1 / 18

Thomas K Hemmick, Stony Brook University for the PHENIX Collaboration

The PHENIX Experiment at RHIC: Can We Rewind the Clock to Catch a Glimpse Near the Beginning of Time?. Thomas K Hemmick, Stony Brook University for the PHENIX Collaboration. The Beginning of Time. Time began with the Big Bang:

markandrew
Download Presentation

Thomas K Hemmick, Stony Brook University for the PHENIX Collaboration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The PHENIX Experiment at RHIC:Can We Rewind the Clock to Catch aGlimpse Near the Beginning of Time? Thomas K Hemmick, Stony Brook University for thePHENIXCollaboration

  2. The Beginning of Time • Time began with the Big Bang: • All energy and matter of the universe was in a state of intense heat and compression. • Since then the Universe has cooled • While cooling, the material of the universe underwent several phase changes. • 2.7 Kelvin is the temperature of most of the universe today. • However, there exist a few “hot spots” where the expanding matter has collapsed back in upon itself. • What do we know and what can we learn from laboratory experiments about this past history? T.K. Hemmick

  3. Too hot for quarks to bind!!! Standard Model (N/P) Physics • Collisions of “Large” nuclei convert beam energy to temperatures above 200 MeV or 1,500,000,000,000 K • ~100,000 times higher temperature than the center of our sun. • “Large” as compared to mean-free path of produced particles. Too hot for nuclei to bind Nuclear/Particle (N/P) Physics HadronGas Nucleosynthesis builds nuclei up to He Nuclear Force…Nuclear Physics E/M Plasma Universe too hot for electrons to bind E-M…Atomic (Plasma) Physics SolidLiquidGas Today’s Cold Universe Gravity…Newtonian/General Relativity Stars convert gravitational energy to temperature. They “replay” and finish nucleosynthesis ~15,000,000 K in the center of our sun. Reheating Matter Evolution of the Universe Quark-GluonPlasma?? T.K. Hemmick

  4. Relativistic Heavy Ion Collider (RHIC)Pioneering High Energy Nuclear Interaction eXperiment (PHENIX) • 2 counter-circulating rings, 3.8 km circumference • Any nucleus on any other. • Top energies (each beam): • 100 GeV/nucleon Au-Au. • 250 GeV polarized p-p. • Maximal Set of Observables • Photons, Electrons, Muons, ID-hadrons • Highly Selective Triggering • High Rate Capability. • Rare Processes. T.K. Hemmick

  5. Nature is in Charge • RHIC provides the energy to reheat matter. • PHENIX observes the debris of the collision. • Creation of a primordial medium is out of our hands: • How and whether the collisions express the energy as new phases of matter cannot be controlled by us. • The collisions are so fleeting (Dt ~10-22 sec) the signals from a single such collision travel only several nuclear diameters before the system breaks apart. • Nature must create both the medium and its diagnostic signatures. • We set the stage and fill the audience, Nature puts on the show. T.K. Hemmick

  6. Thermally-shaped Soft Production “Well Calibrated” Hard Scattering The Medium and the Probe p+p->p0 + X • At RHIC energies different mechanisms are responsible for different regions of particle production. • The rare process (Hard Scattering or “Jets”) is the probe of whether the soft production products form a medium. • Calibrated Probe • “The tail that wags the dog” (M. Gyulassy) T.K. Hemmick hep-ex/0305013 S.S. Adler et al.

