2 pi Analysis Log

May 02, 2002

We've written up a Gottfried-Jackson boost and ran all the data (minus a few faulty disks) as well as 1.5 M Monte Carlo events through the analysis code.

Because the four-vector of the recoil particle is used in the Gottfried-Jackson boost, we needed to ensure that the reconstructed recoil particle was reasonably close to the theoretical expectation.

Accordingly, we plotted the dot product of the reconstructed recoil direction with beam-forward. This is shown below. In the data we cut on this below .9.

Recoil Comparison (postscript)

We studied acceptance as a function of invariant mass, t, cos(theta), and phi in the GJ frame. The acceptances, uncorrected distributions, and corrected distributions are shown in the links below.

Invariant Mass Distributions
Momentum Transfer Distributions
Cos(theta) Distributions
Phi Distributions

May 14, 2002

During the course of debugging the Gottfried-Jackson distributions, we looked at distributions of generated events coming from mcwrap. The expectation was that the events should be generated flat in these variables. The generated distributions are shown below.

Generated GJ cos(theta) (postscript)

Generated GJ phi(theta) (postscript)

Clearly, the generated events are flat in phi but have some structure in cos(theta)

We began to investigate the Monte Carlo more closely. Alex Dzierba provided me with a simple Monte Carlo which had geometry and the following cuts:

All photons separated by at least 10 am
All photon energies > 100 MeV
Photons at the LGD are contained in the active area of the LGD located 1.02 m from target - inner radius 10 cm and outer radius 52 cm

This simple Monte Carlo was specifically designed to generate events flat in the Gottfried-Jackson variables. A comparison of this Monte Carlo with mcwrap in acceptances and acceptance-corrected distributions is shown in the link below.

Monte Carlo Comparisons

This page was last updated May 14, 2002.

It is maintained by Dan Krop.