The student (Waltteri Leinonen, Nijmegen) will work on a twofold project in the Flavour Tagging area. On one side, he will concentrate on extending the functionality of the existing CDI framework with the aim to deliver improved calibration results to the ATLAS analyses. Support for combined calibration of all the jet flavours will be added with the goal to better treat the correlation of the common sources of systematic uncertainties. In parallel a review of the pruning techniques to reduce the number of nuisance parameters will be performed.
In addition, the task involves maintaining the CDI framework used to deliver calibration results to the collaboration, extending the corresponding set of validation tools. Walter will also work on improving the documentation of the comparison between calibration of fixed-cut working points and that of the corresponding tag weight bins in PCBT. This will allow a better communication, between physics analysis developers, on the peculiarities of the two approaches. Any studies needed for this part of the project can be carried out using release 21.
On the other side, he will work on the development of a low-level algorithm targeting features useful to identify charm jets, e.g. partial reconstruction of their exclusive decay chains. The implementation in Athena will have to produce and prepare such variables so that they can be used by high-level taggers. The studies will be based on release 22.
The progress will be reported in the Flavour Tagging calibration meetings (part 1) and algorithms meetings (part 2), and the corresponding software will be made available in GitLab. The tagger development work will be documented in an internal note while the CDI related work will be documented in both GitLab repo (SW details) and twiki (user instructions).