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!