Overview of Relativistic Heavy-Ion Collisions at SIS Energies 고려대학교 홍 병 식 12-8-2002 서울대 핵물리세미나

Schematic Understanding of the Relativistic HI Collisions Evolution Pre- equilibrium Thermalization QGP? Mixed phase Hadronization (Freeze-out) + Expansion V>0.9c Compression Thermalization Some of the energy they had before is transformed into heat and new particles right here ! 12-8-2002 서울대 핵물리세미나

Nuclear Phase Diagram T(MeV) Density(n0) Early Universe (RHIC) ~150 ~10 Early Universe (RHIC) Color Superconductor Neutron Star Hadron Gas Quark-Gluon Plasma Phase Transition Atomic Nuclei SIS explores Nonperturbative regime of QCD 12-8-2002 서울대 핵물리세미나

HE Heavy-Ion Accelerators c.m. Energy (GeV) Status SIS 18 (GSI, Germany) 2A (A=mass number) Running AGS (BNL, USA) 5A Finished SIS 200 8A Just approved; Plan to run from ~2010 SPS (CERN, Switzerland) 20A Finish soon RHIC 200A Running since 2000 LHC 5500A Plan to run from ~2007 12-8-2002 서울대 핵물리세미나

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 12-8-2002 서울대 핵물리세미나

CBM Experiments at GSI HADES KaoS FOPI 12-8-2002 서울대 핵물리세미나

FOPI Setup Au+Au@1.5AGeV 1 K- in 104 events -IPNE Bucharest, Romania HI-Beam -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 12-8-2002 서울대 핵물리세미나

KaoS Setup 12-8-2002 서울대 핵물리세미나

PID & Detector Acceptance Examples of FOPI dE/dx vs p/Z in drift chambers Bethe-Bloch parameterization Additional use of plastic to differentiate Z Ru+Ru at 400A MeV Phase-space covered by the FOPI detectors p 12-8-2002 서울대 핵물리세미나

Collision Centrality Peripheral Central FOPI invented the Erat variable which is extremely sensitive, especially, for the most central collisions. 12-8-2002 서울대 핵물리세미나

Particle Spectra B. Hong et al., (FOPI) Phys. Rev. C66, 034901 (2002) 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) 12-8-2002 서울대 핵물리세미나

Particle Spectra 12-8-2002 서울대 핵물리세미나

Stopping Mean rapidity shift of protons defined by where yb(yt) is the beam(target) rapidity 12-8-2002 서울대 핵물리세미나

Stopping Introduce a new variable to test a nuclear transparency We use the heaviest isobaric nuclei available(9644Ru & 9640Zr) 12-8-2002 서울대 핵물리세미나

Stopping 0.4A GeV Ru(Zr)+Ru(Zr) B. Hong et al., (FOPI) Phys. Rev. C66, 034901 (2002) 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) 12-8-2002 서울대 핵물리세미나

Stopping Rp steeper Trend predicted by IQMD. B. Hong et al., (FOPI) Nucl. Phys. A 721, 317c (2003) 1.5A GeV Ru(Zr)+Ru(Zr) Rp steeper More transparency Trend predicted by IQMD. Absolute values of Rp are not described quantitatively. 12-8-2002 서울대 핵물리세미나

Stopping 0.4A GeV Ru(Zr)+Ru(Zr) Zr+Zr Ru+Ru 12-8-2002 서울대 핵물리세미나

Stopping 1.5A GeV Ru(Zr)+Ru(Zr) 12-8-2002 서울대 핵물리세미나

Comparison Eb(GeV) dyp/yb Nf 1) Nb 2) Mpr 3) Remark 0.256 9.46 6.14 0.21 1.5A 0.258 23.4 9.70 0.41 More Transparent Number of projectile nucleons in forward hemisphere Number of projectile nucleons in backward hemisphere Mixing parameter: more transparent for a larger Mpr 12-8-2002 서울대 핵물리세미나

Collective Flow Reaction plane time reaction plane transverse plane (at midrapidity) v2<0 v2 >0 elliptic flow RN=(1+ v2)/(1-v2) v1<0 v1 >0 sideward flow px = v1 pt 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) 12-8-2002 서울대 핵물리세미나

