On the migdal-watson approach to FSI effects in meson production in NN collisions
The influence of the nucleon-nucleon final-state interaction (FSI) on properties of the meson-production amplitude near threshold is discussed. For nucleon-nucleon interaction, a simple Yamaguchi potential and realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like η′ or φ FSI do effects become universal. The Jost function approach to FSI effects is critically examined.
A covariant OBE model for η production in NN collisions
Abstract A relativistic covariant one boson exchange model, previously applied to describe elastic nucleon-nucleon scattering, is extended to study η production in NN collisions. The transition amplitudes for the elementary BN → ηN processes with B being the meson exchanged ( B = π , σ , η , ϱ , ω and δ ) are taken to be the sum of four terms corresponding to s and u-channels with a nucleon or a nucleon isobar N ∗ (1535 MeV) in the intermediate states. Taking the relative phases of the various exchange amplitudes to be +1, the model reproduces the cross sections for the NN → Xη reactions in a consistent manner. In the limit where all η's are produced via N ∗ excitations, interference terms between the overall contribution from the exchange of pseudoscalar and scalar mesons with that of vector mesons cancel out. Consequently, much of the ambiguities in the model predictions due to unknown relative phases of different vector and pseudoscalar exchanges are strongly reduced.
The Liverpool Cholera Epidemic of 1832 and Anatomical Dissection--Medical Mistrust and Civil Unrest
Asiatic cholera reached Britain for the first time in late 1831, with the main epidemic occurring during 1832. The disease caused profuse diarrhea, severe dehydration, collapse, and often death. There was widespread public fear, and the political and medical response to this new disease was variable and inadequate. In the summer of 1832, a series of "cholera riots" occurred in various towns and cities throughout Britain, frequently directed against the authorities, doctors, or both. The city of Liverpool, in the northwest of England, experienced more riots than elsewhere. Between 29 May and 10 June 1832, eight major street riots occurred, with several other minor disturbances. The object of the crowd's anger was the local medical fraternity. The public perception was that cholera victims were being removed to the hospital to be killed by doctors in order to use them for anatomical dissection. "Bring out the Burkers" was one cry of the Liverpool mobs, referring to the Burke and Hare scandal four years earlier, when two men had murdered people in Edinburgh in order to sell their bodies for dissection to the local anatomy school. This issue was of special concern to the Liverpool citizenry because in 1826, thirty-three bodies had been discovered on the Liverpool docks, about to be shipped to Scotland for dissection. Two years later a local surgeon, William Gill, was tried and found guilty of running an extensive local grave-robbing system to supply corpses for his dissection rooms. The widespread cholera rioting in Liverpool was thus as much related to local anatomical issues as it was to the national epidemic. The riots ended relatively abruptly, largely in response to an appeal by the Roman Catholic clergy read from church pulpits, and also published in the local press. In addition, a respected local doctor, James Collins, published a passionate appeal for calm. The Liverpool Cholera Riots of 1832 demonstrate the complex social responses to epidemic disease, as well as the fragile interface between the public and the medical profession.