Insights from Electron Scattering as Input to Precision Neutrino Studies or The “MINERe-A” program at Jefferson Lab John Arrington Physics Division, Argonne ANL HEP seminar, Nov 20 th, 2013

Outline  Direct electron/neutrino complementarity – JUPITER, MINER A and more –Cross sections and L/T separations on range of nuclei and low Q 2 –Reaction mechanisms: Hadron production, reinteraction, absorption in nuclei –Flavor decomposition, valence/sea separation [EM + + parity-violating electron scattering + Drell-Yan] –Reaction mechanisms studies with neutrinos: e.g. TEM of Bodek, Christy (Not specific to scattering, but accessible because of detectors)  Nucleon electromagnetic form factors –Polarization measurements –Two-photon exchange –Quark structure, flavor decomposition, pion cloud, proton radius, etc…  Nucleon electromagnetic form factors –Polarization measurements –Two-photon exchange –Quark structure, flavor decomposition, pion cloud, proton radius, etc…  Nuclear structure at high energies –Short-range correlations/high-momentum nucleons in nuclei –Impact of density on pdfs of nuclei –Proton, neutron PDFs at large x  Nuclear structure at high energies –Short-range correlations/high-momentum nucleons in nuclei –Impact of density on pdfs of nuclei –Proton, neutron PDFs at large x

John Arrington Argonne National Lab I. What does electron (muon) scattering tell us about proton structure: Form Factors

Nucleon Electromagnetic Form Factors  Fundamental properties of the proton and neutron –Contain information on charge, magnetization distributions –Connect to distribution, dynamics of quarks in hadrons  Experimental program reinvented –Considered by many to be well understood by mid/late 80s –Polarization techniques  dramatic advances in Q 2 range, precision  Many applications of these new data/techniques –Precise knowledge of FFs needed by other experiments –Advances in other programs, relying on same techniques

Where Were We 15 (or 25) Years Ago?  Proton form factors have similar Q 2 dependence –Similar charge, magnetization distributions –Consistent with non-relativistic models where quarks carry charge and magnetization  Neutron has positive core and a negative cloud –Consistent with “pion cloud” picture: n  p    Testing models of the nucleon structure –G Mp (Q 2 ) well measured over wide range Helps constrain model parameters –Others not measured as well; more complete data set needed to test models in detail

New techniques: Polarization and A(e,e’N)  Mid ’90s brought measurements using improved techniques –High luminosity, highly polarized electron beams –Polarized targets ( 1 H, 2 H, 3 He) or recoil polarimeters –Large, efficient neutron detectors for 2 H, 3 He(e,e’n) Polarized 3 He target BLAST at MIT-Bates Focal plane polarimeter – Jefferson Lab Unpol:  G M 2 +  G E 2 Pol:  G E /G M

Nucleon Form Factors: Present status Proton Neutron

Two Photon Exchange 8 Golden mode: e + -p vs. e - -p elastic scattering JA, PRC 69, (2004) Existing e+p/e-p data show some evidence for TPE TPE calculations largely resolve discrepancy Rosenbluth data WITHOUT TPE correction Polarization transfer JA, W. Melnitchouk, and J. Tjon, PRC 76, (2007)

Two Photon Exchange 9 Golden mode: e + -p vs. e - -p elastic scattering JA, PRC 69, (2004) Existing e+p/e-p data show some evidence for TPE TPE calculations largely resolve discrepancy Rosenbluth data WITH TPE correction Polarization transfer JA, W. Melnitchouk, and J. Tjon, PRC 76, (2007) IFTHEN IF TPE corections fully explain the discrepancy, THEN they are constrained well enough that they do not limit our extractions of the form factor Three new e+/e- experiments BINP Novosibirsk – internal target JLab – mixed e+/e- beam, CLAS DESY (OLYMPUS) - internal target

