the cbm experiment at fair
DESCRIPTION
The CBM Experiment at FAIR. Volker Friese [email protected]. CPOD 2007 GSI, 13 July 2007. The FAIR Facility at GSI. 2 x 10 9 /s 238 U 35 GeV/u (Ni: 45 GeV/u) 10 13 /s protons 90 GeV Unique possibility to study extremely rare probes in heavy-ion collisions. First beam on CBM target: 2015. - PowerPoint PPT PresentationTRANSCRIPT
Volker Friese CPOD 2007, GSI, 13 July 2007 2
SIS100/SIS300
CBM
HESR
PANDASuper- FRS
NUSTAR
NESR
CR
GSIAcceleratorFacilities
SIS18
PP
AP
The FAIR Facility at GSI
2 x 109/s 238U 35 GeV/u(Ni: 45 GeV/u)
1013/s protons 90 GeV
Unique possibility to study extremely rare probes in heavy-ion collisions
First beam on CBM target: 2015
Volker Friese CPOD 2007, GSI, 13 July 2007 3
CBM Observables and Requirements
Strangeness
Flow
Open charm
Fluctuations
Hyperons
Dileptons
Charmonium
Hadron ID
Lepton ID
High resolution tracking
High resolution vertexing
Extreme interaction rates
Large acceptance
Radiation hardness
Fast detectorsand eletronics
Online event selection
Volker Friese CPOD 2007, GSI, 13 July 2007 4
The CBM Detector: Overview
Radiation hard Silicon Tracking System in dipole field
Electron ID in RICH+TRD+ECAL
Hadron ID in TOF (RPC)
γ, μ, π in ECAL
High-speed DAQ and trigger system
Volker Friese CPOD 2007, GSI, 13 July 2007 5
The CBM Backbone: Main Tracker (STS)
Arrangement of silicon detector stations inside magnetic dipole field
Large area coverage: strip sensors
High occupancy regions: hybrid pixel detectors /small strips
Volker Friese CPOD 2007, GSI, 13 July 2007 6
STS: Task and Challenges
UrQMD, central Au+Au @ 25 AGeV Task:• track reconstruction in high
track- density environment with high efficiency
• Momentum resolution 1 %• Acceptance coverage 2.5 – 27
degrees
Challenges:• high track density: up to 600
charges tracks per event in the acceptance
• fast sensor / readout: up to 107 events per second
• low mass detector• suitable for fast (online) event
reconstruction algorithms
Volker Friese CPOD 2007, GSI, 13 July 2007 7
STS: Conceptional Layout
target
beam
z = 50 cm – 100 cm:
double sided strip sensors, pitch 60 μm, stereo angle 15 degrees, material budget 200 – 300 μm Si
z = 20 cm – 50 cm:
hybrid pixel sensorsor small strips
other technologies under discussion
Volker Friese CPOD 2007, GSI, 13 July 2007 8
STS: Design of Si-Strip Stations
readout & cooling
readout & cooling
modular design with few (≈ 3) different wavers
connection of sensors by long-ladder technology
readout and cooling outside of acceptance
low-mass cables occupancy < 5 %
Volker Friese CPOD 2007, GSI, 13 July 2007 9
STS: Layout Studies
Ongoing layout and design
studies:
number / position of stations
pixel vs. strip sensors
strip densors: length, pitch, stereo angle
low-mass mechanical support and cabling
CAD drawing of target / STS region
Volker Friese CPOD 2007, GSI, 13 July 2007 10
STS: R&D
CIS 4"280 µm Si
GSI-01
Strip sensor development with CIS ErfurtFirst test sensor delivered July 2007
Fast self-triggered readout chip n-XYTER in collaboration with DETNIprospect: CBM-XYTER
Volker Friese CPOD 2007, GSI, 13 July 2007 11
STS: Gaining Expertise
International workshop on Silicon Detector SystemsGSI, May 2007:
o Review of detector concepto Discussion on (alternative)
technologieso Strategies for R&D and
prototyping
Volker Friese CPOD 2007, GSI, 13 July 2007 12
STS: Hit Pattern for Strip Stations
Track inpact points Occupancy Hit pattern
Large number of fake hits due to projective strip geometry:challenge for track finding
Volker Friese CPOD 2007, GSI, 13 July 2007 13
STS: Track Reconstruction
effic
ienc
y [%
]
momentum [GeV/c]
pixels + strips: 97.02 ± 0.09
only strips: 94.88 ± 0.12
pixels +strips: 92.17 ± 0.14
only strips: 90.01 ± 0.15
