Red Giant Branch Bump Brightness and Number Counts in 72 Galactic
  Globular Clusters Observed with the Hubble Space Telescope
  We present the broadest and most precise empirical investigation of red giant
branch bump (RGBB) brightness and number counts ever conducted. We implement a
new method and use data from two \textit{Hubble Space Telescope (HST)} globular
cluster (GC) surveys to measure the brightness and star counts of the RGBB in
72 GCs. The brightness is measured to a precision better than 0.01 mag while
the precision in number counts reaches 10%. The position of the main-sequence
turnoff (MSTO) and the number of horizontal branch (HB) stars are used as
comparisons where appropriate. Several independent scientific conclusions are
newly possible with our parametrization of the RGBB. Both brightness and number
counts are shown to have second parameters in addition to their strong
dependence on metallicity. The RGBBs are found to be anomalous in the GCs NGC
2808, 5286, 6388 and 6441, likely due to the presence of multiple populations.
Finally, we use our empirical calibration to predict the properties of the
Galactic bulge RGBB if the assumption of similar stellar physics for the bulge
and Galactic GC system holds. The RGBB properties for the bulge are shown to
differ from those of the Galactic GC system, with the former having lower
number counts, a lower brightness dispersion and a brighter peak luminosity
than would be expected from the latter. This discrepancy is well explained by
the Galactic bulge having a higher helium abundance than expected from GCs,
${\Delta}$Y$\sim +$0.06 at the median metallicity.
