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Heavy Ions @ LHC

Heavy Ions @ LHC . Heavy Ion Physics (in VERY general terms) Heavy Ion Physics at LHC ALICE Collaboration Detector Performance. Pretty Messy …. NA35 streamer chamber picture, ca 1990. Heavy Ion Collisions: What for ?. T. D. Lee Two outstanding puzzles that confront us today:

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Heavy Ions @ LHC

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  1. Heavy Ions @ LHC Heavy Ion Physics (in VERY general terms) Heavy Ion Physics at LHC ALICE Collaboration Detector Performance HI@LHC J. Schukraft

  2. Pretty Messy … NA35 streamer chamber picture, ca 1990

  3. Heavy Ion Collisions: What for ? • T. D. Lee Two outstanding puzzles that confront us today: I ) missing symmetries QCD mass generationvia broken chiral symmetry (mu,d¹0) II) unseen quarks confinement The resolution of these puzzles is probably tied to the structure of the vacuum. … in most high energy physics experiments, the higher the energy, the smaller has been the spatial region we are able to examine. In order to study the structure of the ‘vaccum’, we must turn to a different direction; we should investigate some bulk phenomenaby distributing high energy over a large volume. Rev. Mod. Phys., Vol 47 (1975) 267 Nucl. Phys. A553 (1993) 3c

  4. Physics at LHC • Common Questions • generation of mass • elementary particles => Higgs => Atlas/CMS • composite particles => QGP => Alice • missing symmetries • SuperSymmetry: matter <=> forces => Atlas/CMS • ChiralSymmetry: matter <=> vacuum => Alice • CP Symmetry: matter <=> antimatter => LHCb • Different Approaches • ‘Concentrated Energy’ => new high mass particles • ‘Distributed Energy’ => heat and melt matter & vacuum • ‘Borrowed Energy’ => indirect effects of virtual high mass particles

  5. x 28 x 12 BIG Step ahead: SPSRHICLHC Predictions are notoriously difficult, in particular if they concern the future.. H.I. Physics@LHC: Caveat • long distance QCD is difficult to predict • Theory well known, not so its consequences or manifestation • HEP@LHC: Theory unknown, but each candidate makes precise predictions • the fate of 'expectations' at SPS and RHIC • some expectations turned out right: • SPS: strangeness enhancement RHIC: particle ratios, jet-quenching • some turned out wrong: • SPS: large E-by-E fluctuations RHIC: multiplicity dN/dy • a number of unexpected surprises: • SPS: J/Psi suppression RHIC: elliptic flow, 'HBT-puzzle' • lesson when preparing ALICE at LHC • guided by theory and expectations, but stay open minded ! • 'conventional wisdom' • soft physics: smooth extrapolation of SPS/RHIC necessary, but boring ??? • hard physics:new domain at LHC

  6. Hard Processes at the LHC Pb q Q Pb q X 2000 • Main novelty of the LHC: large hard cross section ~2% at SPS ~50% at RHIC ~98% at LHC • Hard processes are extremely useful tools • probe matter at very early times (QGP) !!! • hard processes can be calculated by pQCD -> predicted K. Kajantie (QM02)

  7. ideal energy for jet-quenching:around 100 GeV pQCDapplicable jets measurable above soft background energy loss still relatively large effect DE/E ~ O(10%), decreasing with E ! pt jet > (GeV/c) jets/event accepted jets/month 5 3.5 102 4.9 1010 50 7.7 10-2 1.5 107 100 3.5 10-3 8.1 105 150 4.8 10-4 1.2 105 200 1.1 10-4 2.8 104 Jets in ALICE |h|<0.9 pp L = 1030cm-2s-1 Pb Pb rates: Reasonable rate up to ET ~300 GeV

  8. RHIC LHC Y production R. Vogt, hep-ph/0205330 Heavy Quarks & Quarkonia • copious heavy quark production • charm @ LHC ~ strange @ SPS • hard production => 'tracer' of QGP dynamics (statistical hardonization ?) • 2 mc ~ saturation scale => change in production ? • jet-quenching with heavy quarks visible in inclusive spectra ? • Y ds/dy LHC ~ 20 x RHIC • Y will probably need higher Lumi at RHIC • even at LHC Y'' is difficult

