The Linear Collider Flavour Identification Collaboration consists of particle physicists from five British academic institutions. The collaboration is pursuing an ambitious research and development programme to develop a pixel-based vertex detector for heavy flavour identification at the International Linear Collider. The main areas of research are:
Developing and testing new sensor technology suitable for the International Linear Collider;
Designing readout electronics for the new sensors;
Investigating mechanical options for ultra-thin detector elements.
Bristol University
Glasgow University
Liverpool University
Oxford University
Rutherford Appleton Laboratory
The International Linear Collider (ILC) is a large particle physics facility that is currently being planned. It will consist of two head-to-head linear accelerators, colliding beams of electrons and positrons at energies from 91 to 500 GeV (upgradable to 800-1000 GeV). A large experiment will surround the interaction region to observe the results of the collisions. The complete collider will be about 30 km long and is expected to start operating in about ten years (around 2015).
The Linear Collider, along with the LHC currently under construction at CERN, will probe matter and forces at the most fundamental scales we can reach. Many hypothesised new theories and particles could be discovered and investigated. Examples include the Higgs Boson and Supersymmetry.
The vertex detector is the part of the physics experiment closest to the interaction point, where the incoming particles collide. Its purpose is to measure the outgoing tracks of particles produced in the collision sufficiently accurately to tell whether they were produced directly at the point of collision (the primary vertex), or produced through subsequent decays of unstable particles a short distance from the primary vertex.
Heavy, unstable particles are produced in high energy particle collisions. Among these, tau leptons and particles containing b or c quarks typically travel a few millimetres from the primary vertex before decaying and forming a secondary vertex. Using the information from the vertex detector, the presence and identity of such particles in a given collision can be deduced.
Particles passing through the detector will interact with the material it is made from, disturbing their trajectories and possibly knocking secondary high-energy particles out of it, thus affecting the measurement. A detector has to minimise these effects by reducing the material present without compromising the detection efficiency and accuracy.
Historically, the LCFI collaboration has concentrated on research into Charge Coupled Devices (CCDs). CCD pixel arrays can register particle hits over a large area with high precision and low power consumption, and they have been proven to work in the previous generation of e+e- collision experiments (SLD). The Linear Collider environment will require CCDs that are faster (up to 50 MHz), more radiation hard and with a lower power consumption than those that are currently available.
The collaboration is also beginning to look at alternative sensor types including Imaging Sensors with In-situ Storage (ISIS) and Flexible Active Pixel Sensors (FAPS).