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0001 ---
0002 title: Mixed Signal and Background Samples
0003 description: background_mixed_samples
0004 name: background_mixed_samples
0005 layout: default
0006 ---
0007
0008 {% include layouts/title.md %}
0009
0010
0011 ---
0012 # Case 1: At least 1 Signal in Every Event of a Run
0013
0014 A run is a collection of events and each event represents a 2000 nano second long integration frame.
0015
0016 ## Representation of a "Run" with 5 "Events"
0017 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.
0018
0019 | **Event** | **signal** | **synrad** | **ebrems** | **etouschek** | **ecoloumb** | **p.b.gas**|
0020 | ----------- | ----------- | -----------| --------- | ------------ | ----------- | ----------- |
0021 | **Event 1** | 🔴 | ⚪⚪⚪⚪ | 🔵 | | | |
0022 | **Event 2** | 🔴 | ⚪⚪⚪⚪ | | | 🟡 | 🟣 |
0023 | **Event 3** | 🔴 | ⚪⚪⚪ | | 🟢 | | |
0024 | **Event 4** | 🔴 | ⚪⚪⚪ | 🔵 | | | 🟣 |
0025 | **Event 5** | 🔴 | ⚪⚪⚪ ⚪ | 🔵 | | | |
0026
0027 ## Legend
0028
0029 | Symbol | Process | Description | Sampling Frequency (kHz) | Status Code Shift |
0030 |--------|---------|-------------| ------------------| --------------------- |
0031 | 🔴 | **signal** | DIS NC 18x275 Q²>1 (Deep inelastic scattering neutral current) | 500 | 0
0032 | ⚪ | **synrad** | Synchrotron Radiation | 14000 | 2000
0033 | 🔵 | **ebrems** | Electron bremsstrahlung radiation | 316.94 | 3000
0034 | 🟢 | **etouschek** | Electron Touschek scattering (intrabeam scattering) | 1.3 | 4000
0035 | 🟡 | **ecoulomb** | Electron Coulomb scattering processes | 0.72 | 5000
0036 | 🟣 | **p.b.gas** | Proton beam gas interactions | 22.5 | 6000
0037
0038 N.B.: The sampling frequencies in this example are taken from the [ePIC Background Wiki Page](https://wiki.bnl.gov/EPIC/index.php?title=Background)
0039
0040 ## Location of files
0041
0042 **Simulation Output**
0043
0044 ```
0045 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/
0046 ```
0047
0048 **Reconstructed Output**
0049
0050 ```
0051 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/
0052 ```
0053
0054 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.
0055
0056 ---
0057
0058
0059 ---
0060 # Case 2: Realistic Signal Contribution Per Event of a Run
0061
0062 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.
0063
0064 ## Representation of a "Run" with 5 "Events"
0065
0066 | **Event** | **signal** | **synrad** | **ebrems** | **etouschek** | **ecoloumb** | **p.b.gas**|
0067 | ----------- | ----------- | -----------| --------- | ------------ | ----------- | ----------- |
0068 | **Event 1** | | ⚪⚪⚪⚪ | 🔵 | | | |
0069 | **Event 2** | | ⚪⚪⚪⚪ | | | 🟡 | 🟣 |
0070 | **Event 3** | 🔴 | ⚪⚪⚪ | | 🟢 | | |
0071 | **Event 4** | | ⚪⚪⚪ | 🔵 | | | 🟣 |
0072 | **Event 5** | | ⚪⚪⚪ ⚪ | 🔵 | | | |
0073
0074 ## Legend
0075
0076 | Symbol | Process | Description | Sampling Frequency (kHz) | Status Code Shift |
0077 |--------|---------|-------------| ------------------| --------------------- |
0078 | 🔴 | **signal** | SIDIS pythia6 18x275 Q²<1 (Deep inelastic scattering neutral current) | 500 | 0
0079 | ⚪ | **synrad** | Synchrotron Radiation | 14000 | 2000
0080 | 🔵 | **ebrems** | Electron bremsstrahlung radiation | 316.94 | 3000
0081 | 🟢 | **etouschek** | Electron Touschek scattering (intrabeam scattering) | 1.3 | 4000
0082 | 🟡 | **ecoulomb** | Electron Coulomb scattering processes | 0.72 | 5000
0083 | 🟣 | **p.b.gas** | Proton beam gas interactions | 22.5 | 6000
0084
0085 ## Location of files
0086
0087 **Simulation Output**
0088
0089 ```
0090 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
0091 ```
0092
0093 **Reconstructed Output**
0094
0095 ```
0096 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
0097 ```
0098
0099 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.
