Future Measurements of the Nucleon Elastic Electromagnetic Form Factors at Jefferson Lab G.P. Gilfoyle University of Richmond, Richmond, VA USA S M -W W H L. I Nucleon elastic electromagnetic form factors (EEFFs) describe the distribution of charge and magnetization in the nucleon. I They can reveal the internal landscape of the nucleon and nuclei. I They rigorously test QCD in the non-perturbative regime with different models, constituent quarks, lattice QCD... I Map the transition from the hadronic picture to QCD. S N B EEFFs cross section is described with Dirac (F 1 ) and Pauli (F 2 ) form factors or Sachs form factors (G E and G M ). dσ dΩ = σ Mott ( F 2 1 + κ 2 τF 2 2 ) + 2τ (F 1 + κF 2 ) 2 tan 2 θ e 2 = σ Mott (1 + τ) ( G 2 E + τG 2 M ) where σ Mott = α 2 E 0 cos 2 ( θ e 2 ) 4E 3 sin 4 ( θ e 2 ) G E = F 1 - τF 2 G M = F 1 + F 2 = 1 + 2(1 + τ) tan 2 θ e 2 -1 and κ is the anomalous magnetic moment, E (E 0 ) is the incoming (outgoing) electron energy, θ is the scattered electron angle and τ = Q 2 /4M 2 . W A W N? I G p M reasonably well known over large Q 2 range. I The ratio G p E /G p M from recoil polarization measurements diverged from previous Rosenbluth separations. I Two-photon exchange (TPE). I Effect of radiative corrections. I The neutron form factor ratio G n E /G n M opens up flavor decomposition. I Neutron magnetic FF G n M still follows dipole. Eur. Phys. J., 73, 2397 (2013) PRL 104, 242301 (2010) PRL 105, 262302 (2010) PRL, 102, 192001 (2009) I Theory approaches like Vector Meson Domi- nance and dispersion analyses fit EEFFs, but use many parameters. I Constituent Quark Models highlight relativity, but don’t capture all of QCD. I EEFFs are an early test of lattice QCD because isovector form does not have disconnected dia- grams. P.E.Shanahan et al. arXiv:1401.5862v2 [hep-lat] CSSM and QCDSF/UKQCD Collaborations W A W G? I Flavor Decomposition I With all four EEFFs we can unravel the u and d quark structure. I Assume charge symmetry, no s quarks and use (Miller et al. Phys. Rep. 194, 1 (1990)) F u 1(2) = 2F p 1(2) +F n 1(2) F d 1(2) = 2F n 1(2) +F p 1(2) I The u and d quarks have different, unexplained Q 2 dependence - evidence of di-quarks? I Dyson-Schwinger Equations I Infinite set of coupled integral equa- tions. I Inherently relativistic, and nonper- turbative. I Connected to confinement, dynam- ical chiral symmetry breaking. I Proton form factor ratio sensitive to the shape of the dressed-quark mass function. PRL 111, 101803 (2013) PRL 106, 252003 (2011). H A W G T?-U A Halls A CEBAF Racetrack Hall D B C Continuous Electron Beam Ac- celerator Facility (CEBAF) I Superconducting Electron Accelerator (338 cavities) I 100% duty cycle. I E max = 11 GeV (Halls A, B, and C) and 12 GeV (Hall D) I ΔE/E ≈ 2 × 10 -4 I I summed ≈ 90 μA, P e > 80%. H A W G T?-N D Hall A - High Resolution Spec- trometer (HRS) pair, SuperBig- Bite (SBS), neutron detector, and others. Hall B - CLAS12 high lumi- nosity, large acceptance spec- trometer with forward and central detectors. Hall C - Super High Momentum Spectrometer paired with exist- ing High Momentum Spectrom- eter. Hall D - New GlueX detector will search for exotic states, but not for EEFFs. T M A R JLab Program Advisory Committee (PAC) has ap- proved six experiments to measure all four EEFFs (some twice) with 224 days of running. Anticipated Hall A points Experiment E12-07-108 in Hall A (Arrington, Christy, Gilad, Silkovsky, Wojtsekhowski) will make a precise measurement of the ep elastic cross section and extract G p M . Experiment E12-07-109 (GEp) in Hall A (Cis- bani et al.) will use the polarization transfer method on H( ~ e, e 0 ~ p) to measure the form fac- tor ratio G p E G p M =- P t P l E+E 0 2M tan ( θ e 2 ) . Two experiments E12-07-104 (Gilfoyle, Hafidi, and Brooks) in Hall B and E12- 09-019 (Annand, Gilman, Quinn, Wo- jtsekhowski) in Hall A will use the quasielastic e - n/e - p ratio to extract a precision measurement of G n M . Experiment E12-09-016 in Hall A (Cates, Wojtsekhowski, Riordan) will use the double Polarization Asymmetry A V en from 3 ~ He( ~ e, e 0 n)pp to extract G n E /G n M . Experiment E12-11-009 in Hall C (Arring- ton, Kohl, Sawadsky, Semenov) will use po- larization transfer off 2 H( ~ e, e 0 ~ n)p to measure G n E /G n M complementary to the other G n E /G n M experiment in Hall A. S C I The proton cross section measurement (G p M ) will run in spring, 2016 and the form factor ratio (G p E /G p M ) in 2018. I Remaining elastic form factor measurements will be done in 2018 or later. I Large recent gains in understanding of the EEFFs. I Major changes in our understanding of nucleon structure. I Jefferson Lab will mount a broad campaign on the EEFFs and will significantly expand our physics reach. I Discovery potential in mapping out nucleon structure and understanding QCD. University of Richmond Jerry Gilfoyle