silicon tracker for cbm walter f.j. müller, gsi, darmstadt for the cbm collaboration topical...

Silicon Tracker for CBM

Walter F.J. Müller, GSI, Darmstadtfor the CBM Collaboration

Topical Workshop: Advanced Instrumentation for Future Accelerator Experiments,

Bergen, Norway, 4-6 April 2005

4-6 April 2006 Topical Workshop: Advanced Instrumentation for Future Accelerator Experiments, Bergen, Norway --- Walter F.J. Müller, GSI

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CBM Setup

Radiation hard Silicon pixel/strip detectors in a magnetic dipole field

Electron detectors: RICH & TRD & ECAL: pion suppression up to 105

Hadron identification: RPC, RICH

Measurement of photons, π0, η, and muons: ECAL


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CBM Physics Topics and Observables In-medium modifications of hadrons

onset of chiral symmetry restoration at high ρB

measure: , , e+e- (μ+ μ-) open charm: D0, D±

Strangeness in matter enhanced strangeness production measure: K, , , ,

Indications for deconfinement at high ρB

anomalous charmonium suppression ? measure: D0, D±

J/ e+e- (μ+ μ-) Critical point

event-by-event fluctuations

measure: π, K

Low cross sections→ High interaction rates→ Selective Triggers

Vertex detector

V0 reconstruction

Dalitz and conversion rejection


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Silicon Tracker in CBM – The Mission track reconstruction for all charged particles

above 0.1 GeV/c with a resolution of 1% at 1 GeV/c

primary and secondary vertex reconstruction with a resolution good enough to efficiently trigger on and reconstruct open charm (D0, D±)

V0 track pattern recognition for reconstruction of weak decays of hyperons (K0

s,Λ,....,Ω)


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A Typical Au+Au Collision

Central Au+Au collision at 25 AGeV:URQMD + GEANT

160 p 170 n360 - 330 + 360 0 41 K+ 13 K- 42 K0

~500 charged primaries inacceptance (50-500 mrad)→ high granularity


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Open Charm Reconstruction

GeV3%18.0

mm50 μm;10

MeV14

0

21

021

pX

x

dx

X

x

pdx

D0→K

Some hadronic decay modes

D (c = 317 m):D+ K-++ (9 0.6%)

D0 (c = 124.4 m):D0 K-+ (3.9 0.09%)


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Meson Production in central Au+AuW. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745

SIS300


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Rates and Doses for Open Charm Assume

10-5 D / central collision (for 15 A GeV) 4% branching ratio (for D0 K-+)

50% geometrical acceptance 5% reconstruction efficiency → 10-8 detected D / central collision

Estimate Rates 107 collisions/sec 50% duty cycle → 1000 D/day

Estimate Doses Flux: 3.2 108 part/cm2/sec at z=5cm Θ=100 mrad 1015 part/cm2 or 30 Mrad in a 10 week run


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1st Guess on Geometry

Acceptance: 50 to 500 mrad

Magnet: ~ 1 Tm bending power ~ 1 m field length 1 x 1 m aperture

1st plane: z=5cm ; size 25 cm2

covers 100 to 500 mrad

last plane: z=100cm; size 1 m2

assume 7 planes 3 or 2 pixel 4 or 5 strip

Pixel

Strip

z = 5,10,(20) cm

z = (20),40,60,80,100 cmmostly guided byopen charm needs


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Possible Configuration of 1st+2nd Plane

Inspired by BTeV Detectors can be moved in two

halfs Remove sensors from beam

during focusing Only two module geometries 1st plane and inner part of 2nd

plane should be replaceable after a run


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Vertex Detector: The MAPS Option I

Pros: done with commercial CMOS

process sensor thickness below 100 μm pixel pitch 20-35 μm resolution 3 μm

Under work: fast column based readout

ultimate speed: ~ 5 μs frame time radiation hardness

currently: 1 Mrad

CBM related MAPS R&D in 2005: MIMOSA 11: radiation tolerance MIMOSA 13: current readout

MIMOSA IVIReS / LEPSI Strasbourg

Monolithic Active Pixel Sensors


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Vertex Detector: The MAPS Option IIDouble layer to cover insensitive areas

