Calcutta, J. Schukraft1 The quest for the QGP: 20 years of heavy ion physics

2 Explorations Search for the QGP* Search for a sea passage to India* world map, late 15 th century QCD map, late 20 th century A Mid-Fifteenth-Century European World Map (1466) The Mediterranean basin, known to Ptolemy and later Europeans, is fairly accurately depicted, but the Eastern portions of the map are very incomplete since they were based on often-fictitious travelers’ accounts rather than observation. *Original idea from H. Satz and D. Karzheev, Hard probes WS, Portugal,

3 Explorers ‘In 1493, Columbus wrote a brief report concerning his discoveries of "Islands of India beyond the Ganges." It was intended as a public notice to announce his discoveries and to garner support for another voyage. The first edition of this letter was printed in Spanish in Barcelona in April 1493.’ Quote from US library of Congress Columbus: visionary, enthusiastic adventurer Not afraid to venture far into the unknown with little guidance and marginal preparation. As befits the brave (and lucky), he made a BIG discovery. Headline Barcelona News April 1493

4Explorers Vasco da Gama: methodical explorer Building on years of systematic ‘experimental’ discoveries, one step at a time.. As befits the diligent, he reached his goal in due time For the last leg, VdG was guided by an Indian pilot, arranged for by Ahmed ibn Majid in Malindi. Thomas Kostecki, Vasco da Gama (1998)

5 20 th Century Explorers Hans, the visionary adventurer Louis, the systematic explorer Bikash, the Indian pilot Lessons from the 15 th century: - there are different approaches to make a discovery -you don’t always find what you set out to discover - when venturing into the unknown, have the Indians ‘on board’ India: Strong and recognized partner in quest for QGP - > 60 physicists, > 8 Institutes - participation in SPS, RHIC and LHC programs - 5 th largest nation in ALICE - strong Theory community

Calcutta 2005 J. Schukraft 6 What are we looking for ? NA35 streamer chamber picture, ca 1990Da Gama arriving in India, th century explorers: direct trade route to the ‘Origin of Spices’ 20 th century explorers: understanding the ‘Origins of Matter’

7 QGP: The ‘Original’ State of Matter QGP = true ground state of QCD  melting matter => deconfinement study phase diagram of matter  melting vaccum (gluon condensate) =>chiral symmetry restoration dynamical origin of constituent mass Phase transitions involving elementary quantum fields  phase transitions and spontaneous symmetry breaking central to HEP  QCD transition is the only one accessible dynamically Cosmology & Astrophysics  early Universe at ~ 1  s  interior of neutron stars new domain of hot & dense QCD  surprises ?

8 Melting Matter

9 Elementary Particles0.1%  12 matter particles (quarks, leptons)  only 4 relevant today (u, d, e, )  13 force particles (3 massive, 10 massless) Composite Particles (hadrons)4%  hundreds…  only 2 are relevant (p,n), making nuclei What stuff is the Universe made of ?? We don’t know how and why for ~ 5% We don’t even know what for the other 95% Dark Matter23%  made of unknown particles Dark Energy73%  vacuum energy  of completely unknown origin  should be infinite or exactly 0 The Dark Mystery of Matter SM Higgs mechanism QCD chiral symmetry breaking

10 Recent Lattice QCD ‘Maps’ recent progress  improved actions  improved symmetries  larger lattices crit. temperature energy density EOS T c ~ 175 ± 8 ± 8 MeV  c ~ (6±2) T c 4 (  -3P)  0

11 t = - 3 fm/c t = 0 t = 1 fm/c t = 5 fm/c t = 10 fm/c t = 40 fm/c Heavy Ion Collision hard collisions pre-equilibrium QGP hadron gas freeze-out

12 ?

Calcutta 2005 J. Schukraft 13 Experimental Facilities AGS ( )  Beam: E lab < 15 GeV/N,  s ~ 4 GeV/N  Users: 400 Experiments: 4 big, several small SPS( )  Beam: E lab < 200 GeV/N,  s < 20 GeV/N  Users: 600Experiments: 6-7 big, several small RHIC(>2000)  Beam:  s < 200 GeV/N  Users: 1000  Experiments: 2 big, 2 small LHC(>2007)  Beam:  s < 5500 GeV/N  Users: 1000  Experiments: 1 dedicated HI, 3 pp expts X 5X 10X 30

Roadmap, 3 rd ICPA-QGP Jaipur, March 1997 large systems  thousand of particles  Volume > 4000 fm 3  energy density up to 3 GeV/fm 3 strongly interacting system  hadronic rescattering  collective phenomena (flow)  thermal particle ratios f(T,  ) signs of ‘new state of matter’  e + e - pairs (chiral symmetry rest. ?)  J/  suppression (deconfinement ?) Very complex reactions can be measured and analyzed

Calcutta 2005 J. Schukraft 15 Soft Probes: Elliptic Flow Flow: Correlation between coordinate and momentum space  close particles move at similar velocity and direction  flow builds up in an interacting medium with pressure gradients  for given boundary conditions, flow profile depends on  Equation of State EoS and viscosity  of ‘fluid’  Hydrodynamics of perfect fluid:  = 0,  = 0 (‘strongly interacting’)  p x >  p y Elliptic Flow reduces spatial anisotropy -> acts at early times