Preliminary e+/e- cross section comparisons BINP Novosibirsk – internal target  JLab – mixed e+/e- beam, CLAS  1.5 GeV 2  0.8 GeV 2 Proceed assuming TPE explains difference, hadronic calculations sufficient Impact on other areas: TPE corrections for other precision electron scattering measurements (  -  x Z and  x (  -Z) for parity- violating electron scattering W-  box diagram (neutrino CC)

Nucleon Form Factors: Present status Proton Neutron

S. Boffi, et al. F. Cardarelli, et al. P. Chung, F. Coester F. Gross, P. Agbakpe G.A. Miller, M. Frank G E /G M : Quark Orbital Angular Momentum C. Perdrisat, V. Punjabi, and M. Vanderhaeghen, PPNP 59 (2007) Many calculations able to reproduce the falloff in G E /G M –Descriptions differ in details, but nearly all were directly or indirectly related to quark angular momentum

Insight from New Measurements  New information on proton structure –G E (Q 2 ) ≠ G M (Q 2 )  different charge, magnetization distributions Model-dependent extraction of charge, magnetization distribution of proton: J. Kelly, Phys. Rev. C 66, (2002)

Insight from New Measurements  New information on proton structure –G E (Q 2 ) ≠ G M (Q 2 )  different charge, magnetization distributions –Connection to GPDs: spin-space-momentum correlations A.Belitsky, X.Ji, F.Yuan, PRD69: (2004) G.Miller, PRC 68: (2003) x=0.7 x=0.4 x=0.1 1 fm Model-dependent extraction of charge, magnetization distribution of proton: J. Kelly, Phys. Rev. C 66, (2002)

Transverse Spatial Distributions  Simple picture: Fourier transform of the spatial distribution –Relativistic case: model dependent “boost” corrections  Model-independent relation found between form factors and transverse spatial distribution G. Miller, PRL 99, (2007); G. Miller and JA, PRC 78:032201,2008 PROTON NEUTRON S.Venkat, JA, G.A.Miller, X.Zhan, PRC83, (2011)

Transverse Spatial Distributions  Simple picture: Fourier transform of the spatial distribution –Relativistic case: model dependent “boost” corrections  Model-independent relation found between form factors and transverse spatial distribution   (b,x) = ∑ e q ∫ dx q(x,b) = Transverse density distribution in infinite momentum frame (IMF) for quarks with momentum x Natural connection to GPD picture Not naturally connected to rest- frame intuition   (b,  x): neutron Sea quarks (x<0.1) Valence quarks Intermediate x region G. Miller, PRL 99, (2007); G. Miller and JA, PRC 78:032201,2008 S.Venkat, JA, G.A.Miller, X.Zhan, PRC83, (2011)

Flavor Separation New G En data gave complete p, n FFs to 3.4 GeV 2 (10 GeV 2 planned) Allowed extraction of up, down contributions [S. Riordan, et al., PRL 105 (2010) ] ]G. Cates, et al., PRL 106 (2011) ] [Qattan/Arrington, PRC 86 (2012) ] F 1, F 2 fall faster for d-quarks: signature of diquark contributions: d+(uu) 1 (axial-vector) contribution softer than u+(ud) 0 (scalar) F p (Q 2 ) = 2/3 F u (Q 2 ) - 1/3 F d (Q 2 ) F n (Q 2 ) = 2/3 F d (Q 2 ) - 1/3 F u (Q 2 ) F u (Q 2 ) = 2 F p (Q 2 ) + F n (Q 2 ) F d (Q 2 ) = 2 F n (Q 2 ) + F p (Q 2 )

Flavor Separation G E /G M – down quarks G E /G M – up quarks New G En data gave complete p, n FFs to 3.4 GeV 2 (10 GeV 2 planned) Allowed extraction of up, down contributions [S. Riordan, et al., PRL 105 (2010) ] ]G. Cates, et al., PRL 106 (2011) ] [Qattan/Arrington, PRC 86 (2012) ] Very different behavior for G E /G M for up, down

 Add parity-violating scattering to extract up, down, and strange quark contributions  Matter radius smaller than charge radius (for both up an d down quarks) Charge distribution Matter (quark) distributions Brief detour to low Q 2

