NuMI-L-247 March 17, 1997 D. Ayres Minutes of the MINOS Collaboration meeting at SLAC February 14-16, 1997 Present: Argonne: Dave Ayres, Maury Goodman, Rich Talaga, Jonathan Thron Caltech: Doug Michael Dubna: Yuri Gornushkin, Misha Ignatenko, Sasha Olshevski Fermilab: Bruce Baller, Scott Menary, Jorge Morfin, Adam Para, Gina Rameika, Linc Read, Wes Smart Indiana: Robert Hatcher, Dick Heinz, Lynn Miller, Stu Mufson Livermore: Peter Barnes, Ed Hartouni, Tony Ladran, Doug Wright Minnesota: Ken Heller, Bill Miller, Jeff Nelson, Earl Peterson, Keith Ruddick, Reinhart Schwienhorst Oxford: Hugh Gallagher Rutherford: John Alner, Richard Cotton, Peter Litchfield Stanford: Carlos Arroyo, George Irwin, Stan Wojcicki Swarthmore: Nat Longley U. Texas, Austin: Karol Lang Tufts: Tom Kafka, Rick Milburn, Jack Schneps Univ. College London: Jenny Thomas These notes summarize the important issues which were discussed and decisions which were made at this meeting. They do not attempt to provide a record of individual talks, which are described in the transparency copies and as NumI notes. Transparency copies and minutes of MINOS committee meetings held in conjunction with this collaboration meeting are available as NuMI notes: Transparency Xeroxes: NuMI-L-248 Executive Committee: NuMI-L-244 Institutional Board: NuMI-L-245 Technical Board: NuMI-L-246 Steel Oversight Committee: NuMI-L-254 A. MINOS and NuMI updates Stan Wojcicki, Gina Rameika, Dave Ayres, Wes Smart, Earl Peterson, Bill Miller, Jonathan Thron, Jenny Thomas and Adam Para described recent MINOS developments: 1. Stan reviewed our presentation to the January 17 meeting of the Fermilab PAC and the resulting PAC recommendations, which he had just received in a letter from John Peoples. The committee was pleased with our reports on tau identification (NuMI-L-228) and physics requirements (NuMI-L-229) and concurred with the DRAC commendation of our progress in simulations. The second interim DRAC report was distributed to the PAC, and is now available as NuMI-L-241. The PAC encouraged our gas-detector test beam studies and listed several concerns about our proposed scintillator technologies. They endorsed the collaboration's plan and schedule for the current fiscal year. In the final paragraph of his letter, John requested that realistic NuMI and MINOS plans for future years be developed in the next few months, and presented to the PAC at its June meeting. 2. Stan reported on the January 21 visit to DOE headquarters made by himself, Gina Rameika, Bruce Baller, Dave Ayres, Maury Goodman, Stuart Mufson, and Keith Ruddick. The purpose of the visit was to support Fermilab's request for $500k of supplemental DOE funds for MINOS R&D. He has recently learned from John Peoples that DOE will provide us with an additional $250k, half of the requested amount. The funds are to be distributed directly to university groups, but it was not clear whether this was a requirement or just a suggestion. It was also unclear whether the $250k is meant to include funds for postdoctoral positions which have been requested by Indiana and Minnesota, with collaboration support, 3. Stan summarized several financial developments. The February 1997 President's budget contains $5.5M for NuMI neutrino beam engineering in FY 1998. These funds must still be approved by Congress. The R&D funding situation this year is complicated by our pending request for postdoctoral support funds and by the ~$100k overcommitment of NuMI funds for MINOS. The allocation of the $250k of supplemental DOE R&D funds will be discussed later at this meeting. Stan also mentioned that the NSF has recently shown some interest in providing support for MINOS. 4. Stan reviewed the major tasks now before the collaboration, which will be the focus of this meeting: a. We need to define the main parameters of the MINOS detector: steel thickness, transverse granularity, active detector technology, and 1D vs 2D readout. Realistic studies of the effect of these parameters on physics processes (including event reconstruction, noise, beam properties, etc.) should be completed by the June meeting. He proposed a streamlined version of the physics-detector matrix and the establishment of physics working groups, and group leaders, to address each of the physics topic "columns:" CC energy test: Adam Para NC/CC (trigger): John Cobb tau -> mu nu nu: Doug Michael nu_mu -> nu_e, tau -> e: Stu Mufson tau -> pi: Peter Litchfield muon measurement: Jenny Thomas The streamlined matrix has only four "rows:" Steel thickness Transverse granularity Active detector technology 1D versus 2D readout b. We need to initiate planning for the near detector. Our goal should be to define the detector architecture, location, dimensions, and space requirements in the near hall by the time of the June meeting. c. The collaboration should provide more input to the beam design work which is now proceeding rapidly at Fermilab. 