VINCIA User Reference

July 2011 © P. Z. Skands, W. T. Giele, D. A. Kosower, J. Lopez-Villarejo, M. Ritzmann
The VINCIA code is a shower plugin to the high-energy physics event generator PYTHIA 8. It is based on the dipole-antenna picture of QCD and focusses on describing quark and gluon radiation with high precision. It is currently implemented for QCD final-state showers and includes mass effects for charm and heavier quarks.

Tree-level full-colour matrix elements (from MADGRAPH) are automatically incorporated and are re-interpreted as process-dependent 2→n antenna functions. In hard parts of phase space, these functions generate tree-level matrix-element corrections to the shower. In soft parts, they should improve the logarithmic accuracy of it.

VINCIA also has extensive (and automated) possibilities for estimating the remaining uncertainties by systematic variations of 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 (corresponding to an ordinary unweighted event sample), with the uncertainty variations spreading out around it.

When activated, VINCIA replaces the internal PYTHIA parton cascades. Hadronization is performed as usual in PYTHIA, with the Lund string fragmentation model. The rest of the run proceeds as a normal PYTHIA 8 run, i.e., using the same functions to initialize, generate, and store events as usual.

This documentation contains brief descriptions of each of the user-specifiable parameters of the VINCIA code, together with instructions how to install, link, and initialize 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 Initialization for how to set and change parameters.

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.

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.

Licence

VINCIA is licenced under the GNU GPL version 2. Please respect the MCnet Guidelines for Event Generator Authors and Users. The name VINCIA stands for "Virtual Numerical Collider with Interleaved Antennae".