The MCFast program is used to simulate tracking elements in the solenoid field (B = 2.24 T). One thousand positive pion tracks were generated for 9 different momenta:

P = 0.25, 0.50, 0.75, 1.00, 1.50, 2.00, 2.50, 3.00, 4.00 GeV/c

and for 5^o < theta < 10^o, then they were tracked through the detector. (P_generated - P_simulated) /P_generated = Delta_P/P
is plotted for each momentum bin and for different FDC resolutions, as well as different number of FDC packages (Here, an FDC package is a stack of six chambers, each of which consists of a sense wire plane and two cathode planes).

- 150 um with no CDC end plate,
- 150 um with CDC end plate

By this study, we would like to investigate the following:

Resolution due to multiple scattering:

This study is performed by choosing a very small FDC resolution (10 μm). In this case, Delta_P/P is expected to reflect the resolution that is only due to the material on the way of a charged track. These materials could be the cathode planes, wires, straw tubes, gas inside the chambers, air, the 1-cm thick endplate to hold the straw tubes etc. In this study, we plotted Delta_P/P with and without the Central Drift Chamber (CDC) end plate for 3 FDC packages. Also plotted Delta_P/P with and without the CDC end-plate in the presence of an additional FDC package. The conclusion is that the resolution due to the multiple scattering is ~1%.

Minimum number of packages required for optimal resolution:

Here, we compare the overall resolution if we have 3 FDC packages with 150 μm, 200 μm, 500 μm, and 1000 μm resolution, with 4 FDC packages having 150 μm, 200 μm, 500 μm, and 1000 μm resolution.

Last modified: June 28, 2005
Daniel S. Carman