5. Gina reviewed recent NuMI developments and plans. She summarized the facility engineering and design tasks to be paid for by the $5.5M of FY 1998 DOE funds: the Conceptual Design Report, and the Title I and II documents. She has requested an additional $2M from Fermilab FY 1998 operating funds to cover detector work and other costs. These FY 1998 operating funds probably will not cover all of the MINOS detector work which we have proposed, so that a request for supplemental DOE funds is likely to be necessary. The Schedule 44 request for FY 1999 funds must be submitted soon, and will include estimates for the TEC (Total Estimated Cost), TPC (Total Project Cost), and facility operating costs. The TPC will include a funding profile from FY 1996 to the completion of the project. Gina summarized NuMI beamline work which is now under way: the geotechnical investigation (boreholes along the beamline), the environmental assessment, and the Preliminary Safety Assessment Document. The last two must be completed by this summer. She noted that John O'Fallon is now preparing the NuMI CD-1 document for Martha Kreb's signature. 6. Dave Ayres summarized current plans for MINOS detector funding which were presented to the DOE on January 21. These included a breakdown of our FY 1997 R&D request, including the modifications agreed to at the February 14 Technical Board Meeting (see NuMI-L-246 for details), and our preliminary estimate of $2.2M for detector R&D costs in FY 1998. He reviewed our current estimates for the total detector cost with various detector assumptions (gas and scintillator, 2 cm and 4 cm steel) and compared these to the Lehman Committee estimates. He also showed a possible funding profile for the detector and compared it to Gina's "strawman" profile for Fermilab equipment funds. Although it is too early to worry about small differences in these profiles, they do suggest that we will need several million dollars of supplemental equipment funds from DOE in FY 1999 to keep the detector construction on schedule. 7. Wes Smart reviewed a number of NuMI neutrino beam topics which have been the subjects of recent work at Fermilab: a. Improvements in the NBB (by Jim Hylen and the Protvino group). The full GEANT simulation of the lithium lens beam, with asymmetric collimation and the initial bend angle increased to 28 mrad, gives a reduced low energy tail which is back at the level advertised in the MINOS proposal (from NUADA). About 0.5% of the CC interactions have energies less than 10 GeV in the new design. The full GEANT simulation of the Protvino NBB using parabolic horns and a 15 mrad initial bend gives a low energy tail level which is 1.5 times higher (but still half that of the original lithium lens beam); this is expected to improve if the bend angle is increased. Optimization of the Protvino beam, which gives higher flux at lower energy than the lithium lens beam, is still in progress b. Muon monitoring (by Alan Wehmann). The goal, based on the CC event energy spectrum oscillation test, is to detect any change in the beamline which would cause a change in the neutrino flux of 2% in the worst one GeV neutrino energy bin, between approximately 1 and 35 GeV. To accomplish this, the muon rates in counters installed in slots in the rock shield are monitored. Four planes of counters at distances of 9, 15, 23, and 35 meters are used with the 3-horn WBB. This muon monitor scheme turns out to have sufficient sensitivity to changes in the transverse location of the first horn, but is not sensitive enough (by a factor of eight) to variations in horn currents (all three assumed to change together). c. The Hadronic Hose design (by Jim, Wes, and Rick Milburn). The hadronic hose consists of a current carrying wire along the center of the decay pipe which focuses the meson beam. Detailed GEANT and PBEAM simulations now confirm that the hadronic hose greatly reduces 3-horn WBB near-far beam energy spectrum differences, and also reduces their sensitivity to off-nominal beamline and horn parameters. The sensitivity to the hadron production p_t spectrum is also much reduced. If the primary beam and horns are offset so that the remaining protons and the secondary hadrons enter the decay pipe off center and off axis, interactions with the wire will be reduced. Groundwater activation is also improved, but the overall event rate is also slightly lower with the hadronic hose. Wes concluded with two requests of the collaboration. The beam design group would like to have a complete list of all our requirements on the NBB, and would like us to define a common coordinate system for the beam and experiment. A short discussion produced the following list of NBB requirements: near-far energy spectrum difference requirements similar to those for the WBB (would the hadronic hose work for the NBB also?), narrow Gaussian energy distribution with a small low-energy tail, low nu_e contamination, and ease of changing energies. Probably the beam and detector coordinate systems should be different, since the the z-axis is naturally along the detector axis for the latter, and along the beam axis for the former. There was general agreement that a right handed coordinate system be used and that y will be (approximately) up. 8. Earl Peterson summarized the