Calcutta 2005 J. Schukraft 16 First Flow Measurement at SPS WA93/98 PMD detectors measures azimuthal anisotropy of photons Presented by Indian group (Y. Viyogi) at QM’95 Particle emission is correlated ! Implications: Implications:  strongly interacting ‘matter’  collective expansion  ~1/2 ideal hydrodynamics Remember Columbus: -Elliptic Flow not expected at SPS -PMD meant to look for photon/hadron fluctuations (Centauro like events), discovered flow instead

Calcutta 2005 J. Schukraft 17 Photons: Thermal Radiation ? Thermal photons  ‘heat’ radiation from initial hot phase  ‘El Dorado’ of QGP physics  rate ~ T 4 => sensitive to early phase  rate ~ lifetime => contribution from hadronic phase  very challenging measurement  high p t : direct QCD hard scattering  medium p t :  0 decay photons  finally sighted at very low p t ??? Subtraction method, upper limit Correlation method: Subtraction method Predictions hadronic gas QGP sum pQCD Most probable yield (R o =6 fm) The lowest yield (R o =0) WA98 QM 2004 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)...’

Calcutta 2005 J. Schukraft 18 Hard Probes: J/Psi suppression c c c c c c beams of hard probes: jets, J/  …. normal matter QGP Onset of Deconfinement ? Ca 1986

Calcutta 2005 J. Schukraft 19 NA44 NA49/Ceres SPS Experiments NA49 NA50 Radial expansion, ‘Hubble Flow’ Deconfinement mass generation Thermal particle ratios f( ,T)’

Calcutta 2005 J. Schukraft 20 The Relativistic Heavy Ion Collider Current hunting ground for Quark Gluon Plasma

Calcutta 2005 J. Schukraft 21 RHIC Experiments STAR PHENIX PHOBOS BRAHMS small angle particles Particle Production parton energy loss Elliptic Flow

Calcutta 2005 J. Schukraft 22 Flow at RHIC pypy pxpx Momentum space matter at RHIC: ~ perfect fluid with ~ zero mean free path !  huge effect (almost 2:1 at high pt)  almost perfect agreement with hydro f(impact parameter, p t, particle mass) STAR PRL 86, (2001) 402 |  | < < p t < 2.0

Calcutta 2005 J. Schukraft 23 peripheral Hard Probes : Jet Quenching hadrons q q leading particle NOT suppressed leading particle NOT suppressed high pt partons:  Vacuum: fragment into hadrons => JETS  Matter: additional scattering => more gluon radiation  normal ‘cold’ matter: small effect  QGP: strong effect (up to several 10 GeV)  observables of ‘jet quenching’  leading parton looses energy  energy shows up in soft partons around jet axis beams of hard probes: jets, J/  …. Vacuum QGP central jet quenching measures ‘radiation ‘ length of QGP dE ~  D 2 x L 2  D = Debye screening mass

Calcutta 2005 J. Schukraft 24 India or America ? SPS/AGS: ‘new state of matter’  solid evidence for collective, thermal hadronic matter  new effects: quarkonia suppression & low mass lepton pair spectrum RHIC: dense (thermalized ?) partonic matter  elliptic flow compatible with hydrodynamical limit  Hydro = limit of zero mean-free-path => strongly interacting fluid,  gas !  almost ideal fluid,  /s ~ 0.1 (much better than water !)  jet quenching compatible with complete absorption from interior  strength of interaction seems mysteriously high

Calcutta 2005 J. Schukraft 25 RHIC QCD, early 21 st century QG-Plasma or QG-Molasses ? QGP: weakly interacting ‘gas’ of quarks and gluons  deconfined, chiral symmetry restored sQGP: strongly interacting partonic fluid Columbus: ‘Having now accomplished the undertaking upon which I set out,… I advanced forward, thinking that I could find some town - but at length, perceiving that nothing new was likely to appear - I determined to make no further search.’ The journey must go on ! QCD map, late 20 th century

Calcutta 2005 J. Schukraft 26 The Large Hadron Collider Future place for studying the Quark Gluon Plasma

Calcutta 2005 J. Schukraft 27 ALICE Set-up HMPID Muon Arm TRD PHOS PMD ITS TOF TPC Size: 16 x 26 m Weight: 10,000 tons

Calcutta 2005 J. Schukraft 28 ALICE Collaboration ~ 1000 Members (63% from CERN MS) ~30 Countries ~80 Institutes

Calcutta 2005 J. Schukraft 29 The ALICE Magnet: ready for the experiment to move in! The ALICE Magnet: ready for the experiment to move in!

Calcutta 2005 J. Schukraft 30 Inside the ALICE TPC

Calcutta 2005 J. Schukraft 31 India in Alice PMD prototype Manas electronics chip Muon Chamber

Calcutta 2005 J. Schukraft 32 RHIC Past-Present-Future AGS/SPS: 1986 – 1994 AGS/SPS: 1986 – 1994  existence & properties of hadronic phase  chemical & thermal freeze-out, collective flow,… SPS: 1994 – 2003 SPS: 1994 – 2003  ‘compelling evidence for new state of matter with many properties predicted for QGP’  J/  suppression (deconfinement ?)  low mass lepton pairs (chiral restoration ?) RHIC: ? RHIC: ?  compelling evidence -> establishing the (s)QGP ?  parton flow, parton energy loss LHC: ?? LHC: ??  ‘go west’ or find the ‘Island of India beyond the Ganges’  precision spectroscopy of ‘ideal plasma ‘QGP  heavy quarks (c,b), Jets, Y, thermal photons We are on an exciting and wondrous exploration, not taking any chances: We have the Indian pilot and his crew ‘on board’