1. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Nuclear Matter Course I Properties of strongly interacting systems Course II Creating and investigating nuclear matter under extreme conditions Joachim Stroth, GSI/Univ. Frankfurt

2. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Discovery of the Micro-Cosmos It all started with the observation of Radioactivity. In the late 19th Century Henri Becquerelle discovered Ionising Radiation emerging from Uranium. We now know that   and  -Rays stem from transitions in the nucleus. This event can be viewed as the birth of Nuclear Physics. Further Discoveries: –In Cathode Rays: Electron (Thompson) –In Cosmic Rays: Positron, Myon (Anderson), Pion (Powell) –With Accelerators: Anti-Proton, and and and Decay patterns for the dacay of pions of the type  +   + +  e + + 3

3. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Atomic Nucleus Ernest Rutherford, the real father of nuclear physics found something very heavy and tiny in the interior of atomic nuclei. The observed angular distribution of  -particles was in agreement with the assumption of pure electromagnetic scattering off an object with –M >> M  –R < 3  10 –14 m The probability for an interaction can be calculated for thin targets:

4. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Electron Beam as Particle Microscope Scattering of electrons off point- like objects is..... excellently described by: Exchange of Photons Exchange of Photons ee ee  ee ee  E,p E´,p´ Z

5. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Charge Distribution of Nuclei Experiments on elastic scattering of Electrons at Energies of < 1 GeV (  0.2fm) Nobel Price in Physics 1961 Hofstaedter ee ee  Z Charge Distribution Fourier-Transform of the Form Factor yields the Charge Distribution Pb Ca 0 2 4 6 8 10 R [fm] 0.02 0.08  [fm -3 ]  [Grad] d  / d  [rel. Einh.] 20 30 40 50 60 10 0 10 -2 10 -4 10 -6 10 -8 10 -10 48 Ca 40 Ca

6. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Digging deeper with Deep-Inelastic Scattering

7. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Form Factor of Protons

8. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Struktur des Nukleons Experiments with Electron Beams at the SLAC up to 20 GeV (  0.1fm) Essential Observations: –Nucleons do have diffuse surfaces –Nucleons can be transformed into excited states –Nucleons are composite particles which contain point-like constituents Nobel Price 1990 Kenndall, Friedmann, Taylor

9. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Constituents of the Atomic Nucleus  0 = 0 Protons Neutrons up- and down-Quarksup- and down-Quarks Gluons and virtual Quarks and Anti-Quarks R  1fm; m  1GeV Nucleus (R  1-10 fm) R < 10 -4 fm; m  10 MeV Strong Interaction: QCD 99.9% of the Matter around us consits out of Nucleons

10. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Nucleon is a Complex Object Hadrons are very complex excitations of valence quarks in the present of quark and gluon condensates.

11. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Particle Zoo According to current understanding point-like particles

12. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Particle Zoo II Bosons carry the interaction.

13. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Nature of the Strong Force Along the successful description of electro-weak interaction by gauge theory, the strong interaction can be described by the exchange of gluons. PropertyQEDQCD Chargeelectriccolour Bosonsphoton (carries no charge) gluons (carry charge) Mass of boson00 Screeningreduces bare charge amplifies bare charge Strength   s = 25 

14. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt QCD: Confinement If the distance between two quarks gets larger, more and more gluons contribute to the interaction between the quarks. Hence the potential energy grows with increasing distance. At some point, enough energy is stored in the field to produce a pair of quarks out of the vacuum.

15. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Origin of Matter Criteria of Sacharov for the cre- ation of matter out of radiation: C and CP Violation The decay rate of quarks and anti-quarks are different Violation of Baryon Number Conservation Leptons decay in quarks and vice versa No thermal equillibrium  B =0 if baryon number is not onserved 10 -43 s 10 -10 s 10 -34 s GUT QGP Hadronisation t x Matter was produced about 1  s second after the Big Bang Since particles are always produced in pairs, why is there only matter and no anti-matter left

16. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Production of Heavy Nuclei In the Bing Bang only the light- est nuclei could be formed ! Production of heavier nuclei: –Thermonuclear burning in stars up to Iron ! –Supernova Explosions: Neutron absorbtion with subsequent beta-decay ! r-process Neutron Drip Line s-process 110 1E-90 1E-80 1E-70 1E-60 1E-50 1E-40 1E-30 1E-20 1E-10 1 HAGEDORN Production in Secondary Reaction Relative Yield Atomic Mass Number

17. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Nuclear Matter has Exotic Properties Let‘s quote some macroscopic properties of Nuclear Matter 280 Million Tons per cm 3 Nuclear matter is extremely heavy 280 Million Tons per cm 3 –Less than a mm 3 is enough to built an aircraft carrier. –However, if one would burn it completely, the energy gain would be equivalent to 50 GW for a whole year. Although we know Nuclear Matter only in small portions inside atoms, it exists in nature also in big portions: –Neutron Stars have a diameter of typically 10 km.

18. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Equation of State Around normal nuclear ground- state density the compressibility can be determined from Giant Monopole Resonances. At higher densities the proper- ties can only be extracted from experiment on the basis of theoretical models. Conditions:  E/A(   ) = -16 MeV  (E/A)(   )/   Compressibility     (E/A)/     200 - 400 MeV Compressional Energy E/A Density hard EoS  = 380 MeV soft EoS  = 200 MeV

19. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Effective Interactions between Nucleons Hideki Yukawa described in 1934 the force between nucleons as an exchange of virtual particles. If the exchanged particles carry mass, the range of the interaction is finite: MesonMass [MeV] Type I[J P ]  1401[0 - ]  400-12000[0 + ]  7701[1 - ]

20. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Nuclei can be described assuming nucleons moving independently in a mean nuclear potential: –Phenomenological Square-well, Harmonic, Woods-Saxon –Self-consistent Hartree-Fock The Formation of Nuclei Nuclei form because of the strong effective interaction between nucleons. Although this „residual“ interaction is weaker than the bare strong force between quarks and gluons, it still overcomes Coulomb repulsion of protons by far.

21. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Nucleus as a Liquid Drop The nucleus in the ground state is cold Fermi liquid. At moderate excitation energies (E/nucleon << E B ) nuclei behave like little droplets of water. The Coulomb Barrier: Potential energy of two touching spheres (if r=R 0 )

22. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Heating Nuclear Matter Nuclei store additional energy by transfering nucleons into levels between the Fermi-surface and the barrier: –Single Particle excitations –Collective Excitations It can thermalize by forming a Compound Nucleus And cool down by –(Fragmentation) –Particle Decay ( ,p,n) –Electromagnetic transitions (  ) At E/A of 5 MeV the nuclei transform to a gas of nucleons.

23. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Hadronic Matter Nucleons are composite particles and can therefore transform into excited states. Is the temperature of nuclear matter high enough, internal degrees of the nucleons are excited. e.g.: N + N = N +   = N + N +  These excited states are often called resonances, since their decay width is rather large (due to the strong interaction).  k,    p,n N (1440) N (1520) M [GeV] 0 1 a1a1 Mesonen Baryonen

24. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Melting of Resonances Exiting nucleons by inelastic electron scattering –on liquid hydrogen (protons): Resonances are clearly visible (most prominent the  33 ) –on nuclei: no higher-lying resonances seem to survive

25. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt QCD: Spontaneous Breaking of Chiral Symmtery The groundstate of QCD is characterized by a non- vanishing field of quark – anti- quark pairs, the so-called chiral condensate. This is a non-perturbative effect of QCD

26. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt  k,    p,n N (1440) N (1520) M [GeV] 0 1 a1a1 Vakuum  0 Mesonen Baryonen  k,    p,n N (1440) N (1520) M [GeV] 0 1 a1a1 Vakuum > 0 Mesonen Spontaneously Broken Chiral Symmetry How can almost massless quarks combine to hadron with a mass of typicall 1 GeV and more? The ground state of QCD is spotaneously broken – the vaccum is filled by a condensate of scalar quark – anti-quark pairs! Light mesons (M<<1 GeV) , , K No parity doubletts M(  )  M(a 1 ) The bare quarks gain dynamically mass by coupling to the quark – ant-quark pairs.  k,    p,n N (1440) N (1520) M [GeV] 0 1 a1a1 Vakuum  0 Mesonen Baryonen

27. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Probing the Chiral Condensate Expectation value of the chiral condensate in a simplified model, as a function of baryon density and temperature of nuclear matter. Already in ordinary nuclei the condensate is reduce as compared to vacuum.

28. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Medium Modifications of Hadrons Spectral function of the  -meson in medium

29. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Quark-Gluon Phase of Nuclear Matter At very high energies and/or densities quarks are deconfined

30. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Characteristic Energy Regimes Heavy Ion Accellerators around the world Coulomb Barrier Fermi-Energy Regime Resonance Matter Quark-Gluon Matter E/nucl. [GeV] 0,01 0,1 10 100 10000 Tandems, Linacs CyclotronsSynchrotrons (recently also colliders) Many Univ. and Instituts GANIL, MSU, RIKEN GSI(SIS), LBL(Bevalac), BNL(AGS) CERN(SPS)BNL(RHIC), CERN(LHC) in 2006

31. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Dissipative Collisions In a kinematically complete experiment the following obsevables are derived: –TCM scattering angle –TKELTotal Kinetc Energy Loss –M R,E Mass of Recoil Ion and Ejectile The data show evidence for a smooth transfer of collective energy of motion into internal degrees od freedom

32. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Multi-Fragmentation The ALADIN Experiment! Projectile Fragmentation in inverse Kinematics –Forward focusing (4  detection) –No detector Thresholds

33. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Liquid-Gas Phase Transition Results of the ALADIN collaboration show evidence for transition from a liquid to a vapour phase of nuclear matter.

34. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Creating Nuclear Fireballs At energies above a few 100 MeV/u the non-overlapping parts of the nuclei are abraised and continue on straight trajectories. Nucleons in these „pole caps“ are called spectators. The nucleons in the overlapp zone form the fireball and are called participants. A correlation plot of the two helps to select impact parameter, which is no direct observable: –Z SUM (Small Angle Hodoscope) Sum of all Charge –M(Large Angle Hodoscope) Multiplicity

35. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Cross Properties of Expanding Fireballs A nuclear fire ball is a hot, rapidly expanding gas of hadrons. Below some critical density, all collisions between the particle stop and the system freezes out. In the spectrometer all particles are identified by their mass and charge. From the spectral shape it can be inferred, that the energy of the particles is composed of a thermal and collective part Kinetic Energy of a Particle: E k = E th + E flow = 3/2 kT + m/2  flow  2

36. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt A Typical 4  Experiment Particle IDentification: –Momentum from the bending in a magnetic field –Charge by Ionization Power –Mass from time-of-flight (combined with momen- tum measurement)

37. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Particle Spectra The emission pattern of part- icles show a rich structure if correlated with the reaction plane.

38. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Creation of New Particles (Resonance Matter) Short-lived particles (resonances) can be detected via particle correlations. Observable  Invariant Mass e.g.: N+N  N+    N+N+  ResonanceMass [MeV] I(J P ) P 11 1440½(½+)½(½+) D 13 1520½(1½ - ) S 11 1535½(½-)½(½-) P 33 (  33 )12321½(1½ + )

39. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Pions are Complicated The pion is the lightest hadron. Its existence in nuclear matter is tightly linked to the excitation of the  33 resonance. Data described by „two temperatures“ fit   hole

40. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Strangeness Production The KAOS Spectrometer features a compact dipole combined with a large quadrupole to enlarge acceptance. Various focal-plane detectors allow a dedicated kaon trigger. At 1 AGeV the energy in a single nucleon nucleon is not sufficient to produce kaons. In contrast to pion production is the kaaon production rising as the number of participating nucleons increases.  Clear evidence for multi-step production mechanism  N  K + ,  N  K +  N

41. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Medium Modification of Kaons In medium kaons/anti-kaons experience a density dependent potential which lowers/increases their effective mass. Hence the production of anti-kaons close to the production threshold is enhanced.

42. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt A Thermal Model for the Fireball The Thermal Model assumes that all particles stem from a thermalized fireball, where all inelastic collisions stop at the same temperature. By adjusting only two parameters, the baryon chemical potential and the temperature, relative particle yields can be explained.

43. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Central Collision of two Gold Nuclei About 95% of the velocity of light Simulation: Univ. Frankfurt, Institut für Theoretische Physik

44. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt p n  ++  K  = 2-3  0 T < 100 MeV e.g. Au+Au @ 1 GeV/u Probing the Interior of Fire Balls   p e+e+ e-e- 

45. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The HADES-Spectrometer Geometry  in   Online Pattern Recognition RICH (Ring Imaging Cherenkov Detectors) TOF (Organic Scintillators) SHOWER (Lead-Shower Detector)Tracking ILSE (Super Conducting Magnet) MDC (Multiwire Drift Chambers)

46. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Low-mass Dilepton Pairs Sensitive to changes of in-medium properties of vector mesons (restoration of chiral symmetry) Experimental findings: –Strong enhancement of lepton pairs below the vector meson region –Enhancement already at Bevalac energies

47. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Ultra Relativistic Collisions

48. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Multistrange Hyperons Strangeness enhancement in the QGP should influence in particular the production of multi-strange baryons (hyperons).  : AA/pp = 17/1  Strong enhancement of  over  over  found (  : AA/pp = 17/1) WA97 F. Antinori et al, Nucl. Phys. A 661 (1999) 130c

49. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Suppression of Charmonium Anomalous suppression if screening in a deconfined phase occurs. –Effect establishes as a function of centrality NA50

50. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Composition of a Neutron Star Each arrow indicates a different model for the neutron star Each model represents an other EOS

51. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt The Phase Diagram of Nuclear Matter …... yet another version

52. Nuclear Matter Joachim Stroth, GSI/Univ. Frankfurt Experimental Concept Detector components: 1. magnet (1-2T) 2. Silicon pixel/strip detectors: , , ,  3. RICH: particles with  = 10-100: electrons, (pions, kaons) 4. TRD: electrons (   2000): J/  5. TOF-start (diamond pixel detector) and TOF-stop (RPC): particle identification ( pions, kaons, protons, …) 1.-5. needed for D mesonsTrigger: 1. level: reactions, centrality, hits in TRD and RICH 2. level: electrons, momentum, hit matching, rings in RICH 3. level: displaced vertex