Proton Remains Puzzling

Proton remains puzzling

The 10th Circum-Pan-Pacific Symposium on High Energy Spin Physics Taipei, October 5-8, 2015

Haiyan Gao Duke University and Duke Kunshan University

1 Lepton scattering: powerful microscope! • Clean probe of hadron structure • Electron (lepton) vertex is well-known from QED • One-photon exchange dominates, higher-order exchange diagrams are suppressed (two-photon physics) • Vary the wave-length of the probe to view deeper inside 2 ' " 2 2 % dσ α E GE +τGM 2 θ 2 2 θ = $ cos + 2τGM sin ' 2 2 2 4 θ τ = −q / 4M dΩ 4E sin E # 1+τ 2 2 & 2 Virtual photon 4-momentum! q = k − k' = (q,ω) Q2 = −q2 1 k’ α = 137

2 k € What is inside the proton/neutron?

1933: Proton’s magnec moment 1960: Elasc e-p scaering

Nobel Prize Nobel Prize In Physics 1943 In Physics 1961

Oo Stern Robert Hofstadter

"for … and for his thereby achieved discoveries "for … and for his discovery of the magnec concerning the structure of the nucleons" moment of the proton". g =2 Form factors Charge distributions 6 ! 1969: Deep inelasc e-p scaering 1974: QCD Asymptoc Freedom

Nobel Prize in Physics 1990 Nobel Prize in Physics 2004 Jerome I. Friedman, Henry W. Kendall, Richard E. Taylor David J. Gross, H. David Politzer, Frank Wilczek "for their pioneering invesgaons "for the discovery of asymptoc concerning deep inelasc scaering of freedom in the theory of the strong electrons on protons …". 3 interacon". From J.W. Qiu Tremendous advances in electron scattering Unprecedented capabilities: • High Intensity • High Duty Factor • High Polarization • Parity Quality Beams • Large acceptance detectors • State-of-the-art polarimetry, polarized targets

Focal plane polarimeter Polarized 3He target – Jefferson Lab 4 Proton Charge Radius • An important property of the nucleon – Important for understanding how QCD works – Challenge to Lattice QCD (exciting new results, Alexandrou et al.) – An important physics input to the bound state QED calculations, affects muonic H Lamb shift (2S 1/2 – 2P 1/2) by as much as 2%

• Electron-proton elastic scattering to determine electric form factor (Nuclear Physics)

2 2 dG(q ) < r > = −6 | 2 dq2 q =0

• Spectroscopy (Atomic physics) – Hydrogen Lamb shift – Muonic Hydrogen Lamb shift 5

Muonic hydrogen Lamb shift at PSI (2010, 2013)

2010: new value is rp = 0.84184(67) fm 2013: rp = 0.84087(39) fm, A. Antognini et al., Science 339, 417 (2013) 6 (addional transion)

Recent ep Scattering Experiments

Measurements @ Mainz

– Large amount of overlapping data sets – Cross section measurement – Statistical error ≤ 0.2% – Luminosity monitoring with spectrometer ! Q2 = 0.004 – 1.0 (GeV/c)2 result: rp =0.879(5)stat(4)sys(2)mod(4)group

J. Bernauer, PRL 105,242001, 2010 5-7σ higher than muonic hydrogen result !

(J. Bernauer) Jlab Recoil Proton Polarization Experiment LHRS • Δp/p0: ± 4.5% , • out-of-plane: ± 60 mrad • in-plane: ± 30 mrad • ΔΩ: 6.7msr • QQDQ • Dipole bending angle 45o • VDC+FPP

• Pp : 0.55 ~ 0.93 GeV/c

Ee: 1.192GeV P : ~83% b BigBite

• Non-focusing Dipole • Big acceptance. New pol. Target • Δp: 200-900MeV data soon from • ΔΩ: 96msr Hall A • PS + Scint. + SH X. Zhan et al. Phys. Lett. B 705 (2011) 59-64 C. Crawford et al. PRL98, 052301 (2007) 8 The proton radius puzzle intensified

rp = 0.879(11) fm by Arrington and Sick (2015) from reanalysis of ep data New ep analyses by Griffioen et al, Horbatsch and Hessels 9

Revisits of QED Calculaons…. An addional 0.31 meV to match CODATA value

Evaluation by Jentschura, Annals Phys. 326, 500 (2011) Recent summary by A. Antognini et al., arXiv:1208.2637