Track finding with Cellular Automaton method Good efficiency and performance (78 ms per event on CPU for central
Au+Au) Candidate for high level event selection (implementation in cell processors) Other algorithms (e. g. Hough Transform, suitable for FPGA) also being
developed
primary tracks all tracks
Track fit yields required momentum resolution
Volker Friese CPOD 2007, GSI, 13 July 2007 14
STS: Performance for Hyperons
Detection by weak decay topology with good acceptance and reasonable effiency: 15.8 % 6.7 % 7.7 %
Almost background-free signalsNo identification of secondaries required
Central Au+Au, 25 AGeVFull reconstruction
Volker Friese CPOD 2007, GSI, 13 July 2007 15
The Big Challenge: Open Charm
W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745 CBM measures open
charm close to threshold
extremely low multiplicity to be expected (HSD: <D0> = 2 x 10 -4 for central Au+Au @ 25 AGeV)
For discrimination from prompt background detection of the decay vertex with excellent resolution is required (D0: τ = 127 μm)
Volker Friese CPOD 2007, GSI, 13 July 2007 16
The Key to Open Charm: Vertex Detector (MVD)
Challenge: Determine secondary vertices with a precision of 50 μm or better
Requirements: very low material budget excellent coordinate resolution fast readout radiation hardness
Solution: 2 – 3 thin Si detector layers close to the target (z = 5cm or 10 cm) inside vaccuum vessel
Volker Friese CPOD 2007, GSI, 13 July 2007 17
MVD: Preferred Option MAPS
Monolithic Active Pixel Sensors
developed at IPHC Strasbourg
extremely thin (100 – 150 μm)
excellent position resolution (3 – 5 μm)
- radiation hardness- readout speed (max. 10
μs)Possible running scenario: reduced interaction rate (1 MHz) tolerable pile-up (10 – 20
events per frame) exchange first station (diameter 10 cm) periodically
Volker Friese CPOD 2007, GSI, 13 July 2007 18
MVD: Performance for D Mesons
Open charm performance is the benchmark criterion for the MVD + STS design
Study: D0 π+K-, τ=127 μm, central Au+Au @ 25 AGeV, <D0> = 2 x 10-4
First MAPS at z = 10 cm
without PID for daughterswith proton rejection
Volker Friese CPOD 2007, GSI, 13 July 2007 19
MVD: Open Charm Studies
Ongoing studies:
oD±ππK, τ = 317 μm
o D0K-π+π+π-
o Λc+pK-π+, τ = 62 μm
Preliminary: Four particle channel for D0 seems to be preferrable (stricter constraint on 4-track vertex wins over 4-particle combinatorics)
Volker Friese CPOD 2007, GSI, 13 July 2007 20
Hadrons Identified: The TOF System
Task:
Separate π-K-p over a large rapidityinterval
Requirements:
Location at z = 10 m from target
2π acceptance needed for flow and fluctuation studies large area (120 m2)
Timing resolution <≈ 80 ps
Rate capability > 20 kHz/cm2
Volker Friese CPOD 2007, GSI, 13 July 2007 21
TOF: Design and R&D
Large area requires RPC detectors
Modular design with pad (inner region) and strip (outer region) readout
R&D frontiers: uniform resolution over large
areas rate capability
R&D in close cooperation with FOPI and HADES
single gap RPC, Coimbra
Volker Friese CPOD 2007, GSI, 13 July 2007 22
TOF: Performance
Central Au+Au @ 25 AGeVFull reconstructionTime resolution 80 ps
Total efficiency vs. momentum(tracking + matching with TOF)
K / π separation up to 3.5 GeV, p / K separation up to 8 GeV at efficiencies of 80 % to 90 %
Volker Friese CPOD 2007, GSI, 13 July 2007 23
TOF: Acceptance for Hadrons
Bulk of hadrons can be identified by TOF
ycm
Volker Friese CPOD 2007, GSI, 13 July 2007 24
Electron Identification: RICH
Serves for electron identification up to 10 GeVLocated directly behind STS, outside of the fieldOptical layout: Vertically separated focal planes, shielded by magnet yokes
Volker Friese CPOD 2007, GSI, 13 July 2007 25
RICH: Ring Reconstruction
reconstructed rings in focal planecentral Au+Au @ 25 AGeV
reconstructed ring radius vs. p
