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Multi-hadron correlations and the space-time structure of (heavy ion) collisions

Multi-hadron correlations and the space-time structure of (heavy ion) collisions. Mike Lisa Ohio State University. Featuring Work of: Zbigniew Chajeçki , Mercedes López-Noriega, Dan Magestro, Randy Wells. Outline. R.H.I.C. / RHIC - what and wherefore?

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Multi-hadron correlations and the space-time structure of (heavy ion) collisions

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  1. Multi-hadron correlations and the space-time structure of (heavy ion) collisions Mike Lisa Ohio State University Featuring Work of: Zbigniew Chajeçki, Mercedes López-Noriega, Dan Magestro, Randy Wells mike lisa - University of Rochester nuclear seminar - 4oct2005

  2. Outline • R.H.I.C. / RHIC - what and wherefore? • geometry and bulk physics in p-space - brief • ... & in x-space: pion femtoscopy at RHIC • Au+Au • d+Au , p+p • new puzzles, new techniques, global conservation laws • Summary mike lisa - University of Rochester nuclear seminar - 4oct2005

  3. mass |b| pT (√SNN, b, Npart, A, B, mT, y, ,PID) • Vary signal () • constrain multi-dimensional models • requires flexible detectors, broad approach • Vary colliding system • does physics change? • requires dedicated program • Vary kinematic variables • dynamics and different regimes • requires large acceptance • Vary particle type • consistent picture? • unique probe of dynamical structure • requires good particle identification & acceptance mike lisa - University of Rochester nuclear seminar - 4oct2005

  4. PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS Also: p+p @ 62.4 & 200 GeV Gunther Roland, QM05 Possibilities in a dedicated program: 5 years @RHIC 1 km v = 0.99995c = 186,000 miles/sec mike lisa - University of Rochester nuclear seminar - 4oct2005

  5. Also: p+p @ 62.4 & 200 GeV Gunther Roland, QM05 Possibilities in a dedicated program: 5 years @RHIC mike lisa - University of Rochester nuclear seminar - 4oct2005

  6. PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS STAR ~600 Collaborators Possibilities in a dedicated program: 5 years @RHIC mike lisa - University of Rochester nuclear seminar - 4oct2005

  7. Solenoidal Tracker At RHIC goal: track “all” charged hadrons (bags of quarks) emitted in each collision The STAR Experiment • STAR: Solenoidal Tracker at RHIC • multipurpose detector system for hadronic measurements • large coverage (geometrical acceptance) • tracking of charged particles in high multiplicity environment • measure correlations of observables • study of hard processes (jet physics) mike lisa - University of Rochester nuclear seminar - 4oct2005

  8. Electric field ..generating a cluster of liberated electrons Anode wires with +HV sitting ~5 mm above pads Copper pads ~ 1cm2 “Avalanche” as electrons approach anode wire... V ADC t Amplifying and digitizing electronics connected to each pad bucket # Operation of a Time Projection Chamber Charged particle flies thru TPC gas… DAQ SCA/ADC ..capacitively inducing a signal on nearby pads... ..which is amplified, digitized, and recorded for later analysis mike lisa - University of Rochester nuclear seminar - 4oct2005

  9. One collision seen by STAR TPC Momentum determined by track curvature in magnetic field… …and by direction relative to beam mike lisa - University of Rochester nuclear seminar - 4oct2005

  10. Generating a “deconfined” (?) state • “Present” understanding of Quantum Chromodynamics (QCD) • heating • compression •  deconfined color matter ! Hadronic Matter (confined) Nuclear Matter (confined) Quark Gluon Plasma deconfined ! mike lisa - University of Rochester nuclear seminar - 4oct2005

  11. Expectations from Lattice QCD /T4 ~ # degrees of freedom deconfined: many d.o.f. confined: few d.o.f. mike lisa - University of Rochester nuclear seminar - 4oct2005

  12. Early universe quark-gluon plasma critical point ? Tc Temperature colour superconductor hadron gas nucleon gas nuclei CFL r0 Neutron stars The phase diagram of QCD vacuum baryon density mike lisa - University of Rochester nuclear seminar - 4oct2005

  13. Early universe quark-gluon plasma critical point ? Tc Temperature colour superconductor hadron gas nucleon gas nuclei CFL r0 Neutron stars vacuum baryon density The phase diagram of QCD 99.5% • understanding a theory or phenomenon (superconductivity...) focus on phase transitions • RHIC studies:partonic condensed matter physics • the crucial feature of QCD (theory):long-range behaviour • confinement, etc:soft-sector crucial ? Au+Au mike lisa - University of Rochester nuclear seminar - 4oct2005

