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

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

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?

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

γ-hadron correlations Fragmentation g Jet Prompt g p0 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

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

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

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 baryons mesons

ALICE setup TOF TRD HMPID ITS PMD Muon Arm PHOS TPC 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) ALICE setup TPC

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) 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

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

Readout Control Unit (RCU)

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

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

Drift velocity calibration (II)

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

Trigger hierarchy L1: select events according to centrality (ZDC, ...) 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 1.2 6.5 88 t [μsec]

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

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

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

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

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

HLT online display

Physics contribution to ALICE High pT π0 (calorimeters) High pT π0 from conversions (TPC) High pT charged particles and jet reconstruction Total ET (calorimeters+TPC) High pT 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)

Invariant mass in PHOS in pp@7 TeV

π0 reconstruction from conversion γ γ-ray picture of ALICE

Di-hadron correlations December status for 900 GeV data

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

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 copy previous slide here

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

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

RHIC vs. LHC

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

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

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

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

Summary 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