Quarks and Gluons in the Nuclear Medium – Opportunities at JLab@12 GeV and an EIC

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Quarks and Gluons in the Nuclear Medium – Opportunities at JLab@12 GeV and an EIC. Rolf Ent, ECT-Trento, June 06, 2008. Nuclear Medium Effects on the Quark and Gluon Structure of Hadrons Main Workshop Topics Nuclear effects in polarized and unpolarized deep inelastic scattering - PowerPoint PPT Presentation

Text of Quarks and Gluons in the Nuclear Medium – Opportunities at JLab@12 GeV and an EIC

  • Quarks and Gluons in the Nuclear Medium Opportunities at JLab@12 GeV and an EICRolf Ent, ECT-Trento, June 06, 2008Nuclear Medium Effects on the Quark and Gluon Structure of Hadrons

    Main Workshop Topics

    Nuclear effects in polarized and unpolarized deep inelastic scattering Nuclear generalized parton distributions Hard exclusive and semi-inclusive processes Nuclear hadronization Color transparency Future facilities and experiments

  • The Quark Structure of Nuclei

  • The QCD Lagrangian and Nuclear Medium ModificationsLeinweber, Signal et al.The QCD vacuumLong-distance gluonic fluctuationsDoes the quark structure of a nucleon get modified by the suppressed QCD vacuum fluctuations in a nucleus?

  • Quarks in a NucleusEffect well measured,over large range of x and A, but remains poorly understood1) ln(A) or r dependent?Observation that structure functions are altered in nuclei stunned much of the HEP community ~25 years ago2) valence quark effect only?A=3 EMC Effect at 12 GeV

  • E772Is the EMC effect a valence quark phenomenon or are sea quarks involved?Anti-Quarks in a NucleusSolution: Detect a final state hadron in addition to scattered electronDeep inelastic electron scattering probes only the sum of quarks and anti-quarks requires assumptions on the role of sea quarks Can tag the flavor of the struck quark by measuring the hadrons produced: flavor taggingTremendous opportunity for experimental improvements!

  • g1(A) Polarized EMC EffectNew calculations indicate larger effect for polarized structure function than for unpolarized: scalar field modifies lower components of Dirac wave functionSpin-dependent parton distribution functions for nuclei nearly unknownCan take advantage of modern technology for polarized solid targets to perform systematic studies Dynamic Nuclear Polarization

  • Miller, SmithValence only calculations consistent with Cloet, Bentz, Thomas calculations

    Same model shows small effects due to sea quarks for the unpolarized case (consistent with data)Large enhancement for x>0.3 due to sea quarksSea is not much modifiedChiral Quark-Soliton model(quarks in nucleons (soliton) exchange infinite pairs of pions, vector mesons with nuclear medium)

  • New calculations indicate larger effect for polarized structure function than for unpolarized: scalar field modifies lower components of Dirac wave functionSpin-dependent parton distribution functions for nuclei nearly unknownCan take advantage of modern technology for polarized solid targets to perform systematic studies Dynamic Nuclear PolarizationCurve follows calculation by W. Bentz, I. Cloet, A. W. Thomas.g1(A) Polarized EMC Effect

  • Extend measurements on nucleito x > 1: Superfast quarksCorrelated nucleon pairSix-quark bag (4.5% of wave function)Fe(e,e)5 PAC daysMean field

  • Does the quark structure of a nucleon get modified by the suppressed QCD vacuum fluctuations in a nucleus? Measure the EMC effect on the mirror nuclei 3H and 3HeIs the EMC effect a valence quark only effect?Is the spin-dependent EMC effect larger?Can we reconstruct the EMC effect on 3He and 4He from all measured reaction channels?Is there any signature for 6-quark clusters?Can we map the effect vs. transverse momentum/size?Reminder: EMC effect is effect that quark momenta in nuclei are alteredNow: use the nuclear arena to look for QCD

  • Use the Nuclear Arena to Study QCD

  • Total Hadron-Nucleus Cross SectionsHadron Nucleustotal cross sectionFit toaKppp_Hadron momentum60, 200, 250 GeV/ca < 1 interpreted as due to the strongly interacting nature of the probe A. S. Carroll et al. Phys. Lett 80B 319 (1979) a = 0.72 0.78, for p, p, k

  • Traditional nuclear physics expectation: transparency nearly energy independent.T1.0Energy (GeV)Ingredients s h-N cross-section

    Glauber multiple scattering approximation(or better transport calculation!)

    Correlations & Final-State Interaction effects hNPhysics of Nuclei: Color Transparency From fundamental considerations (quantum mechanics, relativity, nature of the strong interaction) it is predicted (Brodsky, Mueller) that fast protons scattered from the nucleus will have decreased final state interactionsQuantum ChromoDynamics:A(e,eh), h = hadron

  • Search for Color Transparency in Quasi-free A(e,ep) ScatteringConstant value line fits give good description:c2/df = 1

    Conventional Nuclear Physics Calculation by Pandharipande et al. (dashed) also gives good descriptionFit to s = soAa a = constant = 0.75Close to proton-nucleus total cross section data No sign of CT yeta

  • Physics of Nuclei: Color Transparency AGSA(p,2p)Glauber calculationResults inconsistent with CT only. But can be explained by including additional mechanisms such as nuclear filtering or charm resonance states.The A(e,ep) measurements will extend up to ~10 GeV/c proton momentum, beyond the peak of the rise in transparency found in the BNL A(p,2p) experiments.

