Photoproduction of Eta Mesons from Deuterium at 0° and 180° with Photon Energy from 725 MeV to 1225 MeV

Author: Yellin, Steven Joseph

Year: 1971

Degree: Dissertation (Ph.D.)

Advisor: Heusch, Clemens A.

Committee Member: Unknown, Unknown

Option: Physics

DOI: 10.7907/JQ3X-8502

Abstract

In an experiment conducted at the Caltech 1.5 GeV electron synchrotron, we measured the cross section for photoproduction of eta mesons from deuterium. The measurement was performed by detecting and measuring the energies of both photons from the η → 2γ decay mode using two totally absorbing lead glass Cherenkov counters. These counters were placed symmetrically about the photon beam line in order to best detect eta mesons photoproduced along the beam line. By varying the placement of the Cherenkov counters and by varying the synchrotron end-point energy, we were able to obtain information on the forward and backward cross section for photoproduction over an energy range from about 725 MeV to about 1225 MeV.

Within the framework of the impulse approximation, we expressed our results as a sum of the differential cross section for eta photoproduction from protons plus that from neutrons. The unfolding of the cross section was performed by finding the function that was the smoothest (using a well-defined measure of smoothness) function that fit the data to within a given degree of accuracy (as measured by X2).

The results show that for photon energy below 950 MeV, the cross section for photoproduction from neutrons is about equal in the forward and backward directions, and is about the same as the cross section for photoproduction from protons. Above 950 MeV, a significant angular asymmetry is seen, and the neutron cross section shows signs of reaching a minimum, then rising. These results are interpreted in terms of contributing isobars.

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