Future Measurements of the Nucleon Elastic Electromagnetic Form - PowerPoint PPT Presentation

Future Measurements of the Nucleon Elastic Electromagnetic Form Factors at Jefferson Lab G.P. Gilfoyle University of Richmond, Richmond, VA 23173 Outline 1. Scientific Motivation 2. Necessary Background 3. What We Hope to Learn. 4. The Measurements 5. Summary and Conclusions Tlaxcala City Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 1 / 22

Scientific Motivation - What We Hope to Learn. Nucleon elastic electromagnetic form factors (EEFFs) describe the distribution of charge and magnetization in the nucleon. Reveal the internal landscape of the nucleon and nuclei. Rigorously test QCD in the non-perturbative regime. Nuclear models, constituent quarks,... lattice QCD. Map the transition from the hadronic picture to QCD. Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 2 / 22

Scientific Motivation - What We Hope to Learn. Nucleon elastic electromagnetic form factors (EEFFs) describe the distribution of charge and magnetization in the nucleon. Reveal the internal landscape of the nucleon and nuclei. Rigorously test QCD in the non-perturbative regime. Nuclear models, constituent quarks,... lattice QCD. Map the transition from the hadronic picture to QCD. Jefferson Lab has completed the 12 GeV Upgrade which doubled the CEBAF accel- erator energy. Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 2 / 22

Some Necessary Background EEFFs cross section described with Dirac ( F 1 ) and Pauli ( F 2 ) form factors d σ �� � θ e �� + 2 τ ( F 1 + κ F 2 ) 2 tan 2 F 2 1 + κ 2 τ F 2 � d Ω = σ Mott 2 2 where σ Mott = α 2 E ′ cos 2 ( θ e 2 ) 4 E 3 sin 4 ( θ e 2 ) and κ is the anomalous magnetic moment, E ( E ′ ) is the incoming (outgoing) electron energy, θ is the scattered electron angle and τ = Q 2 / 4 M 2 . For convenience use the Sachs form factors. d σ σ Mott ǫ G 2 E + τ G 2 � � d Ω = M ǫ (1 + τ ) where � − 1 � 1 + 2(1 + τ ) tan 2 θ e G E = F 1 − τ F 2 and G M = F 1 + F 2 and ǫ = 2 Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 3 / 22

Where We Are Now. M reasonably well known over large Q 2 range. G p PR12-07-108 The ratio G p E / G p M from polarization transfer measurements diverged from previous Rosen- bluth separations. Two-photon exchange (TPE). Effect of radiative corrections. Neutron magnetic FF G n M still follows dipole. High- Q 2 G n E opens up flavor decomposition. PRL 104 , 242301 (2010) Scholarpedia, 5(8):10204 PRL 105, 262302 (2010) Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 4 / 22

Where We Are Now. Many years of model building - Diehl et al. Eur. Phys. J., 73, 2397 (2013) Vector Meson Dominance, Con- stituent Quarks capture much of the four EEFFs, but use many pa- rameters. Generalized Parton Distributions (GPDs) have also been used. The EEFFs are the first moments of the GPDs. EEFFs are an early test of lattice P.E. Shanahan et al. QCD because isovector form does PRD 90, 034502 (2014) CSM, QCDSF/UKQCD Collaborations not have disconnected diagrams. Blue - lQCD result Red - data parameterization Green - dipole fit to calculation Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 5 / 22

Where We Are Going - Dyson-Schwinger Eqs Equations of motion of quantum field theory. Infinite set of coupled integral equations. Inherently relativistic, non-perturbative, connected to Clo¨ et et al QCD. PRL 111, 101803 (2013) Deep connection to confinement, dynamical chiral symmetry breaking. Infinitely many equations, gauge dependent → Choose well! Recent results (Clo¨ et et al). Model the nucleon dressed quark propagator as a quark-diquark. Damp the shape of the mass function M ( p ). Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 6 / 22

Where We Are Going - Dyson-Schwinger Eqs Equations of motion of quantum field theory. Infinite set of coupled integral equations. Inherently relativistic, non-perturbative, connected to Clo¨ et et al QCD. PRL 111, 101803 (2013) Deep connection to confinement, dynamical chiral symmetry breaking. Infinitely many equations, gauge dependent → Choose well! Recent results (Clo¨ et et al). C.Roberts, arXiv:1509.02925 Black arrow - neutron Model the nucleon dressed quark Red arrow - proton propagator as a quark-diquark. Damp the shape of the mass function M ( p ). Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 6 / 22

