Luminosity Uncertainty

The number of collisions in CMS is not known with absolute certainty. Calculating the uncertainty in the luminosity value requires precision work, and is documented in the CMS luminosity papers. The values for proton-proton collisions are:

• 2011 data: 2.2\%
• 2012 data: 2.6\%
• 2015 data: 1.6\%
• 2016 data: 1.2\%

For heavy-ion data, the uncertainties are:

• 2013 pPb data: 3.4\% for p-Pb, 3.6\% for Pb-p
• 2015 pp reference data: 2.3\%
• 2015 PbPb data: 3.0\%

These uncertainties should be applied to the number of events observed in simulations that are normalized based on the integrated luminsity measurement.