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Electron Ion Collider

Electron Ion Collider. A. Accardi, R. Ent, V. Guzey, Tanja Horn, C. Hyde, A. Prokudin, P. Nadel-Turonski, C. Weiss, … + CASA/accelerator team. LRP 2007. INT10-3 program. EIC White Paper. JLab User Workshops 2010. EIC half recommendation. >500 pages. Under construction.

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Electron Ion Collider

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  1. Electron Ion Collider A. Accardi, R. Ent, V. Guzey, Tanja Horn, C. Hyde, A. Prokudin, P. Nadel-Turonski, C. Weiss, … + CASA/accelerator team LRP 2007 INT10-3 program EIC White Paper JLab User Workshops 2010 EIC half recommendation >500 pages Under construction

  2. Tanja Horn, Electron Ion Collider, JLab Strategic Planning 2011 EIC: Probing the Sea Quarks and Gluons Why care about sea quarks and gluons • Structure of proton • Naïve quark model: proton==uud (valence quarks) • QCD: proton == uud + + + + … • Proton sea has a non-trivial structure and • QCD and Origin of Mass • 99% of the proton mass/energy is due to the self-generating gluon field • Higgs mechanism has almost no role there • Similarity of mass between proton/neutron arises from fact that gluon dynamics are the same • Quarks contribute almost nothing Proton is far morethan just its up + up+down (valence) quark structure

  3. Internal Landscape of the Nucleon Q2 ~ xys • Hadrons in QCD are relativistic many-body systems • Fluctuating number of elementary quark and gluon constituents • Rich structure of the wave function • Components probed in ep scattering: • JLab 12 GeV: valence region • EIC: probes sea quark and gluon components Accessible range of energies and resolution, Q2, for probing components of the hadron wave function • Key physical interests • Transverse spatial distribution • Correlations: transverse, longitudinal, and nuclear modifications • Tests of reaction mechanism radiative gluons/sea valence quarks/gluons sea quarks/gluons

  4. Tanja Horn, Electron Ion Collider, JLab Strategic Planning 2011 Why an Electron-Ion Collider? • Spin physics with high Figure Of Merit (FOM) • Unpolarized FOM= Rate = Luminosity x Cross Section x Acceptance • Polarized FOM = Rate x (Target Polarization)2 x (Target Dilution)2 • No dilution and high ion polarization (also transverse) • No current (luminosity) limitations, no holding fields (acceptance) • No backgrounds from target (Moller electrons) • Easier to reach high Center of Mass energies ( ) • for colliders (e.g., 4 x 10 x 100=4000 GeV2) • for fixed target experiments (e.g., 2 x 11 x 0.938=20 GeV2) • Easier detection of reaction products • Can optimize kinematics by adjusting beam energies • More symmetric kinematics improve acceptance, resolution, particle ID, etc. • Access to neutron structure with deuteron beams ( )

  5. Science of an EIC: Explore and Understand QCD [INT10-3 2010] • Map the spin and spatial quark-gluon structure of nucleons • Image the 3D spatial distributions of gluons and sea quarks through exclusive J/Ψ, γ (DVCS) and meson production • Measure ΔG, and the polarization of the sea quarks through SIDIS, g1, and open charm production • Establish the orbital motion of quarks and gluons through transverse momentum dependent observables in SIDIS and jet production Needs high luminosity and range of energies • Discover collective effects of gluons in nuclei • Explore the nuclear gluon density and coherence in shadowing through e + A → e‘ + X and e + A → e‘ + cc + X • Discover novel signatures of dynamics of strong color fields in nuclei at high energies in e + A → e’ + X(A) and e + A → e’ + hadrons + X • Measure gluon/quark radii of nuclei through coherent scattering γ* + A → J/Ψ+ A • Understand the emergence of hadronic matter from quarks and gluons • Explore the interaction of color charges with matter (energy loss, flavor dependence, color transparency) through hadronization in nuclei in e + A → e' + hadrons + X • Understand the conversion of quarks and gluons to hadrons through fragmentation of correlated quarks and gluons and breakup in e + p → e' + hadron + hadron + X

