Linear Collider Detector R&D
Introduction
A linear collider is currently considered to be the next high energy frontier machine after the LHC. It collides electrons and positrons with center-of-mass energies between 250 and 3000 GeV. The advantage of an electron-positron linear collider compared to a hadron collider is the well-defined center-of-mass energy and that the collisons are very clean, as they lack the backgrounds of a hadron machine. The main motivation for a linear collider are high precision measurements of the Higgs boson, the Top quark and all the new physics that the LHC may find. There are currently two major proposals for the linear collider world-wide, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC).
ILC
The ILC is a 30km long machine based on super-conducting cavities (so- called "cold machine") with an center-of-mass energy range between 250 and 1000 GeV It foresees two detectors sharing a single interaction region. The ILC design effort is driven by the GDE (Global Design Effort). No plans for its location have been made.
CLIC
CLIC is a up to 48 km long machine reaching up to 3000 GeV center-of-mass energy. It is based on normal-conducting cavities (warm machine) and uses an innovative two-beam acceleration mode. The CLIC Design study is driven by CERN.
Detectors for a linear collider
As the main motivation of an LC detector is to measure the new physics discovered at the LHC with high precision, the LC detectors will require an unprecedented resolution for measuring particle momenta and energies (a typical event is shown on the right). A LC detector will require
- Energy Resolution- Need factor of 2 better than LEP
- Tracking Resolution- Need factor of 3 better than CMS
- Calorimeter Granularity - Need factor ~200 better than LHC
- Pixel size - Need factor ~20 smaller than LHC
- Material budget barrel - Need factor ~10 less than LHC
- Material budget forward- Need factor ~ >100 less than LHC
Most LC detector designs are build around the Particle Flow Algorithm (PFA) paradigm, which combines the event information in the tracker and the calorimeter. This paradigm has a big impact on the detector design, for example locating the whole calorimeter inside the solenoid coil and also requiring high granularity everywher ein the detector to aide the PFA track-cluster matching.
Group activities
The RAL group long has been involved in the LC detector R&D and has focussed itself on both silicon pixel development, PFA and Vertexing studies and Detector Optimization. The RAL group is also involved in the SiD Detector concept for the ILC and the CLIC Detector for CLIC. The group consists of 7 physicists including postdocs. We had several graduate students working with the group as well as hosting summer students every year.
Silicon pixel R&D
The RAL PPD group has been working on Column-Parallel CCDs and ISIS pixel sensors for a possible Vertex detector and MAPS based Pixel sensors for digital electromagnetic calorimeter. In all these fields the group made leading contributions. The group has extensive testing facilities for silicon pixels as well as access to sensor bonding (wire-bonding and bump bonding) at RAL. The sensor design for all these sensors is done by the CMOS/ASIC group of the RAL Technology department and there is a close collaboration between the groups. More details can be found on the LCFI collaboration and RAL CALICE pages.
Vertexing, detector optimization and benchmarking
The RAL group has also been working on the Vertex reconstruction and detector optimization using current PFA algorithms. A lot the recent performance studies for SiD have been conducted at RAL. The group contributes to the benchmarking by studing Higgs decays to muons and all-hadronic top reconstruction. More details are available.
SiD and CLIC detectors
The RAL group plays a signifcant cole within the SiD detector concept for the ILC and also contributes to the CLIC detector designe effort. More details are available.
