# Presentation: 863988

## Star Inner  Trackingupgrade

***Star Inner  Tracking******upgrade***

- F. Videbaek
- STAR collaboration
- for the HFT upgrade group

## Overview

- Physics Goals for Heavy Flavour Tracker (HFT)
- Overview of STAR
- Expected Physics Results (Simulations)
- Detector Components for HFT
- Pixel
- IST
- SSD
- Infrastructure
- Summary

**Notes:**
Jan covered good number of details; you will recognize some plots..

## Physics Goals

- New frontier - heavy quark production
- 	- HQ collectivity: test light quark thermalization
- 	- HQ energy loss: explore pQCD in hot/dense medium
- Base line reference spectra for the HI program
- c and b cross section in pp at 200 and 500 GeV
- Method : Topological identification of D’s, c to low pT.

## Heavy Flavor Energy Loss

**Surprising results** -
-  - challenge our understanding of the energy loss mechanism
-  - force us to RE-think about the collisional energy loss
-  - **Requires***** *****direct measurements of C- and B-hadrons.**

- 1) Non-photonic
- electrons decayed
- from  - charm and
- beauty hadrons
- 2) At pT ≥ 6 GeV/c,
- RAA(n.e.) ~ RAA(h±)
- contradicts naïve
- pQCD predictions

- u

|  | Measurements | Requirements |
| --- | --- | --- |
| Heavy Ion | heavy-quark hadron v2 - 
the heavy-quark collectivity | - Low material budget and high efficiency min ≥ 1%
 pT coverage ≥ 0.5 GeV/c
 mid-rapidity 
 High counting rate |
|  | heavy-quark hadron RAA - 
the heavy-quark energy loss |  High pT coverage 
  ~ 20 GeV/c |
| p+p | energy dependence of the heavy-quark production |  - pT coverage down to 0.5 GeV/c |
|  | gluon distribution with heavy quarks | - wide rapidity and pT coverage |

## Overview of Layout, concepts

- Inner high resolution pixels are crucial for physics goal of direct D0 topological identification
- Relies on TPC-SSD-IST-PIXEL tracking for graded point matching and resolution.

## STAR Detectors: 2 Particle Identification  

*HFT*

*TPC*

*FGT*

- STAR Detectors: 2 Particle Identification * *

*EMC*

*TOF*

**Notes:**
Mention that Bates contribution was absolutely critical!

## Inner Tracking Detectors

**20 cm**

## Concept of HFT Layers

| Graded Resolution from the Outside – In | Resolution() |
| --- | --- |
| TPC pointing at the SSD 	( 23 cm radius) | ~ 1 mm |
| SSD pointing at  IST 	    ( 14 cm radius) | ~ 400 m |
| IST pointing at Pixel-2  	    ( 8 cm radius) | ~ 400 m |
| Pixel-2 pointing at Pixel-1	(2.5 cm radius) | ~ 70 m |
| pixel-1 pointing at the vertex | ~ 40 m |

- Purpose of intermediate layers to get increasing resolution power with increasing hit-densities, so the high resolution hits in the inner pixel’s can be found, assigned and displaced vertices determined.

**SSD**

**IST**

**PIXEL**

## DCA Cuts

**DCA Cuts**
**Uses PID from TOF.**

**Estimated mass spectra from 100M central events**

## D0 Reconstruction Efficiency

- D0 Reconstruction Efficiency

- - Central Au+Au collisions: top 10%events.
- - The thin detector allows measurements down to pT ~ 0.5 GeV/c.
- - Essential and unique!

## Charm Hadron v2

- Charm Hadron v2

- - 200 GeV Au+Au minimum biased collisions (500M events).
- - Charm collectivity  drag/diffusion constants  ***medium properties! ***

**Notes:**
Hydro model: Pasi Huovinen, private communication, January 2008.
Just to remind you: these calculations were doen using my "standard" set of parameters: initial time 0.6 fm/c, first order phase transition at T_c=165 MeV, chemical equilibrium all the way until until kinetic freeze-out, freeze-out at T_f=130 MeV reproduces pion spectra and (anti)proton p_T-slope, initial profiles as a combination of participant and binary collision scalings.