  7. schematic view of jet production leading particle hadrons q q hadrons leading particle Fate of Hard Scattered Partons • Hard scatterings in nucleon collisions produce jets of particles. • In the presence of a color-deconfined medium, the partons strongly interact (~GeV/fm) losing much of their energy. • “Jet Quenching” Once quenched, the jets could not re-appear since this would violate the 2nd Law of Thermodynamics T.K. Hemmick

  8. Particle Spectra Evolution “Central” Nuclear Physics Particle Physics K. Adcox et al, Phys Lett B561 (2003) 82-92 “Peripheral” T.K. Hemmick

  9. Nuclear Modification Factor: RAA • We define the nuclear modification factor as: • RAA is what we get divided by what we expect. • By definition, processes that scale with the number of underlying nucleon-nucleon collisions (aka Nbinary) will produce RAA=1. Au+Au->p0+X RAA is well below 1 for both charged hadrons and neutral pions. The neutral pions fall below the charged hadrons since they do not contain contributions from protons and kaons. T.K. Hemmick nucl-ex/0304022 S.S. Adler et al.

  10. Proton/deuteron nucleus collision Nucleus- nucleus collision d+Au Control Experiment • Collisions of small with large nuclei were always foreseen as necessary to quantify cold nuclear matter effects. • Recent theoretical work on the “Color Glass Condensate” model provides alternative explanation of data: • Jets are not quenched, but are a priori made in fewer numbers. • Color Glass Condensatehep-ph/0212316; Kharzeev, Levin, Nardi, Gribov, Ryshkin, Mueller, Qiu, McLerran, Venugopalan, Balitsky, Kovchegov, Kovner, Iancu • Small + Large distinguishes all initial and final state effects. T.K. Hemmick

  11. d+Au Spectra • Final spectra for charged hadrons and identified pions. • Data span 7 orders of magnitude. T.K. Hemmick

  12. RAA vs. RdA for Identified p0 Initial State Effects Only d+Au Initial + Final State Effects Au+Au d-Au results rule out CGC as the explanation for Jet Suppression at Central Rapidity and high pT T.K. Hemmick

  13. Cronin Effect: Multiple Collisions broaden high PT spectrum Charged Hadron Results • Striking difference of d+Au and Au+Au results. • Charged Hadrons higher than neutral pions. T.K. Hemmick

  14. “PHENIX Preliminary” results, consistent with PHOBOS data in submitted paper Centrality Dependence Au + Au Experiment d + Au Control Experiment • Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control. • Jet Suppression is clearly a final state effect. Final Data Preliminary Data T.K. Hemmick

  15. Escaping Jet “Near Side” Lost Jet “Far Side” “PHENIX Preliminary” results, consistent with STAR data in submitted paper The “Away-Side” Jet • Jets produced on the periphery of the collision zone coming out should survive. • However, their partner jet will necessarily be pointed into the collision zone and be absorbed. d+Au Au+Au 60-90% Min Bias 0-10% Near Far Near Far PHENIX Preliminary PHENIX Preliminary • Peripheral Au+Au similar to d+Au • Central Au+Au shows distinct reduction in far side correlation. • Away-side Jet is missing in Au+Au T.K. Hemmick

  16. What’s Next • We must investigate other probes that look deeply into the medium to characterize it. • Same paradigm, The Rare Processes Probe the Medium: • Heavy Quark States • Dissolution of J/Y & Y’, the bound states of charm-anticharm quarks probes quark deconfinement. • Electromagnetic Probes (no strong interaction) • Lack of strong interaction allows them to penetrate the black medium and see through the hadronic veil • Direct Photons, e+e-, m+m- • PHENIX plans to make these measurements in the next Au+Au run. T.K. Hemmick

  17. Summary • We have seen via Au+Au Jet Quenching and the d+Au control experiment that a medium with strong final state effects is formed in Au+Au collisions at RHIC. • Our announcement today is that we indeed have the opportunity to learn about the conditions of our universe soon after the Big Bang. • We have set the stage and Nature has granted us a show. We will measure the properties of the medium and will learn whether or not the quarks are confined. • It would be presumptuous without having measured the additional medium probes to now label the medium in accordance with our preconceptions as being the Quark-Gluon Plasma. • Nature has been known to include surprise endings, the observation and understanding of which represent the real progress in science. T.K. Hemmick

  18. T.K. Hemmick

More Related