E08-010 (N-Delta) Simulated Cross Sections

E08-010 ~ N-Delta
Simulated Cross Sections

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, average 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.

Central Cross Sections

In addition to the average cross sections produced by MCEEP, "central" or "point" cross sections can be calculated directly from multipoles provided by the theoretical models. By comparing the average cross sections with the cross sections calculated for the central value of each bin, an average-central ratio can be determined, much like the ratio between the radiatively-corrected and non-radiatively-corrected yields.

The hope is that the average "non-radiatively-corrected" experimental yields can be turned into into average "non-radiatively-corrected" experimental cross sections by dividing by the phase space, and then this average-central ratio can be used to determine central or point experimental cross sections.

XS_{experimental (point)}	=	XS_{simulation (point)}
XS_{experimental (avg)}	=	XS_{simulation (avg)}

The plots below show both the average simulated cross sections and the central or point simulated cross sections for each of the different models used, as well as the average-central correction factor for each bin.

return to main page