The LHCb VErtex LOcator · 2010. 9. 22. · The LHCb VErtex LOcator Olaf Behrendt INSTR08 • LHC experiment dedicated to heavy flavour physics • CP-violation and rare decays of

The LHCb VErtex LOcator

Olaf Behrendt

on behalf of the VELO group

Novosibirsk, 29.02.08

The LHCb VErtex LOcator INSTR08Olaf Behrendt

• LHC experiment dedicated to heavy flavour physics

• CP-violation and rare decays of beauty and charm hadrons

• constrain unitarity triangles and search for new physics

• forward spectrometer: 1.9 < < 4.9 [bb-pairs produced correlated in space]

• luminosity: 2 1032 cm-2s-1 [1012 bb-pairs per year]

Detector requirements:

• reconstruction in harsh radiation environment

• selective trigger system [bb-production cross-section small]

• good vertex resolution [proper time]

• good particle identification [K/ separation]

The LHCb Experiment

Bs

Btag

K-

K+

+

+,K+

p p

PV

~1 cm

SV


Role of the VELO in LHCb

Reconstruction Trigger

• precise tracking

• primary/secondaryvertices [lifetime]

• B-decay selection

• suppression ofmultiple interactions

• absoluteluminositymeasurement

4 Tm


Outline

• Design

• Module Production and Assembly

• Installation

• Control and DAQ

• Expected Performance

• Summary

• VELO alignment: see talk of M. Gersabeck


Layout

• 2 retractable detector halves

• 21 stations per half with an R and sensor

• 2 Pile-Up stations per half [trigger]

injection

stablebeams

RF box

module

Pile-Upmodules

base

LHCvacuum

zx

y

x

y

6 cm

p

p partly overlappingsensors

IP


Sensors

• divided into quadrants

• pitch: 40 - 100 μm

• divided into short andlong strip region

• pitch: 35 - 100 μm

• stereo angle

r = 0.8 cm

r = 4.2 cm

2048strips

-sensor R-sensor

type invert

ed

not

type invert

ed after 1 year of irradiation

[2 fb-1]

R [cm]

Udep [V]

n+ in n-bulk sensors [300 μm]

• inherently radiation tolerant

• strip isolation via p-spray

• expected radiation dose:

- 1.3 · 1014 neq/cm2/year at r = 0.8 cm

- 5 · 1012 neq/cm2/year at r = 4.2 cm

after 3-4 years [~8 fb-1]: run partially depleted


Modules

• double-sided hybrid to balance stressesdue to “bi-metallic” effects

• typical non-planarities: 250 μm

• sensor-sensor accuracy: < 10 μm

• analogue front-end read-out:2 x 16 Beetle chips

• cooling: 2-phase CO2 [silicon @ -7° C]

carbon fibrepaddle

cooling block

carbonfibre

-sensor

R-sidecircuit

-sidecircuit

R-sensor

thermal pyrolyticgraphite

x

yz


Module Production

receive and validate components

hybrid assembly

wire bonding on the hybrid

glue sensors on hybrid

wire bonding of sensors to hybrid

glue to carbon-fibre paddle

electrical check

module metrology

visual re-inspection

module burn-in- electrical test in vacuum- thermal stress- electronics burn-in

I/I

(%)

# module

good stability during burn-in

rejected

bonding failure rate:

• Backend: 0.000 %

• Frontend: 0.010 %

• Sensorend: 0.002 %

bad channels:

• R-sensors: 0.7 %

• -sensors: 0.5 %


Fully Assembled VELO Half


Vacuum System

LEFT DETECTOR BOX

• silicon detectors operated in vacuum

• RF shield of 300 μm Al [3% Mg]

- constitutes beampipe in VELO region

- shape allows for overlapping sensors [alignment]

• avoid deformations:P = Pbeam - Pdetector < 10 mbar

• requirements beam vacuum:Pbeam = 10-8 mbar

• expected VELO vacuum:Pdetector < 10-4 mbar

This is what the LHC beams see …


Installation

Lowering into the LHCb cavern …

… ready for installation …

… insertion of one half

October 2007:

• installation of both VELO halves

• transport and installation withoutany damage [IV curves]

installation rail

RF box


Pumpdown

[m

ba

r]

+2 mbar

-5 mbar

after 100 hoursdetector: 9 · 10-5 mbar

beam @ VELO: 2 · 10-9 mbar [without ion pumps]

absolute pressure

differential pressure


DAQ and Control System


ARX

ARX

ARX

ARX GBE

TTCRx

CCPC

• originally developed for the VELO, now used for (almost) all of LHCb

• analog input from 64 links

• 10 bit analog to digitalconversion @ 40 MHz [A-Rx]

• pre-processing FPGAs[cross-talk, common mode, pedestals, clustering]

• data sent out via GigabitEthernet [GBE]

• max. L0 output rate: 1.1 MHz

• control via credit-cardsized PC [CCPC]

Readout Board (TELL1)


Commissioning

installation of cables and boards

Tests:

• ADC cards [A-Rx]

• Readout Boards [TELL1]

• Control Boards

• each readout slice– timing

– cable check

– noise level

Control and DAQ system (almost) completely commissioned

adjustment of timing to 0.65 nsproblematic A-Rx card


Testbeam

• 10 modules

• 180 GeV beam

• small scale CO2 cooling system

• 6 modules readout simultaneously[full readout chain with final electronicsboards]

• software: DAQ, ECS, tracking,vertexing, online monitoring

x = 0 mm,d = 2 mm

x = 15 mm,d = 5 mm

• data for 0, 4 and 8 degrees

• interaction data- 4 layers with 2 Pb targets [300 μm]

- test vertex reconstruction- emulate open and closed VELO

• > 50 million events to disk

November 2006

y

z

x


binaryresolution

linear fitto data

Testbeam Results

-sensors

R-sensors

• S/N: 20 - 24[decreases with r due to increasing strip length]

• resolution: 9 - 25 μm [pitch: 40 - 100 μm]

• S/N: 24 - 29

• resolution: 9 - 20 μm [pitch: 35 - 100 μm]

Landau Gaussian

active region

R-sensors

expected resolution improvements: cross-talk and corrections

R-sensors

full sensorsimulation


Expected Tracking Performance

reconstructed track - hits in 3 stations

LHCb acceptance: 1.9 < < 4.9

= -ln tan( /2)

For typical B decay modes:

• primary vertex resolution:- x,y: ~10 μm, z: ~60 μm

• proper time res.: ~40 fs

• B mass res.: 12 - 25 MeV

B decays


Status

• module production and burn-in:

completed March 2007

• module assembly on detector

halves: completed March 2007

• vacuum/detector positioning

system: installed

• installation of detector halves:

October 2007

• cooling system: installed

• HV-/LV-system: installed

• Electronic boards/cables:

installed

• system checkout: ongoing

• system test foreseen within the

next two months

CO2 cooling system

positioning system

LV system


• VErtex LOcator is small but complex detector

• precision tracking very close to the interaction region

• radiation tolerant design

• results from the testbeam in November 2006

– S/N: 24 - 29 ( ), 20 - 24 (R)

– resolution: 9 - 20 μm ( ), 9 - 25 μm (R)

• on schedule for first beams in 2008

Summary

Backup Slides


Luminosity Measurement

10-7 mbar Xe1011 p/bunch

30 H

zper

bunch

Method:

• injection of a tiny bit of gas into VELO region

• reconstruction of beam-gas interaction vertices

- beam angles, profiles & relative positions

- calculate luminosity

• simultaneous reconstruction of beam-beam

interaction vertices

- calibrate ‘reference’ cross-section

test setup for gas injection

• expected beam size: x y 70 μm

• expected vertex resolution: pv 30 μm

expected accuracy: ~1%

LHCbmachine

Documents

The LHCb VErtex LOcator · 2010. 9. 22. · The LHCb VErtex LOcator Olaf Behrendt INSTR08 • LHC experiment dedicated to heavy flavour physics • CP-violation and rare decays of