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Beam Energy Programs in HIC Part II: Present Christoph Blume University of Frankfurt.

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Presentation on theme: "Beam Energy Programs in HIC Part II: Present Christoph Blume University of Frankfurt."— Presentation transcript:

1 Beam Energy Programs in HIC Part II: Present Christoph Blume University of Frankfurt

2 Outline: Experiments Beam energy scan programs with heavy ions Part I: Past AGS: E895 (mainly) SPS: NA49 (NA45, NA57) Part II: Present RHIC: STAR, PHENIX SPS: NA61 Part III: Future NICA: MPD FAIR: CBM 1Christoph Blume, Dubna Aug. 2012

3 RHIC Beam Energy Scan (BES) Christoph Blume, Dubna Aug. 20122 Physics goals Search for indications of a (1 st order) phase boundary Softening of Equation of State (EOS) Search for the QCD critical point Year√s NN (GeV)Events(10 6 ) 201039130 20112770 201119.636 201011.512 20107.75 2012*5Test Run

4 RHIC-BES Observables Christoph Blume, Dubna Aug. 20123 Particle Yields Chemical freeze-out conditions Transverse momentum spectra Kinetic freeze-out conditions Flow Radial, direct, and elliptic flow Sensitive to EOS Partonic contribution to elliptic flow Fluctuations Sensitive to critical point High p t suppression Sensitive to color charge density STAR Preliminary

5 Relativistic Heavy Ion Collider Christoph Blume, Dubna Aug. 20124

6 The STAR Experiment 5Christoph Blume, Dubna Aug. 2012

7 The PHENIX Experiment Christoph Blume, Dubna Aug. 20126

8 Fixed Target Collider Christoph Blume, Dubna Aug. 20127 Fixed Target Measurement of projectile spectator energy possible Reaction volume better determined Centrality measured away from central fireball Easier to achieve high rates Dense solid target No extreme requirements on beam Acceptance depends on energy Can to limited extend be adjusted by scaling of magnetic fields But: easier to cover large rapidity ranges Collider Spectator energy cannot be measured Centrality is usually determined via multiplicities Autocorrelations need to be avoided High luminosities require additional efforts E.g. electron cooling Good beam quality and focusing needed Acceptance does not change with energy But: acceptance usually limited to mid-rapidity

9 Acceptance Christoph Blume, Dubna Aug. 20128 Rapidity p T (GeV/c) Au+Au 7.7 GeVAu+Au 200 GeV ππ p p NA49 PRC79, 044910 (2009) NA49 PRC79, 044910 (2009) STAR L. Kumar QM12 STAR L. Kumar QM12

10 Particle Ratio Fluctuations Christoph Blume, Dubna Aug. 20129 S/B fluctuation as QGP signal V. Koch, A. Majumder, and J. Randrup, PRL95, 182301 (2005) T < T c : S and B can be unrelated (Kaons: S = -1, B = 0) T > T c : S and B are correlated (s-Quark: S = -1, B = 1/3) Experimentally: K/p fluctuations Examples: K/π, p/π, K/p Dynamical fluctuations quantified relative to mixed events reference

11 Sensitivity to CP ? No evidence for non-monotonic behavior in energy dependence Comparison NA49 ↔ STAR Good agreement for p/π Deviations for K/π + K/p at lowest √s NN Likely due to different acceptances: Particle Ratio Fluctuations T. Tarnowsky, SQM11 J. Tian, SQM11 T. Schuster, QM11 T. Tarnowsky, SQM11 J. Tian, SQM11 T. Schuster, QM11 NA49, PRC83, 061902 (2011) NA49, PRC79, 044910 (2009) STAR, PRL103, 092301 (2009) K/π p/π K/p 10Christoph Blume, Dubna Aug. 2012

12 Acceptance Effect on K/p Fluct. Christoph Blume, Dubna Aug. 201211 A. Rustamov, QM12

13 Chemical Freeze-Out Christoph Blume, Dubna Aug. 201212 L. Kumar, QM11 Statistical model fits Freeze-out parameters: V, T, μ B, (γ S )

14 Kinetic Freeze-Out → p t -Spectra Christoph Blume, Dubna Aug. 201213 p t -Spectra Sensitive to radial flow → mass dependence Blast wave fits: T kin, 〈 β T 〉 L. Kumar, QM11 E. Schnedermann and U. Heinz, PRC50, 1675 (1994).

