EGamma_ElectronTrackingValidation/docs/reports/report_2018_05_16.md

Authors: Caleb Fangmeier Date: May 16, 2018

Fake Rate Investigation

Note: I have adopted a more intuitive naming scheme for the seeding working points.

• old-default: Just the old pair-match seeding with default settings
• new-default: The new triplet-match seeding with the HLT settings
• new-wide: The new triplet-match seeding with the double-size window settings

We define a "Full Fake Rate" as:

$ \frac{N{fake}}{N{scl}} $

Where, $N{scl}$ is the number of superclusters in the sample with $HOE<0.15$ and resulting in at least one gsf-track, and $N{fake}$ is the number of denominator superclusters resulting in only non-truth-matched GSF-tracks.

fig::full_fake_rate_all|\"Full Fake Rate\" as a function of supercluster $p_T, \eta, \phi$.

To help understand the above plots, I'll also include the numerator and denominator distributions.

fig::full_fake_rate_all_num|\"Full Fake Rate\" numerator

fig::full_fake_rate_all_den|\"Full Fake Rate\" denominator

A few observations:

1. The $p_T$ distribution of the $Z\rightarrow ee$ events has a clear peak around 60GeV which seems about right for electrons coming from $Z$s.
2. The fake rate in $t\bar{t}$ is roughly 4x higher than in $Z\rightarrow ee$ events. Looking at the num/den distributions, the difference seems to arise from both the numerator being larger (ie, more superclusers with no truth-matched gsf-tracks) and fewer small-HOE super-clusters overall. (both samples consist of about 100 thousand events)
3. Looking at the denominator, the number of super-clusters seems to drop quite dramatically going from tt-old-default to tt-new-default. At first glance, The reason for this is just that the denominator requires that the super-cluster result in at least one gsf-track, and the more restrictive new-default setting results in fewer superclusters that fulfill that requirement. However, the new-wide setting ends up being comparable to old-default.
4. Overall, it looks like this these plots confirm what other measurements (ie efficiency, purity) have shown: which is that the performance of the new-wide setting is comparable to the old-default setting.