Tracking
5.0.1
Tracking
Tracking
5.0.2
Tracking Table of Contents
Table of Contents and Overview .................................................................................... 5.0
42. Development and Testing Linear Collider Forward Tracking (LCRD; Michael
Strauss)............................................................................................................................ 5.1
43. Development of a GEM based Forward Tracking Prototype for the NLC (LCRD; Lee
Sawyer) ........................................................................................................................... 5.2
44. Straw Tube Wire Chambers for Forward Tracking in the Linear Collider Detector
(UCLC; Keith Baker) ...................................................................................................... 5.3
45. Fabrication, investigation and simulation of Gas Electron Multipliers for charged
particle tracking (LCRD; Peter Fisher) ........................................................................... 5.4
46. Studies of the Use of Scintillating Fibers for an Intermediate Tracker which Provides
Precise Timing and Bunch Identification: Progress Report and Request For Funds
(LCRD; Rick VanKooten) .............................................................................................. 5.5
47. Tracking Detector R&D at Cornell and Purdue Universities (UCLC; Dan Peterson)
......................................................................................................................................... 5.7
48. Tracking simulation studies and alignment system R&D (UCLC; Keith Riles) ...... 5.8
49. Tracking Software Optimization for the Silicon Detector Option (LCRD; Milind
Purohit) ........................................................................................................................... 5.9
50. R& D Towards a Low - Mass Silicon Strip Central Tracker for the LC (LCRD; Bruce
Schumm) ....................................................................................................................... 5.10
51. R&D towards a Silicon drift detector based main tracker for the NLC-SD option
(UCLC; Rene Bellwied) ............................................................................................... 5.11
52. Negative Ion TPC as the NLC main tracker (UCLC; Giovanni Bonvicini) ........... 5.12
Tracking
5.0.3
Overview of Tracking Proposals
Experimental physics goals for a future Linear Collider create challenges for charged
particle tracking, particularly in regard to momentum resolution, multi-track separation,
and the precise and efficient reconstruction of tracks at forward angles. The momentum
resolution is driven in part by the need to measure the di-lepton recoil mass spectrum in
the process e  e   HZ , with Z      . Ensuring that the mass spectrum be limited
by the beam energy spread, and not by momentum resolution, requires that
 (1 / pt )  2  10 5 GeV 1 [1]. The momentum-resolution target is also driven by the
need to measure high-energy isolated charged particles [2], expected to be prevelant in
new physical processes (supersymmetric interactions, heavy lepton production,
production of leptopquarks, etc.), as well as Standard Model processes with a propensity
to produce high-energy leptons ( tt , W W  , ZZ , l  l  production). All in all, the
requirement on the precision of the momentum measurement is an order of magnitude
more demanding than that of existing collider detectors. Clearly, the full exploitation of
the physics potential of a Linear Collider places stringent demands on the performance of
the tracker.
The Linear Collider presents several other challenges that are more demanding than that
faced at previous electron-positron colliders. Linear Collider backgrounds are expected to
be somewhat worse than those experienced at previous high-energy electron-positron
colliders, while hadronic jets associated with underlying parton-level processes will be
denser and more energetic. Accurate reconstruction of hadronic jets in this environment
will be an essential tool in unraveling the physics of the Linear Collider. Particle-flow
algorithms, discussed in the section on calorimetry, are only effective to the extent that
charged tracks are individually accounted for and associated with discrete calorimetric
clusters. Achieving the jet-energy resolution promised by the energy-flow approach will
require excellent charged-particle pattern recognition, superior two-track separation
resolution, as well as the precise determination of particle trajectories as they exit the
tracking volume.
Forward (high cos ) tracking will be of particular importance at the Linear Collider.
Flagship supersymmetric processes (selectron and chargino production) have the
potential to exhibit forward-peaked cross sections. The process of diboson (WW and ZZ)
production, which may prove essential to uncovering the secret of electroweak
symmetry-breaking, is also increasingly forward-peaked at high energies, with the
corresponding jets more tightly collimated about the underlying parton trajectory. Finally,
adequate modeling of beamsstrahlung requires a precise in-situ differential luminosity
measurement, which in turn requires that the acolinearity of bhabha-scattered electrons be
measured to the accuracy of ~0.01 mrad.
Tracking
5.0.4
Overview of Tracking Proposals
Tracking proposals of the LCRD groups are coordinated with those of the NSF-based
UCLC groups, and cover three broad areas. Work on the simulation of physics processes
is oriented towards establishing tracker performance criteria that are required for the full
realization of the physics potential of the Linear Collider. Simulation of detector response
and performance is focused upon assessing the capabilities of specific tracking scenarios,
and of their ability to achieve the established performance criteria. The goal of research
and development work on instrumentation hardware is to provide a proof-of-principle for
the more promising of those tracking scenarios. All three of these components are
essential for the design and optimization of a tracker that will be capable of exploiting the
great potential of the Linear Collider physics program.
At this point, the choice of technology for the central tracker remains open. The most
mature candidates are a large-volume TPC, an axial drift chamber, and an all-silicon
tracker, although the axial drift chamber seems to be falling out of favor at this point. The
baseline designs, established in March 2001, employ disks of silicon strips in the forward
region. This choice, however, was not motivated by studies (other than closed-form
calculations of tracking errors expected under ideal circumstances), and a broad and
open-minded R&D effort is called for. Groups contributing to the joint LCRD/UCLC
proposal are considering, in addition to the basline choice of silicon strips, CCD and
active pixel layers, and both GEM- and straw-tube based forward tracking.
