# Presentation: 102173

## The Silicon Vertex Upgrade

- Measuring heavy quarks at RHIC

- Hubert van Hecke – Feb 7 2005

- 7 Feb 2005

## Outline

- Why measure heavy quarks
- Can confirm the existence of the QGP
- Silicon vertex detector – barrel project
- 4.3M$
- Silicon vertex detector – endcap proposal
- 4.6M$
- Expected endcap performance
- Current LDRD-DR proposal

- 7 Feb 2005

## Why heavy quarks?

- Heavy quarks are not present in the incoming nuclei, but are produced in the collision
- They live relatively long, escape from the fireball, and travel macroscopic distances before decaying – this is the key to their identification
- On the theory side, the large quark mass makes pQCD calculation of their production and propagation easier
- Use the heavy quarks to probe the properties of the matter through which they travel (QGP)

- 7 Feb 2005

## Heavy quarks - signals

- Energy loss
- Energy loss of heavy quarks in QGP is expected to be much larger than in normal nuclear matter

- Debeye screening
- J/ dissociates into DD in the QGP
- Flow
- Heavy quarks that thermalize in the QGP will show hydrodynamic flow
- Total charm
- In a QGP, increase from thermal production

- Screening radius (fm)

- Lattice

- 7 Feb 2005

## Heavy quark detection by displaced vertices

- B is identified by z>1mm
- and by  pair with J/ mass.
- Similar technique for semileptonic decays

- 7 Feb 2005

## Vertex detector - barrel

- 2 pixel layers

- 2 layers of 80mx3mm strips
-    3.9M channels
- 2 layers of 50x425mm pixels
-    0.38M channels
- Coverage:
- ||<1.2
-  ~ 2
- Z ~ +-10cm

- 7 Feb 2005

## Barrel – LANL involvement

- Lead mechanical engineering
- 200k$ R&D funds
- Integration support
- Cooling, power, signal
- Other detectors
- Help develop detailed requirements for mechanical design

- strip layers

- pixel
- layers

- power, cooling, readout

- 7 Feb 2005

## Barrel – LANL roles

- Mechanical design will be done by Hytec
- Support structure
- Cooling systems
- Hytec will build these structures
- 900k$ construction funds
- LANL will function as the liaison to the company

- Modular: endcaps and barrel can be installed separately.
- A preliminary study was done by Hytec in 2002, initiated by LANL

- carbon composite support structure

- beam pipe

- 7 Feb 2005

## Endcaps

- LANL-led effort
- In the DOE Barrel proposal as an appendix
- Full proposal to DOE later this year, 4.6 M$
- Cover the muon arm acceptance of 12-34

**0**

- beam

- beam

- 7 Feb 2005

## Endcaps

- 2 Endcaps, 4 layers each.
- Silicon mini-strips
- 50m x 2-13 mm
- 2.7 M channels
- Use new readout adapted from FNAL electronics for BTeV

- endcaps

- barrel

- 7 Feb 2005

## Endcap performance - vertex resolution

- B lifetime is ~ 1 mm at low pT()=1.7 GeV
- c (B+-) = 496 um, c (B0) = 464 um
- c(D+-) = 315 um, c(D0) = 124 um

- Charm: =290 m

- Beauty: =230 m

- Simulated endcap z-vertex resolution for
- D    +X     and
- B    +X

- 7 Feb 2005

## Heavy quark identification with endcap detector

- pT  GeV/c

- 7 Feb 2005

## Heavy quark identification with endcap detector 

- Performance for B   J/+X
- By making a z-cut, eliminate prompt J/Y and identify B decays

- Decay Distance (cm)

- B decays

- Prompt
-    J/

- 1mm cut

- Ratio of B decay
- to prompt J/
- ~ 1%

- 7 Feb 2005

## Current LDRD-DR proposal

- P-25-T-8 joint proposal
- Next 3 years – aimed at  the  2007-08 Au-Au run
- Build 1⁄4 of 1 endcap, using components developed by FNAL, ~ 4.7M pixels
- Serve as prototype for larger endcap DOE project
- Measure open charm via D     +X
- Parallel theory effort understand and interpret the heavy quark signals

- 7 Feb 2005