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ALICE Status

NuPECC Meeting Edinburgh 10 th October 2014. ALICE Status. Orlando Villalobos Baillie University of Birmingham. ALICE Physics. We collide lead ions (& p-p, p-Pb) to study QCD at extreme energy densities over large volumes and long time-scales.

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ALICE Status

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  1. NuPECCMeeting Edinburgh 10th October 2014 ALICE Status Orlando Villalobos Baillie University of Birmingham

  2. ALICE Physics • We collide lead ions (& p-p, p-Pb) to study QCD at extreme energy densities over large volumes and long time-scales. • Study the role of chiral symmetry in the generation of mass in hadrons (accounts for ~ 99% of mass of nuclear matter). • Study the nature of quark confinement. • Study the QCD phase transition from nuclear matter to a deconfined state of quarks and gluons - The Quark-Gluon Plasma. • Study the physics of the Quark-Gluon Plasma (QCD under extreme conditions).

  3. QCD Phase Diagram Early Universe ALICE colour Only gauge theory phase transition accessible to experiment

  4. Colliders: AGS, SPS, RHIC, LHC Heavy Ion Collisions Create QGP by colliding ultra-relativistic heavy ions SNN (GeV) = 5.4 19 200 2760 (5500) Probe properties of QGP by studying characteristics of all particles produced in collisions. Use p-p & p-Pb collisions as baseline. Jets Open charm, beauty

  5. ALICE Physics • A lot of high-quality data to work with from the PbPb, pPb and ppruns • The harvest of results continues • Over 60 journal publications so far • The impactof physics publications remains extremely high - after the 4 Higgs discovery papers the next threehighest cited LHC physics papers come from ALICE.

  6. The ALICE Experiment Size: 16 x 26 metres Weight: 10,000 tonnes Detectors:18 Collaboration: > 1300 Members>120 Institutes > 35 countries Birmingham-built Central Trigger Processor Electronic Brain of the detector.

  7. Some Highlights of Run 1 • We have measured many of the global features • Phase transition temperature - Agrees with theory Tc ~ 164 MeV • Energy density - Over 10x critical energy density,  > 15 GeV/fm3(> 3X RHIC) • size & lifetime of system ~ 5000fm3,  ~ 10-11 fm/c • Highest temperature ever measured (from low pT photon spectrum) • Very strong radial flow, b≈ 0.66

  8. Thermal Models Fit to extended set of particle species using an equilibrium model (SHARE). 2/ndf ~ 2 One of the largest contributions to 2 comes from low yield of protons w.r.t. pions.

  9. y z x QGP is Perfect Liquid Study angular dependence of emitted particles • Elliptic Flow: • Collective effects of data fit hydro-dynamical models •  Most ideal liquid ever created Reaction Plane • Viscosity/Entropy density, h/S  0.2 • AdS/CFTprediction limit: h/S > 1/4p ≈ 0.08

  10. Flow – Ideal Liquid V2 = elliptic flow Collective effects of data fit hydro-dynamical models  Most ideal liquid ever created Evidence for flow from D-mesons suggests collective effects from charm.  More data needed (Run 2)

  11. 10-20% peripheral 168 GeV 192 GeV Dh Df 0-10% central 102 GeV 47 GeV Df Dh Jet Quenching Large suppression of jets seen in central collisions 11

  12. High pT Suppression (RAA) • High pT particles supressed by factor 7 in central Pb-Pb w.r.t. weighted p-p data • No such suppression seen in p-Pb • Direct photons, of course, not supressed in Pb-Pb. < 1 : Medium effect = 1 : No medium effect

  13. First measurement of RDAA/RpAA Probe QGP with different quark flavours: u, d, s, c (b only after upgrade) Theoretical expectation: Elightquark > Emassive quark High pT Suppression of charm First indication of mass effects ?

  14. p and Pb at the LHC • When b > (R1 + R2), hadronic interactions are very much suppressed, and photon processes become important. • Photon flux  Z2 • Photons are quasi-real; virtuality limited by size of nuclei. •  from p  Q2~ (250 MeV)2 •  from Pb  Q2 ~ (35 MeV)2 • Photon energy determined by boost of emitting particle. •  from p (4 TeV): •  from Pb:

  15. J/ photoproduction • J/ photoproduction cross-section is proportional to square of gluon structure function (at LO) • J/ sets a hard scale GeV2. • At LHC energies, xBj~10-2-10-5is accessible. • J/ photoproduction in Pb-Pb UPC gives information on gluon shadowing in nuclei at low x. Leading Order

  16. p-PbMeasurements • Our knowledge of the photon emitter allows us to solve for (Wp) using the measured d/dy • A power law fit ((W)~W) to ALICE data points gives =0.670.06. HERA Measurements H1 =0.670.03 ZEUS =0.690.02

  17. ALICE Upgrade Opens a new and unique window of discovery with rare charm and beauty physics

  18. ALICE Upgrade • Focus on rare probes, study their coupling with QGP medium and their (medium-modified) hadronisation process • precision studies of charm and beauty at low-pT • low mass lepton pairs and thermal photons • -jet and jet-jet with particle identification from low momentum up to 30 GeV. • exotic nuclear states • low-transverse momentum observables (complementary to the general purpose detectors ATLAS and CMS) • Many features not triggerable => need to examine full statistics. • Target: • Pb-Pbrecorded luminosity ≥ 10 nb-18 x 1010events • pp(@5.5 Tev) recorded luminosity ≥ 6 pb-11.4 x 1011events • Gain a factor 100 over the statistics of the approved programme • Operate ALICE at high rate while preserving its uniqueness, superb trackingand PID, and enhance its vertexing capability and tracking at low-pT

  19. Summary of Upgrades Muon Forward Tracker (MFT) MAPS Inner Tracking System (ITS) Muon Arm Readout Trigger electronics (CTP + LTUs) Data Acquisition (DAQ) High Level Trigger (HLT)

  20. UK Objectives To build upon and significantly enhance the UK’s current prominence & leadership in ALICE. • Design, build & commission new trigger system for ALICE Upgrade • Build upon the Birmingham’s existing leadership & prominence within ALICE. (Responsible for the current trigger system. Represented on the ALICE Management, Technical, & Physics Boards) • To make a major contribution to the Inner Tracking System (ITS) Upgrade. • The key sub-detector for the proposed enhanced physics programme post Long Shutdown 2 (LS2). • Utilise the strong international reputation of Liverpool & Daresburyin Si tracking systems. • Significantly strengthen the UK’s role in this important field and place us in an ideal position to fully exploit ALICE physics post LS2.

  21. Summary • An exciting long-term Research • Programme at the LHC • Related STFC Roadmap questions: • How did the universe begin and how • is it evolving? • What is the physics of the early • universe? • What are the fundamental constituents and fabric of the universe and how do they interact? • What is the nature of nuclear and hadronic matter? • Studying the phase diagram of strongly interacting matter • New probes, properties of deconfined matter • Thermodynamics of the Standard Model? • A major opportunity for UK to play a leading role in: • Construction of ALICE Upgrade (Trigger and Inner Tracking System)

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