  14. STAR, PRC66 (2002) 034904 STAR, PRL93 (2004) 252301 Spacetime - the defining aspect of RHI physics • Non-trivial space-time - the hallmark of rhic • Initial state: dominates further dynamics • Intermediate state: impt element in exciting signals • Final state: • Geometric structural scale is THE defining feature of QGP mike lisa - University of Rochester nuclear seminar - 4oct2005

  15. Ann.Rev.Nucl.Part.Sci. 46 (1996) 71 Spacetime - the defining aspect of RHI physics • Non-trivial space-time - the hallmark of rhic • Initial state: dominates further dynamics • Intermediate state: impt element in exciting signals • Final state: • Geometric structural scale is THE defining feature of QGP • Temporal scale sensitive to deconfinement transition (?) mike lisa - University of Rochester nuclear seminar - 4oct2005

  16. Is it bulk? Is it a “system?” 1) Superposition of independent p+p: momenta pointed at random relative to reaction plane mike lisa - University of Rochester nuclear seminar - 4oct2005

  17. Is it bulk? Is it a “system?” 1) Superposition of independent p+p: high density / pressure at center momenta pointed at random relative to reaction plane 2) Evolution as a bulksystem Pressure gradients (larger in-plane) push bulk “out”  “flow” “zero” pressure in surrounding vacuum more, faster particles seen in-plane mike lisa - University of Rochester nuclear seminar - 4oct2005

  18. N N   0 0 /4 /4 /2 /2 3/4 3/4 -RP (rad) -RP (rad) Is it bulk? Is it a “system?” 1) Superposition of independent p+p: momenta pointed at random relative to reaction plane 2) Evolution as a bulksystem Pressure gradients (larger in-plane) push bulk “out”  “flow” more, faster particles seen in-plane mike lisa - University of Rochester nuclear seminar - 4oct2005

  19. Azimuthal distributions at RHIC STAR, PRL90 032301 (2003) b ≈ 6.5 fm b ≈ 4 fm “central” collisions midcentral collisions mike lisa - University of Rochester nuclear seminar - 4oct2005

  20. Azimuthal distributions at RHIC STAR, PRL90 032301 (2003) b ≈ 10 fm b ≈ 6.5 fm b ≈ 4 fm peripheral collisions mike lisa - University of Rochester nuclear seminar - 4oct2005

  21. “v2” Elliptic flow – collectivity& sensitivity to early system • “Elliptic flow” • evidence ofcollective motion • quantified by v2 • geometrical anisotropy momentum anisotropy • sensitive to early pressure • evidence for • early thermalization • QGP in early stage STAR, PRL90 032301 (2003) Hydrodynamic calculation of system evolution mike lisa - University of Rochester nuclear seminar - 4oct2005

  22. RHIC serves the perfect liquid Perfect... ? mike lisa - University of Rochester nuclear seminar - 4oct2005

  23. Finally, we understand it! Gyulassy 1995 Just one event! v2 - huge systematics... 6 decades of E/A (2 decades of sNN) Art’s talk. Compiled by A. Wetzler (2005) mike lisa - University of Rochester nuclear seminar - 4oct2005

  24. It starts... ideal hydro: sharp 1st-order rather than lattice EOS ? P. Houvinen, nucl-th/0505036 Also: Hirano, Gyulassy... mike lisa - University of Rochester nuclear seminar - 4oct2005

  25. More direct connection to geometric substructure • Two-particle correlation functions probe femtoscopic scales • “HBT” etc. mike lisa - University of Rochester nuclear seminar - 4oct2005

  26. The Bottom line… if a pion is emitted, it is more likely to emit another pionwith very similar momentumif the source is small Creation probability r(x,p) = U*U F.T. of pion source Measurable! probingsource geometry through interferometry p1 r1 x1 p source r(x) 1 m x2 r2 p2 experimentally measuring this enhanced probability: quite challenging 5 fm mike lisa - University of Rochester nuclear seminar - 4oct2005

  27. Au+Au R ~ 6 fm p+p R ~ 1 fm d+Au Correlation functions for different colliding systems STAR preliminary C2(Qinv) Qinv (GeV/c) Different colliding systems studied at RHIC First opportunity to directly compare AA, pp, (&pA) mike lisa - University of Rochester nuclear seminar - 4oct2005

