Information for Using the 250 GeV stdhep files and miniDST files

To download a particular stdhep file from this site, use the command-line command wget. For example, for "higgs",

Similarly, to download a miniDST file, use the wget command with the corresponding directory. The server is open for downloads; no credentials should be needed.

The total event sample represented here corresponds to about 250 fb-1 of data for e+e- collisions at 250 GeV, generated by Whizard 1.95. The total Standard Model event sample is divided into a number of categories, as described below. Events were generated for all four possible configurations of 100% polarized beams (e-Le+L, e-Le+R, e-Re+L, e-Re+R). In an analysis, samples with the four polarizations would be mixed to create the polarizations expected from the collider (for example, +- 80% electron polarization, -+ 30% positron polarization for the ILC baseline). If you would like to make your own stdhep samples or analyze the stdhep files directly, there are some further details that you need to know. These are described in a paragraph below.

The full set of generated events has been separated into the categories listed below. The initial partons at an e+e- collider are electrons, positrons, and photons. These have luminosity spectra that include the effects of initial state radiation and beamstrahlung. The the beamstrahlung component depends on the accelerator parameters; the spectra used are those corresponding to the 2013 ILC TDR accelerator design.

In W, Z production, the heavy bosons are allowed to go off the mass shell. Whizard accounts this consistently by including all tree-level electroweak Feynman diagrams contributing to the same partonic final state. For example, in 4-fermion production, Whizard includes the nonresonant background diagrams in addition to the diagrams with explicit WW and ZZ boson production and decay. This is why the categories are labelled with the number of fermions in the final state. Each category includes the relevant QCD and photon radiation as generated by PYTHIA.

The files here include both samples of general Standard Model events and special samples created to study machine-related backgrounds, processes with large missing energy, and other more specific goals. The general Standard Model sample is divided into the following categories:

These samples are disjoint and sum to the complete contribution of the Standard model except for the elementary QED processes e+e--> e+e-, e+e--> gamma gamma, gamma gamma-> e+e-, e-e-->e-e-, and e+e+->e+e+. (A small subset of radiative Bhabha events is included in the category 2f.) It is complex and time-consuming to generate this SM sample, so we recommend that you use the samples given here to represent the SM background rather than generating your own.

The samples not on the list above are more specialized samples created for specific analyses. If these samples are interesting to you, please ask us for more information about them.

The categories of events stored here are the following:

The ILC Generators Group is now preparing a 10 ab-1 sample of 250 GeV events using the updated ILC 250 GeV accelerator parameters and the updated Whizard 2.8.4. We will offer those events from this page when they become available. We expect only minor changes, so please begin your studies with the samples already posted here.

If you would like to make your own stdhep samples or analyze the stdhep files directly, there are some further details that you need to know:

The stdhep files stored here contain 250 fb-1 of data for each setting of 100% polarized beams (e-Le+L, e-Le+R, e-Re+L, e-Re+R). Also, each category above contains a large number of individual processes for which events are generated by Whizard. Each individualprocess has its own cross section, and the events from that process should be reweighted according to the cross section to provide a correct mixture. If you build your own stdhep files using Whizard or MadGraph, you can specify the electron and positron beam polarizations or you can create events with 100% polarization and mix them later. If you include several individual processes, you need to mix these events according to the cross sections for each process. If you do not find an appropriate example in the tutorials, please ask us for assistance. Similarly, to interpret the stored stdhep files, you will need to know the list of individual processes and their cross sections. This information is provided in a json file posted at this site. Please ask us if you have questions about the use of this json file. An email to will reach someone on our team who can help you.

Additional technical information about the event generation can be found at the ILCSoft web site at DESY.