15 Kinetic Freeze-Out Parameter Christoph Blume, Dubna Aug. 201214 Blast wave fits: T kin, 〈 β T 〉 T kin 10 GeV Difference increases with increasing energy (drop of T kin ) → more time for cooling of system Continuous increase of 〈 β T 〉 Steep increase at low energies Moderate increase at higher energies L. Kumar, QM11

16 Trans. Energy per Charged Particle Christoph Blume, Dubna Aug. 201215 J. Mitchell, QM12 Energy dependence changes Steeper slope below √s NN 7-8 GeV Only moderate increase at higher energies observed Might indicate change of EOS Already seen in SPS-BES: aka “The Step”

17 Elliptic Flow B. Zajc, Scientific American 16Christoph Blume, Dubna Aug. 2012

18 Elliptic Flow Measurement Event plane method Fourier decomposition: Includes also non-flow effects ! Multi-particle correlations and cumulants Using higher order allows to get rid of non-flow component Lee Yang Zeroes Q-cumulants For high multiplicities (less combinatorics) 17Christoph Blume, Dubna Aug. 2012

19 Hydrodynamics P.F. Kolb and U. Heinz, nucl-th/0305084 Sensitive to early stages of system evolution → Pressure in partonic phase 18Christoph Blume, Dubna Aug. 2012

20 Elliptic Flow: Energy Dependence Pionen 19Christoph Blume, Dubna Aug. 2012 STAR Preliminary D. Cebra, QM12

21 Elliptic Flow: Energy Dependence Christoph Blume, Dubna Aug. 201220 Almost universal shape of v 2 vs p t Remarkable small variation with energy Integrated v 2 rises mainly since 〈 p t 〉 rises with energy S.S. Shi, QM12 STAR: arXiv:1206.5528

22 Number of Constituent Quarks NCQ Christoph Blume, Dubna Aug. 201221 Evidence for partonic collectivity (?) Picture: hadrons originate via quark coalescence BES: Search for an onset of NCQ scaling Au+Au √s NN = 200 GeV

23 Hadronization Mechanisms Christoph Blume, Dubna Aug. 201222 Fragmentation: Quark-Coalescence (recombination):

24 Energy Dependence of NCQ Scaling Christoph Blume, Dubna Aug. 201223 STAR Preliminary L. Kumar, QM12 ϕ -Meson: Low hadronic cross section Should be sensitive to partonic flow only Disappearance of partonic collectivity below √s NN = 19.6 GeV?

25 Baryons vs. Mesons Christoph Blume, Dubna Aug. 201224 STAR Preliminary Split between baryons and mesons Observed for particles and antiparticles for √s NN ≥ 19.6 GeV Not observed at lower energies for antiparticles (?) Needs more statistics... ParticlesAntiparticles S.S. Shi, QM12

26 Particles vs. Antiparticles Christoph Blume, Dubna Aug. 201225 STAR Preliminary S.S. Shi, QM12 Difference of v 2 observed Increases towards lower energies v 2 (K + ) > v 2 (K - ) for √s NN < 19.6 GeV v 2 (π + ) < v 2 (π - ) for √s NN < 19.6 GeV Possible explanations Baryon transport J. Dunlop et al., PRC84, 044912 (2011) Hadronic potential J. Xu et al., PRC85, 041901 (2012)

27 Directed Flow Christoph Blume, Dubna Aug. 201226 D. Rischke et al, HIP610, 88c (1996) D. Rischke et al, HIP610, 88c (1996) J. Brachmann et al., PRC61, 024909 (2000) J. Brachmann et al., PRC61, 024909 (2000) Sensitivity to EOS HG → QGP: rapid change of the number of degrees of freedom Directed flow: Collapse of proton v 1

28 Directed Flow Christoph Blume, Dubna Aug. 201227 STAR Preliminary v1v1 L. Kumar, QM12 Slope v 1 vs rapidity Always negative for pions Changes sign for (net-)protons

29 Critical Point Observables Critical opalescence Correlation lengths and susceptibilities diverge Heavy ion reactions System size limited ⇒ critical region Correlation length ξ ≈ radius of system Enhanced fluctuations Multiplicity Average p t Particle ratios Conserved quantities Strangeness S Baryon number B Charge Q Higher moments more sensitive M. Cheng et al., PRD79, 074505 (2009) M. Cheng et al., PRD79, 074505 (2009) μ B = 0 28Christoph Blume, Dubna Aug. 2012

