Minutes of the FT Upgrade Meeting, 13/5/97. ------------------------------------------- Present; SBurke,DClarke,JFoster,TGreenshaw,WJHaynes,DHill,RHenderson,SMaxfield, GPatel,JVMorris,DSankey,TSloan,GJRTappern. Motivation for FT upgrade. -------------------------- The arguments for improving the FT discussed at the meeting may be summarised as follows. The HERA accelerator is to be modified to allow higher luminosity running. The study of high Q^2 DIS will thus become possible and this will make the performance of the forward region of the H1 detector more important; both the electron/positron and the hadrons in such events travel in the forward direction. This argument is made all the more powerful by the recent H1 and ZEUS measurements showing that the rate of high Q^2 events is larger than expected. If these events are indications that new physics processes are occurring at HERA, it is crucial that we are able to study them in more detail. Studies of the hadrons in the final state will also help us untangle the processes contributing to the higher than expected rate. The current FT is able to perform these tasks at some level, but the relatively low segment finding efficiency means that, for example, no charge measurement can be made for the scattered lepton in a significant number of cases (20 to 30%) in which in principle a charge measurement is possible (ie. no shower generated in CJC end wall). A FT with higher efficiency and with improved momentum resolution at high momentum is thus desirable. It is also important to increase the proportion of final state hadrons for which a momentum measurement is available. Failure to do this will mean that studies of p_T spectra of charged tracks etc. are seriously hampered by the model dependence of the large corrections that will have to be made as too few of the tracks have been measured. This is particularly so if new physics is involved! Specifically we aim for improvements to determine the charge of the scattered lepton up to momenta of 100 GeV/c and to improve the tracking efficiency from the present level of ~50% in complicated events to over 90%. Options for FT upgrade. ----------------------- Rob Henderson presented the options for the FT outlined in the recently circulated note. The various options were discussed in detail. It was decided that project feasibility studies should be carried out for three options: A) Complete rebuild of the tank. Removal of TR volumes. Rearrangement of existing planars and construction of three new planar orientations to allow configuration consisting of (in order of increasing z) six planar orientations, MWPC, three radials, MWPC, six planar orientations, MWPC. (This is option A of the circulated note). B) Removal of TR volume. Removal of MWPCs. Construction of nine new (smaller radius) planar orientations to allow insertion of three planar orientations at the positions of the TR volumes/MWPCs with minimal modification of the gas tank. C) As B) but with trigger with similar functionality to current MWPC system. All these options should involve the refurbishing of the FT, ie. replacing connectors at the CDA and tank etc. Rob Henderson expressed the opinion that the amount of CPU time necessary to reconstruct events in a FT of type A), B), or C) is unlikely to be significantly longer than that currently needed. Actions. -------- Geoff Tappern et. al. are requested to look at the above options, ie. mechanical feasibility, manpower,time necessary and cost. (GJRT et al) Tim Greenshaw will investigate whether it is desirable to maintain or improve the forward trigger functionality and how this might be achieved. (TG) This information is necessary before progress on C) can be made! Don Clarke suggested that rebuilt planars may be constructed with less material than used in the current planars. He will investigate this. If a significant decrease in the amount of material is possible, it would be worth considering rebuilding the existing planars using the new technology. (DC) The above studies are needed for a presentation to the H1 collaboration meeting to be held 7^th July (1997). Forward Si ---------- Steve Burke stressed that the case for installing forward silicon is not clear-cut. The current proposal is essentially that the BST be installed in the forward direction. This means that stand-alone pattern recognition is unlikely to be feasible in any but the simplest (background free!) events and even if possible the attainable momentum resolution will be poor. However, the FSi will contribute significantly to physics analyses if it allows improved momentum resolution for FT tracks. This requires that there be unambiguous association between these tracks and FSi points. Rob will compare the present expected linkage performance with that of the proposed upgrades. Action ------ RCWH and SB to compare the ellipses of confusion at the position of the FSi for the present FT and for the upgrade options. (RCWH,SB) CJC End Wall ------------ Steve Burke stressed the importance of reducing the amount of material in the CJC end wall as far as is possible. Carsten Niebuhr has expressed some interest in the idea of replacing the CJC pre-amps and FADCs with ASICs attached to the CJC end wall, thereby reducing the amount of material (cables in particular) in this region. Steve will investigate the effect of doing this using the MC, with the help of Dave Sankey and Girish Patel. It was suggested that two processes be studied for the detector as it is and following the removal of all the CJC electronics, cables etc. (in the MC!), namely: elastic J/psi production (with decay to e^+ e^-); NC DIS at high Q^2. For the former we should determine: a) How the J/psi reconstructon efficiency changes (with sensible cuts in a sensible angular range). b) How the mass resolution is affected. For the latter we should find out: 1) How the detection efficiency of the electron changes (requiring perhaps two planar segments) as a function of angle in the FT. 2) How the quality of the determination of the electron's momentum (charge) changes for sensible cuts as a func of angle. 3) How the efficiency and purity of a sample of measured primary hadron tracks changes in the FT angular range. 4) How the average momentum resolution of the measured primary tracks changes (as a function of momentum) for generic physics analysis cuts. 5) How the momentum resolution of well measured tracks changes (three planar segments?). This may well be a deterioration at low momentum, dependent on the amount of material in the new FT, but will allow us to assess one of the possible disadvantages of the FT upgrade. (ACTION SB,GDP,DPCS) Study the secondary production in the Pt analysis (JVM). It was pointed out that the BDC group have similar problems with the end wall at the opposite end of the chamber. They may be interested in these studies and able to help with them. (ACTION TG to contact BDC group). MC studies for options A), B) and C) ------------------------------------ We would like to know the answers to questions 1)..5) above for options A), B) and C). These cannot be obtained using a ``real'' simulation, as this would involve the writing of the MC and of all the reconstruction software for all three options. Intelligent guesses can be made as to the effects of some of the modificatons however. Rob has already estimated the improvement in single track finding efficiency that will result from A) and can do the same for B) and C). An estimate of the effects of these options in high Q^2 events can be made by setting the segment finding efficiency to 100% in the MC. Dave Sankey suggested that an estimate of the effects on the momentum resolution of well measured tracks (at least two planar segments?) may be made by increasing the amount of material in the TR volume in the simulation so it represents that present in the additional chambers to be installed. ACTION; RCWH SB GDP DPCS TS. High Lumi magnets ----------------- The current plans for the high lumi magnets that affect the FT region directly involve the insertion of a magnet of external diameter 18cm through the LAr cryostat up to 1.8m from the IP. PRC Presentation etc. --------------------- We must give a preliminary presentation to the collaboration meeting 7 July followed by a detailed description of our plans in Sept. 1997. These would be presented to the PRC on Nov 4^th, if the collaboration is satisfied with the proposals we make. At about the same time we must present our proposal to the PPESP and request funding. Tim Greenshaw will produce a working document (Letter of Intent/Proposal) as an aid to identifying questions requiring further work, and to communicating our intentions to Bill Haynes and others who must consider what the proposals imply for the DAQ system (and write the DAQ part of the Proposal!) Planar Noise? ------------- There is evidence for the presence of occasional very large and long pulses in the planars. Joe Foster outlined some measurements that could be made relatively simply to look for spikes in the HV supply. If found, these would suggest that these pulses are associated with breakdown somewhere. Date of Next Meeting. ---------------------- 19-20 June in Liverpool. (Commencing 9.30AM 19/6/97). Thanks to all who attended for making this a very useful meeting!