Fermilab Physics Advisory Committee

June 19 - 25, 1999

Reports and Discussions

Welcome to the new Fermilab Director

On the first day of its June meeting in Aspen, the Committee congratulated John Peoples on the completion of his successful 10-year term as Fermilab Director, and especially on the recent successful commissioning of the Fermilab Main Injector. The Committee also welcomed the new Director Designate Michael Witherell, who joined us throughout our subsequent discussions.

CDF and D0 upgrade status

The Committee listened to presentations about the Collider upgrade projects and schedules from both CDF and D0. Both collaborations have recently completed a DOE Project Review (Lehman review), and the Committee was presented with the central recommendations of that committee.

The roll-in schedules of both detectors are limited by the production and delivery of silicon sensors by Micron. Although production has significantly improved due to the efforts of both collaborations with Micron, delivery completion dates are still uncertain and estimates range from January to March 2000. Both collaborations expect to be ready for final roll-in about six months after this completion date.

CDF is also having difficulty with its SVX3 chips both in production and in assembly onto hybrids; at present these problems are not quite on the critical path, but they are a concern. Other systems are progressing very well, and all systems other than the silicon tracker are expected to be ready for roll-in by March 2000. CDF has proposed roll-in for the engineering run without its silicon detectors during March-June 2000, followed by final roll-in with silicon in November. Without this engineering run, CDF could be ready for final roll-in with silicon in September 2000. D0 has had problems with the Fiber Tracker construction and Mini-Drift-Tube production, both of which are near the critical path for a proposed roll-in schedule for July 2000. The Lehman committee expressed serious concern about the D0 schedule, describing it as "brittle," and asked D0 to provide a re-evaluated schedule. Both collaborations have been asked for updated milestones spanning the period until roll-in.

Work is also proceeding with "Beyond-the-Baseline Upgrades" in both collider detectors. CDF has been able to obtain funding to support a new L00 silicon layer, which will be installed with the inner detector before roll-in. It is proceeding with work on the time-of-flight system and has secured about 70% of the needed funding. D0 is also proceeding with work on a forward detector and a track trigger, and has obtained partial funding for each of these.

W. von Rüden presented a report from the recent review by the Offline Review Committee for Run II Upgrade of the offline computing developments in both experiments. This report was very positive and concluded that no further reviews are needed before roll-in. Both collaborations and the Computing Division have made excellent progress, and the common CDF/D0/CD projects in particular have been quite successful. Although the von Rüden committee made a number of specific recommendations, there were no major problems or serious concerns. The PAC congratulates the von Rüden committee as well as the collaborations and the Laboratory on their impressive progress.

MINOS status

The Committee was presented with a status report of the NuMI Project and the MINOS detector, and a summary of the May 1999 DOE Project Review (Lehman review) of NuMI. Work on both the detector and the NuMI facilities is proceeding satisfactorily. Civil construction at Soudan has begun, and civil construction at Fermilab is scheduled to begin in late 1999. A four-plane prototype of the detector is under construction now, tests of the NuMI target are underway, and work on both software and electronics appears to be progressing satisfactorily. The experiment seems to be on schedule for data-taking to begin in early 2003, although the schedule is very tight and needs to be monitored closely.

The MINOS collaboration is also studying the possibility of an emulsion target module which could allow the direct detection of nt interactions, and has requested R&D support for this project.

Other discussions

The Committee was presented with reports on the projected improvements in Collider luminosity and accelerator capabilities over the next years, on Fermilab involvement in future accelerator R&D, and on magnet development being carried out at Fermilab for the Large Hadron Collider (LHC) under construction at CERN.

Most of the meeting was devoted to discussing Fermilab's scientific priorities and possible experimental programs for the next decade. The Committee extensively discussed the status of work on the BTeV proposal and on a number of fixed-target experiments which have been proposed. These discussions were based on presentations to the Committee at the May meeting, on the answers to questions from the Committee to the various collaborations, and on work carried out by PAC subcommittees prior to and during the Aspen meeting. A summary of the Committee's recommendations is given below.

General Recommendations

Scientific priorities

During the next six years (2000-2005), the highest priority of the Laboratory will be the successful operation of the Run II Collider program. This is an enormously significant extension of the productive physics program of Run I, which included the discovery of the top quark. With the successful commissioning of the Main Injector and the Recycler, the Tevatron in Run II is expected to run at luminosities an order of magnitude higher than it has in the past, and at the higher center-of-mass energy of 2 TeV. Both collider detectors are undergoing extensive upgrades, which will allow them to take maximal advantage of these accelerator improvements. Run II will extend the physics reach of the Tevatron beyond that of any previous experiment and could well lead to the discovery of one or more Higgs bosons, supersymmetry, technicolor, or other new physics. It is vital that the Laboratory do everything it can to maximize the scientific output of the Collider experiments in this critical period before LHC turn-on.