Birse and McGovern, arXiv:1206.3030 0.015(4) meV (proton polarizability) J.M. Alarcon, et al. 1312.1219 0.008 meV

G.A. Miller, arXiv:1209.4667

New experiments at HIGS and Mainz on proton polarizabilies

Talk by S. Karshenboim Incomplete list • New physics: new particles, Barger et al., Carlson and Rislow; Liu and Miller,…. New PV muonic force, Batell et al.; Carlson and Freid; Quantum gravity at the Fermi scale R. Onofrio;……. • Contributions to the muonic H Lamb shift: Carlson and Vanderhaeghen,; Jentschura, Borie, Carroll et al, Hill and Paz, Birse and McGovern, G.A. Miller, J.M. Alarcon,…. • Higher moments of the charge distribution and Zemach radii, Distler, Bernauer and Walcher,….. • J.A. Arrington, G. Lee, J. R. Arrington, R. J. Hill discuss systematics in extraction from ep data, no resolution on discrepancy • Donnelly, Milner and Hasell discuss interpretation of ep data,……… Discrepancy explained by some but others disagree • Dispersion relations: Lorentz et al. • Frame transformation: D. Robson • New experiments: Mainz (e-d, ISR), JLab (PRad), PSI (Lamb shift, and MUSE), H Lamb shift 11 Charge Radius of Other Light Nuclei

Deuterium Helium

Electron scattering consistent with µ-spectroscopy PRad Experimental Setup in Hall B at JLab

PRad Setup (Side View) Hydrogen GEM gas chamber

HyCal 2H00 Cryocooler Harp bellows bellows Collimator bellows Tagger 0.3 m New cylindrical target vacuum box cell 1.7 m 1.2 m

1.7 m 5.0 m 1.5 m

! High resolution, large acceptance, hybrid Spokespersons: A. Gasparian, HyCal calorimeter (PbWO4 and Pb-Glass) D. Dutta, H. Gao, M. Khandaker ! Windowless H gas flow target 2 Future sub 1% measurements: ! Simultaneous detection of elastic and Moller electrons (1) ep elasc scaering at Jlab (PRad) (2) μp elasc scaering at PSI - 16 U.S. ! Q2 range of 2x10-4 – 0.14 GeV2 instuons! (MUSE) ! XY – veto counters replaced by GEM detector (3) ISR experiments at Mainz ! Vacuum box Ongoing H spectroscopy experiments 13

PRad Projected Result

15 The incomplete nucleon: spin puzzle

Jaffe-Manohar, 90 Ji, 96 1 1 = ⌃ +G +(L + L ) 2 2 q g

Proton Spin

Quark helicity Best known Gluon helicity Orbital Angular Momentum Start to know of quarks and gluons Little known 30% ⇠ 20%(STAR Data) Net eﬀect of partons’ ⇠ transverse moon? 16 Unified View of Nucleon Structure

W u(x,k ,r ) Wigner distribuons p T T 5D Dist.

2 2 d rT d kT

u TMD PDFs f1 (x,kT), .. GPDs/IPDs u h1 (x,kT)‏ 3D imaging

dx & 2 d kT 2 Fourier Transformaon d rT

Form Factors PDFs 2 GE(Q ), f u(x), .. h u(x)‏ 1D 2 1 1 GM(Q )‏

17 Extraction of GPD’s

Cleanest process: Deeply Virtual Compton Scattering hard verces

σ↑ - σ↓ Δσ A = ξ=x /(2-x ) σ↑ + σ↓ = 2σ B B t Polarized beam, unpolarized target: ~ ΔσLU~ sinφ{F1H+ ξ(F1+F2)H+kF2E}dφ H(ξ,t)

Unpolarized beam, longitudinal target: ~ ~ ΔσUL~ sinφ{F1H+ξ(F1+F2)(H+ξ/(1+ξ)E)}dφ H(ξ,t)

Unpolarized beam, transverse target: E( t) ΔσUT~ sinφ{k(F2H – F1E)}dφ ξ, Quark Angular Momentum

→ Access to quark orbital angular momentum

19 SIDIS Electroproduction of Pions

• Separate Sivers and Collins eﬀects • Previous data from HERMES,COMPASS, JLab • New landscape of TMD distributions • Access to orbital angular target angle momentum

hadron angle

• Sivers angle, eﬀect in distribuon funcon: (φh-φs)

• Collins angle, eﬀect in fragmentaon funcon: (φh+φs) 12 GeV Upgrade at JLab

Upgrade is designed to build on existing facility: vast majority of accelerator and experimental equipment have continued use New Hall

Upgrade arc magnets and supplies Add 5 cryomodules

20 cryomodules CHL upgrade Maintain capability to deliver lower pass beam energies: 2.2, 4.4, 6.6…. Add arc The completion of the 20 cryomodules 12 GeV Upgrade of CEBAF was ranked the highest Add 5 priority in the 2007 NSAC cryomodules Long Range Plan.

