The Norwegian ALICE Project

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The Norwegian ALICE Project

• The ALICE experiment at LHC
• Activities of the Norwegian ALICE group
• Photon Spectrometer
• High Level Trigger
• Community structure
• Local and national collaborations
• Expertise
• Conclusions

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1. The ALICE experiment at LHC

• Heavy ion collisions
• Study the behavior or matter at large energy
  density
• Learn about
• Equilibration of stongly interacting matter
• Deconfinement and chiral symmetry restoration
• ...
• Proton-proton program
• Study of low-pt phenomena
• Beauty baryons
• ...
• Norwegian emphasis
• Hard probes
• High-pt photons
• Heavy flavours
• Jets and jet quenching
• Thermal radiation, i.e. direct photons

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2. Activities of the Norwegian ALICE group (1)

• Photon spectrometer (PHOS)
• Detection of photons with 0.5 GeV/c lt pt lt 100
  GeV/c
• Crystals
• Lead tungstate crystals (PWO), crystal size
  2222180 mm3
• Frontend electronics
• Avalanche Photo Diode (APD) readout
• Low-noise preamp
• L0 trigger
• Norwegian contribution
• Design of preamp
• low noise, large dynamic range
• fast timing signal for TOF and generating of
  high-pt trigger
• DAQ
• Simulation of detector response and physics
  performance
• APD vs PIN
• Trigger rates and efficiencies
• System tests
• Overall detector design

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PHOS
Preamp and APD
Preamp
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Activities of the Norwegian ALICE group (2)

• High Level Trigger (HLT)
• Bergen Budapest Frankfurt Heidelberg Oslo
• collaboration

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Data flow
TPC
detector
TRD
detector
Other detectors
data volume
30
Mbyte
/
event
Acquisition time 80µs
Acquisition time 2.0µs
front
-
end
front
-
end
front
-
end
electronics
electronics
electronics
25 Gbyte/sec
DDL
FEPLDC
FEPLDC
FEPLDC
FEPLDC
FEPLDC
FEPLDC
High Level Trigger System
lt 2 Gbyte/sec
Event Building
lt 1.25 Gbyte/sec
Permanent Storage System
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TPC event(only about 1 is shown)
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HLT tasks

• Trigger
• Accept/reject events
• verify dielectron candidates
• sharpen dimuon transverse momentum cut
• identify jets
• ...
• Select
• Select regions of interest within an event
• remove pile-up in pp
• filter out low momentum tracks
• ...
• Compress
• Reduce the amount of data required to encode the
  event as far as possible without loosing physics
  information

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Physics case studies
Quarkonium - dielectrons

• Transition Radiation Detector L0 trigger rates
  ptsingle gt 1 GeV/c ptsingle gt 0.8
  GeV/c ptpair gt 3 GeV/c
• J/?/event 0.007 0.0006
• background/event 0.39 0.15

• Quarkonium spectroscopy
• dielectrons
• dimuons
• Open Charm physics
• Jets
• ...

HLT system
TRD
TPC
Online track reconstruction 1) selection of
eepairs (ROI) 2) analysis of
eepairs (event rejection)

• Rejection factor (estimated)
• 5 (singles)
• 25 (pairs)

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HLT key components

• Real-time pattern recognition and event
  reconstruction
• Operation of O(500) node cluster
• Distributed, massive parallel computing
• FPGA-coprocessor
• Trigger efficiency simulations

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Real-time pattern recognition and event
reconstruction - fast cluster finder and track
follower

• Reconstruction efficiency in pp
• ? 98
• Pileup removal
• Full event reconstruction

pp pileup event one triggered event 20 ghosts
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Real-time pattern recognition and event
reconstruction - Hough transformation

• Tracking in high multiplicity PbPb events

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Operation of O(500) node cluster High Level
Trigger architecture
TPC sector 1
TPC sector 2
...
...
ITS
TRD
Trigger detectors Dimuon, TRD, ...
sub-sector level - 216 nodes
sector level - 108 nodes
.........
.........
supersector level - 72 nodes
network
event level - 12 nodes
trigger level - 1 node
(sub/super)-sector numbers TPC only
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Distributed, massive parallel computing
Cluster prototype
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FPGA co-processor

• FPGA co-processor for data intensive tasks
• Local pattern recognition on-the-fly
• Cluster finder
• Hough transformation tracker

PCI bus
DIU
-
CMC
FPGA
Memory
PCI bridge
Glue logic
interface
Coprocessor
D32
³
internal
detector
2 MB
DIU card
SRAM
2 MB
Memory D32
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FPGA co-processorPCI board(design and layout in
collaboration with University of Heidelberg)
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FPGA co-processor

• Simulation with TPC data
• verification of VHDL cluster finder
  functionality

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3. Community structure

• National and local collaborations
• Excellent collaboration between the groups in
  Oslo and Bergen
• Excellent collaboration between the different
  sections at both Universities (Nuclear Physics
  groups / Electronics groups)
• Excellent collaboration between the University of
  Bergen and the Bergen College
• Good working contacts within the subatomic
  experimental group and with the theory team

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Norwegian ALICE groups

• UiO
• Nuclear physics group
• G. Løvhøiden
• T. Tveter
• T. Vik (PhD student)
• J. Wikne (engineer)
• Electronics group
• B. Skaali
• D. Wormald (engineer)
• 1 student

• UiB
• Nuclear physics group
• D. Røhrich
• NN
• A. Klovning
• A. Vestbø (PhD student)
• Z. Yin (PhD student)
• B. Pommersche (engineer)
• 2 students
• Microelectronics group
• K. Ullaland
• W. Olsen (engineer)
• 2 students

• HiB
• Technical computing group
• H. Helstrup
• K. Fanebust
• J. Lien (PhD student)
• 10 students

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Expertise

• Electronics design (ASIC, FPGA, PCB)
• analogue
• fast digital
• Hardware/software co-design
• FPGA coprocessor
• DAQ and real-time programming
• Operation of O(500) node cluster
• Distributed, massive parallel computing
• distributed interprocess communication
• parallel applications
• High-level programming
• simulations
• event reconstruction
• data analysis
• High Energy Nuclear Physics

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Budget

• Budget 1998-2005 21.47 MNOK
• CORE deliverables (in kind or cash)
  7.70 MNOK
• PHOton Spectrometer (PHOS) 0.75 MCHF
• High Level Trigger (HLT) 0.51 MCHF
• Common Fund 0.14 MCHF
• Personell 3.36 MNOK
• Stipends 3.67 MNOK
• Operation (RD, travel) 6.74 MNOK

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4. Conclusions

• Team has doubled over the last three years need
  more travel money
• Refilling of staff positions in the next years
• More (and more flexible) PhD positions
• Urgent need for PostDoc position
• Possibility to fund interdisciplinary projects
  
  Nuclear
  Physics/Microelectronics/Computer Science