Sideward Flow –integrated FOPI Collaboration, Phys. Rev. C67, 034907 (2003) pt integrated 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 12-8-2002 서울대 핵물리세미나

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. 12-8-2002 서울대 핵물리세미나

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 12-8-2002 서울대 핵물리세미나

Elliptic Flow -systematic study FOPI Collaboration, Nucl. Phys. A679, 765 (2001) pt dependence Centrality dependence Eb dependence A dependence 12-8-2002 서울대 핵물리세미나

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 12-8-2002 서울대 핵물리세미나

Elliptic Flow -comparison Model cannot explain the experimental observation. 12-8-2002 서울대 핵물리세미나

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 12-8-2002 서울대 핵물리세미나

Phase-space distribution Ni+Ni 1.93A GeV KaoS Collaboration, Phys. Lett. B 495, 26 (2000) Isotropic thermal source central (b≤4.4 fm) non-central Fit function : 2 12-8-2002 서울대 핵물리세미나

K-/K+ Ratio FOPI measures the target rapidity region: Eur. Phys. J. A9, 515 (2000) Nucl. Phys. A 625, 307 (1997) with without in-medium potentials RBUU calculation by E.Bratkovskaya, W.Cassing (Giessen) similar trends by G.Q.Li (Stony Brook) 12-8-2002 서울대 핵물리세미나

Equivalent Energy Analysis KaoS Collaboration, Phys. Rev. Lett. 78, 4007 (1997) Ni+Ni at various beam energies 40° < θlab < 48° 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. 12-8-2002 서울대 핵물리세미나

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. Parameterizations by H. Müller, ZPA353, 103 (1995) Indicates the importance of the multiple collisions for the strangeness production 12-8-2002 서울대 핵물리세미나

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. 12-8-2002 서울대 핵물리세미나

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. 12-8-2002 서울대 핵물리세미나

Collective Flow of K+ (v1) FOPI Collaboration, Phys. Lett. B486, 6 (2000) 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 1.7A GeV Ru + Ru Rapidity interval: -1.2 < y(0) < -0.5 <bgeo>=3.8fm <bgeo>=2.3fm RBUU model calculations by E.Bratkovskaya & W.Cassing 12-8-2002 서울대 핵물리세미나

Collective Flow of K+ (v2) Au+Au 1A GeV KaoS Collaboration, Phys. Rev. Lett. 81, 1576 (1998) b≤5 fm due to the absorption 5<b≤10 fm b>10 fm due to the scattering 12-8-2002 서울대 핵물리세미나

Collective Flow of K+ (v2) RBUU model calculations by G.Q. Li et al., Phys. Lett. B 381, 17 (1996) with in-medium potential without in-medium potential 12-8-2002 서울대 핵물리세미나

F Production K+K- invariant mass spectra Ni+Ni at 1.93A GeV 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: ?? 12-8-2002 서울대 핵물리세미나

Long-Term Future Exploring nuclear matter at the highest-density B. Friman et al., Eur. Phys. J. A3, 165(1998) 12-8-2002 서울대 핵물리세미나

Motivation-Strangeness QGP already at 30A GeV? Unique maximum in AA When this enhancement of hyperons starts? 12-8-2002 서울대 핵물리세미나

Motivation-e+e- pair 12-8-2002 서울대 핵물리세미나

Motivation-Charm SIS18: strangeness production near threshold (1-3 n0) SIS200: charm production near threshold (5-10 n0) In-medium effects 12-8-2002 서울대 핵물리세미나

Simple Estimates of Open Charms Quark-meson Coupling model Sibirtsev, K. Tsushima, A.W. Thomas, EPJA6, 351 (1999) (dc) PYTHIA calculation for open charm meson production 12-8-2002 서울대 핵물리세미나

More explicit channel, e.g., Simple Estimates B. Hong, JKPS43, 685 (2003) More explicit channel, e.g., 12-8-2002 서울대 핵물리세미나

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 12-8-2002 서울대 핵물리세미나

How? Accelerator Side Detector 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 12-8-2002 서울대 핵물리세미나

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 CBM Detector Concept 12-8-2002 서울대 핵물리세미나

Conclusions Stopping Collective flow Particle Production 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). 12-8-2002 서울대 핵물리세미나

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. 12-8-2002 서울대 핵물리세미나