Berndt Müller. H-QM Opening Symposium GSI, November 9, 2006

Transcription

1 Berndt Müller H-QM Opening Symposium GSI, November 9,

2 Nucleons + mesons Genre: Comedy / Crime / Romance / Thriller Eating Takoyaki (squid balls) fresh from the grill in Osaka/Japan Quarkgluon plasma Melting nuclear matter (at RHIC / LHC / FAIR) 2

3 What heat does to matter: Increases disorder (entropy) Speeds up reactions Overcomes potential barriers States / phases of matter: Solid [long-range correlations, shear elasticity] Liquid [short-range correlations] Gas [few correlations] Plasma [charged constituents] (solid / liquid / gaseous) 3

4 Matter governed by the laws of QCD can also take on different states: Solid, e.g. crust of neutron stars Liquid, e.g. all large nuclei Gas, e.g. nucleonic or hadronic gas (T 7 MeV) Plasma - the QGP (T > T c MeV) The QGP itself may exist in different phases: Gaseous plasma (T Tc) Liquid plasma (T, near T c, c?) Solid, color superconducting plasma ( c ) 4

5 RHIC T Quark- Gluon Critical end point Plasma Hadronic matter Chiral symmetry broken 1 st order line Chiral symmetry restored Color superconductor Nuclei Neutron stars B 5

6 gluons quarks 7 2 Degrees of fr eedom : (2 8) 4 (2 3 Nf ) 1 O( g ) spin color spin color flavor MeV 30 RHIC LHC? Indication of weak coupling? Lattice QCD (Bielefeld) 6

7 2 g ( ) g ( ) a a b a b G Q Induced color density a 2 a N wit h ( gt ), ( gt ) F 2 G Q a Static color charge (heavy quark) generates screened potential t a a s r r e 7

8 B 8

9 Color correlation length M. Strickland, hep-ph/ Time Quasiabelian Nonabelian Noise Length (z) 9

10 QCD mass Higgs mass u d s c b t quark quark Higgs field Quark qq qq condensate QCD mass disappears above T c : (partial) chiral symmetry restoration 10

11 XY X 2 Y ln Z( T, ) XY X Y i XS i x s n i i i C XS 3 XS X S S 2 S 2 R. Gavai & S. Gupta, hep-lat/ pqgp 11

12 Arrow of time quarks gain QCD mass and become confined 12

13 is hexagonal and 3.8 km long Relativistic Heavy Ion Collider STAR 13

14 Detectors Computers BG-J Phenomenology pr ovides t he connect ion 14

15 Pre-equil. phase Liberation of saturated low-x glue fields (CGC) eq Bjorken formula dn( )/ dy s( ) dv( )/ dy 0 ( dn / dy) eq R 2 final s( 1 fm/c) 33/fm or T ( ) 275 MeV in Au+Au (200 GeV) 15 3

16 Some important results from RHIC: Chemical equilibration (incl. s-quarks!) u, d, s-quarks become light and unconfined Elliptic flow rapid thermalization, low viscosity Collective flow pattern related to valence quarks Jet quenching parton energy loss, high color opacity Strong energy loss of c and b quarks (why?) Charmonium suppression is not increased compared with lower (CERN-SPS) energies 16

17 Y1 ( m1 m2 ) exp Y T 2 ch Increase in flavor correlation length r c 1 fm (?) + gluon thermalization 17

18 No suppression for photons Suppression of hadrons R AA ( p ) T Yield in A+A 2 d NAA / T 2 AA NN / T dp dy T d dp dy Area density of p+p coll s in A+A Cross section in p+p coll s Without nuclear effects: R AA = 1. 18

19 q q Radiative energy loss: 2 2 E L k T q L q Scattering centers = color charges g Density of scattering centers d dq i ˆ q dq k 2 T dx Fi ( x ) F (0) q Scattering power of the QCD medium: Range of color force 19

20 Eskola et al. RHIC RHIC data sqgp?? QGP Baier plot Pion gas Cold nuclear matter 20

21 Where does the lost energy go? p+p Au+Au Away-side jet Trigger jet Lost energy of away-side jet is redistributed to angles away from 180 and low transverse momenta p T < 2 GeV/c ( Mach cone?). 21