  6. 3D partonic picture of the nucleon Information about 3D partonic picture is encoded in Generalized Parton Distributionsand Transverse Momentum Dependent Distributions Wigner distribution Transverse Momentum Dependent distributions Generalized Parton Distributions SIDIS DES

  7. Tanja Horn, Electron Ion Collider, JLab Strategic Planning 2011 Transverse Spatial Imaging through GPDs Mesons select definite charge, spin, flavor component of GPD ~30 days, L=1034 s-1cm-2 Cross section √s~30 GeV 40<W2<60 GeV2 pointlike? π, ρ, K, K* J/Ψ, φ γ EIC: Gluon size from J/Y and felectroproduction (Q2 > 10 GeV2) 80<W2<100 GeV2 [Weiss INT10-3 report] -t (GeV2) ~100 days, ε=1.0, L=1034 s-1cm-2 Λ, Σ 1.6E-3< xB < 2.5E-3 EIC: singlet quark size from deeply virtual compton scattering √s~140 GeV 3<Q2<6 GeV2 √s~140 GeV [Geraud, Moutarde, Sabatie 10+, INT10-3 report] ep → e'π+n ep → e'K+Λ EIC: Imaging of strange sea quarks! ~100 days, ε=1.0, L=1034 s-1cm-2 √s~30 GeV EIC enables a comprehensive program of transverse imaging of gluons and sea quarks -t (GeV2) [Horn et al. 08+, INT10-3 report]

  8. Image the Transverse Momentum of the Quarks 3D partonic picture is encoded in TMDs Only a small subset of the (x,Q2) landscape has been mapped here: terra incognita Gray band: present “knowledge” of TMDs with current experimental data Dark gray band: EIC (1) [Prokudin, Qian, Huang] [Prokudin, Qian, Huang] Exact kT distribution presently poorly known! Mapping of kT distribution is crucial to our understanding of interplay of collinear and 3D partonic pictures An EIC with good luminosity & high transverse polarization is the optimal tool to study this!

  9. Nucleon Structure: Orbital Motion Goal: explore quark/gluon orbital motion and its polarization dependence through both deep exclusive and semi-inclusive multi-dimensional processes Potential new insight from jets or p’T of target fragmentation? EIC: wide kinematic range low to high pT Can we learn about orbital motion from a comprehensive approach based on TMDs, GPDs, etc., even if model-dependent?

  10. Gluons in Nuclei What do we know about gluons in a nucleus? Ratio of gluons in lead to deuterium NOTHING!!! • EIC: access gluons through FL (needs variable energy) and dF2/dln(Q2) • Knowledge of gluon PDF essential for quantitative studies of onset of saturation

  11. L p+ e’ pT g* DpT2 = pT2(A) – pT2(2H) e Hadronization: Parton propagation in matter EIC: Explore the interaction of fast color charges with matter • Time scales for color neutralization • tCN and hadron formation tF • eA/gA complementary to jets in AA: • cold vs. hot matter EIC: Understand the conversion of color charge to hadrons through fragmentation and breakup DpT2 vs. Q2 • Comprehensive studies possible: • wide range of energy v = 10-100 GeV •  move hadronization inside/outside nucleus, distinguish energy loss and attenuation • wide range of Q2: QCD evolution of fragmentation functions and medium effects • Hadronization of charm, bottom •  Clean probes with definite QCD predictions • High luminosity •  Multi-dimensional binning and correlations • √s > 30: jets and their substructure in eA [Accardi, Dupre INT10-03 Report]

  12. To cover the physics we need… s Q2 ~ xys s Range in y • For large or small y, uncertainties in the kinematic variables become large • Detecting only the electronymax / ymin ~ 10 • Also detecting all hadrons ymax / ymin ~ 100 • Requires hermetic detector (no holes) C. Weiss Range in s C. Weiss C. Weiss [Weiss 09] • Accelerator considerations limit smin • Depends on smax(dynamic range) pQCD radiation Vacuum fluct. Range of kinematics • At fixed s, changing the ratio Ee / Eioncan for some reactions improve resolution, particle identification (PID), and acceptance radiative gluons/sea valence quarks/gluons non-pert. sea quarks/gluons

