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John Campbell Hot Quarks 2012 – 10/16/12

Can baryon stopping explain the breakdown of constituent quark scaling and proposed signals of chiral magnetic waves at RHIC?. John Campbell Hot Quarks 2012 – 10/16/12. Outline. NCQ Scaling Breakdown of NCQ Phase Change? Chiral Magnetic Waves? Baryon Stopping? Multi-component coalescence

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John Campbell Hot Quarks 2012 – 10/16/12

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  1. Can baryon stopping explain the breakdown of constituent quark scaling and proposed signals of chiral magnetic waves at RHIC? John Campbell Hot Quarks 2012 – 10/16/12

  2. Outline • NCQ Scaling • Breakdown of NCQ • Phase Change? • Chiral Magnetic Waves? • Baryon Stopping? • Multi-component coalescence • Formalism • UrQMDSimulations • Comparison of CMW and MCC to data • Summary

  3. Number of Constituent Quark (NCQ) Scaling Scale each by Number of Constituent Quarksn, and the curves all line up! Intermediate : Ordered by baryon/meson Low : Ordered by mass, consistent with Hydro The “NCQ” scaling pattern of hadron at RHIC indicates flowing quarks, which then coalesce. This Should break down at low if quarks are no longer dynamical degrees of freedom.

  4. What could cause NCQ to break down? • Maybe: Phase transition occurs! • No partonicDoF → No NCQ • But no specific predictions... • Maybe: Chiral Magnetic Waves occur! • Induced quadrupole moment gives negative particles an in-plane boost • predict for negative particles always more than for positive particles Burnier, et al. Phys.Rev.Lett. 107 (2011) 052303  • Certainly: Baryon stopping occurs! • Data: At BES energies, ~50% of light quarks at midrapidity are transported from the entrance channel • what effect could this have...?

  5. More stopping… 6.41 GeV 8.86 GeV Fractions of down (up) quarks transported to midrapidity from the entrance channel Midrapidityyields of common particles from central Pb+Pb collisions measured by the NA49/SPS Collaboration At lower BES energies, ~50% of quarks are transported from the entrance channel! J. Dunlop et. al., Phys.Rev. C84 (2011) 044914

  6. Multi-component coalescence • Basic Idea • Multi-component coalescence (MCC) model: • two populations of quarks with different flows • transported (stopped) quarks with • produced quarks with • hadronization by quark coalescence specific prediction • What does MCC predict? • Hadron has two components: from transported quarks and from produced quarks. In pions, for example: produced () quarks transported () quarks produced () quarks Fractions of down (up) quarks transported to midrapidity from the entrance channel positive in MCC scenario

  7. MCC vs. CMW • What does CMW predict? • Negative particles get a boost: , regardless of species • is proportional to the Charge Asymmetry. The proportionality constant is the (positive) quadrople moment of the plasma. • What does MCC predict? • Species dependence for sign of r > 0 Prevalence of down quarks to be stopped over up quarks Charge Asymmetry • For pions, CMW and MCC give similar predictions: , in agreement with preliminary data • CMW model goes further: predicts a positive correlationbetween and • MCC model goes further: predicts a positive correlationbetween and • To compare the two, we must examine the correlation between and

  8. How are and correlated? • Why might it be a positive correlation? Well increased baryon stopping will… • Inject charge to midrapidity INCREASING • Enrich the down quark population more than the up quark population  INCREASING • (event-by-event fluctuations ofnumber of stopped baryons) • Why might it be a negative correlation? But increased isospin will… • Inject charge to midrapidity INCREASING • Enrich the up quark population more than the down quark population DECREASING • (event-by-event fluctuations ofisospin of stopped baryons) • Surely both fluctuations occur. Which type dominates? UrQMD: Pb+Pb, • Simulations show that and have a strong negative correlation! • This means that MCC predicts a negative correlationbetween and • Negative slope and non-zero intercept • Can check with data!

  9. Preliminary Data At low energies we see the same species dependence as predicted by Multi-Component Coalescence! STAR Preliminary Shusu Shi for the STAR collaboration Quark Matter 2012 “Event Anisotropy v2 in Au+Au Collisions at √sNN = 7.7 – 62.4 GeV with STAR”

  10. Preliminary Data Preliminary data show a positive correlationbetween and, as predicted by Chiral Magnetic Waves r > 0 Gang Wang for the STAR collaboration Quark Matter 2012 “Search for Chiral Magnetic Effects in High-Energy Nuclear Collisions”

  11. Summary • NCQ scaling implies partonic degrees of freedom→QGP • Can Baryon Stopping explain NCQ breakdown? Yes! ... but so can Phase Change and Chiral Magnetic Waves • Neither explanation explains data fully Phase Change No specific predictions Baryon Stopping + MCC Species dependence for : and are negatively correlated: Chiral Magnetic Waves , regardless of species: and are positivelycorrelated:

  12. Backup Slide – Slope Parameter at different energies Gang Wang for the STAR collaboration Quark Matter 2012 “Search for Chiral Magnetic Effects in High-Energy Nuclear Collisions”

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