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K. Slifer, UNH

Nucleon Resonances and Spin Structure. NSTAR 2011. The 8 th International Workshop on the Physics of Excited Nucleons
May 17-20, 2011. K. Slifer, UNH. This talk. Brief overview of spin structure Recent Results from JLab Spin Duality (Hall A) RSS (Hall C)

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K. Slifer, UNH

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  1. Nucleon Resonances and Spin Structure NSTAR 2011 The 8th International Workshop on the Physics of Excited Nucleons
May 17-20, 2011 K. Slifer, UNH

  2. This talk Brief overview of spin structure Recent Results from JLab Spin Duality (Hall A) RSS (Hall C) Finite Size effects in bound state Q.E.D. Proton Charge Radius Hydrogen HF splitting Role of SSF measurements Upcoming Measurements E08-027 and E08-007

  3. This talk Brief overview of spin structure Recent Results from JLab Spin Duality (Hall A) RSS (Hall C) Finite Size effects in bound state Q.E.D. Proton Charge Radius Hydrogen HF splitting Role of nucleon resonances Upcoming Measurements E08-027 and E08-007

  4. This talk Brief overview of spin structure Recent Results from JLab Spin Duality (Hall A) RSS (Hall C) Finite Size effects in bound state Q.E.D. Proton Charge Radius Hydrogen HF splitting Role of nucleon resonances Upcoming JLab Measurements E08-027 and E08-007 “g2p & gep”

  5. Inclusive Scattering 1st order Feynman diagram Kinematics Q2 : 4-momentum transfer X : Bjorken Scaling var W : Invariant mass of target ° *

  6. Inclusive Scattering 1st order Feynman diagram Q2 : 4-momentum transfer X : Bjorken Scaling var W : Invariant mass of target ° * deviation from point-like behavior characterized by the Structure Functions Inclusive Cross Section

  7. Inclusive Scattering When we add spin degrees of freedom to the target and beam, 2 Additonal SF needed. ° * Inclusive Polarized Cross Section SFs parameterize everything we don’t know about proton structure

  8. BC Sum Rule H.Burkhardt and W.N. Cottingham Annals Phys. 56 (1970) 453. Assumptions: the virtual Compton scattering amplitude S2 falls to zero faster than 1/x g2 does not behave as d(x) at x=0. Discussion of possible causes of violations R.L. Jaffe Comm. Nucl. Part. Phys. 19, 239 (1990) “If it holds for one Q2 it holds for all”

  9. How Big are Higher twist contributions at low X? If we assume BC to hold, we can learn something about the low x region using only our high x measured data.

  10. HT 0 leading twist part satisfies BC exactly

  11. HT well known 0

  12. HT

  13. HT we can’t access this low x contribution we measure this

  14. what we measure

  15. what we measure places an upper limit on the low-x HT contribution to G2

  16. RSS Experiment (Spokesmen: Rondon and Jones) Q2 = 1.3 GeV2 K.S., O. Rondon et al. PRL 105, 101601 (2010)

  17. RSS Experiment (Spokesmen: Rondon and Jones) Q2 = 1.3 GeV2 (proton) consistent with zero => low x HT are small in proton. K.S., O. Rondon et al. PRL 105, 101601 (2010)

  18. RSS Experiment (Spokesmen: Rondon and Jones) Q2 = 1.3 GeV2 (proton) consistent with zero => low x HT are small in proton. non-zero by 2.6s =>Significant HT at low x needed to satisfy Neutron BC sum rule. (neutron) K.S., O. Rondon et al. PRL 105, 101601 (2010)

  19. Neutron HT contribution to low x Global Analysis of JLab Neutron g2 Data PRELIM 1/Q2 fit P. Solvignon et. al, in Prep Plot courtesy of Nilanga Liyanage

  20. Neutron HT contribution to low x Global Analysis of JLab Neutron g2 Data Consistency across all exps. (E94010, RSS, E01012) Follows rough 1/Q2 trend HT contribution  0 by about Q2=3 GeV2 PRELIM 1/Q2 fit P. Solvignon et. al, in Prep Plot courtesy of Nilanga Liyanage

  21. Applications to Bound State Q.E.D. nucleus ≈ 10-15 Atom ≈ 10-10 The finite size of the nucleus plays a small but significant role in atomic energy levels.

  22. Applications to Bound State Q.E.D. Hydrogen HF Splitting nucleus ≈ 10-15 Atom ≈ 10-10 The finite size of the nucleus plays a small but significant role in atomic energy levels.

