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DIS-Parity 12 GeV

DIS-Parity 12 GeV. Kent Paschke University of Massachusetts. Physics opportunities in PVeS with a Solenoidal Spectrometer. Many slides liberated from: P. Souder, K. Kumar (… and their sources). PV Asymmetries. Weak Neutral Current (WNC) Interactions at Q 2 << M Z 2.

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DIS-Parity 12 GeV

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  1. DIS-Parity 12 GeV Kent Paschke University of Massachusetts Physics opportunities in PVeS with a Solenoidal Spectrometer Many slides liberated from: P. Souder, K. Kumar (… and their sources)

  2. PV Asymmetries Weak Neutral Current (WNC) Interactions at Q2 << MZ2 Longitudinally-Polarized Electrons Scattering off Unpolarized Fixed Targets (gAegVT+gVegAT) • The couplingsgTdepend on electroweak physics as well as on the weak vector and axial-vector hadronic current • For DIS-Parity, both new physics at high energy scales as well as interesting features of hadronic structure come into play • A program with a broad kinematic range can untangle the physics DIS Parity at 12 GeV Kent Paschke

  3. PVeS and Physics Beyond the SM: Qweak and Møller Kurylov, Ramsey-Musolf, Su To be relevant, new SM tests must have small enough errors to show up on plots like this DIS Parity at 12 GeV Kent Paschke Examples:

  4. Add DIS-Parity: ± 1% DIS-Parity requires a factor of 5-10 improvement In δA/A to be competitive with Qweak, Møller No 1-4sin2θW suppression of APV DIS Parity at 12 GeV Kent Paschke

  5. Parity Violating Electron DIS e- e- * Z* X N For an isoscalar target like 2H, structure functions largely cancel in the ratio: as x gets large, the sea is negligible DIS Parity at 12 GeV Kent Paschke

  6. Hall C “Standard” Upgrade New Physics: measuring sin2(qW) Note that each of the Ciq are sensitive to different possible S.M. extensions. DIS Parity at 12 GeV Kent Paschke

  7. Exp. Constraints on C1u, C1d, C2u and C2d From P. Reimer, describing PV-DIS possible with “standard” upgrade Combined result significantly constrains 2C2u–C2d. PDG 2C2u–C2d = –0.08 ± 0.24Combined d(2C2u–C2d) = ± 0.014 DIS Parity at 12 GeV Kent Paschke

  8. Hall C “Standard” Upgrade What happened to NuTeV? NuTeV result on sin2qW is 3s from standard model… why isn’t everyone more excited? Various problems in interpretation, mostly in the hadronic physics… PV-DIS will have the same problem! Too bad if you want to test the Standard Model… …but very cool if you like hadronic physics! • PV-DIS Standard Model test interpretation might be “clouded” by: • Isospin-symmetry violation for PDFs • Contributions from higher twist The silver lining: one can study the clouds! DIS Parity at 12 GeV Kent Paschke

  9. PV-DIS and hadronic physics In principle, PV-DIS is sensitive to: • Contributions from higher twist • Isospin-symmetry violation for PDFs • d/u PDF ratio as x->1 • Nuclear effects (parton shadowing, EMC, ….) • What is needed: • Large kinematic range (Q2 range at fixed, moderate xBj) • Large acceptance • High luminosity • Excellent background suppression DIS Parity at 12 GeV Kent Paschke

  10. Higher Twist is any Q2-dependent deviation From the SM prediction (Does not Evolve) Remember: for 2H at moderate x, structure functions largely cancel in APV Higher Twist Coefficients in parity conserving (Di) and nonconserving (Ci) Scattering Evolves according To DGLAP equations Higher Twist is what is left over DIS Parity at 12 GeV Kent Paschke

  11. Interpretation of Higher Twist • APV sensitive to diquarks: ratio of weak to electromagnetic charge depends on amount of coherence • Do diquarks have twice the x of single quarks? • If Spin 0 diquarks dominate, likely only 1/Q4 effects  Clean observation of a higher twist operator may be possible. DIS Parity at 12 GeV Kent Paschke

  12. Higher Twist unlikely at (moderately) low x, possible at high x Q2=(W2-M2)/(1/x-1) Q2min=Q2(W=2) F2(x,Q2)=F2(x)(1+D(x)/Q2) MRST ‘04 If C(x) acts like D(x), PVeS might show higher twist at high x without needing QCD evolution. DIS Parity at 12 GeV Kent Paschke

  13. quark mass difference: n-p mass difference: Charge Symmetry Violation Charge symmetry Charge symmetry Violation (CSV) Sather: Analytic Quark Model Approximation for Valence Parton CSV. Leads to analytic results (model-dependent) “QED Splitting” Londergan,Murdock,Thomas hep-ph/0603208 MRST, Eur.Phys.J. 39, 155 (05); Glueck, Jimenez-Delgado, Reya, PRL95, 022002 (05) • Contributes even if mu = md and Mn= Mp • add to quark model CSV term • MRST incorporate QED splitting with PDFs • in global fit to high energy data Figures from T.Londergan DIS Parity at 12 GeV Kent Paschke

