# Presentation: 363192

## Heavy flavor physics and Vertex detector

## People involved

- RNC Group
- Howard Wieman
- Hans-Georg Ritter
- Fred Bieser (Lead Electronic Engineer)
- Howard Matis
- Leo Greiner
- Fabrice Retiere
- Eugene Yamamoto
- Kai Schweda
- Markus Oldenburg
- Robin Gareus (Univ. of Heidelberg)

- LEPSI/IReS (Strasbourg)
- Claude Colledani, Michel Pellicioli, Christian Olivetto, Christine Hu, Grzegorz Deptuch Jerome Baudot, Fouad Rami, Wojciech Dulinski, Marc Winter
- UCIrvine
- Stuart Kleinfelder + students
- LBNL Mechanical Engineering
- Eric Anderssen (consultation – ATLAS Pixels)
- Design works
- BNL Instrumentation Div (consulting)
- Ohio State U
- Ivan Kotov

## Heavy flavor in ultra-relativistic heavy-ion collisions

- Heavy Q pair
- formation
**How many?**

- c/b quarks in matter
**Thermalization? **
**Coalescence? Flow?**

**Heavy flavor hadrons**
**to detectors**

**Heavy quark energy loss**

**High p****T**

**Low**
**Intermediate p****T**

## Measuring yields

- Large uncertainties
- In data
- In theory
- Way to improve
- Measure and identify all charm hadrons
- Measure precise spectra

- STAR preliminary

## Heavy-quark energy loss

- Heavy quarks radiate less energy than light quarks (prediction)
- Yield of charm and beauty (leading) hadrons less suppressed
- May be measured by D → X+e- and B → X+e-
- Without vertex information systematic error from background substraction

- STAR preliminary

## Flow and thermalization

- Flow: spectra and v2

- Charm thermalization by chemistry

- J. Nagle, S. Kelly, M. Gyulassy,
- S.B. JN, Phys. Lett. B 557, pp 26-32

|  | e-p & e+ e- | Thermal |
| --- | --- | --- |
| f(c→D0) | 0.557 | 0.483 |
| f(c→D+)
 | 0.232 | 0.21 |
| f(c→Ds+)
 | 0.101 | 0.182 |
| f(c→c+)
 | 0.076 | 0.080 |

## Measuring heavy flavor with the Vertex detector

- Goals
- Heavy flavor energy loss
- Remove background
- Charm flow
- Precise D0 spectra
- D0 v2
- Charm thermalization
- Yield of D+, Ds+, c+ (challenging 3 body decays)

- Vertex strategy
- Separate charm and beauty decay product from primary tracks
- Typically D0 c = 124 m
- Vertex requirement: a very good vertex resolution
- Position resolution < 10 m
- Thickness < 0.2% of rad length to limit multiple scattering

## STAR Vertex Detector

- STAR Vertex Detector

- Two layers
- 1.5 cm radius
- 4 cm radius
- 24 ladders
- 2 cm by 20 cm each
- < 0.2% X0
- ~ 100 Mega Pixels

## Charm hadron reconstruction performances

| System | N events for 3 D0 signal | N events for 3 D+s signal
In progress |
| --- | --- | --- |
| TPC+SVT | 12.6 M | ~500 M (K0s + K+) |
| TPC+SVT+TOF | 2.6 M  | ~1,000 M (++) |
| TPC+SVT+Vertex | 100 K | ~100 M (++) |
| TPC+SVT+Vertex+TOF | 10 K | ~1 M (++) |

## STAR Vertex Detector

**New vertex detector centered in existing SVT, supported one end only**

**End view showing 3 of 6 ladder modules**

## Support: thin stiff ladder concept

- Under development
- Will be tested for vibration in our wind tunnel

## Sensors: Active Pixel Sensors

- Advantages
- Precise
- Can be thin
- Rather fast
- Low power
- Disadvantages
- Small signal
- Not that fast
- New
- Need R&D

- p-well

- p-well

- n-well

- p-epi

- p-substrate

- 5-20 m

- CMOS electronic
- Analog & digital

## Sensors: 2 generations

- 1st Generation: 5-10 ms readout time
- MIMOSTAR1 designed by LEPSI/IRES (Strasbourg)
- 640*640 pixel of 30*30 m2 pitch
- Purely analog
- Parallel readout on-chip multiplexed to 2 kind of outputs
- 1 * 100MHz driver
- 10 * 10 MHz drivers

- 2nd Generation: Faster but need more R&D
- R&D with UCIrvine and LEPSI/IRES
- Improve charge collection and remove need for CDS
- Photogate, Active reset, ...
- Some digital processing
- Up to cluster-finder?

## Readout

- Analog to end of the ladder (~1 m away)
- Challenge to drive analog signal at 100 MHz over 1m
- Piggy back chip
- ADC and memory on a chip bounded to the pixel chip
- On-chip processing in 2nd generation
- Data reduction at the end of the ladder
- Hardware reduction (zero suppression)
- Single board computer

## Budget

- FY02-FY04 LBNL LDRD (total 375K$)
- FY04 RHIC R&D (200 K$ through Brookhaven)
- Expected to continue until project is funded
- Preparing a strategic LDRD fund request geared towards the development of future tracking apparatus with the Physics Division (Linear Collider)

## The time-scale

- Proposal in April 2004
- 1st ladder prototype this fall (2004)
- Investigate mechanical support, cabling and some readout issues
- Sensor: MIMOSA5 large but slow and “noisy”
- 2nd ladder prototype next year (fall 2005)
- Sensor: MIMOSTAR1 (submitted in July)
- R.Gareus’s Readout chip (submitted in July)
- The real thing starting in 2006
- Pending funding and success of prototypes

## Summary

- A lot of work ahead of us!