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John Arrington Argonne National Laboratory

PR12-11-112 Precision measurement of the isospin dependence in the 2N and 3N short range correlation region. Spokespersons : J. Arrington, D. B. Day, D. Higinbotham, P. Solvignon. John Arrington Argonne National Laboratory. PAC38 August 25, 2011. Short range correlations (SRC).

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John Arrington Argonne National Laboratory

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  1. PR12-11-112Precision measurement of the isospin dependence in the 2N and 3N short range correlation region Spokespersons: J. Arrington, D. B. Day, D. Higinbotham, P. Solvignon • John Arrington • Argonne National Laboratory PAC38 August 25, 2011

  2. Short range correlations (SRC) • Short-range NN interaction generates high momenta • Universal mechanism for all nuclei • Similar shape for k>kFermi Cioffi Degli Atti et al, PRC53, 1689 (1996) 2

  3. Short range correlations (SRC) • Short-range NN interaction generates high momenta • Universal mechanism for all nuclei • Similar shape for k>kFermi Mean-field region: collective behavior, strongly A-dependent Cioffi Degli Atti et al, PRC53, 1689 (1996) 3 3

  4. Short range correlations (SRC) • Short-range NN interaction generates high momenta • Universal mechanism for all nuclei • Similar shape for k>kFermi High-momentum region: short-range physics, largely A-independent. Dominated by 2N-SRC tail A(e’,e) at x>1: For momentum sufficiently above kFermi, mean field contributions small; dominated by 2N-SRCs Cioffi Degli Atti et al, PRC53, 1689 (1996) 4 4

  5. Pmin vs. x, Q2 k>kFermi Short range correlations (SRC) A(e’,e) at x>1: For momentum sufficiently above kFermi, mean field contributions small; dominated by 2N-SRCs Cioffi Degli Atti et al, PRC53, 1689 (1996) 5 5

  6. SRC evidence at JLab • Experimental observations: • Clear evidence for 2N-SRC at x>1.5 • Suggestion of 3N-SRC plateau • Isospin dependence ? K. Egiyan et al, PRL96, 082501 (2006) • Simple SRC Model: • 1N, 2N, 3N contributions dominate at x≤1,2,3 • 2N, 3N configurations “at rest” (total ppair = 0) • Isospin independent N. Fomin, et al, arXiv:1107.358 (2011) 6 6

  7. R. Subedi et al, Science 320, 1476(2008) Tensor force dominance • Simple SRC Model: • 1N, 2N, 3N contributions dominate at x≤1,2,3 • 2N, 3N configurations “at rest” (total ppair = 0) • Isospin independent R. Schiavilla, R. Wiringa, S. Pieper and J. Carlson, PRL98, 132501 (2007) pp np Scaled deuteron momentum distribution From A(p,p’pn) and 12C(e,e’pN): 90% of observed pN pairs are pn; tensor force  isosinglet dominance R(pp/pn) = 0.0560.018 R(T=1/T=0) = 208% 7

  8. Main physics goals: E12-11-112 • Isospin-dependence • Triple coincidence: • Demonstrated isoscalar dominance • Good precision: R(T=1/T=0) = 208% • Large FSI: Dominates the high-Pm12C(e,e’p) events used to look for SRCs • Inclusive 3H/3He: • Improved precision: Extract R(T=1/T=0) to 3.8% • FSI much smaller (inclusive) and expected to cancel in ratio • No Pm dependence • 3N SRCs structure (momentum-sharing and isospin) • Q2 dependence can test models of the momentum sharing • 3He/3H ratio very sensitive to isospin-momentum correlations • Improved A-dependence in light and heavy nuclei • Average of 3H, 3He  A=3 “isoscalar” nucleus • Determine isospin dependence  improved correction for N>Z nuclei, extrapolation to nuclear matter • Absolute cross sections (and ratios) for 2H, 3H, 3He • Test calculations of FSI for simple, well-understood nuclei 8 8

