Information for Using the 500 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",
- wget -r
http://osggridftp02.slac.stanford.edu:8080/sdf/group/lcddata/ilc/prod/ilc/mc-dbd/generated/500-TDR_ws/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 500 fb-1 of data
for e+e- collisions at 500 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:
- SM = 2f + 4f + 6f + 1f + 3f + 5f + aa_2f + aa_4f + higgs
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:
- general Standard Model sample:
- 2f: e+e- -> 2 fermion processes. This includes the
process e+e- -> Z gamma. Also, it includes a sample of
e+e- -> gamma e+e- events with small e+e- invariant mass.
- 4f: e+e- -> 4 fermion processes. This includes e+e- ->
WW, ZZ, with the heavy boson decays, and other diagrams
contributing to the same partonic final states. This sample also
includes e+e- -> e+e- 2f diagrams with two virtual photons, for
m^2(photon) < -10 GeV^2.
- 6f: e+e- -> 6 fermion processes. This includes e+e- ->
t tbar, with the top decays, and other diagrams
contributing to the same partonic final states. This sample also
includes e+e- -> e+e- 4f diagrams with two virtual photons, for
m^2(photon) < -(10 GeV)^2.
- 1f: e gamma -> e gamma processes.
- 3f: e gamma -> e Z , nu W , and contributios from more general e gamma
-> e, nu + 2 fermion diagrams
- 5f: e gamma -> e , nu + 4f processes, including 4f =
WW, tb
- aa_2f: gamma gamma -> 2 fermion processes. This sample
is disjoint from the 4f sample, including contributions from
beamstrahlung photons (m^2 = 0) and ISR
photons with smaller virtuality.
- aa_4f: gamma gamma -> 4 fermion processes. This sample
is disjoint from the 6f sample, including contributions from
beamstrahlung photons (m^2 = 0) and ISR
photons with smaller virtuality.
- higgs: e+e- -> Z h and e+e- -> nu nubar h (W fusion), e+e- ->
e+e- h (Z fusion), e+e- -> Z hh, e+e- -> nu nubar hh, followed
by general SM higgs decays
- Special Standard Model samples: The categories listed
here are used for specialized studies.
- aa_lowpt: A sample of high cross section but very low
pT gamma gamma -> 2 fermion events, used for studies of pileup due to
collisions in the same or nearby bunch crossings.
- aa_minijet: A sample of gamma gamma -> hadrons events at very low
CM energy (~ few GeV), used for studies of pileup due to
collisions in the same or nearby bunch crossings.
- eepairs: Low mass, forward e+e- pairs created in an
ILC
bunch-bunch collision, to be used to understand the occupancy of
the forward calorimeters.
- seeablepairs: A small subset of the eepairs sample, including
the pairs most likely to appear as backgrounds.
- 4f-lowmee : A sample of e+e- -> e+e- 2f events filling
in the region m(ee) < 4 GeV not covered by 4f.
- flavortag : A special sample for e+e- -> 2f events to be
used for detailed studies of heavy flavor tagging.
- Beyond-Standard-Model processes
- np-light-higgs : e+e- -> Zh events with varying Higgs
boson mass, to be used for studies of non-standard Higgs discovery using Z
recoil.
- SUSY : e+e- -> SUSY pair production for a particular parameter set.
- np-susy-higgsinos-verylowdm : e+e- -> higgsino pairs for
a parameter set with very small
higgsino mass splitting.
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 500 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
ilc-snowmass@slac.stanford.edu 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.