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Experimental Probes of Strongly Coupled Plasmas

Experimental Probes of Strongly Coupled Plasmas. Workshop on Modeling the QCD Equation of State at RHIC Barbara Jacak Stony Brook Feb. 10, 2006. (my favorite way to probe my favorite strongly coupled plasma). outline. What’s a plasma?

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Experimental Probes of Strongly Coupled Plasmas

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  1. Experimental Probes of Strongly Coupled Plasmas Workshop on Modeling the QCD Equation of State at RHIC Barbara Jacak Stony Brook Feb. 10, 2006 (my favorite way to probe my favorite strongly coupled plasma)

  2. outline • What’s a plasma? • Why we think the quark gluon plasma at RHIC is strongly coupled • Other strongly coupled plasmas • and their properties • What do we know and what will be measured next? • suggest modeling needed to interpret the data

  3. what is a plasma? • 4th state of matter (after solid, liquid and gas) • a plasma is: • ionized gas which is macroscopically neutral • exhibits collective effects • interactions among charges of multiple particles • spreads charge out into characteristic (Debye) length, lD • multiple particles inside this length • they screen each other • plasma size > lD

  4. Energy density of matter high energy density: e > 1011 J/m3 P > 1 Mbar I > 3 X 1015W/cm2 Fields > 500 Tesla

  5. ideal gas or strongly coupled plasma? how does it compare to interesting EM plasmas? • Huge gluon density! • estimate G = <PE>/<KE> • using QCD coupling strength g • <PE>=g2/d d ~1/(41/3T) • <KE> ~ 3T • G ~ g2 (41/3T)/ 3T • g2 ~ 4-6 (value runs with T) for T=200 MeV plasma parameter G ~ 3  quark gluon plasma should be a strongly coupled plasma G > 1: strongly coupled, few particles inside Debye radius

  6. A little more on coupling • potential V as/r <KE>  T r=interparticle distance • QCD matter:r1/r3 rT3 and so we see that r  1/T • G = <PE>/<KE>  (as/r)/T asT/T as T cancels, but does affect as • lD = {T/(4pe0e2r)}1/2 so lD {T/(asT3)}1/2  1/(Tas1/2) • as • We know 1/G #particles inside Debye volume ND • ND= N/VD= rVD VD= 4/3 plD3 1/(as3/2T3) • so ND=  1/as3/2 T cancels again • for as large, ND is large (lD fairly large, but included in ND) • for as small, ND is small (lD smallish)

  7. putting in some numbers • both G and ND depend on as • at RHIC dNg/dy ~ 800 • so r = 800/(1 fm * pR2 fm2) = 800/100 = 8 /fm3 • r = 0.5 • from lattice as= 0.5-1 for quarks • for gluons multiply by 3/(4/3) = 9/4. It’s big! • from pQCD as= 0.3 for quarks and ~0.7 for gluons

  8. Karsch, Laermann, Peikert ‘99 ~15% from ideal gas of weakly interacting quarks & gluons quite different from ideal gas of q, g! e/T4 T/Tc Tc ~ 170 ± 10 MeV e ~ 3 GeV/fm3 Lattice says

  9. Lattice also tells us spectral function hadrons don’t all melt at Tc! • hc bound at 1.5 Tc Asakawa & Hatsuda, PRL92, 012001 (2004) • charmonium bound states up to ~ 1.7 Tc Karsch; Asakawa&Hatsuda • p, s survive as resonances Schaefer & Shuryak, PLB 356 , 147(1995)

  10. strongly coupled gas of Li atoms • M. Gehm, S. Granade, S. Hemmer, K, O’Hara, J. ThomasScience 298 2179 (2002) • cool the atoms to make KE<PE, excite a resonance strongly coupled ↓ elliptic flow! weakly coupled

  11. strongly coupled Astrophysical plasmas • Astrophysical phenomena • how do neutron stars, giant planet cores, gamma ray bursters, dusty plasmas, jets work? • Fundamental physics questions • properties of the matter, interactions with energy under extreme conditions

  12. High Energy Density Physics in Stockpile Stewardship Facilities (NIF, Omega, Z-pinch) • Materials Properties • warm, dense matter: • behavior between solid, fluid and plasma. • found in giant planet cores, laser heated foils • Compressible Dynamics • how do strong shocks and high Mach number • flows interact with ambient medium: • astrophysical jets, black hole • accretion disks, ignition targets, • weapons…

  13. Plasma properties generally studied • density and opacity • electrical and thermal conductivity • transport properties • diffusion • hydrodynamic expansion velocity, shock propagation • waves in plasma and dispersion relation • plasma oscillations and instabilities • radiation • bremsstrahlung, blackbody, collisional and recombination

  14. Shock and interface trajectories are measured by x-ray radiography • Slope of shock front yields Us • Slope of pusher interface gives Up streak camera record R. Lee, S. Libby, LLNL P-P0=r0UsUp

