Summary of UCLC tracking group teleconference

(May 14, 2002 at 2:00 p.m. EDT)

Present:
    Keith Baker(Hampton), Rene Bellwied(Wayne State), Mikhail Dubrovin(Wayne State),
    Rich Galik(Cornell), Dean Karlen(Carleton), Dan Peterson(Cornell), Keith Riles(Michigan),
    Mike Ronan(LBNL), Bruce Schumm(Santa Cruz), Ron Settles(MPI-Munich)

(The initial discussion was guided by a list of simulation and R&D issue s first circulated at the inaugural tracking session at Cornell. Nominally, discussion resumed at simulation item 9, but in fact many broader simulation issues were revisited in detail. The following is meant as a brief summary of discussions that sometimes veered from topic to topic, not as detailed minutes.)

Simulation issues:

Discussion began with simulation issues. In particular, it was agreed there was need for robust, efficient pattern recognition for all of the major tracker designs in order to allow quantitative evaluations / comparisons.
Dan expressed strong interest in pursuing the implementation of the CLEO tracking program in the linear collider environment. The code has been developed for an axial drift chamber and would be applied to a TPC. He provided background information on what he has in mind.
KeithR summarized the history of the present pattern recognition code in JAS. Mike adapted it from Babar mini-TPC C++ code which itself had been adapted from the old PEP TPC experiment's fortran tracking code. Nic Sinev (Oregon) has done further work on tuning tracking parameters / algorithms and on adding background hits. Haijun Yang (Michigan) has worked on evaluating the tracking performance, and Mike continues to refine the original algorithms.
Bruce reported that Steve Wagner (SLAC) is also interested in gas chamber pattern recognition.
Rene reported that Vladimir Rykov (Wayne State) is looking hard at silicon drift detector (SDD) pattern recognition.
Bruce mentioned his group's interest in optimizing pattern recognition for a silicon microstrip tracker (Wolfgang Walkowiak?)
There was worry expressed at the apparent duplication of efforts above, but given the four different technologies on the table now (TPC, DC, SDD, Si strips) and the difficulty in optimizing pattern recognition for just one detector, multiple efforts, particularly centered on particular technologies seems reasonable. Dean pointed out that the usual factorization assumed between pattern recognition (track finding) and track fitting does not always apply and may become important in the presence of dense jets and high machine backgrounds.

Detector R&D issues:

Ron disagreed with the "low priority" assigned by KeithR to mechanical support and calibration of a TPC. He felt that to have a serious detector proposal ready soon, one could not neglect any important issue.
Mike mentioned that a proposal he submitted recently to LBNL for developing next-generation TPC electronics had been turned down because the lab felt it was too soon to be developing LC electronics. He argued that this belief was misguided because electronics are a strong cost driver for the TPC when one tries to fully exploit the intrinsic granularity of the chamber. The electronics also strongly affects the choice of pad readout in, e.g., a GEM-based system.
KeithB raised the issue of gas mixture importance in R&D, an area where his group could carry out studies. Dean felt that the optimum gas mixture was still an open and important issue, despite the virtues of ArCF_4. Ron agreed and mentioned the work of the Krakow group. KeithR mentioned the work of the MIT group, reported by Ulrich Becker at the January Chicago meeting.
Rich wondered whether test beams would be available in the coming years for R&D work. Mike mentioned beams coming on line at Saclay and DESY, both of which will offer regions of strong, uniform magnetic field (Saclay - 2 T, 0.5 m diameter; DESY - 5 T, 0.27 m diameter). Saclay also has access to a beam line at the CERN SPS.
Bruce talked briefly about a nascent international collaboration in silicon tracker development for a linear collider ( SILC ), modelled after the TPC effort coordinated by Ron. In regard to setting priorities, he prefers to separate along the lines of readout technology, with two mutually exclusive approaches defined by long strips / shaping times vs short strips / shaping times, where one would face very different optimization problems. The differing bunch train profiles in NLC/JLC vs Tesla affect this optimization problem.Bruce has submitted a proposal to DOE to pursue R&D on long shaping time readout (which was approved shortly after this meeting - KeithR). He mentioned that the Paris group (Aurore Savoy-Navarre) is carrying out a similar program.
Rene mentioned that in addition to the SDD built by Wayne State and BNL for RHIC's STAR detector, there is a now an effort to build a SDD for LHC's ALICE detector. R&D goals include better integration, longer ladders (via daisy chaining), and thinning of layers down to about 0.5% of a radiation length.

Interests of the UCLC group members

Each group represented on the line was asked to summarize briefly its interests w.r.t. a joint proposal via the UCLC consortium. [A list based largely upon a signup sheet circulated at the inaugural session was posted on the agenda page.]
Hampton - KeithB - Interested in exploring gas mixtures for a TPC design. Will look at the efforts going on in Japan, Europe and at MIT before settling on a focus. Issues suggested by others on the line included the tradeoff between drift velocity and attachment problem and neutron backgrounds.
Wayne State - Rene & Mikhail - (signed off earlier in meeting - KeithR reported) - Continuing work in SDD pattern recognition and timing. Longer-term interest in developing new SDD prototype detectors in collaboration with BNL.
Cornell - Dan & Rich - Initially will "port" the CLEO track finding code into JAS. Longer-term interest in pursuing TPC readout technology in Cornell lab in collaboration with Purdue (Ian Shipsey) which is already active in micropattern gas detector development.
Michigan - KeithR - Will continue simulations work on global tracking issues (physics impact of tracker design & pattern recognit ion evaluation). Longer-term interest in electronics development.

Preparing the tracking section of the consortium proposal:

KeithR reminded everyone of the 15-page total page limit on the UCLC proposal, which will probably mean only 2-3 pages for tracking. Given the boilerplate discussion of general tracking issues needed, each group will have only a short paragraph in which to described its proposed work. As a supplement to this brief information, KeithR suggested that each member group provide a longer document on the web with more detail, a document/page that would be frozen on the tracking group web at the time of proposal submission, but which could refer to additional links maintained by the member groups. He asked that each group provide a draft of both the short paragraph and the web documentation before the Santa Cruz meeting. He also volunteered to write the boilerplate and assemble the tracking pieces into a whole. No one objected.
There was also discussion of coodinating with the consortia being organized in parallel in the midwest (April FNAL meeting) and on the west coast (May SLAC meeting). A trio of tracking coordinators (Bruce, Dean, KeithR) will soon be organizing a U.S. / Canada working group on linear collider tracking, as part of the ALCPG.. This group is meant to guide the tracking efforts on this continent, regardless of funding source. KeithR expressed the hope that eventually the artificial distinction between NSF and DOE groups will become a minor formality as everyone works together. Groups known (or thought) to be interested in linear collider tracking R&D in the near future (not proposing as part of the UCLC) include Colorado State, Indiana, LBNL, MIT, Notre Dame, Oklahoma, Santa Cruz, and SLAC. Groups that might join a UCLC proposal in future years include Ohio State (K.K. Gan) and Stony Brook (John Hobbs).
Plans for the Santa Cruz "day after" meeting (LCCOM2) were still uncertain, but it was assumed that there would be some time for parallel sessions for discussion. It was not yet clear whether individual groups would make presentations on proposed work in parallel session or plenary. It also wasn't clear how much time would be available to present proposed work in parallel sessions of the Santa Cruz workshop itself (day 2).