MDI (Machine-Detector Interface)

contact egroup | Mandate | Intro slides @PSC

Initial page to gather recipes for FCCee MDI-related software. You will find information about the following set of procedures:

  • MDI geometry definition & recommendations on how to use it in the simulation
  • Beam-Induce Background (BIB) sample production info & where to find the files
  • How to simulate a BIB file through a detector
  • How to extract occupancy numbers for a specific sub-detector

MDI geometry (mdi_v2)

NOTE: 29/May/2026 update: The xml files to be used to produce samples are in aciarma k4geo fork, mdi_v2 branch:

#aciarma/k4geo/tree/mdi_v2
k4geo/FCCee/ALLEGRO/compact/ALLEGRO_o1_v03/ALLEGRO_o1_v03_CAD.xml
k4geo/FCCee/IDEA/compact/IDEA_o1_v03/IDEA_o1_v03_CAD.xml
k4geo/FCCee/ILD_FCCee/compact/ILD_FCCee_v01/ILD_FCCee_v01_CAD.xml
k4geo/FCCee/CLD/compact/CLD_o2_v08/CLD_o2_v08_CAD.xml

Please remember that the IR antisolenoid field map does not match perfectly the flat 2T field which is currently in the detectors k4geo description.

More accurate maps will be produced once the detectors provide and implement a realistic field map for their own solenoid and return fields.

Click for more details on the 2nd iteration of the cryostat model Second iteration of the cryostat model. Details on [MDI#79](https://indico.cern.ch/event/1679641/). - Starts at 1400mm from IP Max radius 220mm Profile follows 100mrad - 5mm Tungsten layer shielding. - Quadrupoles and 2 SR masks for L*=2.4m - Not an engineered model. Screenshot 2026-05-28 alle 16 58 25 Field map for IR antisolenoid produced by B. Parker for the non-local compensation scheme - only screening anti-solenoid - The field map was produced starting from a realistic field map for IDEA. The k4geo description instead uses a flat 2T field. Thus when overlapping the two fields we get some non-zero field inside the screening solenoids. - This is not 100% correct but still better then having 2T. Similar behaviour for the other detector concepts. Once every concept provide (and use in k4geo) a realistic field map, a dedicated antisolenoid field map can be produced. Screenshot 2026-05-28 alle 16 59 15 The use of a field map for the IR antisolenoids allows us to have the fringe fields (Br component) due to the transition between detector field and screening antisolenoid field. Fringes are important for the transport of low pT low angle particles that can spiralize along the field lines and enter the detectors. In the non-local compensation scheme this is much reduced w.r.t. the local scheme (which foresees a -5T compensation antisolenoid in front of the screening antisolenoid). Screenshot 2026-05-28 alle 17 00 04

BIB samples to be used (and where to find them)

NOTE: To access the files on the EOS directories, you need to join the fcc-ee-MDI egroup.

The latest background samples are produced for the LCC V106.2 lattice, found here:

The following background sources are to be considered:

  • Incoherent Pair Creation (IPC): generated with GuineaPig
  • Synchrotron radiation (SR): halo and core, generated with bdsim
  • Collimation backgrounds (beam gas: Bremsstrahlung and Coulomb scattering): generated with Xsuite and FLUKA

Each of the background sources has a readme file with more information about the generation and the contact persons.

The following backgrounds are not yet considered or generated for this lattice:

  • Injection backgrounds: these are drastically suppressed in the LCC lattice design
  • Radiative Bhabha: expected to be smaller than the IPC background

Detector simulation

Uses ddsim (see docs). Simulation recipe currently in bib-studies repo here.

This will produce root files you can process; see below how.

If you produce good files (i.e. not too experimental), they may be placed in the common EOS space; make sure you follow the existing folder naming and structure!

#location
/eos/experiment/fcc/ee/simulation
#inner structure:
/eos/experiment/fcc/ee/[simulation,generation]/Key4HEP_release(only for simulations)/ENERGY/EXPERIMENT/STAGE/SAMPLE

Detector concept groups should attempt to produce their own files, with our support.

NOTE: we produced the SIM files for the 4 detector concepts (IDEA_o1_v03, CLD_o2_v08, ALLEGRO_o1_v03, ILD_v01), compatible with the latest MDI settings, and for all the background samples:

/eos/experiment/fcc/ee/simulation/key4hep_2026_04_08/91GeV/IDEA_o1_v03_mdi_v2_CAD/sim
/eos/experiment/fcc/ee/simulation/key4hep_2026_04_08/91GeV/CLD_o2_v08_mdi_v2_CAD/sim
/eos/experiment/fcc/ee/simulation/key4hep_2026_04_08/91GeV/ALLEGRO_o1_v03_mdi_v2_CAD/sim
/eos/experiment/fcc/ee/simulation/key4hep_2026_04_08/91GeV/ILD_v01_mdi_v2_CAD/sim

The key4hep stack used for the generation of these samples is 2026-04-08.

bib-studies

See bib-studies for how to simulate BIB samples through a detector and produce occupancy plots.

test

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