Due to the falling energy-scale at the edges of our detector acceptance, it may become advantageous to set limits on the η range of what we accept for our cross-section and asymmetry measurements. To try to understand sensible limits, I revisit the energy-scale for poton-gun set-8, which is thrown at p_T = 10 GeV/c across the range of 1.086 < η < 2.0 for 30º φ wedges centered at φ = 0. In an earlier update, we saw that there are several towers with extremely low energy response. For this study, I wanted to avoid those regions; so that the observed fall-off in energy is due to the limits of acceptance reach and not tower behavior. To this end, I focus on runs-1 and -2, which span -15º < φ < 45º. One issue to keep in mind is that, unless I am mistaken, these photons are thrown from a vertex of (0,0,0). Thus, this cut effectively amounts to a cut on "detector-η." One may want to revisit the matter to determine an ideal window on "physics-η."

Figure 1

In Fig. 1, I show the energy-scale as a function of p_T, η, and phi; of reconstructed photons from photon-gun set-8 runs-1 and -2. As you can see, I've limited myself to regions of φ which avoid the tower issues discussed in a previous update. In the middle panel, I plot a dashed, red line at 0.98 as an arbitrary lower limit on energy scale. Within the window of 1.11 < η < 1.96, denoted by black lines, the energy scale remains above this limit. I have fit the energy-scale profile with a constant (1.0288±0.0002) across this range, shown by the solid, red line. The fit is not very good, but it does give a sense of the average scale across the proposed fiducial acceptance.