The second important goal of the Laboratory during this period is the definitive observation of neutrino oscillations in an accelerator experiment. The construction of the NuMI facility is underway, and the MINOS experiment is scheduled to begin data-taking in 2003. MINOS will extend the reach of accelerator neutrino experiments to encompass the regions of Dm2 and sin22q that are now indicated by the Super-Kamiokande measurements of atmospheric neutrino interactions; it should also be able to distinguish between nm->ntand nm-> n sterile oscillations. MINOS can run simultaneously with Collider operations, although with a moderate reduction in Collider luminosity caused by the longer Main Injector cycle time required. A second neutrino oscillation experiment, MiniBooNE, will be able to run using the Booster beam without interfering with either Collider or NuMI operations, and will explore the oscillation region indicated by the LSND experiment. A definitive measurement of neutrino oscillation parameters is likely to be a landmark achievement of the Fermilab program during the next decade.

During this period, it is also of the highest priority for Fermilab to continue and to expand its pursuit of the development of new accelerator technologies and designs, with the goal of developing plans for the next major high-energy accelerator facility in the United States. The Committee is unanimous in its recommendation that these studies be aggressively pursued, and on more than one front. The options under consideration at this time include a Very Large Hadron Collider with a center of mass energy of 100 TeV; a muon collider program with the ultimate goal of collisions at 4 TeV; and a linear electron-positron collider with a center of mass energy in the range of 1 TeV. Fermilab is a potential site for any of these facilities. The Committee supports the ongoing research into VLHC magnet and tunnel options, which are primarily directed at reducing costs. The Committee is pleased that the inter-laboratory MuTAC committee has been formed to study the muon collider option. The Committee supports the ongoing work on muon cooling, and notes that a muon storage ring could be used for neutrino physics as an intermediate step. The Committee believes the Laboratory's role in linear electron collider studies should be significantly increased, and endorses the new Director's initiatives in this regard. The Committee is delighted by what is perceived as a new level of cooperation between Fermilab and SLAC, and fully supports the development of a common framework for addressing future accelerator issues. The Committee welcomes the Director's initiative in forming an Accelerator Advisory Committee to address these issues. The Committee strongly endorses the Laboratory's continuing cooperative efforts with other national laboratories and with the international accelerator community.

Fermilab is providing an important contribution to CERN's Large Hadron Collider through the development and production of LHC magnets at Fermilab. The Laboratory is also playing a leadership role as the host laboratory for the US-CMS collaboration, and will be a major force in the CMS experiment and in LHC physics throughout the next decade.

During the next six years, other Laboratory programs including test-beam activity and low-intensity fixed-target running may be carried out concurrently with the Collider and neutrino programs. The Laboratory should work to provide such fixed-target facilities without significantly compromising the beam requirements of the two leading programs. The Committee expects that at least one significant shutdown of the Tevatron will be required during this period to replace radiation-damaged silicon detectors in both the collider detectors. With sufficient preparation this could provide a useful opportunity for fixed-target activity and/or accelerator improvements to increase Collider luminosity.

Beginning in about 2006, it is likely that the high-energy frontier will move to CERN with the beginning of the LHC program and that the Fermilab Collider experiments will have exploited most of the high-pt physics potential of the Tevatron. Fermilab will still offer important physics opportunities in a number of different areas, and the LHC era is the time in which these should be fully exploited. The Committee has examined two such possible physics programs in some depth.

One of these is a dedicated B-physics experiment operating in the Tevatron Collider; the BTeV collaboration is actively developing a proposal for such a detector. A hadron collider B experiment can carry out measurements of fundamental parameters, such as the mixing angles a and g, to a precision beyond the reach of e+ e- collider programs. Such an experiment at Fermilab would have to be able to compete effectively with LHCb, which will be running at CERN during the same period of time.

A second opportunity would be provided by a 120 GeV fixed-target program using a beam extracted from the Main Injector. Proposals have been or are being developed for both large and small experiments which could become the components of such a program. Two of these, the KAMI and CKM experiments, are especially attractive in that they would provide measurements of rare kaon decays (Ko -> ponn(bar) and K+ -> p+nn(bar) ) which have a theoretically clean relation to quark mixing angles (i.e., to CKM matrix elements). Another experiment (P-907) would provide measurements of particle production spectra which could be important in reducing systematic uncertainties in the MINOS neutrino flux.

It is feasible for both of these programs to run concurrently with MINOS, either under a staggered schedule or with reduced intensity. The Committee recommends that the Laboratory work to develop plans in both of these areas during the next two years, with the goal of making approval decisions in FY2001. The period beginning in 2006 is a reasonable target for beginning both a Collider B experiment and a fixed-target run with significant intensity (although a major discovery in the Collider program could affect this scenario). Some amount of beam will need to be provided during the 2001-2006 period for test beam work for these experiments, for engineering runs, and for possible low-intensity physics runs.

New discoveries over the next decade may well lead to new ideas for experiments. The Committee urges the Laboratory to continue to encourage and to be receptive to creative initiatives.

Other Recommendations