Experimental High Energy Nuclear Physics in Norway Kalliopi

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

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

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? 3

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 4

γ-hadron correlations p 0 Jet Fragmentation g Prompt g • 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 5

Direct photons Sources of direct γ • p. QCD (“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 6

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

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

Size: 16 x 26 meters Weight: 10, 000 tons TOF TRD HMPID ITS PMD Muon Arm PHOS ALICE setup TPC Added since 1997: -V 0/T 0/ACORDE 9 - TRD(’ 99) - EMCAL (’ 06)

Technical contribution to ALICE • Time Projection Chamber (TPC) • radiation tolerant readout electronics • calibration and online processing • PHOton Spectrometer (PHOS) • readout electronics and trigger (L 0 and L 1) • calibration and online processing • High Level Trigger (HLT) • calibration framework – interfaces to other systems (ECS, DAQ, CTP) • online event reconstruction/display and analysis software • Commissioning of all the above • GRID computing – part of Nordic distributed Tier 1 center 10

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 Ge. V/c in combination with other detectors (e. g. TOF, HMPID) • momentum resolution ~1% for pt < 2 Ge. V/c • tracking efficiency 90% • d. E/dx resolution < 10% • 557 568 readout channels • rate capabilities > 1 k. Hz for pp 11

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Readout Control Unit (RCU) 13

alignment electrostatic distortions E x B effects t 0, drift velocity reconstruction electron attachment calibrated data raw data gain reconstructed tracks momentum and d. E/dx TPC calibration 14

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 15

Drift velocity calibration (II) 16

The ALICE PHOS spectrometer • • • Pb. O 4 W crystal calorimeter for photons, neutral mesons (1 - 100 Ge. V/c) Crystal size 2. 2 × 2. 2 cm 2, 20 X 0, APD readout, operated at – 25° C σ(E)/E ≈ 3%, σ(x, y) ≈ 4 mm, σ(t) ≈ 1 ns at 1 Ge. V |η| < 0. 12, Δφ = 100° at R = 460 cm L 0 trigger available at < 900 ns 17

Trigger hierarchy Collision L 0: Trigger detectors detect collision (V 0/T 0, PHOS, SPD, TOF, dimuon trigger chambers) L 1: select events according to • centrality (ZDC, . . . ) • high-pt di-muons • high-pt di-electrons (TRD) • high-pt photons/π0 (PHOS) • jets (EMCAL, TRD) L 2: reject events due to past/future protection HLT rejects events containing • no J/psi, Y • no D 0 • no high-pt photon • no high-pt pi 0 • no jet, di-jet, γ-jet 0 1. 2 6. 5 88 t [μsec] 18

The PHOS L 0 and L 1 triggers Array of crystals + APD + preamp + trigger logic + readout DAQ L 0 trigger • tasks • shower finder L 0/L 1 trigger • energy sum • implementation • FPGA • VHDL firmware 19

The ALICE High Level Trigger • • • d. Nch/dη = 2000 – 4000 for Pb+Pb After L 0, L 1 and L 2 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 k. Hz for p+p and 200 Hz for central Pb+Pb Physics triggers application for event characterization 20

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

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 22

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 23

HLT online display 24

Physics contribution to ALICE • • • High p. T π0 (calorimeters) High p. T π0 from conversions (TPC) High p. T charged particles and jet reconstruction Total ET (calorimeters+TPC) High p. T direct γ (calorimeters) γ-hadron and π0 -hadron correlations (calorimeters+TPC) Collective flow Ultra-peripheral collisions Online D 0 reconstruction (ITS+TPC) Online π0 reconstruction (TPC) 25

Invariant mass in PHOS in pp@7 Te. V 26

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

Di-hadron correlations December status for 900 Ge. V data 28

D 0 in ALICE Implementation of online D 0 trigger in the HLT framework 29

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 30

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 31

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 32

RHIC vs. LHC 33

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 34

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

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 Ui. B 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 36

Other activities (III) • Next generation pixel detectors • Sensor: Monolithic Active Pixel Sensor • 3 D 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 Ui. B 37

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 38