List of previous students

Nicola Orlando
Faten Hariri
Emma Kuwertz
Spyridon Argyropoulo
Sabrina Sacerdoti
Simone Amoroso
Jesper Roy Christiansen
Nathan Hartland
Christian Roehr
Benjamin Watt
Philip Ilten
Nishita Desai
Sercan Sen
Miroslav Myska
Sudha Ahuja
Holger Schulz
Avi Gershan
Aleksander Kusina
Magdalena Slawinska
Flavia Dias
Kenneth Wraight
Irais Bautista Guzman
Sparsh Navin
Paolo Francavilla
Riccardo Di Sipio
Seyi Latunde-Dada
Devdatta Majumder
Martijn Gosselink
Christopher Bignamini
Marek Schönherr
Michal Deak
Noam Hod
Florian Bechtel
Jonathan Ferland
Manuel Bähr
Alexander Flossdorf
Piergiulio Lenzi

The objectives of the LHC physics program include tests of the Standard Model, searches/studies of the Higgs boson(s), and searches for physics beyond the Standard Model. In all three areas polarization of gauge bosons and heavy fermions such as the tau and top quark will play an important role, and yet currently Pythia does not include spin correlation effects except in a few cases. Because of the importance of Pythia and the need for spin handling, it is critical that spin correlation effects are incorporated into Pythia as soon as possible.

Specifically, tau polarization is critically needed, and is not handled natively. An external package, TAUOLA, can be interfaced with Pythia and provide polarizations, but must operate on the event record after Pythia has performed all decays to ensure proper spin correlations. Additionally, the source code for TAUOLA is in FORTRAN, which we strive to get away from.

In the course of this project, a re-implementation of tau production and decay was performed, using the proper helicity matrix elements, inspired by the TAUOLA and Herwig++ handling of taus. This has become a standard part of Pythia and used by the LHC collaborations.

A short writeup of the project can be found in P. Ilten, "Tau decays in Pythia 8", Nucl.Phys. B253 (2014) 255 [arXiv:1211.6730 [hep-ph]]

Philip Ilten subsequently joined the Pythia collaboration, has continued to support and further develop the tau machinery, and has also contributed to other topics.