VINCIA User Reference

October 2017 © The VINCIA Collaboration

The VINCIA code is a plugin to the high-energy physics event generator PYTHIA 8. It is based on the dipole-antenna picture of Quantum Chromodynamics (QCD) and focusses on describing jets and jet substructure with high precision.

The current version includes both initial- and final-state showers, with some limitations; decays of coloured resonances (eg top) are not yet handled, nor are any non-QCD shower branchings included.

LO matrix elements can be incorporated in the evolution, as process-dependent 2→n antenna functions. In hard parts of phase space, these functions generate matrix-element corrections to the shower. In soft parts, they should improve the logarithmic accuracy of it, via unitarity.

The remaining perturbative uncertainties are estimated by systematic (and automated) variations of scales, shower functions, evolution variables, etc. In the automated mode, a vector of output weights is produced for each event, the central value of which is unity (for an ordinary unweighted event sample), with the uncertainty variations spreading out around it. The calculation is significantly faster than generating N separate samples, and there is only one event sample to analyse, pass through detector simulations, etc.

Event Generation. When activated, VINCIA replaces the internal PYTHIA parton cascades. Hadronisation is performed as usual in PYTHIA, with the Lund string fragmentation model. Instead of the PYTHIA initialisation step in the main program the same function is called on the VINCIA object. In addition, runtime displays with plots updated in realtime can be created using the VINCIAROOT interface.

This documentation contains brief descriptions of each of the user-specifiable parameters of the VINCIA code, together with instructions how to install, link, and initialise it. Use the menu to the left to navigate. These files are purely for documentation and should not be modified by the user. Instead, see the section on Initialisation for how to set and change parameters.

Types of Parameters

As in PYTHIA 8, there are 4 types of parameters:

Note: both PYTHIA and VINCIA interpret parameter names in a case-insensitive (but spelling-sensitive!) way.

Quoting Results obtained with VINCIA and PYTHIA

To ensure accurate reproducibility, when quoting VINCIA results, please state both the exact PYTHIA and VINCIA versions used, along with any relevant non-default settings (for both programs). On plots, please give both PYTHIA and VINCIA versions.

VINCIA relies on PYTHIA 8 for both technical aspects (everything from four-vectors and the event record to its particle and settings database structures) and physics (e.g., particle decays and hadronisation). When citing the VINCIA code, please respect the work of the PYTHIA authors by including a reference to PYTHIA as well.

The main references for VINCIA and PYTHIA 8 are, respectively:

We also encourage users to take a look at the MCnet Guidelines for event generator authors and users.

The VINCIA Collaboration

The authors of the current version, taking active responsibility for code development and day-to-day maintenance, are

In addition, the following people have made significant individual contributions to the underlying formalism and code development of VINCIA:

Name

The name VINCIA stands for "VIrtual Numerical Collider with Interleaved Antennae". The naming of VINCIA is intended to allude to a progression from PYTHIA - a name originating in ancient Greece - to the renaissance era of Leonardo da Vinci. The logo of VINCIA is the "Vitruvian Man", by da Vinci, a choice which also reflects the combination of art and accuracy which is necessary to write a good event generator. Classical antiquity is still indirectly represented, via the namesake of the logo, Vitruvius, a first-century (BC) Roman author, architect, and engineer.

Licence

VINCIA is licenced under the GNU GPL version 2. Please respect the MCnet Guidelines for Event Generator Authors and Users.