  9. my pre-RHIC guess (QM2001) still expect conditions to be significantly different only LHC will give the final answer on dn/dy! Central collisions SPS RHIC LHC s1/2(GeV) 17 200 5500 dNch/dy 430 700-1500 2-8 x103 e (GeV/fm3)t0=1fm 2.5 3.5-7.5 15-40 Vf(fm3) 103 (?)7x103 2x104 tQGP (fm/c) <1 1.5-4.0 4-10 t0 (fm/c) ~1 ~0.5 <0.2 Initial Conditions Significant gain in e, V, t » x 10 SPS -> LHC » x 3-5 RHIC -> LHC Hotter - Bigger - Longer lived

  10. changes in expansion dynamics & freeze-out ARE expected thermal freeze-out temperature ? how will charm fit into particle ratios ? Event-by-Event fluctuations ? measurement accuracy ~ Ö#particles will elliptic flow continue to rise ? will the measured transverse HBT volume (finally) increase ? Freeze-out Hyper surface SPS LHC The Soft Stuff Biggest surprise would be none..

  11. Chinese Participation in Heavy Ions • AGS/SPS program: from the very start …. • EMU01(1986): 3 Institutes, 4 people (Beijing IHEP, Shanxi NU, Wuhan CCNU) • E815(1986): (Beijing IHEP, Shanxi NU, Wuhan CCNU) • EMU12 (1991): 3 Inst., 20 people (Beijing IHEP, Hunan, Shanxi NU, Wuhan CCNU) • E863 (1990): (Wuhan CCNU) • RHIC programvia the first collider…. • PHENIX: 1 Institute, ~ 5 people • CIAE Beijing (muon detectors) • STAR: 6 Institutes, ~ 50 people • USTC, Tsinghua U,. Shanghai INR (SINR), IHEP Beijing, Wuhan CCNU, IMP Lanzhou (MRPC-TOF detector) • LHC programto the ultimate machine (?) • ALICE (since 1993 !): 3 Institutes, ~ 30 people • CIAE Beijing, Wuhan CCNU, Wuhan CCUST, …. • successful R&D on large area PIN diodes, PHOS electronics & mechanics • large activity in theory • at home: CIAE (event generators LUCIAE,JPCIAE, PACIEA), Wuhan CCNU, ….. • and abroad: T.D. Lee, X.N. Wang, …. Quark Matter 2007 In Shanghai !

  12. ALICE Set-up Size: 16 x 26 meters Weight: 10,000 tons TOF TRD HMPID TPC PMD ITS Muon Arm PHOS

  13. ALICE Collaboration ~ 1000 Members (63% from CERN MS) ~30 Countries ~90 Institutes

  14. ALICE Design Philosophy • General Purpose Heavy Ion Detector • one single dedicated HI expt at LHC • ATLAS/CMS will participate, butpriority is pp physics • AGS/SPS: several (6-8) 'special purpose expts' • RHIC: 2 large multipurpose + 2 small special purpose expts • cover essentially all known observables of interest • comprehensive study of hadrons at midrapidity • large acceptance, excellent tracking and PID • state-of-the-art measurement of direct photons • excellent resolution & granularity EM calo (small but performing !) • dedicated & complementary systems for di-electrons and di-muons • cover the complete spectrum: from soft (10's of MeV) to hard (100's of GeV) • stay open for changes & surprises • high throughput DAQ system + powerful online intelligence ('PC farm‘, HLT) • flexible & scalable: minimum design prejudice on what will be most interesting

  15. still largest magnet • magnet volume: 12 m long, 12 m high • 0.5 T solenoidal field The ALICE Magnet: ready for the experiment to move in!

  16. Inner Tracking System (ITS) Silicon Pixels (RD19) Silicon Drift (INFN/SDI) Silicon Strips (double sided) low mass, high density interconnects low mass support/cooling TPC gas mixtures (RD32) new r/o plane structures advanced digital electronics low mass field cage em calorimeter new scint. crystals (RD18) PID Pestov Spark counters Parallel Plate Chambers Multigap RPC's (LAA) low cost PM's solid photocathode RICH (RD26) DAQ & Computing scalable architectures with COTS high perf. storage media GRID computing misc micro-channel plates rad hard quartz fiber calo. VLSI electronics ü ü ü ü ü ü ü ? ? ? V V V V V ALICE R&D 1990-1998:Strong, well organized, well funded R&D activity • R&D made effective use of long (frustrating) wait for LHC • was vital for all LHC experiments to meet LHC challenge !