status of items on a long list of jobs which are under way to prepare for the Soudan excavation. During the past few weeks working meetings have been held between CNA mining engineers and University and DNR personnel to discuss both engineering and environmental issues. A professional environmental planner is preparing the Environmental Assessment Worksheet (EAW) for submission by the DNR in late May. The main EAW issues are runoff water, minimization of bat disturbance, rock disposal, and completion of the detector safety document which we are providing. Other laboratory construction planning issues include lease negotiations, compliance with MCCI report recommendations for improvements to the hoist system, and CNA engineering work on the detector support structure and the handling of MINOS steel plates. Most of the MCCI recommendations can be implemented using the $400k of State funds which will be administered by the DNR on our behalf. Earl described a number of support structure engineering issues which are being studied by CNA, and showed the latest schedule for the excavation work. The current plan is to advertise for bids during March 1998, award the contract in April, and begin work in May. However, the possibility of moving this schedule earlier by a month or more is under investigation. 9. Bill Miller summarized the recent work by the MINOS Installation Committee (MIC) and reported on their January 18-20 meeting (meeting minutes are available as NuMI-L-253). The MIC's primary task is to prepare WBS cost estimates and companion Basis of Estimate (BOE) documents for the three technologies now under consideration (APT's, liquid and plastic scintillator). These documents are to cover both the manufacture and installation of each detector system. The MIC is also coordinating preparation of WBS cost estimates and BOE documents for the steel and magnet fabrication and installation, and for the Soudan cavern excavation. Livermore's current plan for installation of the magnet coil requires more time, space, and resources than expected; the MIC's suggestions are currently being reviewed by the Livermore group. Review of the coil fabrication plan should be performed by either the MIC or the SOC, but is not included in the charge of either committee. The MIC has also noted that the increase of cavern excavation cost with length is apparently quite nonlinear, and that detector fabrication labor costs may be lower than those which have been used in cost estimates (for northern Minnesota). The MIC reviewed preliminary BOE's for both APT's and liquid scintillator and has suggested a number of improvements. A preliminary plastic scintillator BOE and and cost estimate was nearly ready for distribution at the time of the SLAC meeting. 10. Jonathan Thron reviewed the preparation of WBS cost estimate spreadsheets (using Excel) and of the MINOS Safety document which is needed for the Fermilab safety review of MINOS. The safety document describes our plans for installing and operating each of the three possible detector types, and identifies potential safety issues associated with each of them (for example flammable gas, liquid, and plastic). It also discusses our current plans for safety systems. An initial draft of the safety document has been submitted to Bruce Baller. Jonathan reviewed the general procedure which is being used for estimating the costs of manufacturing and installing the MINOS detector, and showed examples from the APT BOE and spreadsheet. He pointed out the importance of estimating costs as accurately as possible, and in a consistent fashion for the different detector types, since these estimates will be used as one factor in the choice of active detector technology in a few months. Current versions of the BOE's and cost estimates are available to anyone who would like to review them. 11. Jenny Thomas summarized the current status of planning for the MINOS near detector. A working group consisting of Jenny, Adam Para, Hugh Gallagher, and Dave Tovee is studying a number of design issues and is preparing a document describing their work and recommendations. They have devised a simple, fast simulation using PAW to provide preliminary answers to basic questions. Three issues are being studied now: detector geometry, event rate, and detector location. They are evaluating both the baseline rectangular (dipole) geometry and the octagonal (toroidal) geometry from the standpoint of CC event acceptance and muon momentum resolution. They have also considered the spacing of detector planes which is needed at different depths and have concluded that even very coarse sampling in the downstream two thirds of the detector provides good muon momentum resolution. This could give substantial cost savings. The hadron calorimeter section of the near detector would still have fine sampling in order to be as similar as possible to the far detector. Event rate studies concluded that time slicing of near detector events in ~10 usec bins would be needed to reduce event overlaps to a negligible level. Jenny pointed out that earlier conclusions about moving the near detector as far downstream as possible to reduce near-far beam differences may be irrelevant if the hadronic hose scheme is used. The rate of neutrino-produced muons from the upstream shield wall appears to be a negligible problem even if the MINOS near detector is located quite close to E-803. 