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Overview of Relativistic Heavy-Ion Collisions at SIS Energies

Overview of Relativistic Heavy-Ion Collisions at SIS Energies. 고려대학교 홍 병 식. Schematic Understanding of the Relativistic HI Collisions. Pre- equilibrium. Thermalization. QGP?. Mixed phase. Hadronization (Freeze-out) + Expansion. Compression. Thermalization. V>0.9c.

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Overview of Relativistic Heavy-Ion Collisions at SIS Energies

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  1. Overview of Relativistic Heavy-Ion Collisions at SIS Energies 고려대학교 홍 병 식 서울대 핵물리세미나

  2. Schematic Understanding of the Relativistic HI Collisions Pre- equilibrium Thermalization QGP? Mixed phase Hadronization (Freeze-out) + Expansion Compression Thermalization V>0.9c Some of the energy they had before is transformed into heat and new particles right here ! Evolution 서울대 핵물리세미나

  3. T(MeV) Early Universe (RHIC) Quark-Gluon Plasma ~150 Phase Transition SIS explores Nonperturbative regime of QCD Color Superconductor Neutron Star Hadron Gas Atomic Nuclei ~10 Density(n0) Nuclear Phase Diagram 서울대 핵물리세미나

  4. HE Heavy-Ion Accelerators 서울대 핵물리세미나

  5. Heavy-Ion Collisions at SIS • Properties of hot and dense nuclear matter by studying • Nuclear Equation-of-State (EoS) • In-medium properties of hadrons • Test of QCD • Experimental Observables • Nuclear stopping phenomenon • Nonstrange meson production • Collective flow • Strangeness production • Comparison to various models 서울대 핵물리세미나

  6. HADES CBM KaoS FOPI Experiments at GSI 서울대 핵물리세미나

  7. Au+Au@1.5AGeV 1 K- in 104 events HI-Beam FOPI Setup -IPNE Bucharest, Romania -ITEP Moscow, Russia -CRIP/KFKI Budapest, Hungary -Kurchatov Institute Moscow, Russia -LPC Clermont-Ferrand, France -Korea University, Seoul, Korea -GSI Darmstadt, Germany -IReS Strasbourg, France -FZ Rossendorf, Germany -Univ. of Heidelberg, Germany -Univ. of Warsaw, Poland -RBI Zagreb, Croatia 서울대 핵물리세미나

  8. KaoS Setup 서울대 핵물리세미나

  9. Phase-space covered by the FOPI detectors p • dE/dxvs p/Z in drift chambers • Bethe-Bloch parameterization • Additional use of plastic to differentiate Z PID & Detector Acceptance Examples of FOPI Ru+Ru at 400A MeV 서울대 핵물리세미나

  10. Collision Centrality Peripheral Central • FOPI invented the Eratvariable which is extremely sensitive, especially, for the most central collisions. 서울대 핵물리세미나

  11. B. Hong et al., (FOPI) Phys. Rev. C66, 034901 (2002) Particle Spectra Ru+Ru at 400A MeV • Two independent detectors (CDC and HELITRON) give identical results. • Nice backward and forward symmetry • Dotted lines: fit functions by the Siemens-Rasmussen blast model • PRL 42, 880(1979) 서울대 핵물리세미나

  12. Particle Spectra 서울대 핵물리세미나

  13. Stopping Mean rapidity shift of protons defined by where yb(yt) is the beam(target) rapidity 서울대 핵물리세미나

  14. Stopping Introduce a new variable to test a nuclear transparency We use the heaviest isobaric nuclei available(9644Ru & 9640Zr) 서울대 핵물리세미나

  15. B. Hong et al., (FOPI) Phys. Rev. C66, 034901 (2002) Stopping 0.4A GeV Ru(Zr)+Ru(Zr) • Experimental data support the transparency scenario. • We need higher energy data to figure out which model is valid: • More stopping (CBUU model) • More transparency (IQMD model) 서울대 핵물리세미나

  16. B. Hong et al., (FOPI) Nucl. Phys. A 721, 317c(2003) Stopping 1.5A GeV Ru(Zr)+Ru(Zr) • Rp steeper • More transparency • Trend predicted by IQMD. • Absolute values of Rp are not described quantitatively. 서울대 핵물리세미나

  17. Stopping 0.4A GeV Ru(Zr)+Ru(Zr) Zr+Zr Ru+Ru 서울대 핵물리세미나

  18. Stopping 1.5A GeV Ru(Zr)+Ru(Zr) 서울대 핵물리세미나

  19. Comparison • Number of projectile nucleons in forward hemisphere • Number of projectile nucleons in backward hemisphere • Mixing parameter: more transparent for a larger Mpr 서울대 핵물리세미나

