From JLab12 to EIC: QCD in nuclei

Transcription

1 The EIC Science case: a report on the joint BL/IT/JLab program Gluons and the quark sea at high energies: distributions, polarization, tomography Institute for uclear Theory, University of Washington, USA September 3 to ovember 9, 00 Editors: D. Boer, Universiteit Groningen, The etherlands M. Diehl, Deutsches Elektronen-Synchroton DESY, Germany R. Milner, Massachusetts Institute of Technology, USA R. Venugopalan, Brookhaven ational Laboratory, USA W. Vogelsang, Universität Tübingen, Germany Brookhaven ational Laboratory, Upton, Y Institute for uclear Theory, Seattle, WA Thomas Jefferson ational Accelerator Facility, ewport ews, VA From JLab to EIC: QCD in nuclei C. Weiss (JLab), 08 JLab User Group Meeting, 9-Jun-08 e A e ucleon interactions Hadronic and QCD description on-nucleonic degrees of freedom Partonic structure of nuclei EMC effect > 0.3 JLab, EIC interactions Antishadowing 0. EIC Shadowing, coherence 0. UPC, EIC onlinear effects and saturation arxiv:08.73v [nucl-th] 8 ov 0 arxiv:.70v3 [nucl-e] 30 ov 04 QCD phenomena in final states Color transparency, propagation JLab, EIC

2 ucleon interactions: Contet Q: How do nucleon interactions arise from QCD? Intellectual gain: Emergent phenomena General concept in comple systems Predictive power: EFT methods and matching Effective DoF and dynamics at scales M π, ǫ d m Import short-distance information through effective interactions derived from QCD Etreme temperatures and densities Astrophysical systems, neutron stars, early universe Heavy-ion collisions

3 ucleon interactions: Hadronic description 3 r = + + T M +... Interactions involve non-nucleonic degrees of freedom: QM + relativity Low-energy nuclear structure and reactions (k k F ) do not resolve intermediate states: potential, EFT contact interactions V(r) fm fm r High-energy processes can resolve intermediate states: Origin of interactions JLab 6/ GeV: Short-range correlations, high-momentum components Talks Cruz Torres, Schmookler, Schmidt, Hauenstein

4 ucleon interactions: QCD description 4 = configs qqq... qq...g... coherent superposition int = (...) (...) + other configs! interactions change superposition of quark/gluon configurations compared to free nucleons ( non-nucleonic DoF) Frankfurt, Strikman 8+ High-energy short-distance processes on nuclei (DIS, etc.) can give insight into QCD origin of interactions

5 ucleon interactions: uclear parton densities 5 A PDF Σ = +... "interactions" DIS on nucleus: QCD factorization, nuclear PDF A Ô QCD (µ ) A Compare nuclear PDF with sum of nucleons Fermi motion interactions Physical questions What are the modifications of quarks/gluon densities at different? What are the relevant distances in the nucleon interactions? What are the relevant non-nucleonic configurations/states? Different interactions & configurations are at work at different!

6 ucleon interactions: Physical regimes 6 uclear quark ratio R uv () EPPS6 µ =.69 GeV A = shadowing antishadowing u valence EMC effect uclear gluon ratio R g () EPPS6 µ =.69 GeV A = gluons 0.3 < < 0.8 EMC effect 0.05 < 0. antishadowing < 0.0 shadowing Global analysis Eskola et al. 6 EMC effect Suppression of valence quark density in nucleus Likely caused by short-range interactions r < fm Configurations? Dynamical models and critique Review: Malace, Gaskell, Higinbotham, Cloet 4 Basic properties unknown: Isospin, spin dependence? Gluons? Distances?

7 EMC effect: JLab Ca 48 Ca - no isoscalar dependence 48 Ca - with isoscalar dependence Leading vs. higher twist Q scaling of F A at large uclear dependence of R = σ L /σ T Ca/ 48 Ca Relative orm. (.4%) Isospin dependence 3 H 3 He comparison, 40 Ca/ 48 Ca ratio EMC ratios Q = 5GeV ρ = 0.6fm 3 I. Sick and D. Day, Phys. Lett. B 74, 6 (99). EMC effect Polarized EMC effect Polarized valence quarks Model predictions Cloet, Bentz, Thomas 05+ [ Tagging, EMC-SRC connection later JLab: Comprehensive study of EMC effect in valence quarks

8 EMC effect: EIC 8 uclear gluon ratio g A () / [A g ()] present uncertainty EPS09 with EIC F (charm) µ = GeV A = Gluonic EMC effect? Relevant quark/gluon configurations? EIC: Q -dependence of F A,F LA Wide kinematic coverage EIC: Heavy quark production Good sensitivity to large- gluons e, A e B, Q G, A c, b _ c, b () _ Medium-energy collider well suited (e/ 0/00 GeV) ew methods of charm reconstruction Feasibility and impact studied JLab LDRD Project 06/7 CW et al. [webpage] [arxiv: ], [arxiv: ] See also: Aschenauer et al. PRD (07)