## Work is continuing to refine details of the detector design/performance

- Simulations of the
- most challenging
- 3-body decays
- are encouraging
- so far

- This capability, which will be provided uniquely at RHIC by the HFT, is crucial for determining whether the baryon/meson anomaly extends to
- heavy quark hadrons

## Detector Realization

- Briefly discuss
- PIXEL
- IST  (intermediate Silicon Tracker)
- SDD (Silicon Strip Detector) - existing
- Infrastructure

## PIXEL

**2 layers of 18x18 ********m pixels at 2.5 and 8 cm radius, 20 cm long**
**Very low material budget to limit multiple scattering**
**Data reduction and formatting on chip**
**Rapid insertion and removal**
**Precision positioning**
**Air cooling **
**Ongoing APS technology R&D with Strasbourg**
**For RHIC luminosities needs ‘fast’ detector with better than 200 ********sec integration time.**
**Efficiencies degrade with ‘pile-up’ within sample time**

## Active Pixel Sensors

**Properties:**
- Signal created in low-doped epitaxial layer (typically ~10-15 μm)
- Sensor and signal processing integrated in the same silicon wafer
- Standard commercial CMOS technology

- pixel chips (MAPS) produced by
- IReS/LEPSI  IPHC (Strasburg)

**Notes:**
So, moving on to the sensors. We are using CMOS pixel sensors which are being developed by our collaborators at IRES, now IPHC. There’s a lot of information here but I just want to make a few points about our sensor technology. First is that we are using CMOS technology which is widely available, so we can use any standard CMOS foundry and are not limited to special silicon processes with limited availability. Also, the sensors have full active area, there are no dead areas between the pixels. This type of sensor does not use electron avalanche type gain, the charge is collected and appears as a voltage on the source follower structure. This voltage is buffered, amplified, and read out.

## IPHC Functional Sensor Development

- _IPHC Functional Sensor Development_

_**Data Processing in RDO and on chip by generation of sensor.**_

- The RDO system design evolves with the sensor generation.

- 30 x 30 μm pixels => 18x18 μm
- CMOS technology
- Full Reticule = 640 x 640 pixel array=> 1024 x 1088 array

- _Mimostar 2_ => full functionality 1/25 reticule, 1.7 μs integration time (1 frame@50 MHz clk), analog output. *(in hand and tested)*

- _All sensor families:_

- _Phase-1_ and _Ultimate_ sensors => digital output *(in development)*

**Leo Greiner,LBNL**

**Notes:**
We are following a sensor development programme in collaboration with our colleagues at Strasbourg. There are two series of sensor that we follow with our mechanical and readout development. The first series is the mimostar series which we plan to use to produce a full prototype detector with analog readout. The characteristics are as shown... The ultimate series is the what we intend to use in the final detector. It has mostly the same pixel and physical characteristics as the mimostar series but with much more processing on chip such as on chip CSD, a much shorter 200 us integration time. Programmable dual discriminators and digital output via LVDS

## Some pixel features and specifications

| Pointing resolution | (13  19GeV/pc) m |
| --- | --- |
| Layers | Layer 1 at 2.5 cm radius
Layer 2 at 8 cm radius |
| Pixel size | 18.4 m X 18.4 m  |
| Hit resolution | 10 m rms |
| Position stability | 6 m (20 m  envelope) |
| Radiation thickness per layer | X/X0 = 0.28% |
| Number of pixels | 436 M |
| Integration time (affects pileup) | 
0.2 ms |
| Radiation tolerance | 300 kRad |
| Rapid installation and replacement to cover rad damage and other detector failure | Installation and reproducible positioning in a shift |

- critical
- and
- difficult

- (ATLAS Pixels 1.2%)

## Pixel support structure

*Inner layer*
*Outer layer*

*End view*

*ALICE style carbon support beams (green)*

*2.5 cm radius*

*8 cm radius*

*‘**D-Tube Duct and Support*

*Since modified to increase Sensor Clearances*

*‘**D-Tube Duct and Support*

## Sensor Development Status

- _Sensor Development Status_

_**Mimostar-2**_
- Testing complete – MS-2 Sensor telescope used at STAR for telescope test in previous run.
- Description and results are published in:
- Nuclear Instruments and Methods in Physics Research A 589 (2008) 167–172

