DEEPGen event generator

Deep Exclusive Electro- and Photo-production Generator

This event generator is intended to study some exclusive processes at kinematics of JLab current and future experiments. The current version (4.0) supports deep exclusive photo- and electro- production of lepton pairs and photons. These reactions involve Deeply Virtual Compton Scattering (DVCS), Timelike Compton Scattering (TCS) and Double Deeply Virtual Compton Scattering (DDVCS).

For more details and history, look at the "old" webpage of the event generator (2015-2018) DDVCS and TCS event generator

How to run

Generate events

Go to the directory where you copied the generator binary files, then:

1) ./set.csh

2) modify parameters in (process).input file

3) ./DEEPGen (process) (index) (seed)

- just do: ./DEEPGen to see the available options

- (process) = dvcs, tcs, ddvcs, ps_eeel_fix, ps_eephoto_fix, ps_vcs_fix (...) see input options - (index) = run number index of the output file - (seed) = random seed, only needed in batch mode

Process options

1. tcs = generation of TCS+BH 5 or 6-fold (un)polarized differential cross section for p and n weights in dt.dQ'2.dphi.dtheta

2. ddvcs = generation of DDVCS+BH 7-fold unpolarized differential proton cross section weights in dxbj.dt.dQ2.dQ'2.dphiL.dphi.dtheta

3. dvcs = generation of DVCS+BH 4- or 5-fold (un)polarized differential proton cross section for p and n weights in dxbj.dt.dQ2.dphiL

4. vcs = generation of VCS+BH (in progress, generated BH now)

11. ps_ee_photo_fix = phase space generation for dilepton pair photoproduction (real photon) in fix target experiment

12. ps_eeel_fix = phase space generation for dilepton pair electroproduction in fix target experiment

13. ps_vcs_fix = phase space generation for gamma electroproduction in fix target experiment

21., 22., 23. = collider mode (in progress)

Normalization

For each generated file, save the "TrueEventNumber" of the last generated event. It is the number of event which ideally where thrown in a N-D hypercube, if there where no kinematic cuts from correlations affecting the distributions.

The weights (W_tot_unpol...) are polarized or unpolarized cross sections. They have to be multiplied by the luminosity and the dimension of the phase space to get the number of counts in a specific experiment. Beam energy is generated flat for TCS from a photon beam and is fixed for DVCS and DDVCS. To get the proper energy distribution for TCS, rescale the flat distribution by a bremsstrahlung or any other profile normalized function.

For asymmetries (BSA...): no normalization needed, just divide by the number of events in the bin to get an average.

Phase space factor

Definition ΔA = A(max) - A(min) from user input file

• TCS (electron or photon)

event weights: dσ/(dt dQ'² dθ dφ)

phase space factor: luminosity*Δ(t)*Δ(Q'²)*Δ(θ)*Δ(φ) / Σ(TrueEventNumber of last event of each files)

• DVCS:

event weights: dσ/(dt dQ² dxbj d_φ)

phase space factor: luminosity*Δ(t)*Δ(Q²)*Δ(Xbj)*Δ(φ_L) / Σ(TrueEventNumber of last event of each files)

• DDVCS:

event weights: dσ/(dxbj dt dQ² dQ'² dθ dφ dφ_L)

phase space factor: luminosity*Δ(t)*Δ(Q²)*Δ(Xbj)*Δ(Q'²)*Δ(θ)*Δ(φ)*Δ(φ_L) / Σ(TrueEventNumber of last event of each files)

Files

Output

Name: DEEPGen_(xxx).root = root file DEEPGen_hep_(xxx).root = HEP file (text) DEEPGen_kin_(xxx).root = relevant information to read associated to the HEP file (text)

Generic output root files contain 2 Trees:

"SIM_Tree" contain all generated events important information such as 4-vectors for incoming and outgoing particles, kinematic invariants, event weights, event number, polarization information. We detail below the content for each supported process. Note that depending polarization option and event weighting options (phase space or full generation), some of the Tree Branch may not be present.

"Dump_Tree" contain additional information such as 4-vectors in different reference frames, initial options... Only the first 50 events are printed.

HEP files (see standard HEP format). Associated files can be related by the line numbers.

TCS mode

ALV_minus_lab = 4-vector or outgoing lepton- in lab frame (all 4-vector "ALV_xxx" are arrays containing: E, px, py, pz) ALV_plus_lab = outgoing lepton+ in lab frame ALV_gamma_in = incoming photon in lab frame ALV_el_in = incoming electron in lab frame (case of quasi-real beam) ALV_Recoil_lab = recoil proton in lab frame

Get output files

Depending options, the event output is a ROOT and/or HEP file. We advice to generate Root files in order to save as much information as possible in a more efficient way. If a specific input format is needed to plug the files to Geant (or other) simulation framework, the generated events can then be easily printed through a loop in any format needed, with any weighting option.

Public version

Binaries

The generator binary files are available to users of the JLab ifarm. Copy the whole directory to a place on your home directory. For test purpose, also see examples that where generated with specific options.

- Binaries for the generator are in: /work/halla/solid/mboer/public/Generator_publicversion/version4

- Example files (root file + used input file) are in: /work/halla/solid/mboer/public/Generator_publicversion/examples/version4 look at directories for the different processes.

Old versions and history of the generator

The "old" webpage of the event generator (2015-2018), for versions 1.0 to 3.1, is available DDVCS and TCS event generator

Contact

For all questions such as how to use the generator, new versions and example files, please contact Marie Boër, mboer@jlab.org