9 EMC effect: Tagging 9 What distances cause modification? e e d uclear breakup detection can control nucleon configuration during DIS process Deuteron: Spectator nucleon tagging average size small size JLab: Tagged DIS eperiments CLAS BOuS, Hall A Talk Horn EIC: Spectator tagging program e e Forward detection of p, n d pol. High energy process p, n Forward detection Good coverage and momentum resolution Polarized deuteron tagging possible JLab 04/5 LDRD project CW et al. [webpage] Theoretical questions Initial-state effects vs. final-state interactions in spectator momentum distribution Ciofi degli Atti, Kopeliovich, Kaptari 03+; Strikman CW 08

10 Antishadowing: Physics 0 uclear quark ratio R uv () EPPS6 µ =.69 GeV A = shadowing antishadowing u valence EMC effect uclear quark ratio R u () EPPS6 µ =.69 GeV A = u sea uclear gluon ratio R g () EPPS6 µ =.69 GeV A = gluons Enhancement of nuclear quark density q + q at 0. Likely caused by interactions at average distances Quarks vs. antiquarks, flavor separation? ucleon interactions through quark or meson echange? Gluon antishadowing? Gluon shadowing at 0. requires compensating antishadowing for momentum sum rule. Dynamical model: Frankfurt, Guzey, Strikman 7 quark echange meson echange

11 Antishadowing: EIC e e h =, π + π K +, K Charge-flavor separation of nuclear PDFs at 0. with semi-inclusive π ±,K ± Same techniques as ep SIDIS u, u, d, d D f h () Separate charges/flavors using cross section ratios A q f ( ) Distinguish initial-state effects from nuclear final-state interactions using A dependence e Simulations in progress Zhihong Ye, Hauenstein, Higinbotham, CW e B, Q c, b _ c, b _ uclear gluons at 0. with open charm Large antishadowing effect epected, A G, A () Enlarged data set for global analysis

12 Shadowing: Physics X A PDF = (same ) + A... A ucleon: Removal of gluon with 0. can leave nucleon intact g + X +. Diffraction. Observed at HERA uclear gluon density: Interference of gluon attachments to different nucleons Interaction effect. QCD analogue of Gribov s theory of shadowing 70s Suppresses nuclear gluon density at 0.. Shadowing. Leading-twist effect! Calculable in terms of diffractive nucleon PDF and nuclear wave function Frankfurt, Guzey, Strikman + Coherent phenomenon, result of action of multiple nucleons

13 Shadowing: Ultraperipheral collisions LHC 3 A A S Pb CMS ALICE LTA+CTEQ6L EPS09 HK07 nds UPCs at LHC enable high-energy photoproduction W GeV Coherent J/ψ production data support leading-twist gluon shadowing γ + A J/ψ + A, involves theoretical analysis Open questions Test interference mechanism? Leading vs. higher-twist shadowing? Quark vs. gluon shadowing, singlet/nonsinglet?

14 Shadowing: EIC 4 X X n p + n p b interference Shadowing in tagged DIS on deuteron Guzey, Strikman, CW, in progress Large shadowing effect in recoil momentum dependence Detailed test of interference mechanism in = system = 3 shadowing from other light ions: 3 He, 4 He,... Shadowing in coherent scattering: Impact parameter dependence Guzey et al., Kowalski, Caldwell 0 Gluon shadowing from global PDF analysis Leading vs. higher twist

15 onlinear effects and saturation 5 ew dynamical scale in nuclei at small small gluons large sources Q s () gluons / transverse area on-linear evolution equations with recombination Balitsky, Kovchegov; JIMWLK Classical fields: Color Glass Condensate McLerran, Venugopalan Phenomena p T Q s in forward hadron/jet production in pa/γa/γ A Correlations and multiple hard processes in pa/aa Breakdown of Bjorken scaling in F A,F LA Etreme form of nucleon interactions LHC pa/γa forward hadron/jet production will see whether it is there: Highest energy/smallest, final-state signatures EIC ea/γa can eplain how it happens: Shadowing, initial condition of small evolution, Q -dependence, transverse geometry

16 QCD phenomena in final states 6 l coh Color transparency Q r Fundamental prediction of QCD σ r (r 0) EIC: l coh R A, Q few 0 GeV ecessary for saturation: Disappearance Color propagation in matter Talk Mineeva time t col thad Mechanisms: Energy loss, attenuation? Time scales: Color neutralization, hadron formation Q, ν? h JLab: Hadronization inside nucleus EIC: ν 0 00 GeV. Move hadronization in/out Q dependence, heavy-quark probes Jets and substructure in ea ew area for EIC. Great interest. Synergies with heavy-ion physics. Topical workshops 08

17 Summary 7 ucleon interactions in QCD as unifying perspective et step after nucleon structure JLab and EIC complementary JLab: Short-range correlations, EMC effect in valence quarks EIC: EMC effect of gluons, antishadowing, shadowing, approach to saturation Tagging etends physics reach of nuclear DIS measurements Control nuclear configuration during high-energy process EIC physics program in contet of LHC Ultraperipheral collisions eplore energy frontier in EM processes onlinear effects should be seen in pa/γa Much to do for EIC: Control partonic kinematics, Q -dependence, initial condition for small- evolution,...