Identification of SUSY events with displaced vertices
Project Description
This project consists of performing physics analysis tasks
with the ATLAS detector of the Large Hadron Collider at CERN.
A number of interaction terms that may appear in
supersymmetric models allow the lightest supersymmetric particle to decay.
Since the couplings involved are probably small such decays may lead
to spectacular signatures of several high pT jets and/or leptons not
originating from the main interaction point.
The aim of this project is to identify such events both in terms
of their acceptance in the trigger and the reconstruction of
their characteristic properties.
Studies will focus on decays in the inner detector allowing
to reconstruct the tracks of the particles produced in the decay.
The tasks include activities in the areas of Trigger and Reconstruction.
Tasks
Work on the Reconstruction
Due to the special nature of the considered events
detailed studies of the ATLAS track finding and
vertex finding algorithms have to be performed.
For the smallest decay length the main background will come from
secondary vertices as resulting from pile-up and in b-jet events.
In general b-tagging techniques may be employed to identify the displaced LSP decays.
These standard techniques have to be tuned and extended for their
application to the signal and ways to separate it from the Standard Model
background have to be explored.
Work on the Trigger
For most analyses in the ATLAS experiment the trigger system is a crucial ingredient.
It has to selects events online with the LHC bunch crossing rate
and must therefore operate extremely fast. Its purpose is to reject uninteresting
events and keep only the relevant ones. In our scenario we are interested in events
with long-lived lightest supersymmetric particles which travel across many layers of the
inner detector before they decay into lighter stable particles.
The resulting displaced decay vertex
is a characteristic signature in this supersymmetric scenario that can be used
to trigger on such events. Assessing the efficiency of the currently availably tracking
trigger algorithms using displaced vertices will help to optimize the selection cuts and
also the performance of the tracking trigger algorithms. A mandatory boundary condition
of all trigger algorithms is that it has to be fast. Therefore improving the discrimination
power of a trigger algorithm should not introduce additional processing time. In the
inner detector this is particularly challenging due to the high number of readout elements
and the large background from pile-up events.
What you will learn
supersymmetry
details of the ATLAS trigger/reconstruction algorithms
analysis techniques
analysis tools (ROOT + Atlas specific tools).
Required Knowledge
No prior knowledge of supersymmetry is required.
Introductory knowledge of particle physics and programming
experience (especially in C++) would be advantageous.
Contacts
Ignacio Aracena
Claus Horn
Last modified: Fr Sep 14 15:16:47 PDT 2007