Where We Are Going - Dyson-Schwinger Eqs Equations of motion of quantum field theory. Infinite set of coupled integral equations. Inherently relativistic, non-perturbative, connected to Clo¨ et et al QCD. PRL 111, 101803 (2013) Deep connection to confinement, dynamical chiral symmetry breaking. Infinitely many equations, gauge dependent → Choose well! Recent results (Clo¨ et et al). C.Roberts, arXiv:1509.02925 Black arrow - neutron Model the nucleon dressed quark Red arrow - proton propagator as a quark-diquark. Damp the shape of the mass function M ( p ). µ p G p E / G p Position of zero in and M µ n G n E / G n M sensitive to shape of M ( p )! Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 6 / 22

Where We Are Going - Flavor Decomposition With all four EEFFs we can unravel the contributions of the u and d quarks. Assume charge symmetry, no s quarks and use (Miller et al. Phys. Rep. 194 , 1 (1990)) 1(2) = 2 F p 1(2) + F p F u 1(2) + F n F d 1(2) = 2 F n 1(2) 1(2) Evidence of di-quarks? d -quark scat- tering probes the diquark. Cates et al. PRL 106 , 252003 (2011). Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 7 / 22

Where We Are Going - Flavor Decomposition With all four EEFFs we can unravel the contributions of the u and d quarks. Assume charge symmetry, no s quarks and use (Miller et al. Phys. Rep. 194 , 1 (1990)) 1(2) = 2 F p 1(2) + F p F u 1(2) + F n F d 1(2) = 2 F n 1(2) 1(2) Evidence of di-quarks? d -quark scat- tering probes the diquark. Cates et al. PRL 106 , 252003 (2011). Agreement with Nambu-Jona-Lasinio model encouraging - no parameter fits to the EEFFs. Cloet et al. PRC, 90 045202 (2014) Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 7 / 22

Where We Are Going - Flavor Decomposition With all four EEFFs we can unravel the contributions of the u and d quarks. Assume charge symmetry, no s quarks and use (Miller et al. Phys. Rep. 194 , 1 (1990)) 1(2) = 2 F p 1(2) + F p F u 1(2) + F n F d 1(2) = 2 F n 1(2) 1(2) Evidence of di-quarks? d -quark scat- tering probes the diquark. Cates et al. PRL 106 , 252003 (2011). Agreement with Nambu-Jona-Lasinio model encouraging - no parameter fits to the EEFFs. The JLab program will double our reach in Q 2 to ≈ 8 GeV 2 . Cloet et al. PRC, 90 045202 (2014) Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 7 / 22

Where We Are Going - Light Front Holographic QCD Based on connections between light-front dynamics, it’s holographic 1 mapping to anti-de Sitter space, and conformal quantum mechanics. Recent paper by Sufian et al. (Phys. Rev. D95, 01411 (2017)) included 2 calculations of the electromagnetic form factors that include higher order Fock components | qqqqq � . Obtain good agreement with all the form factor data with only three 3 parameters, e.g. µ n G n E / G n M . Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 8 / 22

Where We Are Going - Light Front Holographic QCD Based on connections between light-front dynamics, it’s holographic 1 mapping to anti-de Sitter space, and conformal quantum mechanics. Recent paper by Sufian et al. (Phys. Rev. D95, 01411 (2017)) included 2 calculations of the electromagnetic form factors that include higher order Fock components | qqqqq � . Obtain good agreement with all the form factor data with only three 3 parameters, e.g. µ n G n E / G n M . C.Roberts, arXiv:1509.02925 Black arrow - neutron Red arrow - proton Major difference with DSE approach! 4 Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 8 / 22

Where We Are Going - New Experiments The JLab Lineup Q 2 ( GeV 2 ) Quantity Method Target Hall Beam Days G p ∗ Elastic scattering LH 2 7 − 15 . 5 A 24 M G p E / G p Polarization transfer LH 2 5 − 12 A 45 M G n E − p / e − n ratio LD 2 − LH 2 3 . 5 − 13 . 0 B 30 M G n E − p / e − n ratio LD 2 , LH 2 3 . 5 − 13 . 5 A 25 M G n E / G n polarized 3 He Double polarization 5 − 8 A 50 M asymmetry G n E / G n Polarization transfer 4 − 7 C 50 LD 2 M G n E / G n Polarization transfer 4 . 5 A 5 LD 2 M ∗ Data collection is complete. PAC approval for 229 days of running in the first five years. All experiments build on successful ones from the 6-GeV era. Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 9 / 22

How We Will Get There: Jefferson Lab Continuous Electron Beam Accelerator Facility (CEBAF) Superconducting Electron Accelerator (currently 338 cavities), 100% duty cycle. E max = 11 GeV (Halls A, B, and C) and 12 GeV (Hall D), ∆ E / E ≈ 2 × 10 − 4 , I summed ≈ 90 µ A , P e ≥ 80%. Jerry Gilfoyle, ISMD2017 Future Form Factor Measurements at JLab 10 / 22