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Update to E12-10-008: Detailed studies of the nuclear dependence of F 2 in light nuclei

Update to E12-10-008: Detailed studies of the nuclear dependence of F 2 in light nuclei. Spokespersons: J.Arrington, A.Daniel, D.Gaskell. E03-103. EMC ~ (A a – 1). EMC ~ (A a – 1) ~ local density. EMC ~ density. EMC ~ density ~ local density. E12-10-008: EMC effect for A≤12.

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Update to E12-10-008: Detailed studies of the nuclear dependence of F 2 in light nuclei

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  1. Update to E12-10-008:Detailed studies of the nuclear dependence of F2 in light nuclei Spokespersons:J.Arrington,A.Daniel,D.Gaskell

  2. E03-103 EMC ~ (Aa – 1) EMC ~ (Aa – 1) ~ local density EMC ~ density EMC ~ density ~ local density E12-10-008: EMC effect for A≤12 • Map out A-dependence in more detail [E03-103: 3He, 4He, 9Be and 12C] • Very hard to explain large 3He –9Be difference in r-dependent fit • Hard to explain large 3He – 4He difference in mass-dependent fit • Modified fit does somewhat better, but worse for heavier nuclei • “Local density” works well, provides different predictions • Ave. overlap from ab initio GFMC calc. of 2-body correlation function • Similar predictions for <r2>, cluster calculation (arXiv:1008.1313), SRC ratios

  3. I.Cloet, W.Benz, A.Thomas, PRL102, 252301(2009) Special Cases • Comparison of 40Ca and 48Ca sensitive to isospin-dependence of EMC effect • 3He/2H has large isoscalar correction; 3He/(2H+1H) needsno isoscalar correction • Limited to W2>4 due to proton resonance structure contributions

  4. E12-10-008: Overview q=35o for high-x coverage: W2>20.3<x<0.92; improved high-x coverage, mainly needed for “isoscalar” ratios, e.g. 3He/(D+p) • Request 23 days of beam time in Hall C • Higher Q2, expanded range in x • Lower-x coverage improves shape comparison • Large expansion in high-x DIS region • Angle scan to test Q2-independence • More complete set of light nuclei • 40Ca, 48Ca comparison • Improved 3He extraction 11 GeV DIS range 6 GeV DIS range q=20o for most nuclei: W2>20.1<x<0.88 with high cross section, small pion and charge-symmetric backgrounds, reasonable radiative corrections Main 6 GeV setting

  5. Fin…

  6. JLab E03-103 J.Seely, et al., PRL103, 202301 (nov.2009) • EMC ratios for 3He, 4He, Be, C, Al, Cu, and Au • Examine scaling (A-dependence) of EMC effect in light nuclei • Allow quantitative evaluation of traditional nuclear physics • Lower Q2 limits access to large-x region to lower W2 (<4 GeV2) • DIS to x ≈ 0.6-0.65, tight limits on Q2 dependence up to x ≈ 0.8-0.85

  7. Average density, or average overlap?

  8. Isospin dependence • Different EMC effect for up, down quarks? • Neutron excess  effect larger for up, smaller for down quarks • u-quark dominance  increase • As neutron excess grows, begins to decrease • Factor of 2 difference between up, down quarks in Au • For 40Ca and 48Ca in this model, • Same at small x • 5% lower for 48Ca at x=0.75 I.Cloet, W.Benz, A.Thomas, PRL102, 252301(2009)

  9. PR10-008: Details • Request 23 days at 11 GeV • 200 for most complete x range • 350 for some nuclei • Push to largest possible x • Q2 scan for x>0.5 • Q2 dependence for few nuclei • Cross sections: ~3-4% uncertainty • Ratios: 1-1.5% point-to-point (typically 1%) 1-2% normalization (target-dependent) Smaller scattering angle  smaller corrections, backgrounds, than for 6 GeV • SHMS (mainly 35 degrees), HMS (20 deg, Q2 scan) • 6,7Li, 40,48Ca have lower rates, longer runtimes  focus on either 20 or 35 degrees, depending on primary physics goals • Detailed breakdown in backup slides

  10. Overlap with PR10-002 • We take data on proton and deuteron for 3He/(D+p) ratios • Recent examinations of D/p suggest need for additional high-x ratios in extraction of neutron structure function or d(x)/u(x): J. Arrington, F. Coester, R.J. Holt, T.-S.H. Lee, J.Phys.G36, 025005 (2009) A. Accardi, et al., arXiv:0911.2254 • The Q2 scan at high x overlaps with PR10-002 (for proton and deuteron) • We mainly use HMS during long SHMS runs; they use SHMS during long HMS runs • We use 4cm targets, they use 10cm • Only q = 35, 40 degrees take significant time • Overlapping kinematics correspond to at most 1-2 days of their data taking