12. Adam Para reported on his continuing design study of the hybrid emulsion detector. He has now compared the sensitivity of the 10 kton MINOS detector and a 1 kton emulsion based tau detector. The 10 kton detector would obtain a 4 sigma signal from the NC/CC test for oscillation parameters which would produce a signal of 6 clean tau events in the emulsion detector, if a tau efficiency of about 2/3 is assumed. Adam has also looked more closely at the idea of increasing the steel thickness from 1 mm to 2 mm to improve statistics without increasing cost. His preliminary results suggest that the lower tau detection efficiencies with the thicker steel may more than offset any advantage in event rate. Adam has also looked at the possibility of obtaining a momentum estimate from the measurement of multiple scattering angles. The technique appears to work well, and is useful for rejecting low momentum particles to improve the cleanliness of tau signals. Finally, Adam stated that we have had no further contact with the Japanese proponents of the emulsion experiment, and that they are now working with long baseline groups at CERN. The emulsion technique for tau detection is more effective at the high energy of the proposed CERN beam than at NuMI energies. B. Detector R&D progress reports Recent progress on passive and active detector R&D was reviewed by Tony Ladran, Rich Talaga, Sasha Olshevski, Keith Ruddick, Adam Para and Karol Lang. 1. Tony Ladran summarized recent steel and magnet development work at Livermore. The Livermore group hosted more than twenty MINOS collaborators on a day-long tour of laboratory facilities on February 13. The SOC met immediately after the tour to review plans for constructing the full size prototype steel plane. Their report is available as NuMI-L-254, and was discussed with the Technical Board at this meeting (see NuMI-L-246). Tony described the planned construction of the the 2 cm thick plane which should be completed by August. Measurements of the flatness and of the mechanical and magnetic properties of the plane could begin at that time if funding were available (which seems unlikely -- see NuMI-L-246). The flatness of components will be monitored during assembly so that the flatness (and other properties) of a 4 cm thick plane can be predicted from the 2 cm plane results. Other activities at Livermore include planning for magnetic measurements on the prototype plane, structural analysis of the hanging support structure (with CNA in Minnesota), 3D magnetic field calculations, Monte Carlo studies of the magnetic field's effect on muon tracks, requirements on steel metallurgy and radioactivity, and work requested by the installation committee. 2. Rich Talaga described recent studies of aluminum proportional tubes (APT's) at Argonne as well as preparations for the Fermilab test beam run to study the performance of APT calorimeters. Argonne has developed an improved strip plane design using copper-clad glass polyester which is scored by a machine. The production of 150 test beam chambers is about to begin at Argonne, with help from both Dubna and Tufts (one third of the chambers will be assembled at Tufts). A 1 m^2 steel plate structure which can be used for hadron calorimetry studies has been designed and parts have been ordered. The existing Dubna calorimeter is already installed in the test beam. The Argonne group is also preparing to build the first 8-m long chambers and strip planes. Rich reviewed work which is under way to address APT questions posed at the last DRAC meeting. More collaboration help is urgently needed if the gas chamber response software is to be ready in time to meet the June deadline for a comparison of oscillation tests with different detector types. He outlined the schedule for installation and measurements in the test beam and asked for volunteers to help run shifts. 3. Sasha Olshevski described the recent pilot production of PVC sleeves for D0 chambers at Dubna. The sleeves are of acceptable quality and they expect to be able to produce enough for all of the 8-cell wide D0 chambers. They have restarted the Delphi tube assembly facility at Dubna for the manufacture of D0 chambers. They are seriously considering the use of aluminum instead of plastic comb extrusions for these chambers. Sasha described preparations for studies in the Fermilab test beam. The Dubna calorimeter from the SLAC test beam has been set up in the beam at Fermilab and they have used its chambers to measure beam profiles during their first three shifts of beam time. The original plastic chambers have 80 micron anode wires, and three new planes with 50 micron wires have been built. In addition, two planes of aluminum chambers, using components from Argonne, have been built. Strip planes with 1 cm pitch have been built to go with these APT planes along with 32 preamplifier channels to read out the strips. The new 50-micron-wire planes and APT planes will be substituted for 80-micron-wire planes near shower maximum after initial calibration runs with the original chambers are completed. Finally, Sasha showed the results of tests of APT chambers. The aluminum combs give much sharper strip resolution curves than plastic chambers with resistive plastic combs. Although after pulsing gives the APT's shorter useful plateaus than the plastic chambers, they still have an acceptable operating range for use in MINOS. 