22 Trigger jet (Colorless or colorful) sonic shockwave: H. Stöcker, Nucl. Phys. A 750: (2005), J. Casalderrey-Solana & E. Shuryak, hep-ph/ , J. Ruppert & B.M., Phys. Lett. B 618: (2005), T. Renk & J. Ruppert, hep-ph/ Trigger jet Localized heating of medium: A.Chaudhouri, U. Heinz, nucl-th/ (does not work!) Trigger jet Large Angle Gluon Emission: Ivan Vitev, Phys.Lett.B630:78-84,2005 Cherenkov (-like) radiation: A. Majumder & X. N. Wang, nucl-th/ , V. Koch et. al., nuclt-th/ , I. Dremin, hep-ph/

23 J. Ruppert N=4 SUSY YM at strong coupling J. Friess et al. hep-th/ Mach cone requires collective mode with (k) < k and strong coupling f s 0.8. T. Renk & J. Ruppert 23

24 Collision Geometry: Elliptic Flow Reaction plane y z Bulk evolution described by relativistic fluid dynamics, assumes that the medium is in local thermal equilibrium, but no details of how equilibrium was reached. I nput: (x, i ), P( ), (,etc.). Elliptic flow (v 2 ): Gradients of almond-shape surface will lead to preferential expansion in the reaction plane Anisotropy of emission is quantified by 2 nd Fourier coefficient of angular distribution: v 2 prediction of fluid dynamics x 24

25 Elliptic flow: early creation Time initial evolution energy of density the energy distribution: density: spatial eccentricity momentum anisotropy Flow anisotropy must generated at the earliest stages of the expansion, and matter needs to thermalize very rapidly, before 1 fm/ c. 25

26 2 p T Failure of ideal hydrodynamics tells us how hadrons form Mass splitting characteristic property of hydrodynamics 26

27 2 In the recombination regime, meson and baryon v 2 can be obtained from the quark v 2 : Chiho Nonaka v p 2v p M q t B q 2 t 2 2 t 2 2 v p 3v p t 3 q q q Paul Sorensen T,,v q q Emitting medium is composed of unconfined, flowing quarks. 27

28 QGP Relativistic viscous hydrodynamics: T ( P) u u T Pg 0 with ( u u trace) 1 3 np f p 3 tr D. Teaney s / 0 / QGP(T T c ) = sqgp? s Boost invariant hydrodynamics with T 0 0 ~ 1 requires /s 1/10. Exciting theoretical discovery: N=4 SUSY YM theory (g 2 N c 1) and string CFT duality give /s = 1/(4 (Kovtun, Son, Starinets). Absolute lower bound on /s!? 28

29 Is strong coupling really necessary for small /s? Possible resolution: Color instabilities 29

30 Unstable modes in plasmas occur generally when the momentum distribution of a plasma is anisotropic (Weibel-type instabilities). beam p y p x p z Conditions are satisfied in nuclear collisions: Longitudinal expansion locally red-shifts the longitudinal momentum components of released small-x gluon fields (CGC) from initial state: x y s z for Qs p p Q p In EM case, instabilities saturate due to effect on charged particles. In YM case, field nonlinearities lead to saturation (competition with Nielsen-Olesen instability?) 30

31 Wavelength and growth rate of unstable modes can be calculated perturbatively: k z ~ gq s, ~ gq s < k z Mrowczynski Strickland et al. Arnold et al. Exponential growth saturates when B 2 > g 2 T 4. Turbulent power spectrum 31

32 Expansion Anisotropy QGP X-space Perturbed equilibrium distribution: f ( p) f ( p) 1 f ( p) 1 f ( p) f ( p) exp[ u p / T ] QGP P-space For shear flow of ultrarelat. fluid: f 1 ( p) ( u) 5 / s 2 2ET u i j p p u 2 ij i j j i 3 ij 1 3 ij u ij ( u) Anisotropic momentum distributions generate instabilities of soft field modes. Growth rate ~ f 1 (p). Formation of turbulent color fields is controlled by f 1 (p), i.e. ij(u) and /s. But: turbulent color fields control the anomalous viscosity A. 32

33 Classical expression for shear viscosity: 1 3 np f a B p Momentum change in one coherent domain: p p a a gq B rm r m Anomalous (collisionless) mean free path: ( A) f Anomalous viscosity due to random col or field s: A r m p p np p g Q B r st m 3g Q B r g Q B r m m 33

