Mixed Signal and Background Samples
Case 1: At least 1 Signal in Every Event of a Run
A run is a collection of events and each event represents a 2000 nano second long integration frame.
Representation of a “Run” with 5 “Events”
If we assume a signal frequency of 500 kHz, each event contains at least 1 signal contribution. The background contributions get allocated per event based on their sampling frequency. Processes with less than 500 kHz sampling frequency are not guaranteed a contribution in every event.
| Event | signal | synrad | ebrems | etouschek | ecoloumb | p.b.gas |
|---|---|---|---|---|---|---|
| Event 1 | 🔴 | ⚪⚪⚪⚪ | 🔵 | |||
| Event 2 | 🔴 | ⚪⚪⚪⚪ | 🟡 | 🟣 | ||
| Event 3 | 🔴 | ⚪⚪⚪ | 🟢 | |||
| Event 4 | 🔴 | ⚪⚪⚪ | 🔵 | 🟣 | ||
| Event 5 | 🔴 | ⚪⚪⚪ ⚪ | 🔵 |
Legend
| Symbol | Process | Description | Sampling Frequency (kHz) | Status Code Shift |
|---|---|---|---|---|
| 🔴 | signal | DIS NC 18x275 Q²>1 (Deep inelastic scattering neutral current) | 500 | 0 |
| ⚪ | synrad | Synchrotron Radiation | 14000 | 2000 |
| 🔵 | ebrems | Electron bremsstrahlung radiation | 316.94 | 3000 |
| 🟢 | etouschek | Electron Touschek scattering (intrabeam scattering) | 1.3 | 4000 |
| 🟡 | ecoulomb | Electron Coulomb scattering processes | 0.72 | 5000 |
| 🟣 | p.b.gas | Proton beam gas interactions | 22.5 | 6000 |
N.B.: The sampling frequencies in this example are taken from the ePIC Background Wiki Page
Location of files
Simulation Output
root://dtn-eic.jlab.org//volatile/eic/EPIC/FULL/25.06.1/epic_craterlake/Bkg_1SignalPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/DIS/NC/18x275/minQ2=1/
Reconstructed Output
root://dtn-eic.jlab.org//volatile/eic/EPIC/RECO/25.06.1/epic_craterlake/Bkg_1SignalPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/DIS/NC/18x275/minQ2=1/
N.B.: Increment the campaign tag (25.06.1) to get the latest campaigns. Reconstructed output is available for every campaign but simulation output is not always preserved to save storage resources.
Case 2: Realistic Signal Contribution Per Event of a Run
A run is a collection of events and each event represents a 2000 nano second long integration frame. For the SIDIS pythia6 18x275 Q²<1, the signal frequency is 83 kHz which would result in 1 signal contribution every ~5 events.
Representation of a “Run” with 5 “Events”
| Event | signal | synrad | ebrems | etouschek | ecoloumb | p.b.gas |
|---|---|---|---|---|---|---|
| Event 1 | ⚪⚪⚪⚪ | 🔵 | ||||
| Event 2 | ⚪⚪⚪⚪ | 🟡 | 🟣 | |||
| Event 3 | 🔴 | ⚪⚪⚪ | 🟢 | |||
| Event 4 | ⚪⚪⚪ | 🔵 | 🟣 | |||
| Event 5 | ⚪⚪⚪ ⚪ | 🔵 |
Legend
| Symbol | Process | Description | Sampling Frequency (kHz) | Status Code Shift |
|---|---|---|---|---|
| 🔴 | signal | SIDIS pythia6 18x275 Q²<1 (Deep inelastic scattering neutral current) | 500 | 0 |
| ⚪ | synrad | Synchrotron Radiation | 14000 | 2000 |
| 🔵 | ebrems | Electron bremsstrahlung radiation | 316.94 | 3000 |
| 🟢 | etouschek | Electron Touschek scattering (intrabeam scattering) | 1.3 | 4000 |
| 🟡 | ecoulomb | Electron Coulomb scattering processes | 0.72 | 5000 |
| 🟣 | p.b.gas | Proton beam gas interactions | 22.5 | 6000 |
Location of files
Simulation Output
root://dtn-eic.jlab.org//volatile/eic/EPIC/FULL/25.06.1/epic_craterlake/Bkg_RealisticSignalPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/SIDIS/pythia6-eic/1.0.0/18x275/q2_0to1
Reconstructed Output
root://dtn-eic.jlab.org//volatile/eic/EPIC/RECO/25.06.1/epic_craterlake/Bkg_RealisticSignalPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/SIDIS/pythia6-eic/1.0.0/18x275/q2_0to1
N.B.: Increment the campaign tag (25.06.1) to get the latest campaigns. Reconstructed output is available for every campaign but simulation output is not always preserved to save storage resources.