  • Physics of Nuclei: Color Transparency Total pion-nucleus cross section slowly disappears, or pion escape probability increases Color Transparency Unique possibility to map out at 12 GeV (up to Q2 = 10)Total pion-nucleus cross section slowly disappears, or pion escape probability increases Color Transparency? A(e,ep+)

  • Physics of Nuclei: Color Transparency A(e,er+) at 12 GeV(at fixed coherence length)12 GeV

  • Using the nuclear arenaHow long can an energetic quark remain deconfined?How long does it take a confined quark to form a hadron? Formation time tfhProduction time tpQuark is deconfinedHadron is formedHadron attenuationCLASTime required to produce colorless pre-hadron, signaled by medium-stimulated energy loss via gluon emissionTime required to produce fully-developed hadron, signaled by CT and/or usual hadronic interactions

  • Using the nuclear arenadE/dx ~ LDE ~ L (QED) ~ L2 (QCD)? How long can an energetic quark remain deconfined?How long does it take a confined quark to form a hadron?

    Or How do energetic quarks transform into hadrons? How quickly does it happen? What are the mechanisms?

  • How long can an energetic quark remain deconfined?How long does it take a confined quark to form a hadron?

    Or How do energetic quarks transform into hadrons? How quickly does it happen? What are the mechanisms? Deep Inelastic ScatteringRelativistic Heavy-Ion CollisionsInitial quark energy is knownProperties of medium are knownUsing the nuclear arenaRelevance to RHIC and LHC

  • DpT2 vs. n for Carbon, Iron, and LeadCPbFeDpT2 (GeV2)n (GeV)~ 100 MeV/fm (perturbative formula) ~dE/dxPreliminaryCLASHall B

  • Production length from JLab/CLAS 5 GeV data (Kopeliovich, Nemchik, Schmidt, hep-ph/0608044)What we have learned Quark energy loss can be estimated Data appear to support the novel DE ~L2 LPM behavior ~100 MeV/fm for Pb at few GeV, perturbative formula Deconfined quark lifetime can be estimated, ~ 5 fm @ few GeV

    Outstanding questions Higher energy data to confirm plateau for heavy (large-A) nuclei Much more theoretical work needed to provide a quantitative basis for jet quenching at RHIC/LHC?

  • Using the nuclear arenaDpT2 reaches a plateau for sufficiently large quark energy, for each nucleus (L is fixed). DpT2nProjected Data

  • DOE Project Critical DecisionsCD-0 Approve Mission Need

    CD-1 Approve Alternative Selection and Cost RangePermission to develop a Conceptual Design ReportDefines a range of cost, scope, and schedule options

    CD-2 Approve Performance BaselineFixes baseline for scope, cost, and scheduleNow develop design to 100%Begin monthly Earned Value progress reporting to DOEPermission for DOE-NP to request construction funds

    CD-3 Approve Start of ConstructionDOE CD3 (IPR/Lehman) review scheduled for July 22-24DOE Office of Science CD-3 Approval meeting in late Sept 2008

    CD-4 Approve Start of Operations or Project Close-out

  • DOE CRITICAL DECISION SCHEDULE(A) = Actual Approval Date

    CD-0 Mission NeedMAR-2004 (A)CD-1 Preliminary Baseline RangeFEB-2006 (A)CD-2 Performance BaselineNOV-2007 (A)CD-3 Start of ConstructionSEP-2008CD-4A Accelerator Project Completion and Start of OperationsDEC-2014CD-4B Experimental Equipment Project Completion and Start of OperationsJUN-2015

  • 2004-2005 Conceptual Design (CDR) - finished2004-2008 Research and Development (R&D) - ongoing2006 Advanced Conceptual Design (ACD) - finished2006-2009 Project Engineering & Design (PED) - ongoing2009-2014 Construction starts in ~1/2 year!Parasitic machine shutdown May 2011 through Oct. 2011Accelerator shutdown start mid-May 2012Accelerator commissioning start mid-May 20132013-2015 Pre-Ops (beam commissioning)Hall A commissioning start October 2013Hall D commissioning start April 2014Halls B and C commissioning start October 201412 GeV Upgrade: Phases and Schedule(based on funding guidance provided by DOE-NP in June-2007)

  • The Gluon Structure of Nuclei

  • Gluons dominate QCDQCD is the fundamental theory that describes structure and interactions in nuclear matter.Without gluons there are no protons, no neutrons, and no atomic nucleiFacts:The essential features of QCD (e.g. asymptotic freedom, chiral symmetry breaking, and color confinement) are all driven by the gluons!Unique aspect of QCD is the self interaction of the gluons98% of mass of the visible universe arises from glueHalf of the nucleon momentum is carried by gluonsHowever, gluons are dark: they do not interact directly with light high-energy collider!

  • *The Low Energy View of Nuclear Matter nucleus = protons + neutrons nucleon quark model q