  9. Isospin structure of 2N-SRCs Simple estimates for 2N-SRC • 3He/3H is simple/straightforward case: Isospin independent Full n-p dominance (no T=1) • 40% difference between full isosinglet dominance and isospin independent • Few body calculations [M. Sargisan, Wiringa/Peiper (GFMC)] predict n-p dominance, but with sizeable contribution from T=1 pairs • Goal is to measure 3He/3H ratio in 2N-SRC region with 1.5% precision  Extract R(T=1/T=0) with uncertainty of 3.8% Extract R(T=1/T=0) with factor of two improvement over previous triple-coincidence, smaller FSI 9

  10. 3N-SRC configurations Different configurations possible for 3N-SRCs, for example: “Linear configuration” p3 = p1 + p2 extremely large momentum “Star configuration” p1 = p2 = p3 Inclusive measurement can help to differentiate between these configurations and test isospin structure 10 10

  11. Light-cone fraction: a2n Relativistic: x  a[light cone momentum fraction] a = A(Ei-pi,z)/(EA-pA,z) = A(Eilab-pi,zlab)/MA Cannot reconstruct in inclusive scattering, but for scattering from 2N-SRC,a≈a2N For 3N-SRC, equivalent a3N depends on the details of the momentum sharing in the SRC Ratios vs x Combine with E08-014 data on 3He Quality of scaling in a3N tests picture of 3N-SRC momentum sharing Ratios vs a2N 11 11

  12. Momentum-isospin correlations “Linear configuration” p3 = p1 + p2 extremely large momentum “Star configuration” p1 = p2 = p3 (a) yields R(3He/3H) ≈ 3.0 if nucleon #3 is always the doubly-occurring nucleon (a) yields R(3He/3H) ≈ 0.3 if nucleon #3 is always the singly-occurring nucleon (a) yields R(3He/3H) ≈ 1.4 if configuration is isospin-independent, as does (b) R≠1.4 implies isospin dependence AND non-symmetric momentum sharing 12 12

  13. N. Fomin, et al, arXiv:1107.358 (2011) A-dependence of 2N-SRCs Red points: assume isosinglet dominance Cyan points: assume isospin independence Reality is somewhere in between (closer to isosinglet dominance) Large difference for 3He and 9Be, heavy nuclei  modifies A-dependence for light nuclei and extrapolation to nuclear matter (3He+3H)/2H yields `isoscalar’ A=3 result 3He/3H yields improved extraction of (T=1)/(T=0)  better correction for all non-isoscalar nuclei 13 13

  14. Cu,Au EMC effect C 4He 9Be 3He 2N-SRC ratio Extra impact of improved A-dependence Correlation between EMC effect and SRCs suggests that they may both be driven by short-distance physics (density) or high-momentum physics (virtuality) L. Weinstein, et al., PRL 106:052301,2011 Improved measurements of A-dependence of SRCs can test different interpretations; Requires better quantification of isosinglet “dominance”

  15. Quasielastic data Worlds 3H QE data: Q2 ≤ 0.9 GeV2 Propose: 0.6-1.0 GeV2 1.4,1.7 GeV2 2.2-3.0 GeV2 In PWIA, 3He/3H with 1.5% uncertainty corresponds to 3% on GMn *Limited to Q2≤1 GeV2, where QE peak has minimal inelastic contribution * This is the region with ~8% discrepancy between the Anklin, Kubon data and the CLAS ratioand Hall A polarized 3He extractions Nuclear effects expected to be small, largely cancel in ratio For CLAS D(e,e’n)/D(e,e’p) extraction of GMn, nuclear corrections on the ratio were <0.1% over the full Q2 range

  16. PR12-11-112: Experimental setup • Standard Hall A HRS configuration • Gas Cerenkov + Calorimeter PID • 1H, 2H, 3H, 3He room temperature cells, 20 atmospheres (10 for 3H) • Empty cell for window subtraction (check software cut on windows, subtract residual contribution) • Carbon foils for optics 16

  17. Tritium target: updated design • Four identical cells: 1H, 2H, 3He at 20 atmospheres, 3H at 10 atm. • Operate at room temperature • Length: 30cm, Diameter: 1.25cm • 18 mil windows and walls • Technical review last year • Prototype requested and funded • Goal is to be ready by 2014

