HFT Issues that may Bear on the Fate of the SSD

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• HFT Issues that may Bear on the Fate of the SSD
  SVT
• presented by
• Jim Thomas
• 07/07/2006

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The Heavy Flavor Tracker

• A new detector
• 30 mm silicon pixels
• to yield 10 mm space point resolution
• Direct Topological reconstruction of Charm
• Detect charm decays with small ct, including D0
  ? K ?
• New physics
• Charm collectivity and flow to test
  thermalization at RHIC
• Charm Energy Loss to test pQCD in a hot and dense
  medium at RHIC
• Desirable to have it in time for the next long
  Au-Au run
• Proposal moving forward

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Direct Topological Identification of Open Charm
Goal Put a high precision detector near the IP
to extend the TPC tracks to small radius
The STAR HFT will identify the daughters in the
decay and do a direct topological reconstruction
of the open charm hadrons. No Mixed events, no
random background subtraction.
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Surround the vertex with Si
A thin detector using 50 ?m Si to finesse the
limitations imposed by MCS
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The HFT has a Distinguished RD Heritage
Driven by the availability of CMOS Active Pixel
Sensors
1999 2001 2003 2004 2005 2006 2007 2009
Mimosa-1 Mimosa-4 Mimosa-8 MimoSTAR-1 MimoSTAR-2 MimoSTAR-3 MimoSTAR-4 UltraSTAR
Build a full detector with each
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The Need for Substantial RD

• Challenging HFT technologies
• The Silicon Chips
• Further refinement of on-chip electronics
• Readout Electronics
• speed, heat dissipation, compatibility with STAR
  DAQ
• The Mechanical Arms to insert the detector
• Alignment and stability
• Calibration, Tracking Software
• New levels of precision
• The beam pipe
• Smaller than ever before Operation and
  robustness

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Schedule for RD and Construction of the HFT
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HFT RD Installation for the Summer of 2006

• A Three Layer Telescope with MimoSTAR II Chips.
• A full system test from pixel to DAQ.

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Beam pipe
The exo-skeleton for the new beam pipe is
incompatible with inner radius of the SVT. This
conflict determines the final date when the SVT
must be moved.
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HFT Timeline vis a vis the SVT
Install MimoSTAR II Telescope
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SVT Detail beam pipe size mounting issues
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SVT Recommendations

• It would be fun to do HFT RD with the SVT.
  Ideally, we would remove the first layer of the
  SVT and install HFT chips inside this region.
• Long, difficult task but there do not appear to
  be the human resources to do it (nor financial).
• Therefore I recommend
• Remove the SVT in the summer of 2008 so we can do
  HFT prototype detector tests at the IP
• This ensures a success scenario for the HFT
• If this is not possible, the SVT must come out in
  the summer of 2009 so we can install the reduced
  diameter BP and a full version of the MimoSTAR IV
  detector

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The SSD is a Beautiful Detector

• The SSD is thin
• 1 - double sided Si
• The SSD lies at an ideal radius
• 23 cm - midway between IP and IFC
• The SSD has excellent resolution
• (rumor says better than design)
• The SSD is too large to be replaced
• The money is better spent, elsewhere

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• A Toy Model for Pointing at the HFT
• including PT and DCA Resolution
• Jim Thomas
• Lawrence Berkeley National Laboratory
• November 29th, 2005

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To Make a Long Story Short

• Covariance matrix equations from the particle
  handbook
• Include errors due to finite spectrometer
  resolution
• Include errors due to Multiple Coulomb Scattering
• Due to MCS limitations, it is the previous two
  layers that determine the pointing resolution on
  the current layer so a 2 layer approximation is
  a very good approximation for extremely high
  resolution detectors.

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TPC pT Resolution in 2001 (Half field data)
Pions in the TPC without the SSD or SVT
Add a 350 mm vertex constraint
p-bars in the TPC without the SSD or SVT
Add the SSD and the SVT resolution improves but
MCS gets worse
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Pointing resolution at the next Detector
TPC Pointing at the SSD
TPC SSD Pointing at the HFT
TPC Pointing at the SSD with 350 mm Vertex
Constraint
TPC SSD Pointing at the HFT with 100 mm Vertex
Constraint
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SSD Issues Recommendation

• Positives
• The HFT needs the SSD (or something equivalent)
  as part of the pointing package. It points at
  the intermediate tracker and reduces the search
  radius for finding hits.
• It is the third layer in the pointing system.
  Very important for overall tracking efficiency
  because any given layer is only 90 efficient.
• Two layers are 80 efficient
• But three layers are 97 efficient for having two
  hits
• A third layer provides badly needed redundancy
  and insurance that we are successful in putting
  data on tape
• Negatives
• It will have to be remounted on a new cone
• It will need new electronics to keep up with DAQ
  1000
• These appear to be good investments

SSD Recommendation Keep It!