  20. transverse plane (at midrapidity) reaction plane time v1<0 v1 >0 sideward flow px = v1 pt v2<0 v2 >0 elliptic flow RN=(1+ v2)/(1-v2) Collective Flow Reaction plane Fourier expansion of azimuthal distribution gives the phase space distribution w.r.t. the reaction plane. S. Voloshin & Y. Zhang, Z. Phys. C70, 665 (1996) J.Y. Ollitrault, Nucl. Phys. A638, 195c (1998) 서울대 핵물리세미나

  21. Sideward Flow –integrated FOPI Collaboration, Phys. Rev. C67, 034907 (2003) • ptintegrated sideward flow is sensitive to • EoS • MDI (especially at projectile rapidity) • σNN (especially at low beam energies less than ~100A MeV) • SM(soft EoS with MDI) well describe data • Better agreement for larger collision system 서울대 핵물리세미나

  22. Sideward Flow –differential • Differential directed flow (DDF) for • Au+Au collisions at 400A MeV • DDF shows a clear sensitivity on the EoS. • IQMD deviates at large y and large pt for Z=1. • SM(soft EoS with MDI) well describe data. 서울대 핵물리세미나

  23. Sideward Flow -warning • IQMD fails to reproduce the measured integrated sideward flow for Z=2 particles at 90A MeV • Remember that IQMD also fails to reproduce the centrality dependence of the nuclear stopping for Ru+Ru at 400A MeV • previous slides 서울대 핵물리세미나

  24. Centrality dependence Eb dependence pt dependence A dependence Elliptic Flow -systematic study FOPI Collaboration, Nucl. Phys. A679, 765 (2001) 서울대 핵물리세미나

  25. Elliptic Flow –transition energy • Our data agree well with the Plastic Ball data. • Transition from in-plane to out-of-plane azimuthal enhancement near 100A MeV 서울대 핵물리세미나

  26. Elliptic Flow -comparison • Model cannot explain the experimental observation. 서울대 핵물리세미나

  27. Strangeness Production • Motivation (reminder) • Study • the in-medium effect due to the chiral symmetry restoration  • Equation-of-State • By using • the production yields • the momentum distribution 서울대 핵물리세미나

  28. Phase-space distribution Ni+Ni 1.93A GeV KaoS Collaboration, Phys. Lett. B 495, 26 (2000) Isotropic thermal source non-central central (b≤4.4 fm) Fit function : 2 서울대 핵물리세미나

  29. with without in-medium potentials RBUU calculation by E.Bratkovskaya, W.Cassing (Giessen) similar trends by G.Q.Li (Stony Brook) FOPI measures the target rapidity region: Eur. Phys. J. A9, 515 (2000) Nucl. Phys. A 625, 307 (1997) K-/K+ Ratio 서울대 핵물리세미나

  30. 40° < θlab < 48° Equivalent Energy Analysis KaoS Collaboration, Phys. Rev. Lett. 78, 4007 (1997) Ni+Ni at various beam energies • Use equivalent beam energies to correct for different production thresholds • 1.0 GeV/u for K+ • 1.8 GeV/u for K- • each corresponds to • K+ yield at 1.0 GeV/u is almost the same as K- yield at 1.0 GeV/u. 서울대 핵물리세미나

  31. Parameterizations by H. Müller, ZPA353, 103 (1995) Equivalent Energy Analysis KaoS Collaboration, Phys. Rev. Lett. 78, 4007 (1997) Considering the pp→K+/-+X cross section, there is about factor of 7 enhancement in K- production in medium. Indicates the importance of the multiple collisions for the strangeness production 서울대 핵물리세미나

  32. Determination of the EoS KaoS Collaboration, Phy. Rev. Lett. 86, 39 (2001) • Comp. between Au+Au & C+C • Purpose: disentangle soft EoS effect and in-medium effect • Baryon density (ρB) depends on the nuclear compressibility • Au+Au will reach much higher ρB • Subthreshold K+ production by multiple scattering means ~ρB2 at least → will increase the K+ yield in larger collision system → more important at lower beam energies • But UKN depends linearly or less than linearly on ρB → will reduce the K+ yield in larger collision system • MAuAu/MCC(K+) favors the soft Equation-of-State. 서울대 핵물리세미나

  33. Collective Flow of K+ (v1) Ni+Ni 1.93A GeV FOPI Collaboration, Z. Phys. A 352, 355 (1995) Striking results on the kaon sideflow from the FOPI triggered a lot of discussions. 서울대 핵물리세미나