  14. Phenomenological Parton CSV PDFs MRST PDFs from global fits include CSV for 1st time: Martin, Roberts, Stirling, Thorne [Eur Phys J C35, 325 (04)]: Choose restricted form for parton CSV: 90% conf limit (κ) [f(x): 0 integral; matches to valence PDFs at small, large x] Best fit: κ = -0.2, large uncertainty ! Best fit remarkably similar to quark model CSV calculations ADEL (1994) MRST (2004) Slide from T.Londergan DIS Parity at 12 GeV Kent Paschke

  15. Search for CSV in PV DIS • Direct observation of parton-level CSV would be very exciting! • Important implications for high energy collider pdfs • Could explain significant portion of the NuTeV anomaly For APV in electron-2H DIS: Sensitivity will be further enhanced if u+d falls off more rapidly than u-d as x  1 (QED + bag) says ~6% effect! MRST fit suggests ~1% effect at x = 0.7 • Strategy: • constrain higher twist effects at x ~ 0.5 - 0.6 • precision measurement of APV at x → 0.7 to search for CSV DIS Parity at 12 GeV Kent Paschke

  16. APV in DIS on 1H + small corrections Allows d/u measurement on a single proton! • Strategy: • Determine that higher twist is under control • Determine standard model agreement at low x • Obtain high precision at high x DIS Parity at 12 GeV Kent Paschke

  17. d/u at High x Deuteron analysis has nuclear corrections APV for the proton has no such corrections Must simultaneously constrain higher twist effects The challenge is to get statistical and systematic errors ~ 2% DIS Parity at 12 GeV Kent Paschke

  18. Scorecard DIS Parity at 12 GeV Kent Paschke

  19. Coherent PV DIS Program (Including 12 GeV) • Hydrogen and Deuterium targets • Better than 2% errors • x-range 0.25-0.75 • W2 well over 4 GeV2 • Q2 range a factor of 2 for each x point • (Except x~0.75) • Moderate running times • With HMS/SHMS: search for TeV physics • With larger solid angle apparatus: higher twist, CSV, d/u… DIS Parity at 12 GeV Kent Paschke

  20. EMC effect in PVeS This study might be done with 8.5 GeV beam, 50 μa beam Cross section data from J. Gomez et.al. PRD 49 (1994) 4348 • 50 days running. • Targets: • 15 cm LD2 • 0.17 mm Fe Targets • 1% RL C12 Targets

  21. Summary and Outlook • Parity-Violating DIS can probe exciting new physics at high x • One can start now (at 6 GeV) • Do 2 low Q2 points (P-05-007, X. Zheng contact) • Q2 ~ 1.1 and 1.9 GeV2 • Either bound or set the scale of higher twist effects • Take data for W<2 (P-05-005, P. Bosted contact) • Duality • Could help extend range at 11 GeV to higher x • Probe TeV physics in PV DIS off 2H: Hall C at 12 GeV • The bulk of this coherent program requires a dedicated spectrometer/detector • Higher twist must be controlled (or exploited) • CSV can be probed at high x • Standard Model test is interpretable when coupled with hadronic studies • Uniquely clean d/u at high x • EMC effect in PVeS • Additional physics topics could be addressed by dedicated spectrometer • Transverse (beam-normal) asymmetries in DIS • Polarized targets: g2 and g3 structure functions DIS Parity at 12 GeV Kent Paschke

  22. Details on Kinematics Solenoid SHMS 0.4<y<0.8, E’<7GeV 0.4<y<0.8, E’<5GeV • Large range in Q2 for HT study • High x (>0.7) accessible with W2>4 • Large acceptance allows feasible runtime requests • p/e ratio is not extreme, but cannot integrate DIS Parity at 12 GeV Kent Paschke

  23. Details on Kinematics and π/e Ratio Solenoid SHMS 0.4<y<0.8, E’<7GeV 0.4<y<0.8, E’<5GeV • Large range in Q2 for HT study • High x (>0.7) accessible with W2>4 • Large acceptance allows feasible runtime requests • p/e ratio is not extreme, but cannot integrate DIS Parity at 12 GeV Kent Paschke

  24. Reaching Large x at 11 GeV W<2 Need Large θ for large x and Q2 (and large y) 6 GeV HMS and SHMS are fine for small θ 50% azimuthal coverage assumed DIS Parity at 12 GeV Kent Paschke

  25. Range of W and Q2 • 2 to 3.5 GeV scattered electrons • 20 to 40 degrees • Factor of 2 in Q2 range at moderate x • High statistics at x=0.7, with W>2 DIS Parity at 12 GeV Kent Paschke

  26. We know the origins of parton CSV: • quark mass difference: • n-p mass difference: Charge Symmetry Violation Charge symmetry Charge symmetry Violation (CSV) Sather: Analytic Quark Model Approximation for Valence Parton CSV. Leads to analytic results (model-dependent) DIS Parity at 12 GeV Kent Paschke

  27. “QED Splitting”: a New Source of Isospin Violation MRST, Eur.Phys.J. 39, 155 (05); Glueck, Jimenez-Delgado, Reya, PRL95, 022002 (05) “QED evolution”, quark radiates photon Evolve in Q2 • qualitatively similar to quark model CSV • QED varied while quarks “frozen” • contributes even if mu = md and Mn= Mp • add to quark model CSV term • increase CSV ~ factor 2 • MRST incorporate QED splitting with PDFs • in global fit to high energy data Slide from T.Londergan DIS Parity at 12 GeV Kent Paschke

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