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Overview of unpolarized structure function measurements at high x Roy J. Holt

Overview of unpolarized structure function measurements at high x Roy J. Holt. Jefferson Lab 13 October 2010. Outline. Introduction and Motivation New generation of experiments and tools The proton structure function The neutron structure function

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Overview of unpolarized structure function measurements at high x Roy J. Holt

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  1. Overview of unpolarized structure function measurements at high xRoy J. Holt Jefferson Lab 13 October 2010

  2. Outline • Introduction and Motivation • New generation of experiments and tools • The proton structure function • The neutron structure function • The strange quark distribution and Drell-Yan • Concluding statement We are providing benchmark data for hadron structure. Argonne National Laboratory

  3. Four Pillars of Hadron Structure TMD PDFs f1u(x,kT), .. h1u(x,kT)‏ GPDs 3 D d3r d2kT drz See X. Jiang, K. Hafidi, A. Accardi Wpu(x,kT,r ) Wigner distributions dxd2kT drz & FT d2kT d3r Form Factors GE(Q2), GM(Q2)‏ PDFs f1u(x), .. h1u(x)‏ See Z.-E. Meziani, J. Blumlein, J. Soffer 3 Argonne National Laboratory

  4. Structure function Parton model Quark charge Prob. of q in proton Partonic structure of the nucleon hadronic leptonic fraction of the proton’s momentum carried by the struck quark • What is the internal landscape of the hadron? NSAC 2007 • Benchmark: Spatial, spin, flavor and gluonic structure Argonne National Laboratory

  5. Large x is essential for particle physics Large Hadron Collider Lake of Geneva CMS • Parton distributions at large x are important input into simulations of hadronic background at colliders, eg the LHC. • High x at low Q2 evolves into low x at high Q2. • Small uncertainties at high x are amplified. • HERA anomaly: (1996): excess of neutral and charged current events at Q2 > 10,000 GeV2 • Leptoquarks???? • ~0.5% added to u(x) at x > 0.75 S. Kuhlmann et al, PLB 409 (1997) Airport LHCb ALICE ATLAS Argonne National Laboratory

  6. W production at the LHC • W production at the LHC is sensitive to the d/u ratio • W’s and Z will be “standard candles” at the LHC J.-L.Lai et al, hep-ph 14 Jul 2010 Argonne National Laboratory

  7. Proton structure function DIS from proton gives good sensitivity to u, but not to d Plot credit: A. Accardi (See J. Owens, S. Alekhin, A. Guffanti, D. Renner, V. Radescu) Argonne National Laboratory

  8. Why are proton structure function data still interesting? • New data at very high x can reveal information about: • Target mass corrections • High twist effects • Soft gluon resummation • Order in as • Quark-hadron duality • Hadronic models • Recent data from JLab – more to follow after JLab 12 GeV Upgrade and Drell-Yan experiments CTEQ6X, A. Accardi et al, PR D81 (2010) • (See J. Owens, S. Alkhin, T. Hobbs, M. Glatzmaier, S. Kulagin, A. Accardi, • W. Melnitchouk, S. Malace, F. Steffens, S.-H. Lee, S. Liuti, E. Christy) Argonne National Laboratory

  9. Why is high x so difficult? • W > 2 GeV eg. if x =0.9, then Q2 = 27 GeV2 Practical limit at JLab12: x = 0.8 Argonne National Laboratory

  10. Upgraded JLab has unique capability to define the valence region The proton structure function • JLab E12-10-002, S. Malace et al • Utilize resonance region • Invoke duality DOE milestone HP14 (2018) Plot credit: S. Malace, JLab PAC36 Argonne National Laboratory

  11. Proton structure function at an EIC • MEIC simulation • Ee = 4 GeV, Ep = 60 GeV • Luminosity ~ 3 x 1034 • 1 year of running (26 weeks) at 50% efficiency, or 230 fb-1 An EIC is a powerful probe of the valence region. Alberto Accardi, Nuclear Chromodynamics with an EIC Argonne, April 2010 With C. Keppel and R. Ent Argonne National Laboratory

  12. The Neutron Structure Function Parton model -> • Proton structure function: • Neutron structure function (isospin symmetry): • Ratio: • Nachtmann inequality: • Focus on high x: Argonne National Laboratory

  13. Uncertainty in the d(x)/u(x) ratio • Q2 > 4 GeV2 • W > 3.5 GeV • x < 0.7 Argonne National Laboratory

  14. Structure Function Ratio Problem • Convolution model • Fermi motion and binding, covariant deuteron wave function, off-shell effects Melnitchouk and Thomas (1996) • Nuclear density model: • EMC effect for deuteron scales with nuclear density. Frankfurt and Strikman (1988) Nuclear density model Smearing + binding Fermi smearing (See I. Cloet) Argonne National Laboratory

  15. Models of the structure function SU(6)-symmetric wave function of the proton in the quark model (spin up): u and d quarks identical, N and D would be degenerate in mass. In this model: d/u = 1/2, F2n/F2p = 2/3. SU(6) symmetry is broken: N-D Mass Splitting Mechanism produces mass splitting between S=1 and S=0 diquark spectator. symmetric states are raised, antisymmetric states are lowered (~300 MeV). S=1 suppressed => d/u = 0, F2n/F2p = 1/4, for x -> 1 pQCD: helicity conservation (qp) => d/u =2/(9+1) = 1/5, F2n/F2p = 3/7 for x -> 1 . Argonne National Laboratory

