A writup on the basic classes used in psu analysis (pre-Run12)   here  with  headers for these classes

The basic fitting routine uses a model for showers based on six constants a[3] and b[3]. This dates back to code that predates STAR. I reversed engineered it in 2003.  shower shape 2003   part 2

A writup on the basic reconstruction class used back from 2009 does not reflect later changes but is complementary in information provided.  yiqun writup 2009  and  qt class 2008

The most essential application is the calibration of data at the start of a run. This is a link to a HTML program I wrote to monitor data as the calibration proceeds html program

Below are links and an index to other links that track progress in the evolution of shower shape over the last 5 or so years.  more on shower shape  index