Experimental High Energy Nuclear Physics in Norway

1. Experimental High Energy Nuclear Physics in Norway Kalliopi Kanaki University of Bergen

2. Norwegian activities in… • ALICE@CERN • hardware/software contribution • physics analysis • ALICE upgrades • Side activities • CBM@FAIR • Medical physics

3. Physics goals of ALICE • LHC accesses the QCD phase diagram at low μB, high T • What can we learn about the system produced in the collisions? • Does it have the same properties as the state produced at RHIC? • Is the QGP weakly or strongly (fluid) coupled? • Is there a sharp phase transition? • How do partons interact with the medium?

4. Di-hadron correlations & jet quenching • Hard parton scattering observed via leading (high momentum) particles • Strong azimuthal correlations at  =  expected • Result: complete absence of away-side jet • away-side partons are absorbed in the medium • strong energy loss • medium is opaque to fast partons

5. Fragmentation g γ-hadron correlations p0 Jet • The point-like photon remains unmodified by the medium and provides the reference for the hard process • The prompt photon provides a measurement of the medium modification on the jet because they are balanced Promptg

6. Direct photons Sources of direct γ • pQCD (“prompt”) photons • Compton • Annihilation • Bremsstrahlung • Thermal photons  sensitive to initial temperature • Challenging to obtain, necessary for γ-jet studies • measure inclusive spectrum • subtract background from hadronic decays

7. Nuclear modification factor RAA • At RHIC the matter produced is opaque • High pT particles are suppressed • The medium is transparent to photons

8. Collective flow baryons mesons • Initial state spatial anisotropy of reaction zone causes • final state momentum anisotropy • asymmetric particle emission • Higher initial density results in larger pressure gradient • The system has very low viscosity/ideal hydrodynamical fluid • Flow is formed at the partonic level

9. Size: 16 x 26 meters Weight: 10,000 tons TOF TRD HMPID ITS PMD Muon Arm PHOS Added since 1997: • V0/T0/ACORDE • TRD(’99) • EMCAL (’06) TPC ALICE setup

10. Technical contribution to ALICE • Time Projection Chamber (TPC) • radiation tolerant readout electronics • calibration and online processing • PHOton Spectrometer (PHOS) • readout electronics and trigger (L0 and L1) • calibration and online processing • High Level Trigger (HLT) • calibration framework – interfaces to other systems (ECS, DCS, DAQ, CTP) • online event reconstruction/display and analysis software • Commissioning of all the above • GRID computing – part of Nordic distributed Tier1 center

11. The ALICE TPC • main tracking device for momentum reconstruction |η|<0.9 • drift length 2 x 2.5 m • PID for pt up to 100 GeV/c in combination with other detectors (e.g. TOF, HMPID) • momentum resolution ~1% for pt < 2 GeV/c • tracking efficiency 90% • dE/dx resolution < 10% • 557 568 readout channels • rate capabilities > 1 kHz for pp

13. Readout Control Unit (RCU)

14. TPC calibration gain electron attachment reconstruction calibrated data reconstructed tracks momentum and dE/dx alignment raw data electrostatic distortions E x B effects t0, drift velocity

15. Drift velocity calibration (I) • Drift velocity = f(E-field, gas density (T, p), ...) • Monitoring tools: • Laser tracks • Electrons from the central electrode • Tracks from collisions • Traversing central electrode • Matching with ITS • Cosmics • External drift velocity monitor

16. Drift velocity calibration (II)

17. The ALICE PHOS spectrometer • PbO4W crystal calorimeter for photons, neutral mesons (1 - 100GeV/c) • Crystal size 2.2 × 2.2 cm2, 20 X0, APD readout, operated at –25° C • σ(E)/E ≈ 3%, σ(x,y) ≈ 4 mm, σ(t) ≈ 1 ns at 1 GeV • |η| < 0.12, Δφ = 100° at R = 460 cm • L0 trigger available at < 900 ns

18. Trigger hierarchy Collision L0: Trigger detectors detect collision (V0/T0, PHOS, SPD, TOF, dimuon trigger chambers) • L1: select events according to • centrality (ZDC, ...) • high-pt di-muons • high-pt di-electrons (TRD) • high-pt photons/π0 (PHOS) • jets (EMCAL, TRD) L2: reject events due to past/future protection • HLT rejects events containing • no J/psi, Y • no D0 • no high-pt photon • no high-pt pi0 • no jet, di-jet, γ-jet t [μsec] 88 0 1.2 6.5

19. The PHOS L0 and L1 triggers Array of crystals + APD + preamp + trigger logic + readout DAQ • L0 trigger • tasks • shower finder • energy sum • implementation • FPGA • VHDL firmware L0/L1 trigger