  28. p1 Rlong q Rside p2 Rout beam direction More detailed geometry Relative momentum between pions is a vector  can extract 3D shape information Rlong – along beam direction Rout – along “line of sight” Rside –  “line of sight” mike lisa - University of Rochester nuclear seminar - 4oct2005

  29. small RSIDE 6Li released from an asymmetric trap O’Hara, et al, Science 298 2179 (2002) RSIDE big RSIDE  0 /4 /2 3/4 -RP (rad) Source shape • “observe” the source from all angles relative to the reaction plane • expect oscillations in radii for non-round sources reaction plane mike lisa - University of Rochester nuclear seminar - 4oct2005

  30. central collisions Bulk shape evolution mid-central collisions initial= final peripheral collisions Measured final source shape STAR, PRL93 012301 (2004) Expected evolution: ? mike lisa - University of Rochester nuclear seminar - 4oct2005

  31. p1 q p2 Disintegration timescale Relative momentum between pions is a vector  can extract 3D shape information Rlong – along beam direction Rout – along “line of sight”  increases with emission timescale Rside –  “line of sight” Rout Rside mike lisa - University of Rochester nuclear seminar - 4oct2005

  32. Disintegration timescale - expectation 3D 1-fluid Hydrodynamics Rischke & Gyulassy, NPA 608, 479 (1996) with transition with transition “” “” • Long-standing favorite signature of QGP: • increase in , ROUT/RSIDE due to deconfinement  confinement transition • expected to “turn on” as QGP energy threshold is reached mike lisa - University of Rochester nuclear seminar - 4oct2005

  33. Hirano ‘02 Heinz & Kolb, hep-ph/0204061 N() HBT puzzle(s) mike lisa - University of Rochester nuclear seminar - 4oct2005

  34. Why do the radii fall with increasing momentum ?? mike lisa - University of Rochester nuclear seminar - 4oct2005

  35. Why do the radii fall with increasing momentum ?? It’s collective flow !! Directgeometrical/dynamicalevidence for bulk behaviour Amount of flow consistent with p-space mike lisa - University of Rochester nuclear seminar - 4oct2005

  36. Flow-dominated model w/ “hand-tuned” short timescales • Blast-wave model (latest in long series) reproducesp- and x-space • Also non-id, asHBT... F. Retiere, QM04 F. Retiere & MAL, PRC 70 (2004) mike lisa - University of Rochester nuclear seminar - 4oct2005

  37. Bulk size evolution - collisions at 200 GeV • Au+Au reaction zone:two-fold expansion • Preliminary Cu+Cu, d+Au, p+p:smooth interpolation • central Cu+Cu = periph Au+Au • Little expansion for small system • shorter timescalesor... • less bulk collectivity...? mike lisa - University of Rochester nuclear seminar - 4oct2005

  38. Zbigniew Chajecki QM05 Z0 decay @ LEP R Z(fm) DELPHI   R (fm) K p  STAR preliminary mT (GeV) mT (GeV) m, mT (GeV) hep-ph/0108194 femtoscopy in p+p @ STAR 1. Heisenberg uncertainty? • e.g. G. Alexander • “plausible” in z-direction • unlikely in transvrse 2. String fragmentation? (Lund) • p+p and A+A measured in same • experiment • great opportunity to compare physics • what causes pT-dep in p+p? • same cause as in A+A? 3. Resonance effects? • pT dependence maybe (??) • mass dependence probably no [Andersson, Moriond 2000] • e.g. Wiedemann & Heinz ‘97 • maybe, but presumably significantly different effect than for Au+Au • under investigation mike lisa - University of Rochester nuclear seminar - 4oct2005

  39. Zbigniew Chajecki QM05 Z0 decay @ LEP R Z(fm) flow not expected in such a small system as p+p e.g. Shuryak:hep-ph/0405066 • Csorgoet al.: Buda-Lund treatment of p+p collision as bulk system(w/ temperature gradients)hep-ph/0406042  4. Bulk system („hydro”) in pp? DELPHI K 1/(2pmT)d2n/(dmTdy) p   mT-m (GeV) R (fm) • d+Au : Rlong doesn’t change with centrality RSIDE RLONG ROUT K p  STAR preliminary mT (GeV) mT (GeV) mT (GeV) m, mT (GeV) hep-ph/0108194 femtoscopy in p+p @ STAR 1. Heisenberg uncertainty? 2. String fragmentation? (Lund) • p+p and A+A measured in same • experiment • great opportunity to compare physics • what causes pT-dependence in p+p? • same cause as in A+A? 3. Resonance effects? mike lisa - University of Rochester nuclear seminar - 4oct2005

