Axel Drees, Stony Brook University, Lectures at Trento June 16-20, 2008 Electromagnetic Radiation form High Energy Heavy Ion Collisions I.Lecture:Study high T and  QCD in the Laboratory II.Lecture: Quark matter formation at RHIC III.Lecture:EM radiation and pioneering experiments at SPS IV.Lecture: An new era: precision measurements with NA60 V.Lecture: PHENIX at RHIC: the challenge of high energies VI.Lecture:Medium modifications of open charm production VII.Lecture:Modified meson properties: insights with low energies VIII.Lecture:The quest to detect for thermal radiation IX.Lecture: Outlook into the future (mostly RHIC) Tu We Th Fr

Axel Drees GravityGeneral Relativity Electro-weakQuantum Field Theory Strong interaction (QCD) Fundamental Forces in Nature Standard model Although we have fundamental theories for all forces we need ~20 parameters, constants of unknown origin to describe nature. Two outstanding puzzles: unseen quarks  confinement broken symmetries  existence of massive particles Both connected to complex structure of vacuum

Axel Drees Vacuum low resolution

Axel Drees Vacuum high resolution Vacuum is see of  qq pairs (+ gg pairs +..) Vacuum expectation value for u or d quarks ~ - (230 MeV) 3 Vacuum density of u and d pairs ~ 3 fm -3

Axel Drees l Quarks and gluons carry color the charge of QCD l In nature only color neutral objects exist l Bag model: Confinement qqqbaryons  qqmesons 0.8 fm Pressure of vacuum (B) compensated by internal pressure bag constant B 1/4 ~ 200 MeV

Axel Drees String Models  r String with tension  ~ 1 GeV/fm QCD potential: Need infinite energy to separate quarks  confinement V QCD r r < r bag r > r bag  r  1/r (relation to ??) 1 fm 1S 2S 3S 4S  bb 1S 1P 2S  cc charmonuim and bottonium states explore QCD potential

Axel Drees Chiral Symmetry l Chirality (handedness) or helicity for massless particles chirality is conserved l QCD with 3 massless quarks (flavors) symmetry q R does not couple to q L l Masses break symmetry if mass  0 q R couples to q L spin momentum spsp spsp left handed right handed left-handed right-handed

Axel Drees Masses of Quarks l spontaneous breaking of electro-weak interaction  current mass of quark for u & d quarksm o u ~ m o d ~ 5 MeV s quark m o s ~ 175 MeV explicitly breaking of chiral symmetry l spontaneous breaking of chiral symmetry  constituent mass of quarks for u & d quarksm u ~ m d ~ 300 MeV (~1/3 m proton ) s quark m o s ~ 500 MeV spontaneous breaking of chiral symmetry  qq q q coupling G q couples to  qq see

Axel Drees Symmetry Breaking l Spontaneously l Explicit external force V V ground state potential symmetric ground state symmetric potential symmetric symmetry broken for ground state massless Goldstone bosons here       (2 flavors) massive       V potential asymmetric Mass small ~ 140 MeV

Axel Drees 1) all hadrons have well defined parity chiral symmetry  q R q R =  q L q L  expect J  doublets 2)characteristic mass scale of hadrons 1 GeV mass gap to quark condensate except pseudoscaler mesons Goldstone bosons:  and  Consequences of Spontaneous Symmetry Breaking 11 1 + a 1 (1270 MeV) 1 -  (770 MeV)

Axel Drees l current quark mass l generated by spontaneous symmetry breaking (Higgs mass) l contributes ~5% to the visible (our) mass Origin of Mass l constituent quark mass l ~95% generated by spontaneous chiral symmetry breaking (QCD mass)

Axel Drees Fundamental Puzzles of Hadrons l Confinement l Quarks do not exist as free particles l Large hadron masses l Free quark mass ~ 5-7 MeV l Quarks become “fat” in hadrons constituent mass ~ 330 MeV l Complex structure of hadrons l Sea quarks and anti quarks l Gluons l “spin crisis” Spin of protons not carried by quarks! These phenomena must have occurred with formation of hadrons nuclear matter p, n

Axel Drees ~ 10  s after Big Bang Hadron Synthesis strong force binds quarks and gluons in massive objects: protons, neutrons mass ~ 1 GeV/c 2 ~ 100 s after Big Bang Nucleon Synthesis strong force binds protons and neutrons bind in nuclei

