Based on PYTHIA 6.4.28 with radiative corrections and output modifications to support eic-smear.
Currently hosted on GitLab
Contacts
| Subprocess | # | Description |
|---|---|---|
| SOFT VMD | ||
| V N → V N | 91 | elastic VMD |
| V N → X N | 92 | single-diffractive VMD |
| V N → V X | 93 | single-diffractive VMD |
| V N → X X | 94 | double-diffractive VMD |
| V N → X | 95 | soft non-diffractive VMD low-pT |
| QCD 2→2 | ||
| 96 | semihard QCD 2→2 | |
| RESOLVED (hard VMD and anomalous) | ||
| qq → qq | 11 | QCD 2 → 2(q) |
| q qbar → q qbar | 12 | |
| q qbar → gg | 13 | |
| gq → gq | 28 | |
| qg → qg | 28 | QCD 2 → 2(g) |
| gg → q qbar | 53 | |
| gg → gg | 68 | |
| DIRECT | ||
| γ*q → q | 99 | LO DIS |
| γ*T q → qg | 131 | (transverse) QCDC |
| γ*L q → qg | 132 | (longitudinal) QCDC |
| γ*T g → q qbar | 135 | (transverse) PGF |
| γ*L g → q qbar | 136 | (longitudinal) PGF |
VMD Vector Meson Dominance, describing the elastic diffractive
production of Vector Mesons.
QCDC: QCD-Compton, radiation of a gluon
from incoming or outgoing quark lines.
PGF: Photon Gluon Fusion.
In the standard setup in the singularity cvmfs environment or at BNL, the code, executable, steering files, plus shared libraries for PYTHIA and RADGEN, can be found in
$EICDIRECTORY/PACKAGES/PYTHIA-RAD-CORR
$EICDIRECTORY/lib
$EICDIRECTORY/bin
The executable pythiaeRHIC (in the future most likely renamed to pythia-eic) is the program for running PYTHIA.
It is based on PYTHIA 6.4.28 and was modified to include radiative corrections using RADGEN.
To run, the executable reads options from standard input and is controlled via steering cards and input redirection, with optional output redirection to a log file. The name of the output file is specified in the steering card.
pythiaeRHIC < STEER_FILE > out.log
A practical example, assuming $EICDIRECTORY was set and the package installed as above, is:
$EICDIRECTORY/bin/pythiaeRHIC < $EICDIRECTORY/PACKAGES/PYTHIA-RAD-CORR/STEER-FILES-Other/ep_noradcor.20x250.quicktest
The output ASCII format is described below.
pythiaeRHIC < input.data_make-radcor.eic
$EICDIRECTORY/PACKAGES/PYTHIA-RAD-CORR/radgen
Files are named “radgen(electron beam energy)x(proton beam energy)”, for example “radgen10x100” or “radgen4x100”.
To run the code with radiative corrections, simply change the steer file to either input.data_radcor.eic or input.data_radcor.VM.eic and type pythiaeRHIC < input.data_radcor.eic > XXX.log
switch for rad corrections !* 0: no, 1: yes, 2: generate lookup table
However, settings for x and y have to be appropriate. The following should work in most cases:
1e-05,0.99 ! xmin and xmax
5e-03,0.99 ! ymin and ymax
A variety of steering files can be found in the STEER-*
directories. Which ones appropriately reflect the physics you wish to
implement is beyond the scope of this document. Please contact the EIC
UG for advice.
