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The long-range pseudo-rapidity correlations in high-energy collisions

The long-range pseudo-rapidity correlations in high-energy collisions. 王福 强 Purdue University. The Big Bang and the Little Bang. Quark Gluon Plasma ( QGP). Proton, neutron, meson (hadron). Nuclear Phase Diagram. Heavy-Ion Collisions simulation Hadron cascade. STAR. CMS. ALICE. PHENIX.

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The long-range pseudo-rapidity correlations in high-energy collisions

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  1. The long-range pseudo-rapidity correlations in high-energy collisions 王福强 Purdue University

  2. The Big Bang and the Little Bang Quark Gluon Plasma(QGP) Proton, neutron, meson (hadron)

  3. Nuclear Phase Diagram

  4. Heavy-Ion Collisions simulation Hadron cascade

  5. STAR CMS ALICE PHENIX

  6. New York BNL－RHIC Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) STAR and PHENIX experiments

  7. Two types of discoveries • Theoretically predicted, and experimentally verified, e.g. • J/Y • W, Z bosons • Surprises, e.g. • Parity violation • Microwave background radiation Long-range pseudo-rapidity correlations

  8. Variables, observables y f x p pT q pz z STAR: Solenoidal Tracker At RHIC g = 100 13 fm

  9. y z x Hydrodynamic bulk collectivity, elliptic flow py px coordinate space anisotropy momentum space anisotropy -p 0 p fparticle-FR.P. (rad)

  10. Collective expansion of QGP - elliptic (2nd order) and higher order event anisotropic collectivity and its Nquark scaling - hydro-dynamic properties of QGP PHENIX Preliminary, QM12

  11. Elliptic expansion during the partonic (quark-gluon) phase Hadron formation via quark recombination / coalescence Hadron

  12. jet p p Au Au Energy loss (jet quenching) in QGP g q arXiv: 1208.2254 central Au+Au PRL109, 152302 (2012) Phys. Rev. Lett. 91, 072304 (2003)

  13. Au+Au ridge Dh Df Novel phenomena in heavy-ions • Double-peak away-side correlations • Odd harmonics • Long-range ridge correlations • Ridge in small systems • …

  14. Jet Correlations trigger particle pT > 3 GeV/c Df associated particle Jet event in e+e-collision STAR Au+Au collision Jet produces high pT particles  Select a high pT particle to trigger on jet. NB: trigger = off-line trigger

  15. trigger jet Away-side p -1 1 0 Df Dihadron correlations STAR, PRL 95 (2005); PRC82 (2010) STAR, PRL91 (2003) pTtrig=4-6 GeV/c pTassoc=0.15-4 GeV/c • Clear evidence of jet-quenching, and it’s a final-state effect • Low pT enhancement and broadening • Away-side double peak; Large-Dh small-Df ridge correlation • v2 subtracted but not higher harmonics

  16. Relative to the Event Plane Associated STAR, arXiv:1010.0690v1 Todoroki (PHENIX) 1304.2852 Df Trigger • Ep-depcorrel fS EP |Dh| > 0.7 v2max{2,hgap=0.7} v2max{2,hgap=0.7}, v3{2,hgap=0.7} • Evolution of structure seems to remain from in-plan to out-of-plane. • Single away-side peak in-plane, double-peak out-of-plane. • Jet interactions with QGP medium. Physics mechanisms?

  17. Trigger Δ2 Δ1 Three-particle correlations • v2 and v4 subtracted. • Does v3 remove all of the off-diag. peak strength? Need further study. • Deflected jets contributions (to diag. peaks) must be present. • Need to be followed up with v3 subtraction.

  18. assoc. particle pT =1-3 GeV/c trigger particle pT > 3 GeV/c trigger particle pT > 3 GeV/c d+Au h ~ 0 h ~ 1 Df ||<0.7 Dh Au+Au ridge assoc. particle pT =1-2 GeV/c Dh Df The longitudinal ridge

  19. Dh Df Ridge vs trigger angle v2max{2,hgap=0.7} v2max{2,hgap=0.7}, v3{2,hgap=0.7}

  20. Ridge yield vs trigger angle v2max{2,hgap=0.7} v2max{2,hgap=0.7}, v3{2,hgap=0.7} Subtract v3

  21. Ridge in small systems usual p-p collision high multiplicity p-p collision LHC-CMS

  22. Why wasn’t it discovered long ago by HEP? • Two types of discoveries: • Theoretically predicted, and experimentally verified • Surprises • HEP moved on to more exclusive processes • There may be still important physics that were missed in last half century.