  40. Surprising („puzzling”) scaling Ratio of (AuAu, CuCu, dAu) HBT radii by pp • first-ever pp/AA comparison yields a surprise! • similar underlying physics? HBT radii scale with pp Scary coincidence or something deeper? pp, dAu, CuCu - STAR preliminary mike lisa - University of Rochester nuclear seminar - 4oct2005

  41. What the “coincidence” does NOT mean • pp appears to be blasting system (?!) • AA ≠(pp) • would mean local x-p correlations(giving identical p-space...) • More like pp = “little AA” !! mike lisa - University of Rochester nuclear seminar - 4oct2005

  42. Don’t forget where the “radii” come from... long-range correlations for small systems mike lisa - University of Rochester nuclear seminar - 4oct2005

  43. STAR PRC71 044906 (2005) • Harmonic Decomposition Analysis • exploits full symmetry of q-space • explicit isolation of femtoscopic(& non-femtoscopic) effects • full 3D CF seen clearly in few plots • acceptance-robust (*) • Cartesian HDDanielewicz & Pratt nucl-th/0501003 • Spherical HDChajecki,Gutierrez,MAL,Lopez nucl-ex/0505009 out “Gaussian fit” (remember: not Gaussian CF) side long Michael Lisa: “Salient geometrical...” bullet just means: if I want to know “Rlong” or so, I *mostly* just look at width of long projection, but there are also acceptance effects 1D projections: a limited view • Usual 1D out-side-long “Cartesian projections” • limited view of data • ~set of zero measure of 3D CF • Fit-violating trends may be hidden • Salient geometrical effects non-trivially convoluted • acceptance-dependent (unlike 3D CF) mike lisa - University of Rochester nuclear seminar - 4oct2005

  44. QLONG Q  QOUT  QSIDE Spherical harmonic decomposition of CF • Cartesian-space (out-side-long) naturally encodes physics, but is “inefficient” representation • Harmonic Moments -- 1::1 connection to source geometry [Danielewicz,Pratt: nucl-th/0501003] • ~immune to acceptance • full information content at a glance[thanks to symmetries] mike lisa - University of Rochester nuclear seminar - 4oct2005 Chajecki., Gutierrez, MAL, Lopez-Noriega, nucl-ex/0505009

  45. RL < RT ~acceptance free RL > RT RO < RS Simple, Gaussian source calculations RO > RS “Mental calibration” - a Gaussian CF Chajecki., Gutierrez, MAL, Lopez-Noriega, nucl-ex/0505009 • Full 3D structure • (high-L (fine structure) coefficients drop off) • Different geometrical aspects separate & use “all” relevant information in the CF • AL≠0 vanishes in non-femtoscopic region mike lisa - University of Rochester nuclear seminar - 4oct2005

  46. SH Moments C(Qout) A00 A20 C(Qside) Chajecki., Gutierrez, MALLopez-Noriega, nucl-ex/0505009 C(Qlong) A22 STAR preliminary STAR Central Au+Au collisions -- Spherical HD 1D o-s-l projections mike lisa - University of Rochester nuclear seminar - 4oct2005

  47. STAR preliminary d+Au peripheral collisions ad hoc, but try it... Gaussian fit Baseline problems with smallest systems mike lisa - University of Rochester nuclear seminar - 4oct2005

  48. STAR preliminary Spherical harmonics d+Au peripheral collisions L =2 M=0 data NA22 fit L =1 M=0 NA22 fit L =1 M=1 L =2 M=2 Try NA22 empirical form mike lisa - University of Rochester nuclear seminar - 4oct2005

  49. STAR preliminary d+Au peripheral collisions A00 A02 b |Q| |Q| z Gaussian + constant A02, A22 A22 Gaussian fit |Q| “account for” constant offset in L=2 components also ad-hoc, but with correct symmetries, “simple” Q-dep mike lisa - University of Rochester nuclear seminar - 4oct2005

  50. Ad hoc formulation not satisfying... • Detector-induced? No. • Potential physical non-femtoscopic effects at low multiplicity • jet-induced? Studies so far: no • global conservation laws...? With L=2 shifts, message remains Ratio of (AuAu, CuCu, dAu) HBT radii by pp STAR preliminary NEW fit w/ baseline parameterization Fit w/o baseline parameterization mike lisa - University of Rochester nuclear seminar - 4oct2005

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