First material budget assessment

0.29 %

by M. Deveaux


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1st Guess for Strip Tracker I4 Strip tracking stations

Tracking Stations Nr. 4 and 6

Double sided Si-Strip detectors:thickness 100 μmpitch 25 μmStereo angle 15o


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1st Guess for Strip Tracker II

Basic Elements: Inner : 6x4 cm Middle : 6x12 cmOuter : 6X20 cm

+40 cm

-40 cm

Read out

+4cm

- 4cm

by V. Saveliev

Tracking Station Nr. 6

Open questions: strip length

(reduce fake hits) location of read-

out(all at edge ?)


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D0 Reconstruction I Assume:

100 μm pixel layers 200 μm strip layers

D0 K-,+ signal Background

Reco

nst

ruct

ed e

vents

Z-vertex(cm)

Z vertex

IP c

ut

cuts optimized for significance

Au+Au 25 A GeV


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D0 Reconstruction II Assume:

107 interactions/sec 1% momentum resolution

effective


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Impact of Resolution and Thickness I

by I. Vassiliev

Study 3 cases: MAPS: 100 μm thickness 10 μm resolution 'fine-pitch' Hybrid 700 μm thickness 35 μm x 35 μm pixel 'normal' Hybrid 700 μm thickness 50 μm x 350 μm pixel

Signal: D K- π+


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Impact of Resolution and Thickness II Study 3 cases:

MAPS: 100 μm thickness 10 μm resolution 'fine-pitch' Hybrid 700 μm thickness 35 μm x 35 μm pixel 'normal' Hybrid 700 μm thickness 50 μm x 350 μm pixel

D0 efficiency5.10 % 1.70 % 0.01 %

UrQMD (combinatorial background) Conclusion:

700 μm material budget tolerable

conventional sized (~20000 μm2) hybrid pixel detectors are excluded

Note:The dose required for a physics signal increases with decreasing D0 efficiency.


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Tracking I All is fine if

perfect detector response no event pile-up in pixels no fake hits in strips

The full MC environment with realistic digitizers is just beginning to be productive

event pile-up in pixel causes trouble fake hits in strips cause trouble in a nutshell:

forward tracking hampered by pile-up backward tracking hampered by fakes need a clean track seed somewhere....

apparently needed (choose one or more): more planes, more views shorter strips fast pixel with clean event association


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Proposal I

Pixel

Strip(x,u and y,v)

Strip (r,)

Could be likeLHCb-VELO


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Proposal II

MAPS

Strip

Hybrids

Should deliverunambiguous seeds

High resolution tracking with large coverage

Ultimate vertex resolution


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STS is a 'Trigger' Detector I STS is the essential (and possibly only) device

used for first level online event selection (a.k.a. L1 trigger) decision for open charm candidates.

Problem similar to LHCb or BTeV

Very fast online tracking needed 107 interactions/sec → 1.5 109 tracks/sec

Robust tracking needed confusion in 1st or 2nd plane gives detached

tracks...

Speed and robustness of a fast online tracking is thus an essential criterion

This might require 'simple geometry' clear event association additional redundancy


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STS is a 'Trigger' Detector II STS provides information for first level event selection

self-triggered FEE – there is no L0.... high-bandwidth readout - all hits are send see talk tomorrow....


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Low Mass Dilepton Spectroscopy I

CBM has PID after tracker → avoid conversions in tracker (low mass) → reconstruct conversions and Dalitz decays


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Low Mass Dilepton Spectroscopy II

ee 0

ee

If these are notreconstructed ..

.. those will form a fake open pair

tracking efficiencydown to 0.1 GeV/c

important to suppressbackground

Likely we need additional coverage more redundancy an adapted geometry

for dilepton runs


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-electrons – Atomic Physics Background

by P. Koczon

Large cross section for high energetic (> 10 MeV) knock-on electrons.