  23. Applications to Bound State Q.E.D. Hydrogen HF Splitting nucleus ≈ 10-15 Atom ≈ 10-10 The finite size of the nucleus plays a small but significant role in atomic energy levels. Friar & Sick PLB 579 285(2003)

  24. Structure dependence of Hydrogen HF Splitting Elastic Scattering DZ=-41.0±0.5ppm

  25. Structure dependence of Hydrogen HF Splitting Nazaryan,Carlson,Griffieon PRL 96 163001 (2006) Inelastic Dpol≈ 1.3±0.3 ppm Elastic piece larger but with similar uncertainty 0.2265 ppm integral of g1 & F1 pretty well determined from F2,g1 JLab data

  26. Structure dependence of Hydrogen HF Splitting Nazaryan,Carlson,Griffieon PRL 96 163001 (2006) Inelastic Dpol≈ 1.3±0.3 ppm Elastic piece larger but with similar uncertainty 0.2265 ppm weighted heavily to low Q2

  27. Hydrogen Hyperfine Structure E08-027 assuming CLAS model with 100% error Integrand of ¢2 Dominated by this region due to Q2 weighting

  28. Hydrogen Hyperfine Structure E08-027 assuming CLAS model with 100% error Integrand of ¢2 But, unknown in this region: Dominated by this region due to Q2 weighting MAID Model Simula Model So 100% error probably too optimistic E08-027 will provide first real constraint on D2

  29. Proton Charge Radius from mP lamb shift disagrees with eP scattering result by about 6% <rp> = 0.84184 ± 0.00067 fm Lamb shift in muonic hydrogen <rp> = 0.897 ± 0.018 fm World analysis of eP scattering <Rp> = 0.8768 ± 0.0069 fm CODATA world average R. Pohl et.alNature, July 2010 I. Sick PLB, 2003 R. Pohl et al. Nature, 2010

  30. Lamb Shift S-orbital P-orbital Energy difference between the 2s and 2p levels

  31. Lamb Shift e _ + S-orbital P-orbital • radial distance in hydrgenic atom depends • inversely on mass Hydrogen

  32. Lamb Shift m _ + S-orbital P-orbital • muon is about 200 times heaviear than electron • 1st Bohr radius is about 200 times smaller muonic Hydrogen

  33. Lamb Shift m _ + S-orbital P-orbital • muon is about 200 times heaviear than electron • 1st Bohr radius is about 200 times smaller • so Lamb shift is enhanced by about 200 compared to eH muonic Hydrogen

  34. PSI results on Muonic Hydrogen • Muon Beam incident on H gas • mH formed in highly excited state • most decay directly to ground 1S state • small fraction of m decay to the 2s level reproduced from R. Pohl et al. Nature, 2010

  35. PSI results on Muonic Hydrogen • Muon Beam incident on H gas • mH formed in highly excited state • most decay directly to ground 1S state • small fraction of m decay to the 2s level Stimulate transitions from 2S-2P observe increase in decay from 2P-1S xray of 2 keV reproduced from R. Pohl et al. Nature, 2010

  36. PSI results on Muonic Hydrogen • Scan the probe laser frequency • At resonance, stimulating 2S -> 2P transistions • so see an increase in the 2P -> ground state xrays reproduced from R. Pohl et al. Nature, 2010

  37. PSI results on Muonic Hydrogen Observed n=49.882 THz (=206.295 meV) gives rp = 0.84184 ± 0.00067 fm reproduced from R. Pohl et al. Nature, 2010

  38. PSI results on Muonic Hydrogen Observed n=49.882 THz (=206.295 meV) gives rp = 0.84184 ± 0.00067 fm rp = 0.897 ± 0.018 fm Sick (3s) from e-P scattering reproduced from R. Pohl et al. Nature, 2010

  39. PSI results on Muonic Hydrogen Observed n=49.882 THz (=206.295 meV) gives rp = 0.84184 ± 0.00067 fm rp = 0.897 ± 0.018 fm Sick (3s) rp = 0.8768 ± 0.0069 fm CODATA (5s) from H spectroscopy reproduced from R. Pohl et al. Nature, 2010

  40. What could solve the discrepency? rp = 0.84184 ± 0.00067 fm PSI rp = 0.8768 ± 0.0069 fm CODATA (5s)

  41. What could solve the discrepency? rp = 0.84184 ± 0.00067 fm PSI rp = 0.8768 ± 0.0069 fm CODATA (5s) NYT : July 12, 2010 For a Proton, a Little Off the Top (or Side) Could Be Big Trouble Miscalibration of PSI frequency? Very unlikely QED wrong? Exciting! but unlikely  Calculations incorrect? maybe missing some terms... (muon mass) Uncertainty underestimated? This is where SSF program can play a role.

  42. WARNING EXPERIMENTALIST Interpreting Theory ahead

  43. Splitting of 2S and 2P level is sensitive to rp

  44. Splitting of 2S and 2P level is sensitive to rp 2% effect 200X bigger than in eH

  45. Splitting of 2S and 2P level is sensitive to rp Total observed shift is combination of Lamb Shift

  46. Splitting of 2S and 2P level is sensitive to rp Total observed shift is combination of Lamb Shift Fine structure

  47. Splitting of 2S and 2P level is sensitive to rp Total observed shift is combination of Lamb Shift Fine structure 2P Hyperfine structure 2S Hyperfine structure

  48. Splitting of 2S and 2P level is sensitive to rp Total observed shift is combination of Lamb Shift Fine structure 2P Hyperfine structure 2S Hyperfine splitting mostly negligible uncertainty

  49. Explicit dependence on rp comes from the Lamb shift term several dozen terms contribute to the Lamb shift, but only a few are really significant:

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