4. Keith Ruddick summarized recent progress with liquid scintillator R&D. The polypropylene tube extrusion order has been delayed, but should be delivered in two weeks. The first draft BOE for the liquid scintillator detector has been completed. The new Minnesota engineering student, Matt Hansen, has designed an improved coil bypass module and has begun work on scintillator aging measurements. Aging tests at Minnesota have measured the distortion of liquid scintillator filled containment tubes under high temperature and pressure conditions. Significant distortions were observed during initial four-day tests of some samples. Studies to look for possible scintillator degradation caused by interaction with plastic tube materials are just getting started. The group has found a vendor who will perform standard aging tests for a fee. There has been progress with photodetector development. Initial studies on a sample 88-channel MCP PMT obtained from Novosibirsk show significant crosstalk, nonuniformity of response, and saturation effects. Hamamatsu has offered to send samples of their new dynode-type multianode PMT for evaluation over the next few months, and 7-8 samples of our prototype Litton MCP tube are scheduled for delivery in May. 5. Adam Para and Karol Lang summarized recent R&D progress with plastic scintillator technology. Promising light yield measurements have been obtained from short samples using fibers in both holes and surface grooves, with and without optical contact material (e.g. glue). The cost estimate for plastic scintillator has been updated and more manufacturers of plastic extrusions are being contacted. Mechanical aspects of the large detector planes are being studied with models which have been subjected to temperature variations similar to those which might occur during shipping. Adam demonstrated a promising new "partial lamination" design for the construction of plastic scintillator modules with a model he brought from Fermilab. Studies of crazing are continuing, but none has yet been observed with polystyrene sheets. Karol Lang described the program of plastic scintillator R&D work at Austin which includes studies of reflectivity, a comparison of fibers in holes and grooves with and without optical coupling, and light yield studies of scintillator samples with different thicknesses and widths. These results are described in detail in NuMI-L-250. Karol has also prepared a first draft of the plastic scintillator BOE document which is available as NuMI-L-249. C. Physics-detector matrix update Jeff Nelson, Peter Litchfield, Stan Wojcicki, Adam Para and Lynn Miller gave brief updates of their progress on several "matrix" topics since the last meeting. Jeff reviewed the evolution of his analysis of tau -> short events. Since the last meeting this work has been written up in the PAC document and discussed at the PAC meeting. The current focus now is on the effect of oscillation parameters on the shape of the short event hit distribution, which is independent of information obtained from other oscillation tests. Peter Litchfield presented David Petyt's update on his tau -> pi X analysis since the December meeting. The work was written up for the PAC document and then extended to investigate sensitivity for 2 cm and 4 cm thick steel planes and 2 cm and 4 cm transverse granularity. An improved set of cuts has been developed and a new pattern recognition technique has eliminated the need to scan events. His results show that, for large neutrino mixing, there is a clear signal in the case of 2 cm steel with 2 cm cell width. There is a gradual reduction in sensitivity with increasing cell size and plate thickness. Stan reviewed the Stanford group's study of tau -> mu nu nu in the NBB. They have investigated the effect of total energy and muon-hadron angle resolutions on background rejection and efficiency using a neural net technique. The improved low energy tail in the new NBB design improves event identification efficiency by about a factor of two, but results are relatively insensitive to improvements in angular resolution and tracking. Both Jeff and Adam have looked at aspects of NC event triggering on the NC/CC ratio test. Jeff calculated the rates of singles, doubles, and triples for both near and far scintillator detectors with both 1 and 2 photoelectron thresholds. The triple coincidence trigger described in the proposal gives high efficiency for NC events, for both 2 cm and 4 cm steel thicknesses. Adam determined that NC/CC test is