  15. of particular interest for strongly coupled plasmas • kinetic energy distribution (T) • measure electrons radiated from plasma • flow properties (turbulent and non) • measure particle transport using laser induced flourescence • again study electron radiation from plasma • opacity to hard x-rays (time resolved) • thermalization time • photon absorption & ion spectrum vs. time • plasma oscillations • see density fluctuations in electron arrival times • correlations among particles • measure radiated particle pairs • crystallization • viscosity

  16. from S. Ichimaru, Univ. of Tokyo

  17. z y x Almond shape overlap region in coordinate space search for collectivity at RHIC momentum space dN/df ~ 1 + 2 v2(pT) cos (2f) + … “elliptic flow”

  18. Kolb, et al What have we learned already about QGP? • Pressure built up very rapidly during ion collisions at RHIC • large collective flow, calculate w/hydro • interaction s large, fast thermalization • viscosity small • huge energy loss in fast quarks traversing medium • energy, gluon density large • medium is opaque • baryon production enhanced by • factor of 3 compared to p+p

  19. at high pT v2 reflects opacity of medium STAR v2 approximately expected level from jet quenching

  20. black medium after 2.3 fm/c sQGP formation time V. Pantuev Can calculate elipticity parameter v2 as jet surviving probability in and out of plane Data are for high pt pi0s, PHENIX, blue cicles – 4.59 GeV/c, green squares – 5-7 GeV/c No flow needed! picture reproduces other features: reaction plane dependence of Raa away side jet yield

  21. Raa(f) is inclusive measurement and in a particular event you always look at some angle. V. Pantuev x-y projections of Ncoll centers for 40-45% centrality from Glauber model with Woods-Saxon density distribution. Look out-plane, f=p/2 Look in-plane, f=0 L Cutoff L=2.3 fm/c is adjusted for in-plane 50-55% centrality Raa=0.9

  22. charm quarks (via nonphotonic electrons) ~ same energy loss as light quarks  e loss not all radiative show non-zero v2 at modest pT flow? thermalization with the light quarks?

  23. QGP properties • Extracted from models, constrained by data Equation of state? Early degrees of freedom and their s? Deconfinement? Thermalization mechanism? Conductivity?

  24. the rest of the properties need good sensitivity to rare probes and improved background rejection for plasma radiation QGP is not rare in these collisions, but (clean) signals of early-time phenomena ARE! High pT hadrons, γ + jet, di-jets probe density, gluon bremstrahlung Heavy quarks (bound & unbound) probe screening, thermalization Direct photons, electrons radiation from plasma A+A Species scan p+p Energy scan d+A High statistics C,B

  25. Jet tomography • correlations of 2, 3 (more?) particles • from jets traversing medium • g-jet correlations; g fixes jet energy • gq →gq • identify the hadrons: hadronization, charm e-loss • increase PHENIX, STAR calorimeter coverage for g • 2008-2011 • upgrade rate capabilities of data acquisition, analysis • 2007 • increased machine luminosity (2013?) cross section small, so rate is low

  26. STAR Preliminary (1/Ntrig)dN/d(Df) M.Miller, QM04 PHENIX preliminary dN/d(Df) 0 p/2 p p/2 p Df =+/-1.23=1.91,4.37 → cs ~ 0.33 (√0.33 in QGP, 0.2 in hadron gas) speed of sound via a density wave? g radiates energy kick particles in the plasma accelerate them along the jet

  27. jet partners per trigger all baryons from quarks drawn from the medium p+p Npart why so many baryons at medium pT? • sensitive probe of hadronization • quark coalescence: good starting point • small production rate →sensitivity to • correlations of quarks inside the medium! • a tool to probe wakes in the plasma. correlators? • upgrade PID in STAR and PHENIX by ‘09 • increased luminosity to allow scanning collision energy, species (Au+Au, Cu+Cu compare to p+p, d+Au)

  28. dileptons and photons • pT spectrum of soft g, g* reflects Tinitial • interpretation problem: • unfolding time history • of the expansion • note: fixing the EOS • for hydro is essential! • medium modification • of final vector mesons • decays of bound states? • detector upgrades will reduce decay background and allow measurement of charm background • energy & system size scans require luminosity upgrade

  29. RHIC Heavy Quarkonium – a screening probe • map charmonium and bottomonium states to study competition between melting and regeneration • color screening length? Tinitial? • upgraded luminosity will allow: • measurement of Y • v2 of J/y • energy scan for J/y, screening vs. regeneration counts per year comparable to those at LHC!