  23. p-p collision (high Mul.) p-Pb collision (high Mul.) Physical origin unclear

  24. CGC/Glasma Dusling & Venugopalan 1211.3701 Dusling and Venugopalan, arXiv:1302.7018

  25. Another explanation: Hydro flow • In heavy-ions, large Dh small Dfcorrelations: subtract v2  non-zero finite correlation (ridge) • In pp, pA, dA systems, large Dh small Df correlations:subtract flat pedestal  non-zero finite correlation (ridge)

  26. d+Au ridge? PHENIX, arXiv:1303.1794 • Jet contribution within PHENIX acceptance • LHC+RHIC more stringent test on theoretical models. Bozek, PRC85 (2012) 1.25-1.5 GeV/c PHENIX acceptance

  27. Df projections in different Dh(TPC mult. |h|<1 as centrality) 0.15 < pTtrig < 3 GeV/c, 1 < pTassoc < 2 GeV/c STAR PRELIMINARY STAR PRELIMINARY STAR PRELIMINARY ZYAM-ed ZYAM-ed ZYAM-ed STAR PRELIMINARY STAR PRELIMINARY STAR PRELIMINARY Straight difference No ZYAM involved • ZYAM syst. error from different sizes of Df region for ZYAM. • Efficiency corrected: 85 ± 5% .

  28. Dhprojections in different Df(TPC mult. |h|<1 as centrality) 0.15 < pTtrig < 3 GeV/c 1 < pTassoc < 2GeV/c STAR PRELIMINARY STAR PRELIMINARY ZYAM-ed ZYAM-ed STAR PRELIMINARY STAR PRELIMINARY • ZYAM syst. error from different sizes of Df region for ZYAM. • Efficiency corrected: 85 ± 5% .

  29. Central – Peripheral 0.15 < pTtrig < 3 GeV/c, 1 < pTassoc < 2 GeV/c STAR PRELIMINARY STAR PRELIMINARY FTPC 0-20% - 40-100% TPC 0-20% - 50-80% Minimal ridge STAR PRELIMINARY STAR PRELIMINARY TPC 0-20% - 50-80% TPC 0-20% - 50-80% • ZYAM syst. error from different sizes of Df region for ZYAM. • Efficiency corrected: 85 ± 5% .

  30. Very forward correlations

  31. TPC-FTPC correlations Dh triangle acceptance

  32. Sanity check All charged hadrons TPC-TPC PHOBOS, PRC 72 (2005) 031901(R) TPC-FTPC

  33. ZYAM’edDh Correlations(TPC mult. as centrality) Raw correl. Discontinuity because it’s Dh not h distribution. At Dh=2, TPC-TPC and TPC-FTPC pairs come form different h’s. ZYAM’ed

  34. Fourier fit results TPC-TPC d-side TPC-TPC Au-side TPC-FTPC Au-side TPC-FTPC d-side

  35. Fourier fit results (replot of previous slide) Summary • Correlations have v1 and v2 components • v1 appears ~1/N. v2 ~constant over multiplicity • Even at very forward d-side, v2 component is large (maybe even larger than Au-side). • Not sure what the data mean. Au-side d-side

  36. Conclusions • Particle correlations in heavy-ions • Novel phenomenon of v3 • After v3 subtraction, features of jet-medium interactions remain • Ridge in small systems • Intriguing • May contain important physics

  37. The question of v1 • In the pt=1-2 GeV/c region, directed flow fluctuation effect may be negligible. Pandit (STAR), arXiv:1211.7162

  38. Have to rethink about inclusive dihadron • We have used so far <vt{2}*va{2}>=<vt{2}>*<va{2}>. This is OK because fluctuations are already included in v{2}. • However, if v{2} depends on slice, then <vt{2}slice*va{2}slice><vt{2}slice>*<va{2}slice>. • <vt{2}slice*va{2}slice> = (vt{2}1*va{2}1 + vt{2}6*va{2}6)/2 = (vt{2}1*va{2}1 + vt{2}6*va{2}1- vt{2}6*va{2}1 + vt{2}6*va{2}6)/2 = <vt{2}>*va{2}1 - vt{2}6* (va{2}1 - va{2}6)/2 ><vt{2}>*va{2}1 which is the maximum.

  39. ZYAM’edDh Correlations(ZDC as centrality)

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