  13. EIC: Critical Capabilities • Base EIC Requirements per Executive Summary INT Report: • range in energies from √s ~ 20 to √s ~ 70 & variable • fully-polarized (>70%), longitudinal and transverse • ion species up to A = 200 or so • high luminosity: about 1034e-nucleons cm-2 s-1 • multiple interaction regions • upgradable to higher energies (√s ~ 150 GeV) Input passed on to INT10-03 program: But we get there in different ways: Ee=5 GeV Luminosity (x1032) Ee=10 GeV eRHIC-1, Ee=5 GeV Proton Energy (GeV)

  14. Exclusive Meson Production p/A Beam e- Beam Q2 > 10 GeV2→ events of interest for imaging studies √s=100GeV √s=31.6 GeV √s=44.7 GeV Momentum (GeV/c) Momentum (GeV/c) Momentum (GeV/c) Δθ<0.3˚ Δθ=1-2˚ Exclusive measurements at very high CM energy require detection of high energy mesons over a very small angular range Best momentum resolution for symmetric or nearly symmetric collisions Ep = 250 GeV Ep = 30 GeV Lab Scattering angle (rad) Lab Scattering angle (rad) Lab Scattering angle (rad) [Horn 08+, INT10-3 report] • Nuclear Science: Map t between tmin and 1 (2) GeV2 • Must cover between 1-5 deg • Should cover between 0.5-5 deg • Like to cover between 0.2-7 deg t ~ Ep2Q2 Angle recoil baryons = t½/Ep Better t-resolution with lower proton energy and more symmetric kinematics

  15. MEIC: Full Acceptance Detector 7 meters ion FFQs ion dipole w/ detectors detectors solenoid ions IP 0 mrad electrons electron FFQs 50 mrad 2+3 m 2 m 2 m GEANT4 model Central detector TOF Solenoid yoke + Muon Detector RICH or DIRC/LTCC Tracking RICH EM Calorimeter HTCC 4-5m • Detect particles with angles down to 0.5o. Need 1-2 Tm dipole. Muon Detector Hadron Calorimeter EM Calorimeter • Detect particles with angles below 0.5o. • Very-forward detector, Large dipole bend @ 20 meter from IP allows for very-small angle detection (<0.3o) Solenoid yoke + Hadronic Calorimeter 2m 3m 2m

  16. EIC: Design Parameters • Base EIC Requirements per Executive Summary INT Report: • highly polarized (>70%) electron and nucleon beams • - longitudinally polarized electron and nucleon beams • - transversely polarized nucleon beams • ion species from deuterium to A = 200 or so • center of mass energies from √s ~ 20 to √s ~ 70 GeV & variable • electron energies above 3 GeV to allow efficient electron trigger • proton energy adjustable to optimize particle identification • upgradeable to center of mass energy of about √150 GeV • high luminosity ~1034 e-nucleons cm-2 s-1 • optimal luminosity in √s ~ 30-50 region • luminosity ≥1033 e-nucleons cm-2 s-1 in √s ~ 20-70 region • multiple interaction regions • integrated detector/interaction region • non-zero crossing angle of colliding beams • crossing in ion beam to prevent synchrotron background • - ion beam final focus quads at ~7 m to allow for detector space • bore of ion beam final focus quads sufficient to let particles pass through up to t ~ 2 GeV2 (t ~ Ep2Q2) • positron beam desirable

  17. MEIC : Medium Energy EIC Use CEBAF “as-is” after the 12-GeV Upgrade medium-energy IPs polarimetry low-energy IP Ee=5 GeV • Three compact rings: • 3 to 11 GeV electron • Up to 12 GeV/c proton (warm) • Up to 100 GeV/c proton (cold) Luminosity (x1032) Ee=10 GeV eRHIC-1, Ee=5 GeV Proton Energy (GeV)

  18. EIC Realization Imagined (Mont@INT) Note: 12 GeV LRP recommendation in 2002 – CD3 in 2008

  19. Summary • EIC is the ultimate tool to study sea quarks and gluons • Sea quarks and gluons play a prominent role in nucleon structure • Collider environment provides tremendous advantages • polarization • Target fragmentation • EIC is needed to completely understand nucleon structure and the role of gluons in nuclei • EIC is a mature project • Designs ongoing at JLab and BNL • White paper for next LRP under construction • Accelerator R&D funds have been allocated • Joint detector R&D projects have started

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