Heavy Flavour Identiﬁcation at Linear Colliders · Joel Goldstein SLAC 9/3/08 Flavour Physics • Precision detectors close to interaction point • Distinguish tracks from secondary

Heavy Flavour Identification at

Linear Colliders

Joel GoldsteinUniversity of Bristol

LCFI Collaboration

SLAC AIS 9/3/08

Joel Goldstein SLAC 9/3/08

LCFI

- Sensors

- Readout

- Mechanics

- Software

- Physics

2

! Bristol

! Edinburgh

! Glasgow

! Liverpool

! Nijmegen

! Oxford

! RAL

• Linear Collider Flavour Identification

- Has been focusing on ILC


Flavour Physics

• Precision detectors close to interaction point

• Distinguish tracks from secondary vertices

! Identify, separate b, c quarks and " leptons

! Measure charge3

b decay

c decay

e+

e-

primary


Flavour Tagging

• b-tagging fairly robust at the ILC

• c-tagging more detector dependent

! Measure Higgs branching ratios

! . . .

4

Flavour tagging

ee ! Z ! qq @ 91GeVFull Monte Carlo - LDC01_05ScFull reconstruction

6


Vertex Charge

• Add charge of all tracks in vertex

• Identify charge of flavoured hadron

! Can distinguish quark/antiquark

! Measure hadronic asymmetries

! Anomalous couplings, LEDs....

5

b quark

bbar quark

Combined charge b and bbar

Forward – Backward Asymmetry of reconstructed bbar

Reconstructed bbar

Mis-tagged (charge or flavour)

• Sensitive to detector parameters

! Acceptance

! Material

! Geometry...


ILC Vertex Detector

• 800M 20!20µm2 pixels

• 5 layers, inner radius ~ 1.5 cm

• Gas cooling

! 0.1% X0 per layer in active region

! Uniform material distribution

6


Mechanics

Material target equivalent to 100 !m silicon

! Thinning silicon to 50-100 #m becoming routine

! Thinning to epitaxial possible

7

• Ladders with bulkheads

1. Unsupported silicon

- can’t control lateral curl

2. Laterally stiffened silicon

3. Rigid structures


Thin Substrates

• Longitudinal stiffness from tensioning

• Lateral stiffness from thin substrate

! Beryllium: good specific stiffness but bad CTE

! Carbon fibre good candidate

- 0.09% X0 test model

- laterally stability insufficient

8

profile of silicon along the length of a ladder


Foam Ladders

• 25 micron silicon on 1.5mm 8% SiC

! Very rigid

! Achieved 0.14% X0

9

• 20 micron silicon sandwiching 1.5mm 2% carbon

! Could be double-sided

! Achieved 0.07% X0

More exotic rigid structures possible


RVC Foam

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RVC ladder

silicon spacers

ladder block

glue

glue

silicon block

• Reticulated Vitreous Carbon

! 2-3% relative density

! Not stiff enough for one-sided


RVC Results

• Shape due to fabrication technique

! New fixtures look promising

! Difficult to control behaviour

11


SiC Foam Ladder

• Processed 8% SiC Foam

! A fraction of initial shape left

! 30% over material budget

! Now have 3-4% foams

• Minimally constrained

! Eliminate stiction in mountings

12

Negligible deformation over 70 degrees!


Foam Future

• SiC seems extremely promising! Lower density now in hand! Learning how to process

13


Foam Future

• SiC seems extremely promising! Lower density now in hand! Learning how to process! All-SiC foam structure...?

13


Foam Future

• SiC seems extremely promising! Lower density now in hand! Learning how to process! All-SiC foam structure...?

13


The ILC Challenge

14

337 ns

2820x

0.2 s

0.95 ms

ILC bunch structure:


The ILC Challenge

! Once per bunch = 300ns per frame : too fast

14

337 ns

2820x

0.2 s

0.95 ms



The ILC Challenge


! Once per train ~200 hits/mm2 : too slow

14

337 ns

2820x

0.2 s

0.95 ms



The ILC Challenge



! 10 hits/mm2 => 50µs per frame: just right

14

337 ns

2820x

0.2 s

0.95 ms



The ILC Challenge




! 1.6 MPixels in 50µs (commercial ~ 1ms)

14

337 ns

2820x

0.2 s

0.95 ms



The ILC Challenge




! 1.6 MPixels in 50µs (commercial ~ 1ms)

! And gas cooled!

14

337 ns

2820x

0.2 s

0.95 ms



Sensor R&D

• Column Parallel CCDs

! Focus so far - building on past experience

! Readout during bunch train

• Image Sensor with In-situ Storage

! Increased robustness

! Reduced driver requirements

15


CP CCDs

! Separate readout for each column

! 50 MHz clock rate

! Clock drive is real challenge

16

N+1

Column Parallel CCD

Readout time = (N+1)/Fout


CPC-1

• RAL-designed ASIC

! Bump-bonded on 20µm pitch

! Latest has cluster finding17

Charge Amplifiers(inverting)

Voltage Amplifiers(non-inverting)


High Speed CPCCDs

• Two metal layers• Distributed clocks! Faster

! More uniform

• Old and new ASICs

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Stripline

Main clock

Extra pads for

Main clock

CPR-1 CPR-2

Temperatur

Charge

Four 1-stage and

2-stage SF in

Four 2-stage SF Standard Field-enhanced Standard

Clock

monitoring and

No

connection

Image area


CPC-2

• 1, 4, 10 cm long variants

• Custom clock driver ASIC

• Tested up to 45 MHz

19

Noise ~ 75e-


ISIS

• Store charge in CCD register within each pixel

• Orders of magnitude increased resistance to RF

• Much reduced clocking requirements (readout ~1MHz)

• Combination of CCD and CMOS technology on small pitch

20

To column load

Source followerReset transistor Row select transistor

p+ shielding implant

n+

buried channel (n)

storage

pixel #1

storage

pixel #20 sense node (n+)

Charge collection

row select

reset gate

VDD

p+ well

reflected charge

reflected charge

photogate

transfer

gate

output

gate

High resistivity epitaxial layer (p)


ISIS-1

• Proof-of-principle in CCD process

! 16!16 array

! 5 time samples

21


ISIS-1 Tests

• Tested with 55Fe and 6 GeV e-

• X-rays and MIPS clearly seen

• Position resolution ~ 12µm

22

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ISIS-1 at CERN

• Testing in CERN 120 GeV pion beam

23


ISIS-2

• Custom CMOS process

• 800µm2 pixels

• 20 time samples

! Close to targets

! Wafers being diced

24

ISIS2 – Top Level

2Konstantin Stefanov, STFC Rutherford Appleton Laboratory


Summary

• Complete ILC vertex detector package

• Good progress in

! Software and physics studies

! Mechanics

! Sensors

• Applicability beyond ILC

! Continue much as generic R&D

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Documents

Heavy Flavour Identiﬁcation at Linear Colliders · Joel Goldstein SLAC 9/3/08 Flavour Physics • Precision detectors close to interaction point • Distinguish tracks from secondary