# Presentation: 160783

- H. Wieman
- Sept. 19, 2002
- BNL

- EIC Vertexing for A + A

## Motivation for an inner tracker

- A tool for reducing combinatory background to measure yields of particles with short decay times
- Works with collections of many events
- Background can be less than 1 per event, but signal is still less
- Does not extract special decays event by event in the high multiplicity environment of A+A
- Measure D mesons

## Invariant mass reconstruction of D0s k (preliminary simulation)

- Invariant mass reconstruction of D0s k (preliminary simulation)

- M (GeV)

**D****0**

- Number of events required to get a statistically significant result

- S

- B

- Because A+A at RHIC produces very high multiplicity events the vertex detector must be exceptionally good to reduce B

## #1 priority: go thin to reduce Background

- Si thickness (m)

- B

- Shows effects of first layer SI thickness, includes contribution from 760 m beam pipe.

- Preliminary GEANT
- simulation

- Si thickness reduction
- 300 m   50 m
- reduces beam time by factor 19

## The options

- ATLAS style hybrid
- Thick ~ 300 m Si
- High power 800 W/cm2 – requires liquid cooling, more thickness
- CCDs
- Very thin
- Power vs speed ?
- Rad soft
- Active Pixel Sensors (APS)
- Very thin
- Rad hard enough
- Slow? But good potential with low power
- New technology with normal uncertainties

## APS Compromises

- Short, does not cover diamond
- Most running not luminosity limited so not an issue unless run with a very good trigger
- Slow, contains multiple events
- Background rejection is pileup tolerant

## False rejection by pileup

- Purpose of vertex detector – remove primary tracks before calculating invariant mass
- 40 x design luminosity,     5 ms readout
- 400 hits/cm2
- 1.4% pixels filled
**false rejection 0.5%**
- 40 X design luminosity, 20 ms readout
- 1500 hits/cm2
- 5.3% pixels filled
**false rejection 2.9%**

## A Monolithic Active Pixel Sensor for Charged Particle Tracking and Imaging using Standard VLSI CMOS TechnologyJ.D. Berst, B.Casadei, G.Claus, C.Colledani, W.Dulinski, Y.Hu, D.Husson, J.P.Le Normand, R. Turchetta and J.L.RiesterLEPSI, StrasbourgG.Deptuch, Y.Gornushkin, S.Higueret, M.WinterIReS, Strasbourg

- LEPSI - IReS APS
- 20 m  square pixels
- 4 64X64 arrays
- MIMOSA 1, 0.6 m CMOS
- MIMOSA 2, 0.35 m CMOS

## Rapid progress toward fast low power readout with on detector zero suppression  

- Rapid progress toward fast low power readout with on detector zero suppression

- All this on a 23 m by 23 m
- pixel

## LBL APS test with 1.5 GeV/c e-beam

- 17 e RMS per pixel

## LBL APS measured MIP signal

- Sums of 25 pixel regions centered on pixels with ADC  7

- Same sums with empty frames

- Background subtracted APS signal with Bichsel calculation for 8 m Si

- Conclusion, signal to noise is good enough to get good efficiency without excessive false hits
- The above analysis is with CDS and leakage current subtraction

## Active Pixel Sensor (APS)

- 8 cm

- 5.6 cm

- 20 m square pixels
- 5 chips per slat
- 90 million pixels
- 50 m thick chips
- 760 m Be beam pipe

## One of 8 Modules

- LBNL mechanical concept for an inner vertex detector for STAR

- 50 m Silicon supported under tension

- Aluminum/Kapton flex cable under tension

## Slide 14

## END