Informational Questions from the Internal STAR HFT Review Committee

Informational Questions from the Internal STAR HFT Review Committee

Scientific Merit

1)What information regarding D0yields can already be obtained with the STAR detector, including the TOF upgrade, from invariant mass plots? How much improvement in these yields would be gained from using the HFT?

2)Does one need D+-yields in order to get total charm yield?

3)How does one obtain the Au+Au charm yield estimate? How relevant is  background for electrons from B and D measurements? Is not the spectrum from resonance technique enough for open charm measurement?

4)Is electron v2 really not sufficient for charm flow measurement? Can this be sufficiently determined through TPC/TOF measurements?

5)Is the HFT capable of any measurement in a high luminosity pp collision environment, or would it be swamped with pileup?

6)What capabilities will PHENIX have that may complement these measurements with the HFT? Will the HFT measurements be better?

Technical Choice

1)Have active pixel sensors been used in an experiment yet? If so, where?

2)Is there a reference that explains how a sensor design without an epilayer works?

3)What are the results of testing of MIMOSTAR-1? What are the plans and changes to be implemented for the next version?

4)Will IRES be developing the next generations of the active pixel sensors until satisfactory prototypes for STAR are achieved, or is an alternative plan in place for the sensor R&D?

5)Could we get a history/schedule/testing summary of sensor R&D done by the HFT development team during the last several years?

6)What is the status of the sensor thinning attempts? What techniques have been tried? What are the yields? Is a 50 um thick piece of silicon approximately the same dimensions (2 cm x 2 cm) as the sensor presently in hand?

7)With the present status of R&D efforts what is the total radiation thickness and position resolution that could be obtained with an HFT if it were built today?

8)What limits the readout speed of the sensors? Can the pixel readout speed of the sensor (400ns/pixel) be increased?

9)What technology will the readout asic be fabricated in? Has a prototype readout asic been designed and fabricated and tested?

10)Where will the readout/transceiver board be located?

11)How is the background suppression of gamma -> e+e- supposed to work when the tracking algorithm always finds a hit on the HFT? Is a Monte Carlo calculation of this available?

12)Would the HFT in its present design be usable at planned RHIC-II luminosities? If not, is there an upgrade path that could make it usable?

13)Can we get the appendices, and reference 70?

Technical Capabilities/Specifications

1)One obtains 40 pileup events at luminosity L=1027 s-1 cm-2, but the proposal shows 120 on pages 41-42. How is the number of 120 events obtained?

2)Pg. 31 of the proposal: “After including the SVT in the analysis the vertex resolution is approximately 2mm”. What hit resolution/alignment for the SVT is assumed? Is this SVT or SVT-1? Also, does this mean that the DCA of primary tracks is approximately 2mm with one or more SVT points added? What is the vertex resolution (x,y,z) with just TPC tracks?

3)Fig. 12: What hit resolution for the SVT and SSD was assumed, and what alignment accuracy to the HFT did the SVT, SSD and TPC have? Was the “take closest hit to the track projection on the HFT” algorithm used? Were 120 Au-Au gold collisions assumed to be piled up corresponding to the luminosity L=10·1026 s-1 cm-2? If so, what hit densities are obtained in each layer?

4)What causes the extra 20% loss of efficiency in Fig. 12 when the HFT is included in the analysis chain? It appears the ghosting (Fig. 13) cannnot account for more than 5%.

5)Fig. 13: Were the conditions/Monte Carlo used to make Fig. 12 the same as to make Fig. 13, i.e. same pileup, etc?

6)Pg. 34: What is the value of used (or a histogram if it was varied on a track by track basis)?

7)Figs. 14 and 16: What SVT hit resolution is used?

8)Fig. 16: What pileup is included? If so, what was the luminosity and resulting hit densities?

9)Fig. 17: Please explain what are the different calculations for the left and right panels.

10)Fig. 17: Can you explain why the 120 and 240 micron thickness results are similar, but the 360 micron thickness results require far more events?

11)Fig. 20: What is the number of events and luminosity assumed for the “one-year” of data taking?

12)Are there details on pile-up vs conversion-electron rejection available?

13)Are pp comparison runs required for the understanding of charm production cross sections in the heavy ion program? If so, can these be made in a reasonable running rime considering the HFT length is about 20 cm but the interaction diamond sigma is about 60 cm?

14)Related to this, can the small A_LL quoted on page 19 of the proposal be measured in a reasonable time (same problem, HFT length 20 cm, beam length sigma 60 cm)? With such small asymmetries, I would be concerned that systematics effectsmight be a concern due to differences in bunch profiles?

Detector Integration

1)Would the mechanical support concept of the HFT change if there is no SVT, but rather a new pointing detector designed to integrate with the HFT?

Detector Context

1)What kind of track resolution does one need in order to make the HFT achieve its goals?

2)What is the primary vertex resolution assumed for electron impact parameter measurement? Is it going to improve with the HFT?

3)Could we get a sketch showing at least one version of a ladder (e.g. with an asic readout chip) showing how it physically looks, as well as showing the data/power lines? How are the sensors and readout chip bonded and electrically connected?

4)What limits the length of the ladders, especially relative to the beam crossing diamond size in z?

5)Has crosstalk between the HFT and the pointing detector been considered?

6)How long is the narrow section of the beam pipe and what is the angle of the taper?

7)Would the proposed 3 cm diameter beam pipe produce unacceptible conflict for measurements using the proposed Roman Pots?

Resources

1)Is there a resource based WBS available in order to understand the cost and schedule estimates?