Proton Charge Radius (4)0.8758(77) ???0.8770(60) Muon Electron Spectroscopy Scattering Further test and improve electron scattering results TPE experiments (e+/e-) PRAD at JLab – Low Q 2, forward angle MUSE at PSI – compare e ± and  ±

Summary: Form Factors and TPE  Polarization techniques led to dramatic increase in Q 2 range of form factor measurements –Quark dynamics: Orbital angular momentum, potential impact of diquark structure of nucleon, “imaging” of the nucleon, etc… –Paralleled significant progress in theory, model-independent interpretation –Proton charge form factor and neutron form factors significantly different/improved at high Q 2 –First pass updates incorporated into Budd/Bodek/Arrington and later versions –New global fits with improved low, very high Q 2 measurements underway –Proton radius puzzle: muonic hydrogen vs. precision polarization techniques, tour-de-force cross section measurements and atomic hydrogen Lamb shift  Many implications of these new results –Precise knowledge of FFs needed by other experiments Strangeness contributions to nucleon structure –Advances in other programs, relying on same techniques Medium modification of nucleon structure

John Arrington Argonne National Lab II. Clusters, Correlations and Quarks: a High-Energy Perspective on Nuclei

Nuclei: energetic, dense, complex systems Nuclei are extremely energetic –“Fast” nucleons moving at >50% the speed of light (electrons at 1-10%) –“Slow” nucleons moving at ~10 9 cm/s, in an object ~ cm in size [ZHz] Nuclei are incredibly dense >99.9% of the mass of the atom <1 trillionth of the volume ~10 14 times denser than normal matter (approaching neutron star densities) At these densities, nucleons close enough together to interact via short-range repulsive core ( range of ~0.6 fm ) AND have significant spatial overlap ( R RMS ~0.85 fm ) The moon (A ≈ 5x10 49 ) at typical nuclear densities

Ideal packing limit 4He matter density from GFMC calculation, courtesy of B. Wiringa Proton vs. Nuclear Densities  Proton RMS charge radius: R p  0.85 fm  Corresponds to uniform sphere, R = 1.15 fm, density = 0.16 fm -3  Ideal packing of hard sphere:  max = 0.12 fm -3 –Well below peak densities in nuclei

Ideal packing limit 4He matter density from GFMC calculation, courtesy of B. Wiringa Proton vs. Nuclear Densities  Proton RMS charge radius: R p  0.85 fm  Corresponds to uniform sphere, R = 1.15 fm, density = 0.16 fm -3  Ideal packing of hard sphere:  max = 0.12 fm -3 –Well below peak densities in nuclei –Need 100% packing fraction for nuclear matter –Can internal structure be unchanged??

Hard interaction at short range N-N interaction Small N-N separation Large relative momenta Mean field part n(k) [fm -3 ] k [GeV/c] Short-Range Correlations Nucleon momentum distribution in 12 C High-density configurations

Collective behavior vs. two-body physics Cioffi Degli Atti, et al, PRC53, 1689 (1996) Mean-field region: collective behavior, strongly A-dependent

Collective behavior vs. two-body physics Cioffi Degli Atti, et al, PRC53, 1689 (1996) High-momentum region: short-range interactions, mainly 2-body physics, largely A-independent

Inclusive scattering at large x High momentum tails should yield constant ratio if SRC-dominated QE e e’ Nucleus A  Quasielastic scattering x  1 Motion of nucleon in the nucleus broadens the peak N. Fomin, et al., PRL 108 (2012) JLab E02-019, QE scattering from nuclei at x>1 - JA, D. Day, B. Filippone, A. Lung spokespersons - N. Fomin, Ph.D. student

2N correlations (SRCs) in A/D ratios 3 He2.14± He3.66±0.07 Be4.00±0.08 C4.88±0.10 Cu5.37±0.11 Au5.34±0.11 =2.72GeV 2 Focus on light nuclei A/D Ratio N. Fomin, et al., PRL 108 (2012)

