Prof Chris Palmer - Precision at Peak Performance: CMS Delivers the Most Precise Luminosity Measurement at any bunched-beam hadron collider

Monday 6 Oct 2025, 12:00 → 13:30 Europe/London

516 (G.O. Jones Bulding)

https://fnal.zoom.us/j/93197574512?pwd=bGlJTHlGTnVtTFFwRnlpYnhrdm5rdz09

About the speaker: 

Chris got his BS in Astronomy and Mathematics from the University of Southern California in 2007. Then he took a relatively short drive to University of California - San Diego for his PhD. He split his time (almost exactly in half) between San Diego and CERN where he worked on the CMS experiment and was fortunate to work directly on the Higgs boson discovery in the Higgs boson to two photons analysis during LHC's Run 1. After receiving his PhD in 2014, he became a Postdoctoral Researcher at Princeton University during LHC's Run 2.
While there he was a contributor to precision luminosity measurements, the observation of the Higgs boson decay to bottom quarks, and High Luminosity LHC outer tracker upgrades. Now Chris is further pursuing understanding underlying features of the Higgs boson via searches with two Higgs boson signatures.

1 Biscuits/Coffee/Socialization

Precision at Peak Performance: CMS Delivers the Most Precise Luminosity Measurement at any bunched-beam hadron collider

Luminosity measurements are foundational elements of collider physics measurements and searches. Its precise determination is essential for accurate cross-section measurements and new physics searches. In this talk, the most precise luminosity measurement ever achieved at a bunched-beam hadron collider, based on data collected by the CMS experiment during the LHC Run 2 (2015-2018) at sqrt(s) = 13 TeV. Leveraging van der Meer scans, advanced extrapolation techniques, and a suite of calibrated luminometers, CMS reached a relative uncertainty of 0.82% for 2017 and 0.84% for 2018. Combining these updated measurements with the previous 2015 and 2016 precision publications, the CMS luminosity for Run 2 data is just 0.73%--a new benchmark in collider performance. We detail the methodology behind the beam-separation (van der Meer) scans, corrections for detector nonlinearity and efficiency, and the use of Z boson rates to cross check consistency across multiple data-taking periods. This achievement not only enhances the precision of CMS physics results but also establishes a new standard for future luminosity determinations at high-energy colliders.

Convener: Prof. Chris Palmer (University of Maryland / CMS)