  18. Kinematic coverage • Beam current: 25 mA, unpolarized • Raster interlock • Beam energy: 4.4, (2.2) GeV • 17.5 Days 4.4 GeV [main production] • 1.5 days 2.2 GeV [checkout+QE] QE 2N 3N 18

  19. Kinematic coverage • Beam current: 25 mA, unpolarized • Raster interlock • Beam energy: 4.4, (2.2) GeV • 17.5 Days 4.4 GeV [main production] • 1.5 days 2.2 GeV [checkout+QE] QE 2N 3N Left HRS running (380 hours) 19

  20. Kinematic coverage • Beam current: 25 mA, unpolarized • Raster interlock • Beam energy: 4.4, (2.2) GeV • 17.5 Days 4.4 GeV [main production] • 1.5 days 2.2 GeV [checkout+QE] QE 2N 3N Right HRS running (parasitic) Worlds 3H QE data: Q2 ≤ 0.9 GeV2 Left HRS running (380 hours) 20 20

  21. Summary • Study of isospin dependence of 2N-SRC from 3H/3He from inclusive scattering: will complement the results of 2N knockout experiments • Greater precision • Smaller final-state interactions • First look at isospin-momentum structure in 3N-SRC region • Quasi-elastic data on 3H and 3He for Q2-values of 0.6-3.0 (GeV/c)2 • Beam time requested: 19 days including data taking, calibrations, background studies and configuration changes • Hall A spectrometers in standard configuration, same 3H target system needed for the approved MARATHON experiment (E12-10-103) 21

  22. Backup Slides 22

  23. Relationship to E08-014 (“x>2” on light nuclei) • E08-014: Finished data taking in April/May • Extract Q2 dependence for 3He/2H, 4He/3He ratios • Precisely determine scaling regions for 2N, 3N-SRCs in light nuclei • Initial Q2 dependence of ratios vs. different 3N scaling variables (a3N) • Isospin (40Ca/48Ca) • Intrinsic sensitivity is roughly half of 3H/3He • Total uncertainty in R(T=1/T=0) about 12% (40Ca target problems) • PR12-11-112 • Difference of 3H, 3He to study (T=1)/(T=0) • Project 3.8% uncertainty compared to 8% from (e,e’pN), 12% from 40/48Ca • Yield improved isoscalar correction for light and heavy nuclei • Look for asymmetry in momentum-isospin distribution for 3N SRCs • Average of 3H, 3He yields “isoscalar” A=3 nucleus • Improve extraction of A-dependence of SRCs in light nuclei • Comparison to state-of-the-art calculations without isospin structure uncertainties 23 23

  24. Final-state interactions No indication of Q2-dependent FSI * A/D ratios in plateau region No indication of FSI within 2N-SRC * nD(k) from y-scaling vs. calculations * high-k data consistent with calculations * Scatter of NN potentials limits constraints SLAC [Fe] CLAS [Fe] Hall C [Fe] – E89-008 Hall C [Cu] – E02-019 24 24

  25. Dummy and 3He targets (E08-014, kin 6.5)

  26. SRC evidence at SLAC, JLab Hall B, Hall C • Experimental observations: • Evidence of 2N-SRC at x>1.5 • Suggestion of 3N-SRC plateau • Isospin dependence ? Frankfurt, Strikman, Day, Sargsian, PRC48, 2451 (1993) • Naïve SRC Model: • 1N, 2N, 3N contributions dominate at x≤1,2,3 • 2N, 3N configurations “at rest” • Isospin independent 26 26

  27. QE peak at low Q^2

  28. Onset of 2N SRC region is not A-independent 2H 197Au

  29. Systematics * Expect to know relative target thickness to <2%, and be able to normalize to DIS at the 1% level (based on MARATHON proposal) 29

  30. EMC slope vs SRC • EMC slopes are fit from 0.325<x<0.7; preliminary results from SRC, EMC (heavy nuclei) • Some kind of break down for heavy nuclei, SRC factors are more or less same but EMC slope keep on increasing with A Without deuteron “constraint” point, fit does not have expected behavior for deuteron Rescaling assuming n-p only in SRC, all N-N pairs in EMC fixes linearity, deuteron limit. Suggests short-distance over high-momentum?

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