EPOS4: A Monte Carlo tool for simulating high-energy scatterings

Based on the requirement to have at LHC energies a formalism with multiple scatterings happening rigorously in parallel, in pp and AA collisions, we managed for the first time to get a fully selfconsistent scheme, compatible with the factorization approach, but allowing to go much beyond. Theoretical consistency (not fitting data) led to the implementation of variable saturation scales, where the latter depend in a well-defined way on the number of subscatterings. This has major consequences, in particular a hardening of events with increasing multiplicity.

New: EPOS4HQ

Treating heavy flavor properly

Pure EPOS4 creates heavy flavor partons in primary interactions. Via the HQ module, they interact with the plasma created by EPOS4, and a coalescence approach allows under certain conditions to combine plasma partons and HF partons to produce HF hadrons. Alternatively, fragmentation occurs. Parameters have been retuned, considering a very large base of data on light flavor results, but also many HF observables were considered, using in all cases the full EPOS4HQ.

See [The EPOS4HQ project](highlights/epos4hq.html)

EPOS4 in short

A pedagical overview

The EPOS4 approach has already been presented in a series of “technical papers”, providing on 160 pages all the details. There are many (solved) complex problems, but despite all these technicalities, and somewhat hidded behind these, there are really new and unique concepts. There are some recents attempts to present these quite fundamental concepts in a pedagigical fashion:

See [New concepts](highlights/concepts.html)

The basis of EPOS4

A series af four (technical) papers

The fundamental concepts of the approach are very simple (parallel scattering, pQCD ladders, microcanonical decay), but the technical difficulties to realize these issues is quite invoved. A very detailed (somewhat technical) writeup has been done in order to explicitely discuss all the features which are finally translated intro computer code.

See [The basis of EPOS4](highlights/basis.html)

EPOS4 represents a change of paradigm concerning proton-proton scattering, going beyond the conventional factorization picture. The approach is unique, the only one to implement a rigorously parallel scattering scheme, by fully respecting energy-momentum conservation. It is also unique as it connects saturation and factorization.

There ad-hoc assumptions, many details may be improved, but the general formalisms seems to be mandatory, driven by general principles as the parallel scattering requirement and energy-momentum conservation.