable has been measured
for the first time in the resonance region using a circularly
polarized photon beam incident on a longitudinally polarized target at the
Mainz Microtron. This paper reports these results, together with the
model-dependent extraction of four proton spin polarizabilities from fits to
additional asymmetry data using dispersion relation and chiral perturbation
theory calculations, with the former resulting in: , , and
, in units of .Comment: 7 pages, 5 figures, 2 tables, accepted for publication in PR
Characterization of tsunami wave using texture & structure of sediments from South Western coast of Sri Lanka
This research focuses on characterization of Tsunami waves by using tsunami sediments, as the only reliable source of information which a Tsunami leaves after strike are sediments. The sediments contain information about Tsunami waves which can be extracted by analyzing. The study focuses on evaluating wave height, flow velocity
and wave energy by examining of the thickness, grain size distribution, sediment structures and texture of tsunami deposits. These findings can be used for the prediction of Tsunami threats and in the formulation of precautionary measurements