Prospects for strangeness and charm measurements

in the CBM experiment

Volker FrieseGSI Darmstadt

Strangeness in Quark Matter 2009, Búzios, 1 October 2009

Experimental landscape

SQM 2009, Búzios, 1 October 2009Volker Friese 2

RHIC energy scan: Collider, moderate rates, bulk probes

SPS (NA61): Fixed target, moderate rates, emphasis on light ions, bulk probes

NICA (MPD): collider (see talk by A. Sorin)

FAIR (CBM): Fixed target, high rates, bulk + rare probes

CBM: experimental setup

SQM 2009, Búzios, 1 October 2009Volker Friese 3

RICHTRD

TOF ECAL

PSD

absorber +

detectors

Electron + Hadron setup Muon setup

STS+MVD

Tracking in STS Vertexing in MVD Electron ID in RICH + TRD Hadron ID in TOF γ in ECAL Centrality in PSD μ ID in absorber system

Hadron identification by TOF

SQM 2009, Búzios, 1 October 2009Volker Friese 4

TOF: 150 m2 RPCPad / strip readout80 ps resolution at 10 m from target

Charged kaon identification track-by-track up to p = 3.5 GeV

Particle ratio fluctuations

SQM 2009, Búzios, 1 October 2009Volker Friese 5

Sensitivity to K/π fluctuations studied with UrQMD input (central Au+Au, 25A GeV)

No large bias compared to MC truth found after full reconstruction and identification

CBM acceptance appears well suited for fluctuation studies

MC truthCBM

Hyperon measurements

SQM 2009, Búzios, 1 October 2009Volker Friese 6

Λ Ξ- Ω-

Identified by decay topology in main tracker + inv. Mass

Clean signals: almost background free for Λ and Ξ

central Au+Au @ 25A GeV

Multi-strange di-baryons

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{Ξ0, Λ}

Thermal production yields for hyperon clustersStarted to study {Ξ0, Λ} → ΛΛ

Assuming:

m=mΛ + mΞ

cτ = 3 cm (1-5 cm)

BR = 2 % (1-10 %)

J. Schaffner-Bielich, R. Mattiello and H. Sorge, 1999

J. Steinheimer, priv. comm.

ΛΛ simulation and analysis

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Transport event display

Cut on ΛΛ vertexRequire off-vertex Λ

Λ reconstruction

Results and sensitivity for {Ξ0, Λ}

SQM 2009, Búzios, 1 October 2009Volker Friese 9

Thermal multiplicity (7 10-3) Sensitivity limit: 7 10-6

CBM will see {Ξ0, Λ} with thermal yields

Evene three OOM below the signal will be visible above BG

Micro-vertex detection

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For efficient background suppression imn open charm measurements: detection of displaced vertex indispensable

Requires: high-precision, low-mass silicon detector

Current choice: 2 station of MAPS, operated in vacuum

Promising results on vertex resolution

Open charm detection

SQM 2009, Búzios, 1 October 2009Volker Friese 11

D+ -> K- π+ π+ : cτ = 312 μm

Cuts on:

Daughter impact parameter

Vertex geometrical fit

Vertex topological fit

Clean D+ signal observed

Open charm : statistics

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Typical runtime 25 d @ 106 events / s

≈ 16 k D+ decays measured

Good rapidity and pt coverage

Open charm: other channels

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D0 -> K- π+ + c.c.

Λc+ -> p K- π+ Ds

+ -> K- K+ π+

D0 -> K- π- π+ π+

Open charm: summary

SQM 2009, Búzios, 1 October 2009Volker Friese 14

D0+D0 D0 D+ Ds+ c

+

decay channel K-+ - K-+ + K-+ + K-K+ + p K-+

MHSD 1.5·10-4 4.0·10-5 4.2·10-5 5.4·10-6

MSM 8.2·10-4 2.0·10-4 8.4·10-5 1.4·10-4 4.9·10-4

BR(%) 3.8 7.7 9.5 5.3 5.0

geo. acc.(%) 55.7 19.3 39.6 29.6 53.0

s.t. rec. eff. 98 97.7 97.5 97.5 97.6

z-resolution m 54 82 60 73 70

total eff. (%) 3.25 0.37 4.2 1.0 0.18

m (MeV/c2) 11 12 11 12 12

S/B2 4.4 7.1 9.0 0.3(7.9) 0.25

yield(K/1011cen) 5 + 17 1 16 0.3(7.2) 11

Open charm: challenges

• High event rates (105 – 106) indispensable• Requires:

– Online trigger reduction by factor > 100• Online track reconstruction and SV

detection– Fast micro-vertex detector

• MAPS: Limited by readout, 10 μs frame rate possible

• Simulations: Event pile-up of 10 – 20 tolerable

– Radiation-hard detector: up to 1014 neq/cm2/year

• R&D on MAPS radiation tolerance ongoing• Regular replacement of MAPS stations feasible

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Open charm trigger

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Based on:impact parameter of daughtersgeometrical and topological vertex cuts

Rejection factors > 100 in reach

To be implemented in FLES

Performance for charmonium

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e+e- μ+μ-

J/ψ peak well observable; similar performance in electron and muon channel

ψ‘ at edge of feasibility

Measurements requires highest event rates (107 / s)

New DAQ concept

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FEBDet ROC FLES

ABB

ABB

DCB

BN

et

digitization

aggregation

buffering

processing

correlation

Extreme event and data rates (up to 1 TB/s from FEE) require new DAQ and FLES strategies

No convential trigger mode, but self-triggered, free-streaming FEE with time tags

FEE and DAQ components under development and testing at GSI; first successful test of free-streaming R/O chain in 2008

Fast event reconstruction

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CPU time for track reconstruction and fit

FLES has to reduce the raw data rate (1 TB/s) to the recordable rate (1 GB/s)

Necessity of (partial) event reconstruction online at MHz rates

Novel algorithms and implementations to exploit modern / future computer architectures

Paradigmata: vectorisation and parallelisation

Current event reconstruction time in STS: 50 ms

CBM on track: ongoing R&D

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MAPS

radiationhard silicon microstrip detectors

Data Acquisition System

throughput 500 MB/s/node

Readout ASICs for RPC Time-of-flight system: 25 ps time resolution

RPChigh-rateglass substr.

self-triggeringread-out chips128 ch, 32 MHz

GEM for MUCH in beam test AUG09.

TRD high-rate

STS in beam test AUG09

Partial cherenkov ringFrom RICH beam test AUG09