Speaker
Mr
Giacinto Piacquadio
(Physikalisches Institut - Albert-Ludwigs-Universität Freiburg)
Description
A new inclusive secondary vertexing algorithm which exploits the topological
structure of weak b- and c-hadron decays inside jets is presented. The primary goal
is the application to b-jet tagging. The fragmentation of a b-quark results in a
decay chain composed of a secondary vertex from the weakly decaying b-hadron and
typically one or more tertiary vertices from c-hadron decays. The decay lengths and
charged particle multiplicities involved in these decays, as well as the instrumental
resolution, do not allow to separately reconstruct and resolve these vertices
efficiently using conventional secondary vertexing algorithms based on the assumption
of a common geometrical vertex. These difficulties are partially overcome in the
algorithm presented in this paper, that is based on the hypothesis that the primary
event vertex and the vertices of the weak b- and c-hadron decays lie on the same
line, the flight direction of the b-hadron. The algorithm provides detailed
information on the topology of the decay cascade, also allowing the reconstruction of
topologies with only one charged particle from a b- and c-hadron decay, respectively,
which are difficult to access for conventional algorithms.
The algorithm based on this hypothesis is implemented mathematically as an extension
of the Kalman Filter formalism for vertex reconstruction and technically as a set of
flexible software modules integrated in the ATLAS software framework Athena, which
make use of the existing Event Data Model for vertexing and B-Tagging. The
application of the algorithm to b-jet tagging and the impact on its performance is shown.
| Submitted on behalf of Collaboration (ex, BaBar, ATLAS) | ATLAS |
|---|
Primary authors
Dr
Christian Weiser
(Physikalisches Institut - Albert-Ludwigs-Universität Freiburg)
Mr
Giacinto Piacquadio
(Physikalisches Institut - Albert-Ludwigs-Universität Freiburg)
