Speaker
Description
During Run 2, LHC delivered instantaneous luminosities of $\approx 10^{34}$ cm$^{-2}$ s$^{-1}$ at $\sqrt{s}=13\; {\rm TeV}$. This permitted monitoring of the luminosity over a time granularity as short as $60\;{\rm s}$, using the counts of $Z\rightarrow \ell \ell$ events reconstructed by selecting two, well-idenfitied high $p_T$ electrons or muons in the invariant mass range of $66 < m_{\ell \ell} < 116$ GeV.
The poster illustrates the measurement principles based on time-dependent trigger and reconstruction efficiency corrections and shows the stability of using both $Z\to ee$ and $Z\to \mu \mu$ boson counting as luminometers. Emphasis is given to illustrate with selected LHC run examples the robustness of the method with respect to pile-up and the LHC bunch structure, which are of particular importance for reliable luminosity monitoring at the upcoming high luminosity phase of the LHC.