20. The ALICE High Level Trigger • dNch/dη = 2000 – 4000 for Pb+Pb • After L0, L1 and L2 rates can still be up to 25 GB/s • DAQ archiving rate: 1.25 GB/s → imperative need for HLT • Goals: • Data compression • Online reconstruction of all events • Handle rates of > 1 kHz for p+p and 200 Hz for central Pb+Pb • Physics triggers application for event characterization

21. copy sent to HLT raw data DAQ HLT trigger decision for every event mass storage HLT Processing Data Flow

22. HLT cluster status • 2010 Run Setup • 123 front-end nodes • 968 CPU cores • 1.935 TB RAM • 472 DDL • 53 computing nodes • 424 CPU cores • 1.152 TB RAM • Pb+Pb upgrade • 100 computing nodes • 2.4 TB RAM • Full network infrastructure • Full service infrastructure • HLT decision sent to DAQ for every event

23. HLT activities in Norway • Analysis framework • Both online and offline (emulation) version • Analysis software • TPC cluster finder and calibration • ITS reconstruction • PHOS reconstruction and calibration • EMCAL and PHOS analysis integration • ESD production online • Trigger implementation and trigger menu for DAQ • Infrastructure maintainance and improvement • Reconstruction and trigger evaluation • Interfaces to other online systems

24. HLT online display

25. Physics contribution to ALICE • HighpTπ0 (calorimeters) • HighpTπ0 from conversions (TPC) • HighpT charged particles and jet reconstruction • Total ET (calorimeters+TPC) • HighpT direct γ (calorimeters) • γ-hadron and π0-hadron correlations (calorimeters+TPC) • Collective flow • Ultra-peripheral collisions • Online D0 reconstruction (ITS+TPC) • Online π0 reconstruction (TPC)

26. Invariant mass in PHOS in pp@7 TeV

27. π0 reconstruction from conversion γ γ-ray picture of ALICE

28. Di-hadron correlations December status for 900 GeV data

29. D0 in ALICE Implementation of online D0 trigger in the HLT framework

30. Ultra-peripheral collisions • Photon induced interactions with photons produced • by the EM field of the protons/nuclei • Possible in pp and in Pb+Pb interactions • Ongoing work: simulation studies+trigger • conditions (software & hardware) • p+p → p+p+μ++μ- • purely QED part γ+γ→ μ++μ- • photonuclear part γ+p → J/ψ+p → μ+μ-+p

31. ALICE upgrade plans • Timeslots for potential upgrades • 2012: 1 year shutdown (minor upgrades) • 2018 (?): 1 year shutdown (major upgrades, • e.g. beam line modifications) • Ongoing projects • completion of PHOS trigger • upgrade of TPC and PHOS readout • HLT “dynamic” upgrade • Potential new project: Forward calorimeters

32. Forward physics at LHC • Measurements at small angle/large η • low-x parton distributions • Main physics topics • p(d)+A • gluon saturation • study of ”cold” nuclear matter • probing the initial condition • A+A • elliptic flow • jet quenching • long-range rapidity correlations • baryon transfer

33. RHIC vs. LHC

34. Proposal for a forward spectrometer • EM calorimeter for γ, π0, η, J/ψ at y=5 • O(10) meters away from IP • large dynamic range • high occupancy to cope with A+A • two γ separation (π0→ 2γ kinematics) highly segmented (also longitudinally) tracking calorimeter

35. Other activities (I) • CBM@FAIR • Fixed target experiment, Ebeam = 30 AGeV • Production of super-dense baryonic matter • Chiral symmetry restoration/in-medium properties of hadrons • Potential Norwegian contribution: • Monolithic Active Pixel Sensor readout (3D stacking) • Projectile Spectator Detector (forward calorimeter) • High Level Trigger So far no Norwegian funding for FAIR

36. Other activities (II) • Generic R&D projects with potential medical physics applications • Highly segmented calorimeters • Characterization of pixel arrays of G-APD (Avalanche Photodiodes operated in Geiger mode) • Collaboration with the microelectronics • group at UiB and the PET-center of • Bergen University Hospital (HUS) • → high resolution TOF PET-scanner • Radiation effects in microelectronics • SEU in SRAMs: neutron dosimetry • Collaboration with HUS, biophysics@GSI • and CERN (EN/STI) • → hadron therapy purposes

37. Other activities (III) Next generation pixel detectors Sensor: Monolithic Active Pixel Sensor 3D integration high spatial resolution, lower capacitance (and hence, lower noise), and enough logic per pixel cell to implement fast, intelligent readout by thinning the wafers lower material budget is obtained collaboration with the microelectronics group at UiB

38. Norway has a strong presence in: Hardware design/prototyping/construction Software Commissioning of hardware & software Run coordination for detectors & the whole of ALICE Time to harvest the fruit of physics for the next 10-15 years Ambitious ALICE upgrade program Summary