  17. Time of Flight Detectors • aim: state-of-the-art TOF at ~1/10 current price ! • requirements: area > 150 m2, channels ~ 150,000, resolution s < 100 ps • existing solution: scintillator + PM, cost > 120 MSF ! • R&D on cheaper fast PM's in Russia failed to deliver • gas TOF counters + VLSI FEE • Pestov Spark Counter (PSC) • 100 mm gap, > 5 kV HV, 12 bar, sophisticated gas • s < 50 ps, some 'tails' (?), but only (!) ~ 1/5 cost • technology & materials VERY challenging • Parallel Plate Chamber (PPC) • 1.2 mm gap, 1 bar, simple gas & materials • 1/10 cost, but only s = 250 ps • unstable operation, small signal • Multigap Resistive Plate Chambers (MRPC) • breakthrough end 1998 after > 5 years of R&D ! • many small gaps (10x250 mm), 1 bar, simple gas & materials • ~ 1/10 cost, s < 100 ps , simple construction & operation,..

  18. The STAR Barrel TOF MRPC Prototype Prototype Tray Construction at Rice University MRPC design developed at CERN, built in China 28 MRPC Detectors; 24 made at USTC FEE Neighbor CTB Tray EMC Rails   50 ps, 2 meter path Strong team including 6 Chinese Institutions in place Completed Prototype 28 module MRPC TOF Tray installed in STAR Oct. ‘ 02 in place of existing central trigger barrel tray

  19. STAR Tracking Challenge ALICE 'worst case' scenario: dN/dych = 8000 NA49

  20. TPC largest ever 88 m3, 570 k channels drift gas 90% Ne - 10%CO2 HV membrane (25 mm) Field Cage

  21. stable hadrons (p, K, p): 100 MeV < p < 5 GeV dE/dx in silicon (ITS) and gas (TPC) + Time-of-Flight (TOF) + Cerenkov (RICH) dE/dx relativistic rise under study => extend PID to several 10 GeV ?? decay topology (K0, K+, K-, L) still under study, but expect K and L decays up to at least 10 GeV leptons (e, m), photons, h,p0 electrons in TRD: p > 1 GeV muons: p > 5 GeV p0 in PHOS: 1 < p < 80 GeV Particle Identification Alice uses ~ all known techniques! p/K TPC + ITS (dE/dx) K/p e /p p/K TOF e /p K/p HMPID (RICH) p/K K/p 0 1 2 3 4 5 p (GeV/c) TRD e /p PHOS g /p0 1 10 100 p (GeV/c)

  22. Photons CERN Press release in 2000 on ‘Evidence for new state of matter’ ‘It is expected that the present "proof by circumstantial evidence" for the existence of a quark-gluon plasma in high energy heavy ion collisions will be further substantiated by more direct measurements (e.g. electromagnetic signals which are emitted directly from the quarks in the QGP) which will become possible at the much higher collision energies and fireball temperatures provided by RHIC at Brookhaven and later the LHC at CERN.’ • Physics • thermal radiation from QGP (‘background radiation of mini-bang’) • photon rate ~ T4 => huge boost at LHC expected • hard physics: photon-jet correlations • particle spectra ( p0, h ), ...... • Detector: PHOS • LHC: high particle density + large combinatorial background for p0, h • high granularity => dense material + large distance from vertex • good resolution => scintillation crystals • compromise: acceptance

  23. Photon Spectrometer single arm em calorimeter dense, high granularity crystals novel material: PbW04 ~ 18 k channels, ~ 8 m2 cooled to -25o PbW04 crystal for photons, neutral mesons and -jet tagging PbW04: Very dense: X0 < 0.9 cm Good energy resolution (after 6 years R&D): stochastic 2.7%/E1/2 noise 2.5%/E constant 1.3%