34 p E Take moments of D( p) f ( r, p, t) C f with p 2 z t p r p p t a b Dij ( p) dt ' Fi r ( t '), t ' U ab ( r, r) Fj r, t F g E v B a a a = color force 1 2 N F m c g O O 3 N 1 st T 2 c 4 1 ln g 1 3 A C i 2 dt ' Fi ( t ') F ( t) F m q = jet quenching parameter!!! ˆ M. Asakawa, S.A. Bass, B.M., PRL 96:252301,2006 hep-ph/

35 Possible effects on QGP probes: Longitudinal broadening of jet cones (observed ridge ) Jet B Jet Anomalous diffusion of charm and bottom quarks (observed) Synchrotron-style radiation of soft, nonthermal photons? x y z Au+Au 20-30% Field induced quarkonium dissociation? c a b c No unstable modes for quarks: quasi-particle picture of QGP is compatible with low viscosity b 35

36 LHC CMS ALICE ATLAS 36

37 Heavy ion physics at the LHC is only ~2 years away LHC will provide quantitative tests of the models developed to describe the RHIC data: Saturation of the initial gluon density (Almost) ideal hydrodynamic evolution of matter (v 2 ) Scaling of parton energy loss with path length Color screening, quark recombination Major new probes: contained jets and b-quarks, permitting much improved control of theoretical predictions. 37

38 100 GeV jets similar to 2 GeV hadrons at RHIC Bulk physics probes 10-4 < x < 10-3 Forward/backward regions provide access to very small x

39 ~ 1/Q 2 Nonlinear interactions among classical fields lead to the saturation of gluon density in the transverse plane. Q 2 ( x, A) sat Color Glass Condensate parton density xg A ( x, Q ) A x ar ea = 1 R Q Q 2 1 / 3 s A Glassy gluons are liberated quark pairs are produced rapidly. Glasma turns into a quark-gluon plasma.. 39

40 E CM Geometric scaling à la Golec-Biernat & Wüsthoff x A Q ( x, A) Q x R sat 0 2 A with 0.288, 0.79 (Armesto et al. hep-ph/ ) 1/ 3 From fit to HERA e-p and NMC nuclear photoabsorption data. 2 dn dy Q R 2 2 / sat, A A T LHC in 3T 500 MeV RHIC in 40

41 Photon- or Z 0 -tagged jets [g+q q+ (Z)]: Study of jets with known energy. Fully resolved jets (E T > 100 GeV): Measurement of full medium-modified fragmentation function. Tri-jets: Study of gluon propagation. Jets initiated by c- and b-quarks.,, spectroscopy: Improved test of color screening. Nuclear parton distributions down to x ~ (in p+a collisions): probe of gluon saturation. 41

42 Do we have a coherent theoretical framework? High-p T hadrons: YES, but High-p T di-hadrons: MAYBE -jet correlations: YES, but Single jets: YES, but Tri-jets: NO Heavy quarkonia: NO High invariant mass lepton pairs: YES, but High p T photons: MAYBE There are many research challenges for theorists! 42

43 AA Extrapolations to LHC energy vary widely due to modeling differences: Vitev et al (GLV) Armesto et al (ASW) LHC 43

44 Deeper penetration of higher-p T probe leades to increased punch-through of away side jet. Detector T. Renk Vertex distribution for trigger hadrons of p T 25 GeV/c in LHC 44

45 Jet energy is not lost, but just redistributed inside the jet cone to larger k t than in vacuum fragmentation (LPM effect). Separation of fully evolved jet from background will become possible at LHC for large jet energies. k T Soft background: de T 2 dy 400 GeV Distributed over ~300 particles. Medium modifications of jet shape can tell us about the mechanism of energy loss of the initiating parton. Are jets induced by b-quarks modified differently than those induced by light quarks/gluons? 45

46 Outlook The RHIC program has shown that equilibrated matter is rapidly formed in heavy ion collisions; wide variety of probes available at collider energies; systematic study of matter properties is possible. QGP appears to be a turbulent color liquid with novel and unanticipated transport properties. Experimental surprises have become a gold mine for theorists: extreme opaqueness of matter to colored probes; large enhancement of baryon production; collective flow phenomena indicating strong coupling; connection to string theory and AdS/CFT duality. Exciting times for HI physics at the LHC lie ahead! 46

47 THE END OF THIS TALK - BUT THE BEGINNING FOR H-QM 47