  34. Collective Flow of K+ (v1) FOPI Collaboration, Phys. Lett. B486, 6 (2000) 1.7A GeV Ru + Ru • K+ sideflow can be used to study in-medium effect • Strong pt- dependence • Antiflow w.r.t. baryons at small pt • Flow in baryon direction at large pt • Magnitude of flow changes with collision centrality • Favors repulsive potential and increased kaon mass Rapidity interval: -1.2 < y(0) < -0.5 <bgeo>=3.8fm <bgeo>=2.3fm RBUU model calculations by E.Bratkovskaya & W.Cassing 서울대 핵물리세미나

  35. Collective Flow of K+ (v2) KaoS Collaboration, Phys. Rev. Lett. 81, 1576 (1998) Au+Au 1A GeV b≤5 fm due to the absorption 5<b≤10 fm b>10 fm due to the scattering 서울대 핵물리세미나

  36. with in-medium potential without in-medium potential Collective Flow of K+ (v2) • RBUU model • calculations by • G.Q. Li et al., • Phys. Lett. B 381, 17 (1996) 서울대 핵물리세미나

  37. F Production FOPI Collaboration, Nucl. Phys. A714, 89 (2002) • K+K- invariant mass spectra Ni+Ni at 1.93A GeV Φ-yield = K--yield at the same incident energy! Systematics: Φ/K- = 10 - 20 % Theoretical Expectations: ?? 서울대 핵물리세미나

  38. Long-Term Future Exploring nuclear matter at the highest-density B. Friman et al., Eur. Phys. J. A3, 165(1998) 서울대 핵물리세미나

  39. Unique maximum in AA QGP already at 30A GeV? When this enhancement of hyperons starts? Motivation-Strangeness 서울대 핵물리세미나

  40. Motivation-e+e- pair 서울대 핵물리세미나

  41. Motivation-Charm • SIS18: strangeness production near threshold (1-3 n0) • SIS200: charm production near threshold (5-10 n0) • In-medium effects 서울대 핵물리세미나

  42. Quark-meson Coupling model Sibirtsev, K. Tsushima, A.W. Thomas, EPJA6, 351 (1999) PYTHIA calculation for open charm meson production (dc) (dc) Simple Estimates of Open Charms 서울대 핵물리세미나

  43. More explicit channel, e.g., Simple Estimates B. Hong, JKPS43, 685 (2003) 서울대 핵물리세미나

  44. More Motivations • Indications for deconfinement at high baryon density • Anomalous charmonium suppression • Temperature of Hot Nuclear Matter • Virtual photons decaying into e+e- pairs • Equation-of-State • Flow measurement (direct, v2, radial, etc.) • Critical Point • Event-by-Event fluctuations • Color Superconductivity • Precursor effects at T > TC 서울대 핵물리세미나

  45. How? • Accelerator Side • Require high intensity for rare particle measurements: ~109 ions/sec (cf. ~107 ions/sec at the SPS) • High spill fraction: 0.8 (cf. 0.25 at the SPS) • Detector Side • Identification of hadrons at high momentum with high track density environment (~1000 for 25A GeV Au+Au) • Identification of electrons with pion suppression by 104 – 105 (need two electron detectors) • Reconstruction of particle vertices with high resolution • Large acceptance 서울대 핵물리세미나

  46. CBM Detector Concept 2nd Generation Fixed Target Exp. • Magnetic field: 1-2 T • Silicon Pixel/Strip: hyperons and D’s • RICH: electrons, high momentum pions & kaons • TRD: electrons from the J/Psi decay • TOF • Start: diamond pixel • Stop: RPC 서울대 핵물리세미나

  47. Conclusions • Stopping • New experimental approach exploiting N/Z shows incomplete mixing for the most central collisions. • Collective flow • Fourier analysis of azimuthal distributions reveals the detailed event shape over full phase-space. • Particle Production • Pion spectra provides an information of the Coulomb interaction and the modification of the delta-spectral function. • Kaon yields and spectra favor the in-medium modification of kaon masses (it also favors a soft EoS). 서울대 핵물리세미나

  48. Conclusions –continued- • Nuclear EoS is not understood yet. • But many promising experimental observables such as collective flow and strangeness production are available to constrain it. • Evidence for in-medium effects from strange particle observables. • It exists, but more accurate (high statistics) data are needed. • But difficult near threshold energy • Future • CBM experiments at the future GSI facility • We can start the CBM experiment in ten years (far future). • But it takes more than ten years to design and build it. 서울대 핵물리세미나

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