R. Subedi et al., Science 320, 1476 (2008) Summary: Short-Range Correlations SRCs are an important component to nuclear structure –~20% of nucleons in SRC, mainly pn pairs Some 3N-SRCs Some room for more exotic configurations (6q bag) –Impact on neutron stars –Needs to be included in a realistic fashion for electron, neutrino scattering from nuclei [not sure of status in current event generators] These relate to dense, energetic configurations: Natural to look for impact on proton structure, possible connection to the EMC effect Frankfurt and Strikman arXiv:

Deeply-inelastic scattering (DIS) measures structure function F 2 (x) –x = quark longitudinal momentum fraction –F 2 (x) related to parton momentum distributions (pdfs) Nuclear binding << energy scales of probe, proton/neutron excitations Expected F 2 A (x) ≈ Z F 2 p (x) + N F 2 n (x) i.e. insensitive to details of nuclear structure beyond Fermi motion F 2 (x)   e i 2 q i (x) i=up, down, strange R = F 2 A (x) / F 2 D (x) III. Quark distributions in nuclei: EMC effect

EMC effect: x dependence A dependence SLAC E139 -Most precise large-x data -Nuclei from A=4 to 197 Conclusions -Universal x-dependence -No Q 2 dependence -Size varies slowly with A (  ) J. Gomez, et al., PRD 94, 4348 (1994)

Importance of few-body nuclei 4 He much lighter than 12 C, but has similar average density 9 Be much lower density than 12 C, but similar mass 3 He has low A and low density Light nuclei help test scaling with mass vs. density

3 He and 4 He calculations by Pandharipande and Benhar SLAC fit to heavy nuclei (scaled to 3He) HERMES data E03103 projected uncertainty Importance of few-body nuclei Some calculations yielded modified EMC effect for 3 He and 4 He –Most calculations assume nuclear matter, scale to nuclear densities –Few-body nuclei  smaller nuclear structure uncertainties –Predictions of different shapes for 3 He, 4 He, and heavy nuclei Limited previous data –Lower precision for 4 He –No large x data for 3 He JLab E03-103, “EMC effect In few-body nuclei” - JA and D. Gaskell spokespersons - A. Daniel, J. Seely, Ph.D. students Emphasis on 3 He, 4 He, 9 Be, 12 C

36 JLab E03-103: Light nuclei Consistent shape for all nuclei (curves show shape from SLAC fit) 12 C 9 Be 4 He 3 He J. Seely, et al., PRL103, (2009)

A-dependence of EMC effect in light nuclei Density determined from ab initio calculation S.C. Pieper and R.B. Wiringa, Ann. Rev. Nucl. Part. Sci 51, 53 (2001) Data show smooth behavior as density increases… except for 9 Be 9 Be has low average density, but large component of structure is 2  +n Most nucleons in tight,  -like configurations K. Arai, et al., PRC54, 132 (1996) Credit: P. Mueller

Dense clusters  Quark effects? New EMC effect data suggest importance of ‘local density’ Short-range correlations are meant to probe ‘local density’ measure –The experiments measure high momenta study –Aim is study short distance, high density Direct connection between EMC effect and SRCs?

Density dependence? Credit: P. Mueller J.Seely, et al., PRL103, (2009) N. Fomin, et al., PRL108 (2012)

Correlation between SRCs and EMC effect Importance of two-body effects? L. Weinstein, et al., PRL 106, (2011) O. Hen, et al, PRC 85, (2012) J. Seely, et al., PRL103, (2009) N. Fomin, et al., PRL 108, (2012) JA, A. Daniel, D. Day, N. Fomin, D. Gaskell, P. Solvignon, PRC 86 (2012) % suppression in all nucleons? 25-50% change in the ~20% of nucleons at very high momenta?

