starlight

STARlight is a Monte Carlo that simulates two-photon and photon-Pomeron interactions between relativistic nuclei and protons. It produces a variety of final states. For two-photons, it simulates lepton pairs and a variety of mesons. A list of available channels may be found here. For photonuclear interactions, it models coherent and incoherent vector mesons production. A list of available channels may be found here.

A write-up of the code has been published recently:

S.R. Klein, J. Nystrand, J. Seger, Y. Gorbunov, J. Butterworth, Comp. Phys. Comm. 212 (2017) 258.

More details on the physics behind STARlight can be found in these publications:

S.R. Klein, J. Nystrand, Phys. Rev. C 60 (1999) 014903 (coherent vector meson production).
A.J. Baltz, S.R. Klein, J. Nystrand Phys. Rev. Lett. 89 (2002) 012301 (vector meson production accompanied by exchange of additional photons leading to nuclear break up).
S.R. Klein, J. Nystrand, Phys. Rev. Lett. 92 (2004) 142003 (photoproduction of vector mesons in pp collisions).
A.J. Baltz, Y. Gorbunov, S.R. Klein, J. Nystrand, Phys. Rev. C 80 (2009) 044902 (two-photon interactions).

The review article C.A. Bertulani, S.R. Klein, J. Nystrand, Ann. Rev. Nucl. Part. Sci. 55 (2005) 271 provides more general information on the physics of ultra-peripheral collisions.

To install & run STARlight in a *nix based environment, follow these steps(README):

Download the package from the tracker on the left sidebar or from here. The version in the example might be outdated.

wget 'https://starlight.hepforge.org/downloads?f=starlight_r300.tar'
mv 'downloads?f=starlight_r300.tar' starlight_r300.tar
tar xvf starlight_r300.tar

Alternatively, one may obtain the latest version via svn---no longer the case--will update to new phab link.

svn co http://starlight.hepforge.org/svn/trunk

Change to the installation directory of your choice

mkdir /home/my/installation/dir
cd /home/my/installation/dir

Setup the compilation with cmake

cmake /path/to/trunk

Compile with (g)make

gmake

Setup the input file, slight.in, for your simluation needs

cp /path/to/trunk/config/slight.in .
vim slight.in

./starlight >& output.txt&

Interpreting the output

For more information and special scenarios, such as running with PYTHIA or DPMJET, consult the README files located in trunk/

Two-Photon Channels
Particle	Jetset ID
e⁺e^- pair	11
µ⁺µ^- pair	13
τ⁺τ^- pair	15
τ⁺τ^- pair, polarized decay	10015*
ρ⁰ pair	33
a₂(1320) decayed by PYTHIA	115
η decayed by PYTHIA	221
f₂(1270) decayed by PYTHIA	225
η' decayed by PYTHIA	331
f₂(1525) → K⁺K^-(50%),K⁰K̄⁰(50%)	335
η_c decayed by PYTHIA	441
f₀(980) decayed by PYTHIA	9010221

Vector Meson Channels
Particle	Jetset ID
ρ⁰ → π⁺π^-	113
ρ⁰ → π⁺π^- and direct π⁺π^- production, including the interference.	913
ω → π⁺π^-	223
φ → K⁺K^-	333
J/Ψ → e⁺e^-	443011
J/Ψ → µ⁺µ^-	443013
Ψ(2S) → e⁺e^-	444011
Ψ(2S) → µ⁺µ^-	444013
Υ(1S) → e⁺e^-	553011
Υ(1S) → µ⁺µ^-	553013
Υ(2S) → e⁺e^-	554011
Υ(2S) → µ⁺µ^-	554013
Υ(3S) → e⁺e^-	555011
Υ(3S) → µ⁺µ^-	555013
ρ' → π⁺π^-π⁺π^-	999

Reading the output

For each event, a summary line is printed, with the follwing format

EVENT: n ntracks nvertices ,
where n is the event number (starting with 1), ntracks is the number of tracks in the event, and nvertices is the number of vertices in the event (STARlight does not currently produce events with more than one vertex).

This is followed by a line describing the vertex, of the format

VERTEX: x y z t nv nproc nparent ndaughters ,
where x, y, z and t are the 4-vector components of the vertex location, nv is the vertex number, nproc is a number intended to represent physical process (always set to 0), nparent is the track number of parent track (0 for primary vertex) and ndaughters is the number of daughter tracks from this vertex.

This is followed by a series of lines describing each of the daughter tracks emanating from this vertex. Each track line has the format

TRACK: GPID px py py nev ntr stopv PDGPID ,
where GPID is the Geant particle id code, px, py and pz are the three vector components of the track's momentum, nev is the event number, ntr is the number of this track within the vertex (starting with 0), stopv is the vertex number where track ends (0 if track does not terminate within the event), and PDGPID is the Monte Carlo particle ID code endorsed by the Particle Data Group.