  30. Heavy Quarks – open charm • precision measurements to quantify energy loss and v2 as a function of momentum • how opaque IS the medium? • relative role of gluon • radiation and collisional • energy loss • must measure charm yield • to subtract from • intermediate mass dilepton continuum • inner tracker upgrades for PHENIX and STAR needed to tag displaced vertex for clean measurement • ready by 2011

  31. what sQGP plasma properties could these yield? • speed of sound via jet modifications • quark correlations in the medium • baryon formation • medium modifications of jet fragmentation • propagation of jet-induced shocks • constrain radiative vs. collisional energy loss • screening length via onium spectroscopy • T via radiated dileptons, photons • dissipation via energy flow in shocked medium • Would like to identify experimental signatures of • viscosity • Weibel instability in first 0.6 fm/c

  32. RHIC II RHIC Mid-Term Strategic Plan PHENIX STAR EBIS Forward Nose Cone Calorimeter Mu Trigger FMS STAR Integrated Tracking VTX PHENIX & STAR VTX upgrades TOF PID HBD Hi Rate DAQ 1000 PHENIX + STAR Data-Taking e Cooling CD-0 CD-1 CD-2 CD-3 CD-4 e-pair spectrum Jet Tomography Open Charm LHI U+U Heavy Ion Luminosity Mono-Jet SPIN F.O.M. LP4 G/G P-V W± prod. and Transversity

  33. Hydro. Calculations Huovinen, P. Kolb, U. Heinz Kolb, et al Hydrodynamics can reproduce magnitude of elliptic flow for p, p. Mass dependence requires softer than hadronic EOS!! v2 reproduced by hydrodynamics • see large pressure buildup! • anisotropy  happens fast • early equilibration STAR PRL 86 (2001) 402 central NB: these calculations have viscosity = 0 “perfect” liquid (D. Teaney)

  34. 0 1 2 pT/n (GeV/c) • v2 scales ~ with # of quarks! • when the pressure is built up, quarks are the degrees of freedom Elliptic flow scales as number of quarks

  35. suppression persists to 20 GeV/c! nuclear modification factor ratio of data on previous slide

  36. I. Vitev d+Au calculate using an opacity expansion Au+Au Property probed: density interaction of radiated gluons with gluons in the plasma greatly enhances the amount of radiation

  37. Medium is opaque! look for the jet on the other side STAR PRL 90, 082302 (2003) Peripheral Au + Au Central Au + Au

  38. Pedestal&flow subtracted Are back-to-back jets there in d+Au? Yes! no medium ↓ no jet quenching

  39. Hatsuda, et al. Lattice QCD shows qq resonant states at T > Tc, also implying high interaction cross sections How to get fast equilibration & large v2 ? Molnar parton cascade using free q,g scattering cross sections doesn’t work! need s x50 in medium

  40. do heavy quarks lose energy? J. Edgemir, A.Dion, R. Averbeck e± in Au+Au vs <Ncoll>*p+p peripheral collisions central collisions c quark suppression is nearly as large as for pions!

  41. where does the lost energy go? • transferred to the plasma? • does the medium respond? • look at “away side” jet’s particles at thermal pT PHENIX preliminary

  42. At RHIC: J/ymm muon arm 1.2 < |y| < 2.2 measured/expected dAu mm 200 GeV/c AuAu mm 200 GeV/c CuCu mm 200 GeV/c

  43. At RHIC: J/ymm muon arm 1.2 < |y| < 2.2 J/yee Central arm -0.35 < y < 0.35 dAu mm 200 GeV/c AuAu mm 200 GeV/c CuCu mm 200 GeV/c AuAu ee 200 GeV/c CuCu ee 200 GeV/c

  44. At RHIC: J/ymm muon arm 1.2 < |y| < 2.2 J/yee Central arm -0.35 < y < 0.35 ! Factor ~3 suppression in central events dAu mm 200 GeV/c AuAu mm 200 GeV/c CuCu mm 200 GeV/c AuAu ee 200 GeV/c CuCu ee 200 GeV/c CuCu mm 62 GeV/c

  45. At RHIC: J/ymm muon arm 1.2 < |y| < 2.2 J/yee Central arm -0.35 < y < 0.35 ! Factor ~3 suppression in central events Data show the same trend within errors for all beams and even at √s=62 GeV

  46. RAA vs Npart: PHENIX and NA50 • NA50 data normalized at NA50 p+p point. • Suppression similar in the two experiments, although the collision energy is 10 times higher (200GeV in PHENIX & 17GeV in NA50)

  47. What suppression should we expect? Models that were successful in describing SPS data fail to describe data at RHIC - too much suppression -

  48. can get better agreement with data if add formation of “extra” J/y by coalescence of c and anti-c from the plasma caveat: not necessarily unique or correct explanation!

  49. Possibility of plasma instability → anisotropy • small deBroglie wavelength q,g point sources for g fields • gluon fields obey Maxwell’s equations • add initial anisotropy and you’d expect Weibel instability • moving charged particles induce B fields • B field traps soft particles moving in A direction • trapped particle’s current reinforces trapping B field • can get exponential growth • (e.g. causes filamentation of beams) • could also happen to gluon fields early in Au+Au collision • timescale short compared to QGP lifetime • but gluon-gluon interactions may cause instability to saturate → drives system to isotropy & thermalization

  50. The Scope of the Tools (!) STAR specialty: large acceptance measurement of hadrons PHENIX specialty: rare probes, leptons, and photons

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