Case 3: Only Background Contributions Per Event of a Run
A run is a collection of events and each event represents a 2000 nano second long integration frame. There are no signal contributions in any of the events.
Representation of a “Run” with 5 “Events”
| Event | signal | synrad | ebrems | etouschek | ecoloumb | p.b.gas |
|---|---|---|---|---|---|---|
| Event 1 | ⚪⚪⚪⚪ | 🔵 | ||||
| Event 2 | ⚪⚪⚪⚪ | 🟡 | 🟣 | |||
| Event 3 | ⚪⚪⚪ | 🟢 | ||||
| Event 4 | ⚪⚪⚪ | 🔵 | 🟣 | |||
| Event 5 | ⚪⚪⚪ ⚪ | 🔵 |
Legend
| Symbol | Process | Description | Sampling Frequency (kHz) | Status Code Shift |
|---|---|---|---|---|
| ⚪ | synrad | Synchrotron Radiation | 14000 | 2000 |
| 🔵 | ebrems | Electron bremsstrahlung radiation | 316.94 | 3000 |
| 🟢 | etouschek | Electron Touschek scattering (intrabeam scattering) | 1.3 | 4000 |
| 🟡 | ecoulomb | Electron Coulomb scattering processes | 0.72 | 5000 |
| 🟣 | p.b.gas | Proton beam gas interactions | 22.5 | 6000 |
Location of files
Simulation Output
root://dtn-eic.jlab.org//volatile/eic/EPIC/FULL/25.06.1/epic_craterlake/Bkg_OnlyPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/BACKGROUNDS/BEAMGAS/proton/pythia8.306-1.0/275GeV
Reconstructed Output
root://dtn-eic.jlab.org//volatile/eic/EPIC/RECO/25.06.1/epic_craterlake/Bkg_OnlyPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/BACKGROUNDS/BEAMGAS/proton/pythia8.306-1.0/275GeV
N.B.: Increment the campaign tag (25.06.1) to get the latest campaigns. Reconstructed output is available for every campaign but simulation output is not always preserved to save storage resources.
Analyzing the output
It’s possible to separate the contribution from signal and background sources that are simulated by using cuts on the status codes which are represented by the MCParticles.generatorStatus in the edm4hep output file.
| Status code | Meaning | Usage |
|---|---|---|
| 0 | Not defined (null entry) | Not a meaningful status |
| 1 | Undecayed physical particle | Recommended for all cases |
| 2 | Decayed physical particle | Recommended for all cases |
| 3 | Documentation line | Often used to indicate in/out particles in hard process |
| 4 | Incoming beam particle | Recommended for all cases |
| 5–10 | Reserved for future standards | Should not be used |
| 11–200 | Generator-dependent | For generator usage |
| 201– | Simulation-dependent | For simulation software usage |
N.B.: By default, DD4hep takes primary particles (status code 1, 2) and also custom status code provided with
--physics.alternativeStableStatuses="1001 2001 …" --physics.alternativeDecayStatuses="xxxx yyy "
Example: Minimal ROOT script to view counts of processes by status codes
TChain *T=new TChain("events");
T->Add("root://dtn-eic.jlab.org//volatile/eic/EPIC/RECO/25.06.1/epic_craterlake/Bkg_1SignalPer2usFrame/Synrad_18GeV_Vac_10000Ahr_Runtime_10ms_Egas_All_18GeV_Hgas_275GeV/DIS/NC/18x275/minQ2=1/*010*");
T->Draw("MCParticles.generatorStatus", "MCParticles.generatorStatus>0");
gPad->SetLogy();
Example: Charged Primary Particle Distribution in Eta