2012 500GeV Spin QA: Beam Crossing Analysis

 The attached pdf (and PowerPoint if you prefer) outlines steps taken to determine the beam crossing locations for run 12 500GeV longitudinal data using the bx7 counter spectrum. 

It's determined that blue beam bunch (BBB) 1 meets yellow beam bunch (YBB) 1 at bx7 = 0, thus we deduce that BBB 0 collides with YBB 0 at IP2 and IP8 as expected from the cdev record. 

Fills examined: 16732, 16735


**UPDATE: Updated version uses Fill 16731 which has a missing bunch in the yellow beam. This missing bunch confirms the overall shift by 80 bunches between the two beams, and further solidifies that BBB 0 meets YBB 0 at IP2 and IP8. Copies of the PPT/PDF are still attached with fills mentioned above.