0100
0101 ---
0102
0103
0104 ---
0105 # Case 3: Only Background Contributions Per Event of a Run
0106
0107 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.
0108
0109 ## Representation of a "Run" with 5 "Events"
0110
0111 | **Event** | **signal** | **synrad** | **ebrems** | **etouschek** | **ecoloumb** | **p.b.gas**|
0112 | ----------- | ----------- | -----------| --------- | ------------ | ----------- | ----------- |
0113 | **Event 1** | | ⚪⚪⚪⚪ | 🔵 | | | |
0114 | **Event 2** | | ⚪⚪⚪⚪ | | | 🟡 | 🟣 |
0115 | **Event 3** | | ⚪⚪⚪ | | 🟢 | | |
0116 | **Event 4** | | ⚪⚪⚪ | 🔵 | | | 🟣 |
0117 | **Event 5** | | ⚪⚪⚪ ⚪ | 🔵 | | | |
0118
0119 ## Legend
0120
0121 | Symbol | Process | Description | Sampling Frequency (kHz) | Status Code Shift |
0122 |--------|---------|-------------| ------------------| --------------------- |
0123 | ⚪ | **synrad** | Synchrotron Radiation | 14000 | 2000
0124 | 🔵 | **ebrems** | Electron bremsstrahlung radiation | 316.94 | 3000
0125 | 🟢 | **etouschek** | Electron Touschek scattering (intrabeam scattering) | 1.3 | 4000
0126 | 🟡 | **ecoulomb** | Electron Coulomb scattering processes | 0.72 | 5000
0127 | 🟣 | **p.b.gas** | Proton beam gas interactions | 22.5 | 6000
0128
0129
0130 ## Location of files
0131
0132 **Simulation Output**
0133
0134 ```
0135 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
0136 ```
0137
0138 **Reconstructed Output**
0139
0140 ```
0141 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
0142
0143 ```
0144
0145 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.
0146
0147 ---
0148
0149
0150 # Analyzing the output
0151
0152 It's possible to separate the contribution from signal and background sources that are simulated by using cuts on the [status codes](https://arxiv.org/pdf/1912.08005.pdf) which are represented by the MCParticles.generatorStatus in the edm4hep output file.
0153
0154 | Status code | Meaning | Usage |
0155 |-------------|-----------------------------|----------------------------------|
0156 | 0 | Not defined (null entry) | Not a meaningful status |
0157 | 1 | Undecayed physical particle | Recommended for all cases |
0158 | 2 | Decayed physical particle | Recommended for all cases |
0159 | 3 | Documentation line | Often used to indicate in/out particles in hard process |
0160 | 4 | Incoming beam particle | Recommended for all cases |
0161 | 5–10 | Reserved for future standards | Should not be used |
0162 | 11–200 | Generator-dependent | For generator usage |
0163 | 201– | Simulation-dependent | For simulation software usage |
0164
0165 N.B.: By default, DD4hep takes primary particles (status code 1, 2)
0166 and also custom status code provided with
0167
0168 ```
0169 --physics.alternativeStableStatuses="1001 2001 …" --physics.alternativeDecayStatuses="xxxx yyy "
0170 ```
0171
0172 **Example: Minimal ROOT script to view counts of processes by status codes**
0173
0174 ```
0175 TChain *T=new TChain("events");
0176 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*");
0177 T->Draw("MCParticles.generatorStatus", "MCParticles.generatorStatus>0");
0178 gPad->SetLogy();
0179 ```
0180 <img width="488" height="402" alt="image" src="https://github.com/user-attachments/assets/040ccb77-e18c-4311-9a71-9a9a8ee2646a" />
0181
0182
0183
0184 **Example: Charged Primary Particle Distribution in Eta**
0185
0186 <img width="488" height="402" alt="image" src="https://github.com/user-attachments/assets/cd439c91-38b4-4df8-adfe-aa1f2ae66a61" />
0187
0188
0189
0190
0191