relatively insensitive to trigger threshold providing that an event energy trigger is used. Unlike a simple hit trigger, an energy trigger is insensitive to noise and to hadronization models. This trigger scheme uses all hits, down to the 1 photoelectron level, in a box around an event, and may require that the data acquisition electronics be divided into several sections to deal with high data rates at this low threshold. Lynn reported on the Indiana group's work on gas detector response simulation. She described the detailed model used to generate simulated data from tracks and showers in APT detectors. A number of parameters are available for tuning the simulation response to agree with experimental results, including detector geometry, gas gain, occlusion length, energy loss and saturation models. The simulation has produced some preliminary results, but needs more work to ensure that the detector response is well represented. This requires comparison of the simulated response with test data from prototype APT's. The generation of simulated events with the GMINOS program can proceed independently of the fine tuning of the detector response simulation, since the response code is run post-GMINOS using the hits output. Producing large event samples for oscillation test analyses requires significant cpu resources and disk space as well as some effort to oversee this production. The event sample generation can begin as soon as the required resources are in hand. Even so, the schedule for completing this work before the June meeting deadline looks very tight. Jeff described his Monte Carlo simulation of light collection in scintillator cells of various properties and dimensions. This model has been used to calculate photodetector photoelectron yields under different conditions, including fiber location within a cell and several cell shapes. His results are in general agreement with the measurements at Austin reported by Karol Lang. D. Event reconstruction working group Jenny Thomas, Robert Hatcher, and Hugh Gallagher reported on their work as members of the newly formed event reconstruction working group. Robert described the operation of his initial vertex finding algorithm for large hadron showers. He showed initial results for transverse and longitudinal resolutions for 2 cm and 4 cm steel and 2 cm wide strips. The algorithm is not yet optimized and could be tuned for specific topologies. Hugh described his results on hadron shower reconstruction using 4 cm steel and a 2 cm transverse granularity liquid scintillator detector. Energy resolutions obtained are reasonable, and hadron angular resolutions, calculated assuming known vertex positions, are worse than those given in the MINOS proposal. Jenny described results of the muon track reconstruction group, using Carlo Arroyo's method for track finding and a CDHS track fitting algorithm. Initial results on angle and energy resolution are reasonable; energy resolution is dominated by multiple scattering and remains good (Dp/p ~12%) even for very wide strips. Jenny concluded with a brief description of the user friendly reconstruction program which the group will ultimately provide to the collaboration. E. Working group summary reports Three working groups met in parallel for several hours on the afternoon of the second day of the meeting. These sessions were summarized by Working Group leaders on the final day of the meeting. 1. Software: Peter Litchfield The software working group met for only about an hour and then joined the active detector group to discuss the comparison of detector technologies. They reviewed changes in GMINOS and GBEAM since the last meeting and discussed a document on coordinate systems by Robert Hatcher. Four of the five leaders of the new matrix working groups were present, so the organization and membership lists of these groups were started. The overlaps between the new matrix groups and the four event reconstruction subgroups (vertex, hadron energy, hadron angle, and muon measurements) were identified. Near term goals of the software subgroup are to generate events using (1) the gas detector simulation (when it is ready) (2) 4 cm steel with 2D scintillator readout, and (3) 4 cm strip width and 2 cm steel. The group also needs to consider carefully the numbers of events needed for each oscillation test since these large data sets require substantial computer resources. The discussion following Peter's talk focused on the task of completing the gas detector simulation work in time for the June workshop deadline. The detector response code has been completed but still needs checking and tuning. It will be a big job to generate and analyze the large event data sets needed to compare gas and scintillator detectors by June. More effort is needed and volunteers were asked to contact Robert, Jeff, or Stuart. 