30 Higher Moment of Net-Protons Christoph Blume, Dubna Aug. 201229 Baryon number fluctuations Conserved quantity Higher moments More sensitive to divergent correlation lengths (Skewness S, Kurtosis K ) Measure of non-Gaussian behavior Connected to susceptibilities Volume effects cancel Standard deviation: Skewness: Kurtosis:

31 Higher Moments of Net-Protons Christoph Blume, Dubna Aug. 201230 Comparison to Poisson Below for 5% most central for √s NN > 7.7 GeV Above for peripheral for √s NN < 19.6 GeV

32 High p t Suppression Christoph Blume, Dubna Aug. 201231 Partonic energy loss in medium Induced gluon radiation + elastic scattering Depletes high p t part of hadron spectra Nuclear modification factor: Jet tomography Important diagnostic tool at high energies (RHIC + LHC) Gluon densities dN g /dy (GLV) or transport coefficients q (BDMPS) Energy evolution? Onset at low energies observable? ˆ

33 High p t Suppression Christoph Blume, Dubna Aug. 201232 D. Antreasyan et al., PRD19, 764 (1979) P.B. Straub et al., PRL68, 452 (1992) Two competing effects Cronin enhancement Jet quenching Energy dependences: √s NN Cronin Jet quen.

34 High p t Suppression Christoph Blume, Dubna Aug. 201233 E. O’Brien, QM12 PHENIX preliminary arXiv:1204.1526 X. Dong, QM12 STAR preliminary Continuous evolution Suppression at high √s NN Enhancement at low √s NN

35 Outlook RHIC-BES Christoph Blume, Dubna Aug. 201234 Electron Cooling Luminosity increase by a factor ~10 √s NN (GeV)μ B (MeV) Requested Events(10 6 ) Au+Au 19.6206150 Au+Au 15256150 Au+Au 11.531650 Au+Au 7.742070 U+U: ~20~200100 Future plans (BES-II) 2015 – 2017

36 Outlook: Fixed Target with STAR Christoph Blume, Dubna Aug. 201235 1% Au Target Running concurrently with collider operation Reach to lower energies higher μ B (~ 800 MeV)

37 The NA61 / SHINE Experiment Christoph Blume, Dubna Aug. 201236 Upgrade of the NA49 setup New TPC readout and DAQ ⇒ factor 10 higher event rate (80 Hz) Forward TOF wall ⇒ extended PID acceptance Projectile Spectator Detector (PSD) Secondary ion beam line (fragment separator)

38 NA61 Detector Upgrades Christoph Blume, Dubna Aug. 201237 Participant Spectator Detector (PSD) Same development as for CBM at FAIR High resolution: 55%/√E + 2% He beam pipe Reduces background from δ-electrons Important for fluctuation measurements

39 Secondary Ion Beam Christoph Blume, Dubna Aug. 201238 Degrader (Cu plate) for high beam purity

40 PID techniques dE/dx in TPC TOF information Wide momentum range covered Particle Identification Christoph Blume, Dubna Aug. 201239

41 NA61 Experimental Program Christoph Blume, Dubna Aug. 201240 Search for the QCD critical point 2D scan: Energy + system size Already done: p+p energy scan p+C Be+Be (three energies)

42 First Results: p+p Energy Scan Christoph Blume, Dubna Aug. 201241 A. Rustamov, QM12

43 First Results: p+C at 31 GeV/c Christoph Blume, Dubna Aug. 201242 Comparison to FLUKA2008 Phys. Rev. C84, 034604 (2011)

44 First Results: p+C at 31GeV/c Christoph Blume, Dubna Aug. 201243 Phys. Rev. C85, 035210 (2012) K+K+ Identified particles

45 Summary Part II Christoph Blume, Dubna Aug. 201244 Ongoing BES programs at RHIC and SPS RHIC-BES covers energies of previous SPS BES in collider setup 2D approach of NA61 at the SPS: energy + system size Main observations (so far) Comprehensive study of flow phenomena Almost universal shape of v 2 vs p t Indications for an onset of partonic collectivity (φ meson) ? Different energy evolution of elliptic flow of particles and antiparticles Complex energy dependence of directed flow of net-protons (→ EOS) Indications for a non-Poissonian behavior of net-proton fluctuations (→ CP ?) Smooth evolutions of nuclear modification factors at high p t (suppression → Cronin enhancement) First data from recent SPS program (pp energy scan, Be+Be out soon)

46 Christoph Blume, Dubna Aug. 201245

47 Christoph Blume, Dubna Aug. 201246 X. Zhu, SQM11

48 Christoph Blume, Dubna Aug. 201247


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