Physics Simulation
Physics simulations have clarified many of the design goals for the LC detector,
including the central tracker. Studies of sparticle production and decay are needed to
establish more quantitatively the physics requirements on momentum resolution,
including that of low momentum tracks (A).
A. UCLC Tracker simulation studies and alignment
5.8
system R&D
Keith Riles
U Michigan
Silicon Central Trackers
Silicon central trackers have the advantage of compactness, and may prove to be
particularly good at tracking particles in dense jets. Two groups plan to develop the
design for a low-mass silicon strip detector optimized for the environment and physics
context of the Linear Collider. One (A) will address pattern recognition in such a device.
They will start by developing stand-alone pattern recognition in a CCD vertex detector,
and then incorporate reconstruction algorithms for use with an axial-only silicon strip
tracker. Another group (B) will develop a long shaping-time readout chip that limits its
period of operation to the small fraction of time that beams are present in the machine,
Tracking
5.0.5
and work with an international group to develop and test a prototype two-meter-long
silicon detector ladder.
The silicon drift detector is an attractive option because it is compact and offers 3-D
space points, which should make pattern recognition more robust in the presence of
background. One project (C) will further develop this technology. The group will
continue developing the necessary simulation and reconstruction algorithms. On the
hardware side, they will work to increase wafer size, extend the drift length, reduce the
channel count and bring the wafer thickness to 150 microns. Finally, they plan to
develop a CMOS-based front-end chip.
Achieving the resolution goals with a relatively compact silicon central tracker requires
precise control of detector alignment and distortions. A “real-time” tracking device
alignment system will be important at the Linear Collider, particularly for a low-mass,
non-rigid silicon tracking system (A - listed in the section on Physics Simulation.)
A. LCRD
5.9
B. LCRD
5.10
C. UCLC
5.11
Tracking Software Optimization for the
Silicon Detector Option
R& D Towards a Low - Mass Silicon Strip
Central Tracker for the LC
R&D towards a Silicon drift detector based
main tracker for the NLC-SD option
Milind
Purohit
Bruce
Schumm
Rene
Bellwied
U South
Carlolina
UC Santa
Cruz
Wayne State
U
TPC Central Tracker
A TPC promises excellent momentum resolution and resilient pattern recognition. A
number of groups will work on TPC development. Two intend to improve fabrication
techniques for GEMs, and optimize GEM design for use in TPC readout. One of these
groups (A) will focus on photo-lithography and use simulation to optimize design. A
second group (B) will use prototype TPC’s with GEM and MicroMegas readout to
explore resolution, segmentation, noise, ion feedback, etc.
A novel alternative tracker is the Negative Ion TPC, whose hallmark is its very slow drift
velocity and limited diffusion. One group (C) plans both to simulate the performance of
such a tracker and to develop a prototype.
A. LCRD Fabrication, investigation and simulation of
5.4
Gas Electron Multipliers for charged particle
tracking
B. UCLC Tracking Detector R&D at Cornell and
5.7
Purdue Universities
C. UCLC Negative Ion TPC as the LC main tracker
5.12
Intermediate Trackers
Peter Fisher MIT
Dan Peterson Cornell
Giovanni
Bonvicini
Wayne State
Tracking
5.0.6
One group (A) will pursue its studies of a fast scintillating fiber intermediate tracker. The
group will establish the effect on momentum resolution and the impact of being able to
distinguish tracks produced in different NLC bunch crossings. They will also study a
prototype using cosmic rays.
A. LCRD Studies of the Use of Scinitillating Fibers for Rick Van
5.5
an Intermediate Tracker which Provides
Kooten
Precise Timing and Bunch Identification
Indiana U
Notre Dame
Forward Trackers
Forward tracking is more important at the Linear Collider than at previous e+e- machines
because of the increased contributions of t-channel processes at the high center-of-mass
energies. Forward tracking is also important for differential luminosity measurement. A
group (A) will develop the tracking simulation to allow for the evaluation of various
proposed forward tracking scenatios. In the domain of intrumentation, one group (B) will
explore the use of straw tubes for forward tracking, and a second (C) will study the use of
a GEM-based device.
A. LCRD
5.1
B. UCLC
5.3
C. LCRD
5.2
Development and Evaluation of Forward
Tracking in the Linear Collider
Straw Tube Wire Chambers for Forward
Tracking in the Linear Collider Detector
Development of a GEM based Forward
Tracking Prototype for the NLC
Mike Strauss U of
Oklahoma
Keith Baker Hampton U
Lee Sawyer Louisiana
Tech U
[1] “Impact of Tracker Design on Higgs Mass Resolution and Cross Section”, H. Yang
and K. Riles, presentation at the Santa Cruz Linear Collider Retreat, June 27-29, 2002,
http://tenaya.physics.lsa.umich.edu/~hyang/talks/trackres-ucsc.pdf; see updated report at
http://tenaya.physics.lsa.umich.edu/~keithr/LC/HiggsTrackSummer2002.pdf .
[2] J. Brau et al., “International Study on Linear Collider Detector R&D”,
http://blueox.uoregon.edu/~lc/randd.pdf; “The Detector List”,
http://blueox.uoregon.edu/~jimbrau/LC/rdpriorities .