# Event generation

Event generation refers to the computer-based simulation of events, usually using the Monte Carlo method and an event generator.

## Choice of event weight normalisation

There are basically four different choices to normalise event weights. Choosing a notation where $w_i$ denotes the weight of the $i$th event, $N$ is the number of generated events, $\sigma$ is the generated cross section value and $\langle \cdots \rangle$ denotes the average, the different conventions are[1]:

1. $\langle w_i \rangle = 1$ meaning that $\langle \sum_i w_i \rangle = N$
2. $\langle w_i \rangle = \sigma$ meaning that $\langle \sum_i w_i \rangle = N\sigma$
3. $\langle w_i \rangle = 1/N$ meaning that $\langle \sum_i w_i \rangle = 1$
4. $\langle w_i \rangle = \sigma/N$ meaning that $\langle \sum_i w_i \rangle = \sigma$

The sums are over all generated events.

## References

1. Wolfgang Kilian, Thorsten Ohl, Jürgen Reuter: WHIZARD online user manual, section 11.3