  24. 2004 PHOS • mass production of crystals ongoing (> 50% available) • Apatity, Russia • Electronics • production just started ! • R&D, design & production in China • first module ready end 2005 Crystal Light yield vs batch number PHOS mechanics • Collaboration: • Russia, Norway, Czech, France • CHINA: CIAE, CCNU, HUST PHOS FEE card

  25. Dimuon Spectrometer • Study the production of the J/Y, Y', U, U' and U'’ decaying in 2 muons, 2.4 < < 4 • Resolution of 70 MeV at the J/Y and 100 MeV at the U RPC Trigger Chambers 5 stations of high granularity pad tracking chambers, over 800k channels Complex absorber/small angle shield system to minimize background (90 cm from vertex) Dipole Magnet: bending power 3Tm

  26. Muon Absorbers • ~ 100 tons (W, Fe, C, concrete, ..) • W produced in China (AT&M, Beijing, ~ 500 k$)

  27. Muon Magnet • Dipole Magnet • 0.7 T and 3 Tm • 4 MW power, 800 tons • World’s 2ndlargest warm dipole • Progress: • final assembly & test by June

  28. Computing Phase Transition Online: storing up to 1.2 Gbyte/s whole WWW in few hours on tape ! ~ 10 x RHIC ! Offline: 18 MegaSI2000 100,000 PC's in 2000 (500 Mhz) ~ 100 x RHIC !! The Answer: cheap mass market components Industry & Moore's law The Challenge: make 100,000 mice do the work of one elephant new computing paradigm: The GRID ALICE DC III The Problem:

  29. The CORE GRID functionality exists Distributed production in action for the PPR ALICE GRID is there: ALIEN OSU/OSC LBL/NERSC Dubna Birmingham NIKHEF Saclay GSI CERN Padova Merida IRB Bologna Lyon Torino Bari Cagliari Yerevan Catania Kolkata, India Capetown, ZA

  30. Production Status 22773 jobs, ~12CPUh/job, ~1GB output/job up to 450 concurrent jobs 0.5 operators !

  31. Heavy Quarks • Hadronic charm: D -> Kp • uses sec. vertex & PID • acceptance to ~ 0 pt=> stot • full kinematic reconstruction • => 'quark quenching' • under study: D*, D±, Bc, Lb, ...

  32. Short Term Upgrade Plans • Initial detector largely finished & in place by 2007 • exception: TRD coverage only 60% financed • New detectors under discussion • based on recent physics results (RHIC) and theory developments since 1990 • pixel trigger electronics (~ few 100 k$) • allows better study of pp min bias events • PID for large momenta (5 – 20 GeV) (~ few M $) • based on Cherencov radiation (aerogel, gas radiator ?) • large em calorimeter for jet physics (~ 10 M $) • ~ 200 m2 high granularity, shashlik type sampling calorimeter • interested groups in US, Italy, France, …

  33. RHIC Past-Present-Future • AGS/SPS: 1986 – 1994 • existence & properties of hadronic phase • chemical & thermal freeze-out, collective flow,… • SPS: 1994 – 2003 • ‘compelling evidence for new state of matterwith many properties predicted for QGP’ • J/Y suppression (deconfinement ?) • low mass lepton pairs (chiral restoration ?) • RHIC: 2000 - ? • compelling evidence -> establishing the QGP ? • parton flow, parton energy loss • however: soft ~ semihard; lifetime hadron ~ parton phase • LHC: 2007 - ?? • (semi)hard >> soft, lifetime parton >> hadron phase • precision spectroscopy of ‘ideal plasma ‘QGP • heavy quarks (c,b), Jets, Y, thermal photons LHC: will open the nextchapter in HI physics significant step over & above existing facilities THEplace to do frontline research after 2007

  34. Summary • LHC is the ultimate machine for Heavy Ion Collisions • very significant step beyond RHIC • excellent conditions for experiment & theory (QCD) • not only latest, but possibly last HIC at the energy frontier • ALICE is a powerful next generation detector • first truly general purpose HI experiment • addresses most relevant observables: from super-soft to ultra-hard • many evolutionary developments • SSD, SDD, TPC, em cal, … • some big advances in technology • electronics, pixels, TOF, computing Heavy Ion Community can look forward to eventually exploit this unique combination !

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