2. Steel/magnet: Doug Wright The steel working group concurred with the recommendations of the SOC and noted the importance of getting Fermilab funds to Livermore as soon as possible. They discussed the possibly significant levels of Cobalt-60 activation of steel (from the furnace monitoring technique used in the US) and the need to control this radioactivity, which could cause trigger problems. Doug reviewed the results of the finite element analysis of the hanging support design of planes built with 45 degree plate orientation. He described the 3D magnetic field calculations of 2 cm steel plates being performed at Livermore, compared results to those obtained earlier for 4 cm planes, and summarized how field levels would be measured in the prototype plane. Doug also described the Livermore group's updated coil design and installation procedure, which were modified in response to MIC recommendations. Finally, he reported that the working group had considered a steel plane installation scheme which did not require a bridge crane, but had decided that this was not a desirable option. Most of the discussion focussed on the detailed plans for building and measuring the 2 cm steel plane prototype. Doug described how measurements made during assembly would allow the properties (e.g. flatness) of a 4 cm thick plane to be predicted. The importance of measuring the magnetic field outside the steel plane was noted, since some types of photodetectors being considered (e.g. image intensifiers) are quite sensitive to low field levels. Also discussed were the predicted temperature gradients in the steel, the magnetic forces between planes, and the method for spacing the planes apart (which can interfere with active detector mounting). The present coil design could allow a reduction of the planned 15 cm radius of the central hole in the steel planes, but this dimension will not be changed until the coil design is finalized. 3. Active detectors: Doug Michael Doug described the active detector working group meeting as a "Quaker meeting," in which the main proponents of each of the three technologies were asked to publicly state their present opinions on four questions which he posed to stimulate discussion. A number of others also gave their opinions. a. How do you rank the existing technologies for overall promise and likelihood for selection for use in MINOS? b. If you had to choose to focus people/resources NOW on a single technology to pursue, which would it be? c. Would you be willing to "bet" on one technology now? Do you think that is what SHOULD be done? d. If you are not of the opinion that we should focus now, what do you need to see to be satisfied? Doug summarized the answers as follows: a. (and d.): More than 90% named plastic scintillator as their #1 choice. Issues raised in the response to question d. included engineering, costs, full scale prototypes, and photodetectors. About 60% named liquid scintillator as their #2 choice. The only issue raised in response to question d. was stability, but this was a very serious concern. The #3 choice was APT's, which most people believed could work for MINOS, but that we need to demonstrate adequate response for our detector design. b. Most APT proponents would choose to focus resources on APT's, while most liquid and plastic scintillator proponents would choose to focus on plastic. c. Most believed that we would be better off to set a strong priory to focus effort and resources now, but most wanted more information first. There was a general concern that the current default selection path is not going to best serve our needs. Doug concluded that we should try to find a way to redirect resources to plastic scintillator R&D soon. A decision to make a technology choice today is not generally mandated. A decision plan which will focus effort on one technology in April is generally desired and thought to have important benefits. The implicit expectation is that gas should/will be dropped at that time, rather than drop one of the scintillator technologies. Doug suggested that we should agree now to drop one of the three technologies in April. Several issues were raised during the discussion following Doug's summary: (1) The April-August decision process is not rigid -- it can be changed to better serve our needs. We will have more information in April than we have today, so we should not try to define the optimal decision process now. (2) We cannot ignore the specific PAC and DRAC concerns about scintillator. (3) It would not be responsible to drop the gas technology now, since so much effort has gone into setting up the test beam calorimeter studies. In addition, APT's cannot serve as a backup technology if we do not have the test beam data, which will not be possible to obtain at Fermilab after September 1997. (4) Devoting the required resources to the APT test beam work will slow down scintillator work, giving us less information about scintillator for any April decision. (5) Plastic scintillator R&D most urgently needs more physicist and engineering effort, but does not require large financial resources until we get to the stage of testing mass production techniques. F. Closing Discussion Stan led the discussion on our two most pressing issues: active detector decisions and near detector design. Some of the points made are listed here: 1. Active detector decision: a. There is no agreement on whether we can have enough information in April to drop one technology. We will appear to be irresponsible if we change directions too quickly without adequate justification. b. The decision between gas and scintillator depends critically on what transverse granularity is needed. Using strips wider than 2 cm could cut $5-10M from the scintillator cost. We need simulation results to make this choice. c. We cannot choose scintillator in April without having confidence that at least a worst case photodetector scenario is practical, e.g. expensive multianode PMT's with multiplexing, or image intensifier readout. d. We cannot choose plastic scintillator without a much better cost estimate for this technology. We expect to have this by April. e. We need to understand better the possible noise/trigger problems with a scintillator detector. John Cobb (not at this meeting) has calculated some very worrisome rates, but others think that he has used PMT dark currents which are much too pessimistic. f. The urgency of the active detector decision makes it crucial that we decide on detector parameters (especially granularities) at the June workshop. We must have simulation results for this. g. The Fermilab, Argonne and Minnesota groups will try to find engineers to work on plastic scintillator jobs immediately. h. The UK groups will help with the gas detector response simulation work (Hugh Gallagher and possibly David Petyt). 2. Near detector a. If we do not need to use far-detector instrumentation to measure muon momentum, the detector might be made significantly shorter and cheaper. b. We should be very careful not to compromise the physics performance of the near detector just to save money. The sensitivity of some tests will be limited by uncertainties in near detector measurements. c. As long as the hadron shower measurement region of the near detector is instrumented identically to the far detector, the muon measurement region can be separate, with coarser instrumentation. We should require at least 12% muon momentum resolution however. d. The near detector instrumentation should extend to a large enough radius to provide crucial information about the beam (to check our beam simulation model). e. We can probably agree now to use a toroid configuration, with radius larger than 2 meters, and to do no further simulations with the H-magnet geometry. f. The hadronic hose scheme has not been formally adopted and may yet prove to be impractical. We cannot yet plan to use it to reduce near-far systematic errors. We need to keep this in mind when choosing the near detector location. G. Schedule of 1997 meetings and deadlines The collaboration agreed to the following changes to the previous schedule of meetings and deadlines: 1. The April collaboration meeting has been delayed by 9 days (to April 27-29) to be closer to the Main Injector Fixed Target Workshop on May 1-4. MINOS collaborators are strongly encouraged to participate in this workshop (registration deadline is March 15.) 2. The June "week in the woods" workshop in Ely has been lengthened by one day (it will now begin on June 7 instead of June 8) to make it a full week. Meetings on the first two days cannot be held at the Ely Holiday Inn, but a meeting room nearby will be found. The Ely Holiday Inn should be able to provide lodging for most participants for the full 7 days. Bill Miller will distribute information about accommodations soon. 3. The August Collaboration meeting dates are set to be Aug. 15-17. The dates of the August DRAC meeting have not yet been determined. 4. The October collaboration meeting has been moved from England to Fermilab in order to facilitate preparation of the Technical Design Report. The dates of the meeting are now set to be Oct. 24-26. 5. The dates of three important summer conferences are included on the list below: WIN97 (Capri in June), EPS (Jerusalem in August), and TAUP97 (Gran Sasso in September). Collaborators who would like to give MINOS talks at any of these conferences should contact Stan. WIN97 and TAUP97 have explicitly requested MINOS talks. ** Note added: The April PAC meeting has now been cancelled, and it is likely ** that the April DRAC meeting will occur a few days before the rescheduled ** April collaboration meeting. But April DRAC meeting dates have not yet been ** definitely settled. Revised Calendar of MINOS Meetings and Deadlines ------------------------------------------------ MINOS Installation Committee meeting at FNAL 3/15-16 (Sat-Sun) PAC Meeting at FNAL (CANCELLED!) 4/11-13 (Fri-Sun) DRAC Meeting at FNAL 4/23-24 (Wed-Thu) MINOS Meeting at FNAL 4/27-29 (Sun-Tue) Fermilab Workshop on Fixed Target Physics at the MI 5/1-4 (Thu-Sun) MINOS Workshop in Ely, Minnesota 6/7-13 (Sat-Fri) PAC meeting at Aspen 6/14-20 (Sat-Fri) WIN97 (Capri, Italy) 6/22-28 (Sun-Sat) DRAC meeting at FNAL 8/? MINOS Meeting at FNAL 8/15-17 (Fri-Sun) European HEP Conference (Jerusalem, Israel) 8/19-26 (Tue-Tue) TAUP97 Workshop (Gran Sasso, Italy) 9/7-11 (Sun-Thu) MINOS Meeting at FNAL 10/24-26 (Fri-Sun) MINOS Detector TDR submitted 10/31 (Fri)