## Pixel proto in STAR, measured track density at r = 5cm, z = 145cm

- 4*4 mm

**Placed inside STAR during Run-7**
**Located 150cm (z) 8 cm below beam**
**Track density low.**
**Resolves tracks from collision vs. background**

**Notes:**
Close to hit density at

## IST Layout

- Bernd Surrow

- IST - 3D view

- Layout:
-  r = 14 cm
- ~24 ladders
- 12 units (Modules) per ladder (44cm)

- IST
**1 sensor layer: Silicon-pad type**

## Technical realization

- Bernd Surrow

- IST - Ladder design - Overview

**Ladder:**
** ****Carbon fiber base material**
** ****12 modules per ladder**
**Length: 44cm**

- Module:
**Silicon-pad sensors: Dimensions: 4cm X 4cm**
**Pad size structure still being optimized: 400μm X 1cm typically**
**Readout Chip: APV25-S1**
**3-5 chips per sensor**
**liquid cooling**

- Location: APV25-S1 Readout Chips

- (Example: PHOBOS Inner Vertex Sensor)

- Location: Silicon-pad sensor

*42cm*

## Infrastructure

- Infrastructure

- Integration of Mechanical structures is a critical issue for the project.
- Replacement of existing beam pipe -> r ~2cm.
- Support of thin and light weight structures. Recall the total radiation length is aimed at <=3%.
- Ease in replacement of pixel ladders in case of failures, and effect of radiation.
- Support for PIXEL, IST, SSD and FGT

## Conceptual Inner Part of STAR

- Intricate layout for 3 HFT trackers + beam pipe + FGT.

*SSD*

*IST*

*IFC*

*WSC*

*New Cone Structures inside of Inner Field Cage*

*ISC*

*Pixel*

*East Cone*

## Inner Support Cylinder  (ISC)

*ISC fits inside and is supported by the cone*

*ISC supports IST on outside*

*ISC*

*ISC supports pixel and beam pipe inside*

*SSD Supported on outside*

*SSD Services out both sides*

*IST Services out East side on ISC*

## Follower guided insertion operation

*Open*

*Closed*

*Clears Beam Pipe over*
*Large Diameter*

*Clearance for *
*Beam Pipe Supports and*
*Kinematic Mounts*

*Final Motion engages*
*Kinematic Mounts*

*Articulation*
*Region*

## SSD

- The SSD is an integral part of the upgrade. It is an existing detector. It will be upgraded to be compatible with DAQ1000. Redundancy is built with the outer strip layer.

## Summary

** ****Physics of the Heavy Flavor****  Tracker at STAR****1) Au+Au collisions****     **(1) Measure heavy-quark hadron v2, heavy-quark collectivity, to study the medium            properties *e.g.* light-quark thermalization                  (2) Measure heavy-quark energy loss to study pQCD in hot/dense medium* **e.g. **            energy loss mechanism *     (3)  Measure di-leptions to study the direct radiation from the hot/dense medium     (4)  Analyze hadro-chemistry including heavy flavors**2) p+p collisions****     **(1) energy dependence of the heavy-quark production
-    (2)  reference spectra for AuAu                   * *

## 3 year Run Plan when installed

**3 year Run Plan when installed**

**1****) First run with HFT:****	**** 200 GeV Au+Au****	******** v****2**** and R****CP ****with 500M M.B. collisions****2) Second run with HFT: 200 GeV p+p **** ****	**** ******** R****AA****	****3****) Third run with HFT: 200 GeV Au+Au****	**** ****	**** ******** centrality dependence of v****2**** and R****AA**** ****	**** ******** Charm background and first attempt for ****	****     electron pair measurements**** ****	******** Sufficient Statistics for ********c**
**A technical driven schedule would allow complete detector for Run-12.  The real world with budget constraints ??**
**An engineering run with a few pixel ladders is planned.**

## Final word

- An HFT upgrade to STAR than will utilize all the strengths of STAR (2 coverage, TOF,..) and will provide crucial charm and bottom measurements.
- See also Jan Kapitan’s poster at this meeting

**Notes:**
I have not been able in this short presentation to dwell with all the on-going activities; Like to refer you to the proposal, the tup list, and contact with the people in charge.

## The End