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Charge Transport in High-Energy Hadron Collisions

Charge Transport in High-Energy Hadron Collisions. Paul Stankus, ORNL PANIC 05. The most interesting question at RHIC (IMHO). Allowing that “the bulk” of hadrons produced in a RHIC A+A collision are from the decay of an extended QGP, then: How does “the bulk” form?  Initial transport?

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Charge Transport in High-Energy Hadron Collisions

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  1. Charge Transport in High-Energy Hadron Collisions Paul Stankus, ORNL PANIC 05

  2. The most interesting question at RHIC (IMHO) Allowing that “the bulk” of hadrons produced in a RHIC A+A collision are from the decay of an extended QGP, then: How does “the bulk” form? Initial transport? Initial thermalization? Au+Au 200 GeV PHOBOS, Nucl. Phys. A 757, 28 Paul Stankus, ORNL

  3. Transport of conserved quantities BRAHMS, Phys Rev Lett 90, 102301 (2003) Example:Baryon number How does it get to mid-rapidity? How does it get to high pT? Cannot be treated easily in pQCD! PHENIX, Phys. Rev. C 69, 024904 (2004) Paul Stankus, ORNL

  4. Model of a meson q e+ String Break { q q q q q q { e- Meson Formed Position or Velocity Low-brow review of color strings How do we model this process? e+ hadrons hadrons q e- Paul Stankus, ORNL

  5. Enter the Diquark, an anti-colored object (in this case, red+green = anti-blue) qq Model of a Baryon q qq Baryon Formed e+ { q { Baryon Meson Proton { e- { Antibaryon Formed q q qq Proton (Second string not shown) Extension to baryons Baryon transport combinatoric! Paul Stankus, ORNL

  6. Too many baryons? Exponential transport not observed! BRAHMS Phys Rev Lett 93 102301 (2004) Paul Stankus, ORNL

  7. The Junction: A legal QCD object Gluon fields Electrically neutral J J J New Model of a Baryon Proton q q { q Proton Baryon Enter the Junction Montanet, Rossi, Veneziano, Phys Rept. 63 (1980)Kharzeev, Phys LettB378 (1996) Baryon number transported separately from quarks Paul Stankus, ORNL

  8. What’s the big idea? We can measure baryon transport and charge transportindependently and distinguish between different mechanisms: Pure junction stopping Pure quark stopping Paul Stankus, ORNL

  9. A simple plan Assume: All charge in p±, K±, p,pbar All baryon number in p, n, L Notation: “p+” = dNp+/dY “pNet” = p+ - p- = dNp+/dY - dNp-/dY Strategy: Examine RHIC A+A, d+A, p+p, ISR data In theory look at N+-N- = pNet+ KNet + pNet In practice look at (pNet+KNet)/pNet Paul Stankus, ORNL

  10. Junction stopping Quark stopping Paul Stankus, ORNL

  11. 0 Pure Quark -1 Pure Junction Examine RHIC central Au+Au, Y~0, 200 GeV PRL 93 102301 (2004) PRL 94 162301 (2004) PHOBOS PRC 67 021901 (2003) BRAHMS PRL 90 102301 (2003) Dominant! Similar conclusion for RHIC p+p and d+Au data. Paul Stankus, ORNL

  12. Conclusions Inconclusive! at least, with current data pbar/p measures baryon stopping; ±5% precision needed p-/p+ measures charge stopping; ±0.5% precision needed Current RHIC experiments can probably achieve this…. …but how would you design a new precision low-pT experiment? Next: Fix up this calculation (include S±, ISR data, mQ, etc.) Charge transport vspT or YT Control input charges: p+A vsn+A, or Paul Stankus, ORNL

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