Hadron blind up to 6 GeV (with N2 radiator)e / π separation up to 12 GeV
Volker Friese CPOD 2007, GSI, 13 July 2007 26
RICH: Performance
electron efficiency pion suppression
after track reconstruction, ring finding, matching and RICH quality cuts: electron efficiency 70 % - 80 % pion suppression ≈ 500 (misidentification due to false ring-track matches)
Volker Friese CPOD 2007, GSI, 13 July 2007 27
Why Electrons: Low-Mass Vector Mesons
CBM: Electron ID after spectrometer + good inv. mass resolution- opening of conversion pairs
fight electron background: γ conversion, π0 and η Dalitz decays
all identified e+e- after all cuts
ππ0 0 γγee++ee--
ππ00ee++ee--
ηη γγee++ee--
w/o pt cut on single e
ρρ ee++ee--
ee++ee--
φφ ee++ee--
Volker Friese CPOD 2007, GSI, 13 July 2007 28
LVM: Phase Space Coverage
Phase space for ρ after full reconstruction and analysis cuts
with single – e pt cutw/o single – e pt cut
Good coverage in y and pt; w/o single-e pt cut also at low pt and small minv
Volker Friese CPOD 2007, GSI, 13 July 2007 29
Further Electron ID: TRD
Tasks:electron / hadron separation for p > 1 GeVtracking (connection of STS and TOF)
Current design: 4 x 3 layers (radiator + MWPC)Pad readout
Volker Friese CPOD 2007, GSI, 13 July 2007 30
TRD: R&D
R&D frontiers: rate capability and speedPrototypes already tested at GSI
Beam test facility at GSI
Design rates (up to 100 kHz/cm2) well in reach
Volker Friese CPOD 2007, GSI, 13 July 2007 31
target 250 m
Combined RICH+TRD: Performance for J/ψ
combined pion suppression ≈ 10-
4
major background source: electrons from conversion in target; can be reduced by thinner target
J/ m = 38 MeV/c2
' m = 45 MeV/c2
target 25 m
Excellent performance for J/ψ; with thin target also ψ' in reach
Volker Friese CPOD 2007, GSI, 13 July 2007 32
CBM with Muons: MUCH
For muon measurements:RICH replaced by absorber – detector system
Challenges:first detectors in EM showertracking through absorber
TRD / TOF help to eliminate fake track matches
With removed absorber also suited for hadron measurements
Volker Friese CPOD 2007, GSI, 13 July 2007 33
MUCH Design
5 Fe absorbersinterlayed with 3 detector stations
Pad structure of detector layers
Volker Friese CPOD 2007, GSI, 13 July 2007 34
Performance for Di-Muons
Background sources:mis-identified hadrons (mostly fake matches)μ from π and K decay
J/ m = 22 MeV/c2
' m = 33 MeV/c2
Similar S/B as obtained in di-electron channels!
Volker Friese CPOD 2007, GSI, 13 July 2007 35
Summary
• Feasibility studies, including semi-realistic detector response and full event reconstruction demonstrate that the CBM detector concept is suitable for the measurement of the key observables: charm, low-mass dileptons, strangeness
• Tough detector R&D ahead to reach the design specifications
20042005
2006
Progress is fast –stay tuned:
http://www.gsi.de/fair/experiments/CBM
Volker Friese CPOD 2007, GSI, 13 July 2007 36
The CBM collaboration
Russia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg
China:CCNU WuhanUSTC Hefei
Croatia: RBI, Zagreb
Portugal: LIP Coimbra
Romania: NIPNE Bucharest
Poland:Krakow Univ.Warsaw Univ.Silesia Univ. KatowiceNucl. Phys. Inst. Krakow
LIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.Ukraine: Shevchenko Univ. , Kiev
Cyprus: Nikosia Univ.
Univ. Mannheim Univ. MünsterFZ RossendorfGSI Darmstadt
Czech Republic:CAS, RezTechn. Univ. Prague
France: IPHC Strasbourg
Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. Kaiserslautern
Hungaria:KFKI BudapestEötvös Univ. Budapest
India:VECC KolkataSAHA KolkataIOP BhubaneswarUniv. ChandigarhUniv. VaranasiIlT Kharagpur
Korea:Korea Univ. SeoulPusan National Univ.
Norway:Univ. Bergen
Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR Dubna
46 institutions
≈ 400 membersStrasbourg, September 2006