Question PF_1: Forward acceptance

Calorimetric coverage extends in the baseline design to close to 5 mrad. Is it important to extend to such a small angle? What is a realistic goal for a configuration with 20 mrad crossing angle?

Question PF_2: Gaps + barrel/endcap

How important are gaps between the calorimeter components? How important are gaps between the calorimeters and other components such as the TPC? What is the penalty for a round TPC inside an octagonal ECAL, if any? How efficient is the TPC for detecting backscattered particles. How important are these?

What is the optimal transition barrel – end cap done? Is the current scheme of a long barrel in front of the end cap optimal? Are there alternatives?

Question PF_3: Two photon separation

How important is efficient separation between two close-by photons? Or is it enough to separate photons and hadrons in more general terms?

Question PF_4: Composition / segmentation / location

What is the optimal material for the ECAL and HCAL? Tungsten? Lead? Uranium? What is the optimum relation between the Moliere radius and the sampling fraction? What is the optimal transverse and longitudinal separation? What is optimal division between ECAL and HCAL sections? What is penalty for reducing inner radius of barrel and bring the endcaps closer to the interaction point?

Question PF_5: Material in front of calorimeter

How close should the end cap be to the endplate of the TPC? How much material in font of the end cap is acceptable? How much material can be tolerated in front of the barrel calorimeter?

Question PF_6: Calorimeter depth

A typical ECAL presents about 1 interaction length to a particle. The current design for the HCAL corresponds to adding 4 more interaction lengths. The level of pions sailing through the calorimeters is at the percent level. This has two consequences: they constitute a background to muons, and the showers are not well contained. Is the tail catcher a part of the solution? Is the detailed knowledge of the development of the shower a solution? Should we increase the depth of the calorimeter or go from iron to tungsten or part of tungsten? A special case is the end caps. Shouldn’t we consider going to 7 interaction lengths and forget about the muon chambers in that part of the detector to improve the quality of the magnetic field, or conversely reduce the coil length suppressing the return yoke plug?

Using a muon system outside the coil in the current design sets a momentum threshold at around 5 GeV. We need to identify muons at lower energies. What can be the efficiency and the contamination of finding muons in the HCAL? Do we need then to improve the contamination at high energies with an external muon identifier?

Question TR_1: Vertex detector configuration

Length of the vertex detector: The length of the first layer is driven by the backgrounds, the other one by the requirement to have good solid angle coverage. Is the current layout optimal?

Layout of the vertex detector: only barrel, integrated end caps? Does it make sense to revisit the question of end caps in the VTX detector? They introduce complexity, and possibly more material. How does one extract the cables from the barrel in the presence of end caps? Are they needed?

Question TR_2: Alignment

How can we align the VTX relative to the rest of the detector? How do we align the TPC relative to the magnetic field map?

Question TR_3: Vertex materials

Develop a realistic ladder and support structure estimate, electronics, cables, etc. Where are the cables routed? Where does the electronics sit? Is the TDR place on the mask still an alternative, given that the distance between detector and mask has changed significantly?

Question TR_4: SIT and SET

The SIT was introduced for track merging and for V0 efficiency reasons. These studies should be redone. Is the current SIT and SET layout optimal? Which role does the material play in the overall track reconstruction?

Question TR_5: Forward tracking

In the forward direction, the FTD is currently a system of pixels and disks. How important is its material. How stable is forward tracking? What are the important performance goals for tracking in the forward region?

Question TR_6: FCH system

How important is the FCH behind the TPC? Do we need stand-alone tracking capability in there, or is a simple device which adds one or two hits sufficient? Which technology is optimal for the FCH?

Question TR_7: Magnetic field

What quality of the field do we need in the TPC, SIT, and other detectors? How can we measure and monitor the field distortions at the required level of accuracy? Can the large distortions in the large crossing angle be accounted for? Can control samples be used to improve the knowledge of the field map? Does it make sense to eliminate the plug, at the cost of a shorter magnet and thus a less homogeneous field?

See: physics/0507129

Question MU_1: Purpose & Design

Is the muon system needed for mu identification, tail catcher, cosmic veto? Can the muon system play its role as a tail catcher even behind 1 interaction length of magnet?

Is the separation between barrel and endcap optimal? How many layers of sensitive detector do we need? How thick should the muon system be?

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