Run 9 200GeV Dijet Cross Section: Pre/Post Day 153 Comparison

Here I look at the fully unfolded cross sections from the periods before and after day 153 ...

At the collaboration meeting (Nov 3-7) I showed that there is some sort of change, the cause of which has not been determined, in the correlation between the number of dijets reconstructed vs the number of luminosity triggers issued which occurs between day 152 and 154. The spin group felt it was appropriate to look at only part of Run 9 for the cross section analysis, and the general feeling was that the period after day 154 would be more appropriate as it shows much less in-fill variation in the dijet/bbc ratio (see figure 1).

Unfortunately, this period is also when TPC RDO board 18-1 died and was not appropriately taken account of, introducing a change in the invariant mass spectrum. This page shows the shape difference between the fully unfolded cross sections from before and after the day 152-154 split. I also show the cross sections from the two periods compared to theory. In the data / theory comparison, the cross sections from both periods were corrected using the entire simulation sample, but in each case the underlying event and hadronization corrections applied to the theory were calculated seperately for each period.

Figure 1: The ratio of the number of reconstructed L2JetHigh dijets / the number of BBCMB-Cat2 triggers vs run number. The two line show where the day 152 - 154 split occurs (left-most line) and where board 18-1 dies (right-most line).

Figure 2: Ratio of the fully unfolded data cross section (red) as well as the UEH corrected theory cross section (blue) from before day 153 to that after day 153. The integrated luminosities were obtained from the BBCMB-Cat2 triggers.

Figure 3: Same as figure 2, but instead of using an integrated luminosity, the cross sections from the two periods were normalized by the number of dijets reconstruced from those periods. This should remove the overall integrated luminosity change and show just the mass dependence of the difference between the pre and post day 153 cross sections.

Figure 4: Same as figure 2, but instead of using the full simulation sample to unfold the cross sections for both periods, I split the simulation such that only the simu from before day 153 is used to unfold the data from before day 153, and the same for after day 153.

Figure 5: The (Data-Theory)/Theory ratio for the pre (red) and post (blue) day 153 cross sections. Both periods were unfolded using the full simulation sample. The BBC cross section used was 24 mb as opposed to the 26.1 mb which was used in the preliminary result.

Figure 6: Same as figure 5, but now each data set is unfolded using only the embedding sample corresponding to that data set.