Short-distance behavior and the EMC effect 1.EMC effect driven by average density of the nucleons [J. Gomez, et al., PRD 94, 4348 (1994), Frankfurt and Strikman, Phys. Rept. 160 (1988) 235]

Short-distance behavior and the EMC effect 2. EMC effect is driven by Local Density (LD) [J. Seely et al., PRL 103, , 2009] EMC effect driven by high-density nucleon configurations (pairs, clusters) SRCs believe to be generated by short-distance (high-density) NN pairs 3. EMC effect driven by High Virtuality (HV) of the nucleons [L. Weinstein et al, PRL 106, ,2011] EMC effect driven by off-shell effects in high-momentum nucleons SRC measurements directly probe high-momentum nucleons 1.EMC effect driven by average density of the nucleons [J. Gomez, et al., PRD 94, 4348 (1994), Frankfurt and Strikman, Phys. Rept. 160 (1988) 235] Imply slightly different connection between EMC effect, SRCs JA, A. Daniel, D. Day, N. Fomin, D. Gaskell, P. Solvignon, PRC 86 (2012)

LD: Linear correlation: χ v 2 =0.64(0.84) Good extrapolation to deuteron: EMC( 2 H) = ± HV: OK linear correlation (χ v 2 =1.26) Fair extrapolation to deuteron: EMC( 2 H) = ± High Virtuality Local Density # of nucleons at high momentum (relative to 2 H) # of nucleons in small-sized configurations Two Hypotheses for EMC-SRC correlation o o JA, A. Daniel, D. Day, N. Fomin, D. Gaskell, P. Solvignon, PRC 86 (2012)

Two Hypotheses for EMC-SRC correlation HypothesisFit type χ2νχ2ν EMC(D)IMC(D) High Virtuality2-param No constraints ± ±0.011 High Virtuality1-param ±0.004 Local Density2-param No constraints (0.64) ± ±0.006 Local Density1-param(0.57) ±0.002

E140 E139 IV. Neutron Structure Function, d/u ratio at large x Attempts to extract F 2n (x) from deuteron and proton data yield large range of results, depending on the model of nuclear effects in the deuteron “Scaled EMC effect”: Use F 2A /F 2D data as measure of nuclear effects; scale to determine effects in the deuteron  Yields larger n/p  Neglects Fermi motion, difference in F 2p and F 2n, Q 2 dependence of smearing

 Agrees with Whitlow (on-shell) result  Lower than Melnitchouk/Thomas  Newer CTEQ6x analysis yields consistent results (A. Accardi, et al., PRD 81 (2010) )  Ave. Q 2 values for the D/p ratios have a strong dependence on x  We interpolate data to fixed Q 2  Previous extractions treated data as if it were at fixed Q 2  Significant Q 2 dependence in S p at large x, F 2n ~ R dp - S p Much of the “model-dependence” due to evaluating S p, S n at fixed Q 2 Neutron Structure Function JA, F.Coester, R.J.Holt, T.S.-H.Lee, J. Phys. G36, (2009)

Detailed investigations of model-dependence N3L0 Av18 CDBonn WJC2 WJC1 Melnitchouk&Thomas WBA [CTEQ6X] Kulagin&Petti Arrington, et al Rinat, et al Solid: On-shell Dashed: Off-shell [MST or KP] REF: Arrington, MST offshell Extract F 2n /F 2p with a variety of microscopic deuteron calculations Common F 2p, F 2n as input Vary N-N potential (for a single deuteron model) – top plot Vary deuteron model (single N-N potential) – bottom plot

Detailed investigations of model-dependence JA, W. Melnitchouk, J. Rubin, PRL 108, (2012) Extracted n/p ratio with estimate of experimental and model-dependent uncertainties Can test the nuclear models, neutron extraction against 3,4 He/ 2 H data

Extraction of d(x)/u(x) ratio In leading order, simple to extract d(x)/u(x) from n/p ratio Assumes identical higher-twist in neutron and proton, neglects “target mass” corrections, higher order effects, etc… JA, W. Melnitchouk, J. Rubin, arXiv: NOT the right way to extract d/u: pdf style analysis can go beyond LO, include data which is not sensitive to deuteron model A. Accardi, et al., PRD81 (2010) A. Accardi, et al., PRD84 (2011) The pdf extractions and extracted model dependence are consistent with ours, though differences in assumptions yield results which make pdf analysis appear to suggest larger d-quark contributions