  11. Other experiments • These data will provide significant new information on the EMC effect • Model-independent information on A-dependence in light nuclei • More complete x coverage to examine shape of EMC effect • Data for detailed comparison to calculations in well understood nuclei • “There are no unusual theoretical concerns about this work” • Medium-modified form factors, polarized EMC, nuclear dependence of anti-quarks, nuclear ratios in neutrino scattering, tagged EMC,… • All can provide complementary information to traditional EMC effect • Many provide much more specific or detailed information • All have technical challenges and/or reaction mechanism questions and/or issues of interpretation

  12. Scaling of the EMC effect • “Local density” fit: EMC effect scales like average nucleon overlap • Ab initio Greens function monte carlo (GFMC) calculations provide 1-body and 2-body densities for nuclei up to A=12 • Take convolution of 2-body densities, r2(r), with ~gaussian cutoff function that represents the overlap of two nucleons as a function of separation Density Aa-1 Local density (fixed A for 6,7Li ) Ebind, Ebind/A

  13. Run Times at each Setting (hours)

  14. Kinematic/Target Changes 20 min./momentum change, 5 min./target change, * = parasitic For settings with both H and He, we double the number of momentum changes

  15. Production Run Time Summary From table on previous page ….. • SHMS “running hours” = 383.9 • HMS “running hours” = 199 all but 8.6 hours of this can be taken concurrently with SHMS running • Total production time = 392.5 hours • Additional time for aluminum dummy target running = 15% of deuterium dummy run time = 14.1 hours • Total “beam on target” time = 406.6 hours (first line of Table II in proposal)

  16. PR10-008: “Extra” benefits • New measurements of D/p ratio at large x • Recent examinations of D/p suggest need for additional high-x ratios in extraction of neutron structure function or d(x)/u(x): J. Arrington, F. Coester, R.J. Holt, T.-S.H. Lee, J.Phys.G36, 025005 (2009) A. Accardi, et al., arXiv:0911.2254 • Li/D, Li/H ratios go into dilution for polarized LiH, LiD targets • Different assumptions yield range of estimates for EMC effect in Li • 7Li ratios useful for spin-dependent EMC effect measurements in 7Li • Spin structure function ratio includes spin-averaged contribution • Absolute cross sections also available for comparison to detailed calculations for a large selection of light nuclei

  17. Kinematic Changes Summary From table on previous page ….. • Momentum changes = 14 hours • Target changes = 15 hours • Angle changes = 1 hour • 10 minutes each; 2 for SHMS, 4 for HMS • Total assumed time = 24 hours 30 hrs minus time for overlap in HMS, SHMS kinematic changes and HMS momentum changes during longer SHMS runs

  18. E03-103: 3He • EMC effect small, but shape consistent with other nuclei (given normalization, isoscalar correction uncertainties) • Ratio of 3He/(D+p) removes need for isoscalar correction • Limited to x<0.7 due to proton resonance structure contributions

  19. E03-103: Experimental details Main improvement over SLAC due to improved He targets: JLab E03-103 0.5-0.7% 0.4% 1.0% SLAC E139 1.0-1.2% 1.4% 2.1% Source of uncertainty Statistics *Density fluctuations Absolute density *- sizeof correction is 8% at 4 uA vs. 4% at 80 uA 11 GeV, 350 200 ~15% (3%) CSB at x=0.15 (x=0.2) Main drawback is lower beam energy Requires larger scattering angle to reach same Q2 • Larger p- contamination • Larger Coulomb distortion corrections • Large charge-symmetric background Ratio of produced e+ to scattered e-

  20. E03-103 E12-10-008: EMC effect for A≤12 • Map out A-dependence in more detail [E03-103: 3He, 4He, 9Be and 12C] • Very hard to explain large 3He –9Be difference in r-dependent fit • Hard to explain large 3He – 4He difference in mass-dependent fit • Modified fit does somewhat better, but worse for heavier nuclei

  21. EMC ~ (Aa – 1) EMC ~ density E12-10-008: EMC effect for A≤12 • Map out A-dependence in more detail [E03-103: 3He, 4He, 9Be and 12C] • Very hard to explain large 3He –9Be difference in r-dependent fit • Hard to explain large 3He – 4He difference in mass-dependent fit • Modified fit does somewhat better, but worse for heavier nuclei

  22. E03-103 EMC ~ (Aa – 1) EMC ~ (Aa – 1) ~ local density EMC ~ density EMC ~ density ~ local density E12-10-008: EMC effect for A≤12 • Map out A-dependence in more detail [E03-103: 3He, 4He, 9Be and 12C] • Very hard to explain large 3He –9Be difference in r-dependent fit • Hard to explain large 3He – 4He difference in mass-dependent fit • Modified fit does somewhat better, but worse for heavier nuclei • “Local density” works well, provides different predictions • Ave. overlap from ab initio GFMC calc. of 2-body correlation function • Similar predictions for <r2>, cluster calculation (arXiv:1008.1313), SRC ratios

  23. E03-103

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