Geant 3 vis PhysRev D V.54/1 p.134

25 AGeV Au->Au 0.25mm

Relative

Formula

Geant3

In 1st station: 5 per Au ion passing 1% target 500 per min. bias interaction compare: ~150 charged hadrons


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Summary Vertex tracker:

700 μm material budget tolerable about 35 μm x 35 μm pixel size needed only a small part (50 cm2) is exposed to very high doses

replacing this part after a major D run is feasible required dose and also interaction rate depends on D0 efficiency

thin detectors (100 μm) require significantly less than thick (700 μm) ones

fast readout allowing clear event association very valuable (at least)

THUS WANTED: thin (<700 μm) high resolution (σ ~ 10 μm) fast (best <100 ns) radiation tolerant (30, better >100 Mrad) self-triggered, high bandwidth FEE


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Summary II Vertex tracker (cont.):

possible new scenarios from this workshop: 50 μm x 50 μm hybrid pixel

Synergy from rad-hard sensor development improving resolution beyond pixel/sqrt(12) be very helpful definitively new readout chip needed

channel density and low power requirements challenging radiation hardness probably o.k. with DSM CMOS (100

Mrad)

DEPFET array challenge here:

high speed readout


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Summary III Strip tracker:

100 to 150 μm double sided sensordetailed impact of material budget on physics performance yet to be studied in detail.

rad-hard sensors (10 Mrad, should last 10 years)

strip geometry will certainly evolve shorter strips additional planes/views

Can the readout be placed at the sides ? (cooling, material budget,...)

Again: Self-triggered, high bandwidth readout chip needed has to handle hits at random times (not a collider experiment....) best feasible time resolution to help event identification


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Summary IV Many challenges for sensor and readout Timelines:

Technical Proposal: end 2006 Technical Design Reports: end 2009

Open for collaboration with all interested parties


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CBM and HADESAll you want to know about CBM:Technical Status Report (400 p)

now available underhttp://www.gsi.de/documents/DOC-2005-Feb-447-1.pdf


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CBM R&D working packages Feasibility studies Simulations

D Kπ(π)GSI Darmstadt, Czech Acad. Sci., RezTechn. Univ. PragueIReS Strasbourg

,ω, e+e-

Univ. KrakowJINR-LHE Dubna GSI Darmstadt

J/ψ e+e-

INR MoscowGSIRBI Zagreb

π, K, p ID Heidelberg Univ,Warsaw Univ.Kiev Univ. NIPNE BucharestINR Moscow

FrameworkGSI

TrackingKIP Univ. HeidelbergUniv. MannheimJINR-LHE DubnaJINR-LIT Dubna

Design & constructionof detectors

Silicon PixelIReS StrasbourgFrankfurt Univ.,GSI Darmstadt,

Silicon Strip Moscow State UnivMEPHI, MoscowCKBM St. PetersburgKRI St. PetersburgUniv. Obninsk

RPC-TOFLIP Coimbra, Univ. Santiago Univ. Heidelberg,GSI Darmstadt,NIPNE BucharestINR MoscowFZ RossendorfIHEP ProtvinoITEP MoscowRBI ZagrebUniv. MarburgKorea Univ. Seoul

TRD (MWPC)JINR-LHE, DubnaGSI Darmstadt,Univ. MünsterNIPNE Bucharest

TRD (straw)JINR-LPP, DubnaFZ RossendorfFZ JülichTech. Univ. Warsaw

ECAL ITEP Moscow IHEP Protvino

RICH IHEP Protvino GSI Darmstadt Pusan Univ. PNPI St. Petersburg

KIP Univ. HeidelbergUniv. MannheimUni. KaiserslauternGSI DarmstadtJINR-LIT, DubnaUniv. BergenKFKI BudapestSilesia Univ. KatowiceWarsaw Univ.PNPI St. PetersburgNIPNE BucharestMEPHI MoscowWuhan Univ.

Magnet

FEE,Trigger,DAQ

J/ψ μ+μ-

PNPi St. PetersburgSPU St. Petersburg

Λ, Ξ,Ω PNPi St. PetersburgSPU St. PetersburgJINR-LHE Dubna

Ring finder JINR-LIT, Dubna

beam det.Univ. MannheimGSI Darmstadt

JINR-LHE DubnaGSIδ-electrons

GSI Darmstadt


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The End

Thanks for your attention

silicon tracker for cbm walter f.j. müller, gsi, darmstadt for the cbm collaboration topical...

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