pyMaineRHIC_v2.f is the main program used to generate pythiaeRHICepythiaMain.cpp and UsingCardPythiaMain.cpp are C++ implementations using either the class interface functions or the same steering file as the fortran driver. They are not currently producing standard ASCII output however and are meant as demonstrators only. The reason for this is that output generation is hard-coded into multiple places inside the pythia and radgen fortran files.The output file is in a text format which has the following structure:
| I: | 0 (line index) |
|---|---|
| ievent: | eventnumber running from 1 to XXX |
| genevent: | trials to generate this event |
| subprocess: | pythia subprocess (MSTI(1)), for details see table above |
| nucleon: | hadron beam type (MSTI(12)) |
| targetparton: | parton hit in the target (MSTI(16)) |
| xtargparton: | x of target parton (PARI(34)) |
| beamparton: | in case of resolved photon processes and soft VMD the virtual photon has a hadronic structure. This gives the info which parton interacted with the target parton (MSTI(15)) |
| xbeamparton: | x of beam parton (PARI(33)) |
| thetabeamparton: | theta of beam parton (PARI(53)) |
| truey, trueQ2, truex, trueW2, trueNu: | are the kinematic variables of the event. |
| If radiative corrections are turned on they are different from what is calculated from the scattered lepton. | |
| If radiative corrections are turned off they are the same as what is calculated from the scattered lepton | |
| leptonphi: | phi of the lepton (VINT(313)) |
| s_hat: | shat of the process (PARI(14)) |
| t_hat: | Mandelstam t (PARI(15)) |
| u_hat: | Mandelstm u (PARI(16)) |
| pt2_hat: | pthat^2 of the hard scattering (PARI(18)) |
| Q2_hat: | Q2hat of the hard scattering (PARI(22)), |
| F2, F1, R, sigma_rad, SigRadCor: | information used and needed in the radiative correction code |
| EBrems: | energy of the radiative photon in the nuclear rest frame |
| photonflux: | flux factor from PYTHIA (VINT(319)) |
| nrTracks: | number of tracks in this event, includes also virtual particles |
| I: | line index, runs from 1 to nrTracks |
|---|---|
| K(I,1): | status code KS (1: stable particles 11: particles which decay 55; radiative photon) |
| K(I,2): | particle KF code (211: pion, 2112:n, ….) |
| K(I,3): | line number of parent particle |
| K(I,4): | normally the line number of the first daughter; it is 0 for an undecayed particle or unfragmented parton |
| K(I,5): | normally the line number of the last daughter; it is 0 for an undecayed particle or unfragmented parton. |
| P(I,1): | px of particle |
| P(I,2): | py of particle |
| P(I,3): | pz of particle |
| P(I,4): | Energy of particle |
| P(I,5): | mass of particle |
| V(I,1): | x vertex information |
| V(I,2): | y vertex information |
| V(I,3): | z vertex information |
For each subsequent event, lines 7 through X repeat analogously.
The recommended way is to create and use a ROOT tree with the BuildTree function and other tools provided by eic-smear.
Some guidelines regarding Monte Carlo normalization can be found here.
ROOT supports an interface to PYTHIA via the class TPythia6. This allows PYTHIA to be configured, run and analysed from within a ROOT session, which can be a more convenient than using PYTHIA as a separate programme. The EIC installations of ROOT support TPythia6, but be aware that the version of PYTHIA interfaced with ROOT is the “vanilla” distribution, and hence lacks the EIC additions. If you require these for your analysis you should only use the standalone pythiaeRHIC program. This means you miss:
It is recommended to take advantage of the pre-installed versions on the lab farms or the available stand-alone singularity or escalate containers.
However, the package can also be built using cmake and make.
(Adapt directories etc as appropriate.)
cd ${EICDIRECTORY}/PACKAGES
git clone https://gitlab.com/eic/mceg/PYTHIA-RAD-CORR.git
cd ${EICDIRECTORY}/PACKAGES/PYTHIA-RAD-CORR
mkdir build; cd build
cmake ../ -DCMAKE_INSTALL_PREFIX=${EICDIRECTORY}
make -j 8 install
This will produce warnings of the form
Warning: $ should be the last specifier in format at (1)
which should be okay (it is a g77 extension allowed by gfortran).
Executables require LHAPDF5 installed and links executables against it.
The code implemented in PYTHIA to calculate radiative corrections is called RADGEN. The writeup on it can be found here. The following steps have been done to implement it in PYTHIA:
Webpages with codes:
Other references: M. Arneodo, (Turin U. & INFN, Cosenza) , A. Bialas, (Jagiellonian U.) , M.W. Krasny, (Paris U., VI-VII & Paris U., VI-VII) , T. Sloan, (Lancaster U.) , M. Strikman, (Penn State U.) . Sep 1996. 40pp. To be published in the proceedings of Workshop on Future Physics at HERA, Hamburg, Germany, 25-26 Sep 1995. In Hamburg 1995/96, Future physics at HERA 887-926. e-Print: hep-ph/9610423 and the references 5 and 6 in this article. To find them check here.