1Jim Thomas - LBL
HFT Issues that may Bear on the Fate of the SSD & SVT
presented by
Jim Thomas07/07/2006
2Jim Thomas - LBL
• A new detector– 30 m silicon pixels
to yield 10 m space point resolution
• Direct Topological reconstruction of Charm
– Detect charm decays with small c, 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
The Heavy Flavor Tracker
The HFT: 2 layers of Si at mid rapidity
3Jim Thomas - LBL
Direct Topological Identification of Open Charm
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.
Goal: Put a high precision detector near the IP to extend the TPC tracks to small radius
4Jim Thomas - LBL
Surround the vertex with Si
A thin detector using 50 m Si to finesse the limitations imposed by MCS
5Jim Thomas - LBL
The HFT has a Distinguished R&D 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
6Jim Thomas - LBL
The Need for Substantial R&D
• 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
7Jim Thomas - LBL
Schedule for R&D and Construction of the HFT
8Jim Thomas - LBL
HFT R&D Installation for the Summer of 2006
A Three Layer Telescope with MimoSTAR II Chips.
A full system test from pixel to DAQ.
9Jim Thomas - LBL
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.
10Jim Thomas - LBL
HFT Timeline vis a vis the SVT
Install MimoSTAR II
Telescope
06 07 08 09 10
X XX X X
Install MimoSTAR IV
Prototype Detector
Install MimoSTAR III
LadderInstall a
nd run
MimoSTAR IV
Detector (Full)
Install Ultra
STAR
Detector (Full)
Install and test Prototype detector. Highly desirable to install and test with reduced diameter BP
Reduced diameter BP is required. SVT must be out of the way
11Jim Thomas - LBL
SVT Detail – beam pipe size & mounting issues …
12Jim Thomas - LBL
13Jim Thomas - LBL
SVT Recommendations
• It would be fun to do HFT R&D 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
14Jim Thomas - LBL
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
15Jim Thomas - LBL
A Toy Model for Pointing at the HFT
including PT and DCA Resolution
Jim Thomas
Lawrence Berkeley National Laboratory
November 29th, 2005
16Jim Thomas - LBL
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.
17Jim Thomas - LBL
TPC pT Resolution in 2001 (Half field data)
Pions in the TPC without the SSD or SVT
p-bars in the TPC without the SSD or SVT
Add the SSD and the SVT; resolution improves but MCS gets worse
Add a 350 m vertex constraint
18Jim Thomas - LBL
Pointing resolution at the next Detector
TPC Pointing at the SSD
TPC Pointing at the SSD with 350 m Vertex Constraint
TPC & SSD Pointing at the HFT
TPC & SSD Pointing at the HFT with 100 m Vertex Constraint
19Jim Thomas - LBL
SSD Issues & RecommendationPositives• 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!