L2 Jet Algo Study

Here I compare the output from the 2008 and my first version of the 2009 L2 jet code. I analyzed 60k events found here: /star/institutions/mit/balewski/2008-L2events/R9067013.eve.bin-60k

The code used to analyze these events can be found here: /star/u/pagebs/L2Trig/run9_2008-2009/myWork/V1.0/integrated

The original algorithm works by scanning over every 3-bin grouping of the 30 phi bins and noting the starting position of the group with the highest energy. The algorithm can handle groups which wrap around so it is possible to have a group with bins 29-0-1 for example. The algorithm also looks for the second highest 3-bin grouping with the requirement that it must be at least two phi bins away from the first group. Each phi bin is subdivided into 15 eta bins and the algorithm adds the energies from the corresponding eta bins in the three phi bin group. So now, in essence, the three phi bins have been collapsed into one. The algorithm then looks at each 3 eta bin grouping and picks the one with the highest energy. That energy (mod any correction factors) is the jet energy. The scan over eta does not wrap around as that is unphysical, ie you cannot have eta bin groupings of 14-0-1.

My new algorithm follows exactly the same scheme used above only now instead of looking for 3 phi bin by 3 eta bin groupings I look for 5 by 5 groupings. This algorithm will need to be tested using the 2009 framework (modifications ongoing as of 12/15/2008) on the actual L2 machine to see if it is fast enough.

The standard L2jet diagnostic plots are presented for both the old algorithm and my new algorithm.

Fig 1: This plot shows the change in eta bin between the new and old algorithm for the high ET jet plotted vs the original eta bin (left plot) and the new eta bin (right plot).

Fig 2: This plot shows the change in eta bin between the new and old algorithm for the low ET jet plotted vs the original eta bin (left plot) and the new eta bin (right plot).

Fig 3: This plot shows the change in phi bin between the new and old algorithm for the high ET jet plotted vs the original phi bin (left plot) and the new phi bin (right plot).

Fig 4: This plot shows the change in phi bin between the new and old algorithm for the low ET jet plotted vs the original phi bin (left plot) and the new phi bin (right plot).

Fig 5: This plot shows the change in ET between the new and old algorithm for the high ET jet plotted vs the original ET (left plot) and the new ET (right plot).

Fig 6: This plot shows the change in ET between the new and old algorithm for the low ET jet plotted vs the original ET (left plot) and the new ET (right plot).