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
SQM 2009, Búzios, 1 October 2009Volker Friese 7
{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
SQM 2009, Búzios, 1 October 2009Volker Friese 8
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
SQM 2009, Búzios, 1 October 2009 10Volker Friese
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
SQM 2009, Búzios, 1 October 2009Volker Friese 12
Typical runtime 25 d @ 106 events / s
≈ 16 k D+ decays measured
Good rapidity and pt coverage
Open charm: other channels
SQM 2009, Búzios, 1 October 2009Volker Friese 13
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
SQM 2009, Búzios, 1 October 2009Volker Friese 15
Open charm trigger
SQM 2009, Búzios, 1 October 2009Volker Friese 16
Based on:impact parameter of daughtersgeometrical and topological vertex cuts
Rejection factors > 100 in reach
To be implemented in FLES
Performance for charmonium
SQM 2009, Búzios, 1 October 2009Volker Friese 17
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
SQM 2009, Búzios, 1 October 2009Volker Friese 18
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
SQM 2009, Búzios, 1 October 2009Volker Friese 19
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
SQM 2009, Búzios, 1 October 2009Volker Friese 20
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