| E08-010 ~ N-Delta Simulated Yields |
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Introduction The simulation program used for this analysis is MCEEP (Monte Carlo for Electro-Nuclear Coincidence Experiments (e,e'p)), which was written by P.E. Ulmer in Fortran. The program primarily simulates the spectrometers in Hall A at Jefferson Lab. It can produce histograms and ntuples containing the simulated results. In its original incarnation, the program calculated multipoles based on the work of Devnish and Lyth. Modifications to the code allow the user to select multipoles from various models, such as MAID, DMT, Sato-Lee, and SAID, via external table files. These multipoles are used to produce response functions, which are then used to produce cross sections for each simulated event. The code then takes these cross sections and uses them to produce yield and phase space ntuples. Once the simulation is complete, cross sections plots can be constructed by producing yield plots and phase space plots, and dividing the two, bin by bin. These cross section plots are in units of fm2/MeV/sr2. The MeV and sr2 are present due to the momentum acceptance of the electron arm and the angular acceptance of both arms. Energy losses, both due to the particles interacting with physical medium and due to radiative effects, can be calculated for each event. If a radiatively-corrected energy loss is applied, the resulting differential cross section is also dependent on the momentum or energy of the emitted photon. This means that the process of dividing the yield plot by the phase space plot may not produce correct cross sections if a radiative energy loss has been applied. |
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Radiatively-Corrected Energy Loss Because the experimental yield has a naturally-occurring radiative energy loss, an experimental cross section cannot be directly extracted using the phase space as calculated by MCEEP. Instead, an experimental yield without a radiative energy loss must be used. One method for calculating a "non-radiatively-corrected" experimental yield is to produce two sets of simulated yields, one with radiative corrections turned on and one with radiative corrections turned off. A ratio between these two sets of simulated yields would produce a radiative correction factor, which could then be applied to the experimental yield.
The plots below show the simulated yields with radiative correction factors turned off and turned on for each of the different models used, as well as the radiative correction factor for each bin. |
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