Hugonweb | LHE Format Reference

This page describes the LHE file format in a way easier to understand than the way described in ¹ and ² for people younger than the FORTRAN common block generation ;-)

LHE files are XML, beginning with a commented description section. Then a section framed in <init> tags with a line describing the beams and a line for each physics process:

<init>
PDG-ID-Beam1    PDG-ID-Beam2    Energy-Beam1     Energy-Beam2    PDF-Author-Num-Beam1    PDF-Author-Num-Beam2    PDF-ID-Beam1    PDF-ID-Beam2    Weight-Scheme    Num-Processes
xSec(in pb)   xSec-Stat-Error(in pb)   Max-Event-Weight   Process-ID
...same as previous line for more processes
</init>

Next follows a section for each event enclosed in <event> tags. The first line describes the event, while following lines list particles:

<event>
N-Particles-In-Event   ProcessID   Evt-Weight   Scale   QED-Coupling   QCD-Coupling
PDG-ID   Status   First-Mother-Index   Last-Mother-Index   Color-Flow-Index   Anti-Color-Flow-Index   Px   Py   Pz   E   Mass-Gen   Decay-Distance   Spin
...same as previous line for all particles
</event>

See this page for a LHE file splitting script

Particle Status Codes are:

• -1 Incoming
• +1 Outgoing Final State
• -2 Intermediate Space-Like Propagator Defining an $x$ and $Q^2$ Which Should be Preserved
• +2 Intermediate Resonance, Mass Should be Preserved
• +3 Intermediate Resonance, for Documentation Only
• -9 Incoming Beam Paricles at Time t = - \$\inf\$