Measurement of the Z boson cross-section in - Harvard University ...

Chapter 3
Luminosity Measurement at the
LHC and in ATLAS
For a physics process p, the instantaneous luminosity L is the proportionality
factor between the event rate dRP
dt and the cross-section σP :
dRP
dt = LσP (3.1)
The integral Lint of the instantaneous luminosity with respect to time is an estimate of
the total amount of ‘data’ in a given run or set of runs. Knowledge of Lint is therefore
vital for measuring the cross-sections of physics processes. The uncertainty in Lint
is often the dominant source of uncertainty in such measurements and, therefore,
the accurate determination of integrated luminosity is of prime importance in any
high-energy physics experiment.
A number of methods exist for determining the luminosity at hadron colliders.
The following are routinely used:
• parameters of the colliding beams
• purpose-built detector systems integrated with the experiments
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