1. Bulk Correlations 1 Thinking about the correlation landscape in terms of What’s this talk about?? Paul Sorensen 9:06 PM Agnes Mocsy 9:05 PM

2. Bulk Correlations 2 Outline Do 2-particle correlations at intermediate or low p T represent modified jets or mini-jets? Laundry list: Chemical composition of the correlations  Baryon-to-Meson ratios are like the bulk Peak amplitude  Correlations don’t scale with N bin or N part but with M(M-1) instead  Near-side and Away-side have same centrality dependence Longitudinal and Azimuthal Width  They’re both different from fragmentation p T spectra of the ridge and the jet cone  The ridge is soft and the real jet-cone is hard These make me think of correlations as a bulk phenomenon  the jet’s are both diluted and quenched to ~nothing 

3. Bulk Correlations The question 3 Are the correlation structures a modification of structures known in p+p? Or a new feature of the medium? 200 GeV 62 GeV STAR Preliminary Peak Amplitude Peak η WidthPeak φ Width M. Daugherity: QM08 centralperipheral

4. Bulk Correlations 4 above transition ridge yield scales with background Ridge scales with the background! Ridge ratio is independent of minimum p T cut Jet signal diluted by combinatorics as expected. Jet ratio grows with minimum p T cut leading and subleading dihadrons (different quantity than usual associate particle yields) STAR Preliminary Navneet Kumar Pruthi

5. Bulk Correlations Flow + Initial-State-Correlations = Near-side Gaussian 5 Boosted emission function with discrete, correlated source points Similar To Treatments by: Longacre, Lindenbaum: Phys.Rev.C78:054904,2008 Dumitru, Gelis, Venugopalan, McLerran: Nucl.Phys.A810:91,2008 Pruneau, Voloshin, Gavin: Nucl.Phys.A802:107-121,2008 Gavin, McLerran, Moschelli How might we explain the observed correlations?

6. Bulk Correlations Flow + Initial-State-Correlations = Near-side Gaussian 6 σ ≈ 1.32 – 1.10*

7. Bulk Correlations 7 lumpy initial conditions and a QGP expansion collision evolution particle detectors collision overlap zone QGP phase quark and gluon degrees of freedom  ~ 10 fm/c hadronization kinetic freeze-out lumpy initial energy density  0 ~1 fm/c  ~ 0 fm/c distributions and correlations of produced particles quantum fluctuations expansion and cooling  ~ 10 15 fm/c

8. Bulk Correlations The Landscape 8 The Ridge, The Valley, and the Away-side: What does a radial flow induced near-side Gaussian have to do with all these complicated structures? The answer may be related to incomplete equilibration and the finite lifetime of the system “ridge” “jet” STAR Preliminary “valley” p T correlations (STAR)

9. Bulk Correlations What happens with this near-side Gaussian 9 Flow+Initial State correlations yields a near-side Gaussian with a width σ = 1.32 – 1.10* The Fourier transform of a Gaussian is a Gaussian This gives the harmonics v n 2 (n, ) for the flow induced Gaussian. * odd values do not have to be zero (fluctuations) Can azimuth correlations be described by a few harmonics (see next slide)

10. Bulk Correlations Few parameter fit of azimuthal correlations 10 4-5 harmonics give a good description of the data I can name that tune in 5 notes

11. Bulk Correlations 11 The difference between data and the ideal Gaussian The difference between the Gaussian and Data is the suppression of long wavelength modes! See Also Discussions of Superhorizon fluctutions in HIC, Ananta P. Mishra, Ranjita K. Mohapatra, et al.

12. Bulk Correlations 12 The difference between data and the ideal Gaussian The difference between the Gaussian and Data is the suppression of long wavelength modes! See Also Discussions of Superhorizon fluctutions in HIC, Ananta P. Mishra, Ranjita K. Mohapatra, et al.

13. Bulk Correlations 13 Multipole moments and the valley See Also Discussions of Superhorizon fluctuations in HIC, Ananta P. Mishra, Ranjita K. Mohapatra, et al. Short lifetime leads to incomplete equilibration Similar to conclusion from v 4 /v 2 2 (Ollitrault) Valley is indicative of suppression of lower harmonics

14. Bulk Correlations 14 Analogies with the early universe Credit: NASA collision evolution particle detectors collision overlap zone QGP phase quark and gluon degrees of freedom  ~ 10 fm/c hadronization kinetic freeze-out lumpy initial energy density  0 ~1 fm/c  ~ 0 fm/c distributions and correlations of produced particles quantum fluctuations Heavy-ion Collisions: Rapid Expansion expansion and cooling The Universe: Slow Expansion WMAPSTAR

15. Bulk Correlations 15 How Can We Test These Models QGP boundary mapped in an energy scan at RHIC? RHIC beam energy scan will test the models (Qs?) An 8-9 week run in run 10 will allow STAR to gather sufficient statistics for 2-D low p T ridge studies down to √s nn ≈10 GeV (1.5 weeks at 10GeV)

16. Bulk Correlations Conclusions 16 Are we sure correlations at intermediate and low p T require the concept of a jet? Chemistry, Centrality dependence, Spectra and Widths all change from fragmentation expectations. An ideal/instantaneous radial flow model will give you a nearly perfect near-side Gaussian Suppression of long wavelength modes due to finite lifetime effects and acoustic horizons may account for the remaining structure

17. Bulk Correlations 17 Life is short collision overlap zone lumpy initial energy density  ~ 0 fm/c QGP phase quark and gluon degrees of freedom  ~ 10 fm/c hadronization  0 ~1 fm/c quantum fluctuations Correct scale shows: regions remain outside the event horizon

18. Bulk Correlations 18 A Post-summary Question The Baryon/Meson ratio is enhanced in the ridge similar to inclusives The Baryon/Meson ratio is also enhanced at UA1 Does anyones model say something about p+p collisions? Multi-parton effects in p+p? QGP?