Axel Drees ~ 10  s after Big Bang T ~ 200 MeV Hadron Synthesis strong force binds quarks and gluons in massive objects: protons, neutrons mass ~ 1 GeV/c 2 ~ 100 ps after Big BangT ~ GeV Electroweak Transition explicit breaking of chiral symmetry inflation Planck scale T ~ GeV End of Grand Unification

Axel Drees “Travel” Back in Time l QGP in Astrophysics early universe after ~ 10  s l possibly in neutron stars l Quest of heavy ion collisions l create QGP as transient state in heavy ion collisions l verify existence of QGP l Study properties of QGP l study QCD confinement and how hadrons get their masses neutron stars Quark Matter Hadron Resonance Gas Nuclear Matter SIS AGS SPS RHIC & LHC early universe BB T T C ~170 MeV 940 MeV MeV baryon chemical potential temperature

Axel Drees Estimating the Critical Energy Density normal nuclear matter  0 critical density: naïve estimation nucleons overlap R ~ r n nuclear matter p, n Quark-Gluon Plasma q, g density or temperature distance of two nucleons: 2 r 0 ~ 2.3 fm size of nucleon r n ~ 0.8 fm

Axel Drees Critical Temperature and Degrees of Freedom l In thermal equilibrium relation of pressure P and temperature T l Assume deconfinement at mechanical equilibrium l Internal pressure equal to vacuum pressure B = (200 MeV) 4 l Energy density in QGP at critical temperature T c Noninteracting system of 8 gluons with 2 polarizations and 2 flavor’s of quarks (m=0, s=1/2) with 3 colors

Axel Drees Critical energy  C = 6  2 T C 4 critical temperature T C QCD calculations l perturbative QCD calculations applicable only for large momentum transfer  small coupling l for small momentum transfer  large coupling only solution numerical QCD calculations on lattice results from lattice QCD establish the QCD phase transition T C ~ MeV  C ~ GeV/fm 3  jump in energy density:

Axel Drees The QCD phase transition Change of order parameter: deconfinement: Polyakov loop L ~ e -F q chiral symmetry: Quark condensate  qq  chiral restoration and deconfinement at same critical temperature T C ~ 170 MeV temperature deconfinement chiral symmetry restoration Polyakov loop response function chiral susceptibility different quark mass m q 165 MeV 175 MeV

Axel Drees QCD Potential from Lattice Calculations As temperature increases towards T C the QCD potential vanishes at large distances

Axel Drees Restoration of Chiral Symmetry l Temperature axis: l sharp transition at T C (similar to lattice QCD results) l baryon density axis: l smooth transition l at nuclear matter density In hot and dense matter chiral symmetry is restored model calculation (Nambu, Jona-Lasinio) approaching of chiral symmetry restoration should strongly modify hadron properties like  and m

Axel Drees String Theory (AdS/CFT Correspondence) l Standard model describes all phenomena in nature, but is a disjoint framework l Forces: Gravity  general relativity (classical) Electromagnetic, Weak, and Strong  gauge theory (quantum) l Matter: 6 quarks, 6 leptons, plus Higgs l In string theory strings are basis of all forces l Open strings: gauge theory l Closed strings: gravity A new approach to calculate properties of the QGP m (Next slides based on talk by Makoto Natsuume at RHIC/AGS Users Meeting 2008)

Axel Drees Duality of Theories that Look Different l Tool in string theory for 10 years l Strong coupling in one theory corresponds to weak coupling in other theory l AdS/CFT duality (Anti deSitter Space/ Conformal field theory) (N=4 SYM) (in QCD)

Axel Drees Relevance for Heavy Ion Collisions l New matter formed at RHIC resembles fluid l QGP near phase boundary seems a strongly coupled plasma l Lower bound on Viscosity/Entropy from AdF/CFT duality

Axel Drees Exploring the Phase Diagram of QCD l Quark Matter: Many new phases of matter l Asymptotically free quarks & gluons l Strongly coupled plasma l Superconductors, CFL …. Experimental access to “high” T and moderate  region: heavy ion collisions l Pioneered at SPS and AGS l Ongoing program at RHIC Quark Matter Hadron Resonance Gas Nuclear Matter sQGP BB T T C ~170 MeV 940 MeV MeV baryon chemical potential temperature Mostly uncharted territory Overwhelming evidence: Strongly coupled quark matter produced at RHIC Study high T and  QCD in the Laboratory