Exploring Properties of QCD with Proton-Nucleus and Deuteron-Nucleus Collisions

1. Exploring Properties of QCD with Proton-Nucleus and Deuteron-Nucleus Collisions Principal Investigator Stephen Johnson N-Division Co-Investigators Jane Burward-Hoy N-Division Ed Hartouni N-Division Mike Heffner N-Division Ron Soltz N-Division June 18, 2002

2. In this LDRD we propose to: • Develop the capability to characterize proton-nucleus interactions • Add that capability to an existing experiment at the Relativistic Heavy Ion Collider (RHIC): PHENIX • Obtain, analyze, and publish the data from this experiment • Resolve a physics puzzle essential for studying a predicted phase transition in quantum-chromodynamics: the Quark-Gluon Plasma (QGP) • Clear understanding of bulk properties of QCD • Strong force in quantitatively different regime • Astrophysical observations • Properties of the early universe

3. early universe 250 RHIC quark-gluon plasma 200 Chemical Temperature Tch [MeV] Lattice QCD SPS 150 AGS deconfinement chiral restauration thermal freeze-out 100 SIS hadron gas 50 neutron stars atomic nuclei 0 0 200 400 600 800 1000 1200 Baryon Potential B [MeV] (Nuclear Density) The Quark Gluon Plasma Increase Density (or temperature) No. 7Are there new states of matter at ultrahigh temperatures and densities?

4. RHIC and the PHENIX Experiment • RHIC complex designed to study the plasma. • Premier U.S. facility • 1st NSAC** recommendation • A+A, p+p, p+A, A1+A2 • 2 years of data collection: Au+Au, p+p • PHENIX one of 2 large heavy ion experiments (4 total) • 450 collaborators world-wide Livermore designed and built the magnet **NSAC = Nuclear Science Advisory Committee

5. A “typical” event

6. Rside Rside Rout Rout No Plasma Rside Rout theory YieldAuAu/(Nbinary*Yieldpp) With Plasma Plasma opacity experiment Has the plasma been observed? • PHENIX HBT (source size) measurements  short collision lifetime inconsistent with plasma existence • LDRD: 00-ERD-026 • Phys. Rev. Lett. 88, 192302 (2002), written by Soltz and Johnson • Deficit of high momentum particles  high opacity consistent with plasmaexistence • Phys. Rev. Lett. 88, 022301 (2002), Cover and Phys. Rev. Focus Contradictory Signals! Resolution requires further experiment.

7. Proton-Nucleus (Precision Comparisons) Proton-proton  “Hadron Gas” Nucleus-nucleus  QGP(?)  Hadron Gas Proton-nucleus  Hadron Gas Nparticipants = 2 Nbinary = 1 Nparticipants –1 = Nbinary= n In absence of QGP AA= Nbinary*pp?? =pp pA(Nbinary)= Nbinary*pp?? Need to measure grey/black nucleons for Nbinary measurement

8. Simple scaling with Nbinary doesn’t work Npart expectation • Best example of physics from pA centrality is E910 (Co-spokesperson: Ron A. Soltz) at lower energies (AGS) • LDRD 97-ERD-058 • PRL 85 (2000) 4868 • PRC 60 (1999) 024902 • Mystery of ‘strangeness enhancement’ solved by detailed understanding of strangeness production • We propose to measure Nbinary for accurate comparison of pA with AA • Method: • Use grey (knock-out) & black (evaporation) protons Nbinary Need to understand dynamics of proton nucleus collisions

9. Proposed calorimeter 18m Interaction Region Can we apply E910 methodology to RHIC? • Difficulty: measure fragmentation protons in a collider setting • Energy = 100 GeV • Angle = <1 mrad • Our Solution: • Hadron calorimeter downstream of beam magnet • No RHIC Experiment currently has the capability to measure forward protons. PHENIX Experiment Beam pipe Beam pipe Yes, and we can provide a new capability to the scientific community

10. Scrounge-a-cal • State-of-the-art Pb-Sci calorimeter modules fromBNL-E864 experiment • ~$1M • Unused for 5 years • With good energy/timing resolution • Enough sectors for upgrade to all four RHIC experiments • This LDRDPHENIX • Jan `02: PHENIX project management approval of upgrade Data and analysis from LLNL upgrade will resolve the puzzling results

11. Team • Young*, “best and brightest” • Proven recruitment record: • from 25 in 3 years • PHENIX publications year-1 data: • 6 Phys. Rev. Lett. so far • 3 with Livermore stamp • Authorship, simulations, analysis • 1 in preparation (Phys. Rev. C) • Recognized experts in source size (PHENIX, E802) and proton-nucleus (E910, E907) physics • All members spend part- time working on a PDRP funded lower energy proton-nucleus experiment at FNAL (E907)

12. Budget This LDRD buys the physics Outside funds buy the hardware: PHENIX Management: Electronics ($20k) DOE/PHENIX: Support structures + cables ($30k) BNL: E864 calorimeter ($1M) Plan to hire 1 FTE soon G. Kunde (Yale) interviewing in June DOE-OS grant covers 1 postdoc equivalent Leveraged from previous LDRD Expect to increase DOE support to 2 postdocs over course of this LDRD FY03: Commission detectorin PHENIX FY04, FY05: Collect data Analyze results Publish in peer reviewed literature Timescales and Budget

13. In this LDRD we propose to: • Develop the capability to characterize proton-nucleus interactions • Add that capability to an existing experiment at theRelativistic Heavy Ion Collider (RHIC): PHENIX • Obtain, analyze, and publish the data from this experiment • Resolve a physics puzzle essential for studying a predicted phase transition in quantum-chromodynamics: the Quark-Gluon Plasma (QGP) • Clear understanding of bulk properties of QCD • Strong force in quantitatively different regime • Astrophysical observations • Properties of the early universe