High x impacts high energy physics Argonne National Laboratory 50 A. Accardi, arXiv v2 W charge asymmetry vs. rapidity

Clear connection between SRCs and quark structure of nuclei –Naturally explained by both density and virtuality –Experimentally, these are correlated – high-momentum nucleons associated with short-range interactions New experiments planned for 12 GeV upgrade –More nuclei (cluster structure, range of N/Z values) to study correlation between EMC effect and SRCs –“Tag” scattering from in SRCs (very high-momentum nucleons) Measure quark distributions (DIS scattering), form factors (QE) –Model-independent (or nearly so) extractions of F 2n /F 2p BONUS: Tagged measurements to isolate nearly on-shell neutron MARATHON: 3H/3He ratio in DIS region Parity-violating electron scattering at large x Nuclei: Where do we go from here?

EMC and SRCs with JLab 12 GeV Upgrade SRCs at x>1 at 12 GeV [E06-105: JA, D. Day, N. Fomin, P. Solvignon] EMC effect at 12 GeV [E10-008: JA, A. Daniel, D. Gaskell] 1 H 2 H 3 He 4 He 40 Ca 48 Ca CuAu 6,7 Li 9 Be 10,11 B 12 C 3 H 3 He

Nucleon overlap in nuclei? Nucleons are composite objects charge radius ~0.86 fm separation in heavy nuclei ~1.7 fm Nucleons already closely packed in nuclei; Maybe we should expect things to change Average nuclear density 1.2 fm separation

Nucleon overlap in nuclei? Nucleons are composite objects charge radius ~0.86 fm separation in heavy nuclei ~1.7 fm Nucleons already closely packed in nuclei; Maybe we should expect things to change Average nuclear density 0.6 fm separation Are nucleons unaffected by this overlap? Do they deform as they are squeezed together? Do the quarks exchange or interact?

Inclusive scattering at x>1 isolates SRCs High energy scattering probes quark distributions two-nucleon only 5% 6 quark bag Quark distributions of SRC: “Super-fast” quarks 6q bag is ‘shorthand’ for any model where overlapping nucleons allows free sharing of quark momentum (“High Density” effect) High Virtuality would tend to suppress strength at largest x q D (x) Difference only ~1% piece of EMC effect? First Look at 6 GeV: N. Fomin, et al., PRL 105 (2010) Suggests quark distributions can be extracted up to x  1.1

Summary  Direct electron/neutrino complementarity – JUPITER, MINER A and more –Cross sections and L/T separations on range of nuclei and low Q 2 –Reaction mechanisms: Hadron production, reinteraction, absorption in nuclei –Flavor decomposition, valence/sea separation [EM + + parity-violating electron scattering + Drell-Yan] –Reaction mechanisms studies with neutrinos: e.g. TEM of Bodek, Christy (Not specific to scattering, but accessible because of detectors)  Nucleon electromagnetic form factors –Polarization measurements  Change in EM Form Factors, extended Q 2 range –Two-photon exchange  Two-Boson Exchange (Z-  impt for PVES, W-  ?) –Quark structure, flavor decomposition, pion cloud, proton radius, etc…  Nucleon electromagnetic form factors –Polarization measurements  Change in EM Form Factors, extended Q 2 range –Two-photon exchange  Two-Boson Exchange (Z-  impt for PVES, W-  ?) –Quark structure, flavor decomposition, pion cloud, proton radius, etc…  Nuclear structure at high energies –Short-range correlations/high-momentum nucleons in nuclei Important for e-A and -A interactions –Impact of density on pdfs of nuclei PDFs in nuclei, nuclear effects in light nuclei and neutron structure, d(x)/u(x  Nuclear structure at high energies –Short-range correlations/high-momentum nucleons in nuclei Important for e-A and -A interactions –Impact of density on pdfs of nuclei PDFs in nuclei, nuclear effects in light nuclei and neutron structure, d(x)/u(x

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