  16. SU(6) symmetry pQCD DSE: 0+ & 1+ qq 0+ qq only Structure Function Ratio DOE milestone HP14 (2018) Reviews: N. Isgur, PRD59 (1999), S Brodsky et al NP B441 (1995), W. Melnitchouk and A. Thomas PL B377 (1996) 11, R.J. Holt and C. D. Roberts, arXiv:1003.4666 [nucl-th], I. Cloet et al, Few Body Syst. 46 (2009) 1. Argonne National Laboratory

  17. The ratio at high x has a strong dependence on deuteron structure. Extractions with modern deuteron wave functions J. Arrington et al, J. Phys. G 36 (2009) A. Accardi, et al., arXiv:0911.2254 More p/d data at JLab 12 GeV E12-10-008 - J. Arrington, A. Daniel, D. Gaskell PAC 36: recommended approval (See F. Olness, S. Kumano, A. Daniel, S. Kulagin, J. Arrington) • Lorentz invariant convolution relation • Light front with null plane kinematics Argonne National Laboratory

  18. Tagged Neutron in the Deuteron – BONUS + CLAS12 • PAC36: “recommended approval” • JLab E12-06-113, S. Bueltmann, H. Fenker, • M. Christy, C. Keppel et al See S. Bueltmann, M. Sargsian, S. Kulagin Argonne National Laboratory

  19. Nuclear Physicists’ Approach to F2n • Problem: • The deuteron experiments present extraction complications. • Nuclear physicists’ solution: Add another nucleon. • 3H/3He ratio: minimizes nuclear physics uncertainties • I. Afnan et al., Phys. Lett. B493, 36 (2000); Phys. Rev. C68, 035201 (2003) • E. Pace, G Salme, S. Scopetta, A. Kievsky, Phys. Rev. C64, 055203 (2001) • M. Sargsian, S. Simula, M. Strikman, Phys. Rev. C66, 024001 (2002) • No DIS data exist for the triton! Argonne National Laboratory

  20. Tritium target at JLab?? Tritium Target Task Force E. J. Beise (U. of Maryland) B. Brajuskovic (Argonne) R. J. Holt (Argonne) W. Korsch (U. of Kentucky) A. T. Katramatou (Kent State U.) D. Meekins (JLab) T. O’Connor (Argonne) G. G. Petratos (Kent State U.) R. Ransome (Rutgers U.) P. Solvignon (JLab) B. Wojtsekhowski (JLab) E12-06-118 G. Petratos et al PAC 36: recommended conditional approval JLab Review: June 3, 2010 -> “No show stopper” See G. Petratos Argonne National Laboratory

  21. Parity Violating Deep Inelastic Scattering • Proton target only • PAC35 “recommended approval” • Requires special spectrometer • P. Souder – SoLID • JLab E12-10-007 (See P. Souder, T. Hobbs, M. Glatzmaier) Argonne National Laboratory

  22. m- m+ W+ W- d u nm nm Deep inelastic neutrino scattering from the proton • Charge current neutrino/antineutrino scattering MINOS@FNAL MINOS high energy tune: 2 years LH2 target MINERnA: J. Morfin (See J. Morfin, R. Petti) Argonne National Laboratory

  23. Deuteron structure function at an EIC • Ee = 8 GeV, EN = 30 GeV • Luminosity ~ 3.5 x 1033 • One year of running (26 wk) at 50% efficiency, or 35 fb-1 • Detect ~30 GeV proton “Super BoNuS” Alberto Accardi, Nuclear Chromodynamics with an EIC Argonne, April 2010 With C. Keppel and R. Ent Argonne National Laboratory

  24. The strange quark distribution function Strange quark distribution - HERMES A. Airapetian et al, PLB 666 (2008) 446 New data: COMPASS II at CERN, JLab with12 GeV, MINERnA at FNAL Far future: EIC-> also charm distribution, gluonic Sivers effect; LHeC -> beauty distribution Argonne National Laboratory

  25. Projections for strange quarks COMPASS-II JLAB E09-007 K. Hafidi et al. Argonne National Laboratory

  26. What about Drell-Yan experiments? Settled by soft gluon resummation – Aicher, Schaeffer, Vogelsang, hep-ph/1009.248 • Pion structure function shape at very high x ?? • Azimuthal asymmetry for the proton Boer-Mulders vs. pQCD? • High x distribution functions 4u + d soft gluon resummation issues? • The kaon structure function should be measured See J.-C. Peng, P. Reimer • COMPASS-II, FNAL E906 SeaQuest, FAIR, J-PARC Argonne National Laboratory

  27. Concluding statement • Understanding hadrons will be one of nuclear physics’ greatest contributions to science • New 21st century tools have positioned us well for the next decade: • JLab 12 GeV, CERN COMPASS-II, FNAL MINERnA, FNAL E906, RHIC, J-PARC, FAIR, petascale computing. • Far future: EIC, exascale computing • Continue to develop and assess the high x case for the EIC • We are camped on one of the most interesting frontiers in science Argonne National Laboratory

  28. Drell-Yan azimuthal asymmetry R. J. Holt and C. D. Roberts, arXiv:1002.4666 [nucl-th] FNAL E906 SeaQuest Argonne National Laboratory

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