Neventspp

Neventspp is a variable used in particle physics to denote the effective number of proton-proton (pp) collision events in a data sample or Monte Carlo simulation. In high-energy collider analyses, pp collisions produce vast numbers of events, and Neventspp summarizes the size or normalization of the sample for a given process. It may refer to the raw count of generated events (Ngenerated) or to the sum of event weights used to scale the sample to a target luminosity and theoretical cross section.

In Monte Carlo generation workflows, a process is simulated with Ngenerated events, each assigned a weight w_i. The normalization condition is often sum_i w_i ≈ sigma * L, where sigma is the process cross-section and L is the integrated luminosity. In this context Neventspp can be reported as the sum of weights or, when unweighted, as Ngenerated; both describe the same normalized yield when properly scaled.

Neventspp is used to compute expected yields, to normalize histograms, and to compare simulation to data. It is part of the metadata associated with datasets and MC samples, enabling reproducibility and cross-checks of efficiency, acceptance, and systematic uncertainties. In practice, analysts may quote Neventspp alongside sigma, L, and selection criteria, to convey the statistical power of the sample.

See also: cross section, integrated luminosity, event weight, Monte Carlo simulation, data normalization.