Scope of the project includes: Enhanced capabilities • Doubling the accelerator beam energy in existing Halls • New experimental Hall and beamline • Upgrades to existing Experimental Halls Solenoidal Large Intensity Device (SoLID) proposed for Hall A 21 12 GeV Scienﬁc Capabilies

Hall B – understanding nucleon structure via Hall D – exploring origin of confinement generalized parton distributions by studying exotic mesons

Hall A – form factors, future new Hall C – precision determination of valence experiments (e.g., SoLID and MOLLER) quark properties in nucleons/nuclei

22 SoLID-Spin: SIDIS on 3He/Proton @ 11 GeV E12-10-006: Single Spin Asymmetry on Transverse 3He @ 90 days, rang A E12-11-007: Single and Double Spin Asymmetry on 3He @ 35 days, rang A E12-11-108: Single and Double Spin Asymmetries on Transverse Proton @120 days, rang A Two ``bonus’’ experiments approved

International collaboration with 250+ collaborators from 13 countries

Key of SoLID-Spin program: Large Acceptance + High Luminosity " 4-D mapping of asymmetries " Tensor charge, TMDs … "Lattice QCD, QCD Dynamics,

Models. 23 Transversity and Tensor Charge ! Tensor charge (0th moment of transversity): intrinsic property (charge, magnetic moment), also input for beyond Standard Model physics searches Lattice QCD, Bound-State QCD (Dyson-Schwinger) , Light-cone Quark Models, … ! Global model fits to experiments (SIDIS and e+e-) ! SoLID with trans. polarized n & p " determination of tensor charges for d & u Collins Asymmetries Tensor Charges (Transversity (x) Collins Function) 1.5 ® u d 1. Ú Ú Ú Ú Ú Ú Ú Ú 0.5 Ë Ú ¯ Ë Ú Ë

0 Ù Ù Ù Ù Ù Ù

d Ù ¯ Ë Ë Ë Ù Ù Ù d ® -0.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Total 1400 bins in x, Q2, P and z for T 12-GeV SoLID projections together with 11/8.8 GeV beam X. Qian et al in PRL 107, 072003 existing extractions and predictions 6 Tensor charge & EDM

10 #26 dn ! 2.9"10 e$cm DSE 2015

5 Anselmino et al 2013 A cm $

e ! ! Lattice 2015 25

# 0 Anselmino et al 2013 B 10 " u Kang et al 2015 d #5

SoLID projection based on Kang et al #10 #3 #2 #1 0 1 2 3 #25 dd 10 e$cm

neglect strange quark contribution " Next generation nEDM constraint

1 cm

" #26

e dn !2.9"10 e$cm current 25

! 0 #27 dn !2.9"10 e$cm 10

! #28 u !dn!!2.9"10 e$cm " # d !1 ! ! ! ! !2 !0.3 !0.2 !0.1 0.0 0.1 0.2 0.3 !25 dd 10 e"cm

! SoLID projections based on Kang et al 2015 using different nEDM upper limits Summary

• Lepton scattering is a powerful tool to probe the rich internal structure of the nucleon • Proton charge radius puzzle prompts intensive theoretical and experimental efforts • Spin remains important and puzzling for nucleon • Three-dimensional imaging of nucleon helps solve remaining puzzle to the proton spin, and uncovers the rich dynamics of QCD • Electron Ion Collider – A new QCD frontier that US NP QCD community is hoping for (ongoing US NP LRP)

Thanks to J.-P Chen, D. Dutta, R. Ent,, A. Gasparian, R. Holt, M. Khandaker, T.- B. Liu, R.D. McKeown, Z.-E. Meziani, C. Peng, A. Prokudin, J.W. Qiu, C. Roberts, P. Souder, Z. Ye, Z. Zhao, X. Yan, ………

Supported in part by U.S. Department of Energy under contract number DE- FG02-03ER41231 27 Duke Degree -Classroom & Practicum Teaching -Thesis Research -Seminars -Half-Year Study on the Duke University Campus 2 years in 2 countries

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