1 / 22

Parity Violation in eP Scattering at JLab

Explore the latest progress in Parity Violation (PV) studies in electron-proton (eP) scattering at Jefferson Lab (JLab), focusing on elastic and deep inelastic scattering. Learn about technological advancements, theoretical approaches, and experimental results, shedding light on nucleon structure and quark modeling. Discover the potential implications for axion-like particles and leptoquarks.

gudino
Download Presentation

Parity Violation in eP Scattering at JLab

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Parity Violation in eP Scattering at JLab Elastic and Deep Inelastic Scattering Thanks to everyone who helped developed the ideas presented here P. A.Souder Syracuse University PV in Electron Scattering at JLab P. A. Souder

  2. APV Measurements APV ~ to 0.1 to 100 ppm • Steady progress in technology • part per billion systematic control • 1% normalization control • JLab now takes the lead • New results from HAPPEX • Photocathodes • Polarimetry • Targets • Diagnostics • Counting Electronics E-05-007 PV in Electron Scattering at JLab P. A. Souder

  3. Weak-Electromagnetic Interference Electron Scattering off Nucleons & Nuclei PV in Electron Scattering at JLab P. A. Souder

  4. Nucleon charge and magnetization distributions: GE for the neutron GE(Q2), GM(Q2) GEp(0) = 1 GMp(0) = +2.79  p charge distribution: +ρ core, -ρ fringe, charge radius electric and magnetic form factors GEn(0) = 0 GMn(0) = -1.91  n GEn r2 rs(r) r [fm] Q2 (GeV/c)2 Introduction to Elastic Sacttering Neglecting recoil and spin: Obtain Fourier transform of charge distribution PV in Electron Scattering at JLab P. A. Souder

  5. Quark models • Dispersion Relations • Lattice Gauge theory • Skyrme models • Chiral Solitons Various theoretical approaches: Strangeness in Nucleons The charge density of the neutron depends on the radius. Does the strangeness density of the nucleon also depend on the radius?? Data: HAPPEX I; Effects are surprisingly small. Due to cancellations? PV in Electron Scattering at JLab P. A. Souder

  6. The Strangeness Densities can be Measured by Elastic Electroweak Scattering • Measurements must access 0.1 < Q2 < 1 • forward and backward angles, three targets • Sensitivity: GEn(Q2=0.2) ~ 0.05,  ~ -0.6 • MIT-Bates: SAMPLE • Mainz (Germany): A4 • Jefferson Lab: HAPPEX, G0 PV in Electron Scattering at JLab P. A. Souder

  7. Example at JLab: HAPPEX Experiment 1998-99: Q2=0.5 GeV2, 1H 2004-05: Q2=0.1 GeV2, 1H, 4He The HAPPEX Collaboration California State University, Los Angeles - Syracuse University - DSM/DAPNIA/SPhN CEA Saclay - Thomas Jefferson National Accelerator Facility- INFN, Rome - INFN, Bari - Massachusetts Institute of Technology - Harvard University – Temple University – Smith College - University of Virginia - University of Massachusetts – College of William and Mary PV in Electron Scattering at JLab P. A. Souder

  8. New 1H and 4He Data at Q2~0.1 (GeV/c)2 A(Gs=0) = -1.44 ppm 0.11 ppm APV = -1.140.24(stat)0.06(stat)ppm A(Gs=0) = +7.51  0.08 ppm APV = 6.720.84(stat)0.21(syst) ppm PV in Electron Scattering at JLab P. A. Souder

  9. Summary of Published 1H and 4He Results GsE = -0.039  0.041(stat)  0.010(syst)  0.004(FF) GsE + 0.08 GsM = 0.032  0.026(stat)  0.007(syst)  0.011(FF) PV in Electron Scattering at JLab P. A. Souder

  10. Dc2 = 1 95% c.l. Add New HAPPEX Results Optimistic predictions: GEs~0.07, GMs~0.7 PV in Electron Scattering at JLab P. A. Souder

  11. GEs GMs Separate form factors World Data vs Q2: Past, Present, and Future Severe limit on strangeness If GEs~Q2ρsGEp/4M2 GEs+xGMs PV in Electron Scattering at JLab P. A. Souder

  12. Parity Violating Electron DIS e- e- * Z* X N fi(x) are quark distribution functions For an isoscalar target like 2H, structure functions largely cancel in the ratio: Provided Q2 >> 1 GeV2 and W2 >> 4 GeV2 and x ~ 0.2 - 0.4 Must measure APV to fractional accuracy better than 1% • 11 GeV at high luminosity makes very high precision feasible • JLab is uniquely capable of providing beam of extraordinary stability • Systematic control of normalization errors being developed at 6 GeV PV in Electron Scattering at JLab P. A. Souder

  13. 1000 hours (APV)=0.65 ppm (2C2u-C2d)=±0.0086±0.0080 PDG (2004): -0.08 ± 0.24 Theory: +0.0986 2H Experiment at 11 GeV E’: 5.0 GeV ± 10% lab = 12.5o 60 cm LD2 target Ibeam = 90 µA • Use both HMS and SHMS to increase solid angle • ~2 MHz DIS rate, π/e ~ 2-3 APV = 217 ppm xBj ~ 0.235, Q2 ~ 2.6 GeV2, W2 ~ 9.5 GeV2 PV in Electron Scattering at JLab P. A. Souder

  14. (2C2u-C2d)=0.012 (sin2W)=0.0009 Unique, unmatched constraints on axial-vector quark couplings: Complementary to LHC direct searches • 1 TeV extra gauge bosons (model dependent) • TeV scale leptoquarks with specific chiral couplings Examples: Physics Implications PV in Electron Scattering at JLab P. A. Souder

  15. PV DIS and Nucleon Structure • Analysis assumed control of QCD uncertainties • Higher twist effects • Charge Symmetry Violation (CSV) • d/u at high x • NuTeV provides perspective • Result is 3 from theory prediction • Generated a lively theoretical debate • Raised very interesting nucleon structure issues: cannot be addressed by NuTeV • JLab at 11 GeV offers new opportunities • PV DIS can address issues directly • Luminosity and kinematic coverage • Outstanding opportunities for new discoveries • Provide confidence in electroweak measurement PV in Electron Scattering at JLab P. A. Souder

  16. For APV in electron-2H DIS: Strategy: • measure or constrain higher twist effects at x ~ 0.5-0.6 • precision measurement of APV at x ~ 0.7 to search for CSV Search for CSV in PV DIS • u-d mass difference • electromagnetic effects • 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 Sensitivity will be further enhanced if u+d falls off more rapidly than u-d as x  1 PV in Electron Scattering at JLab P. A. Souder

  17. Higher Twist Effects Key: APV is known, so no extrapolations are necessary • APV sensitive to diquarks: ratio of weak to electromagnetic charge depends on amount of coherence • If Spin 0 diquarks dominate, likely only 1/Q4 effects • On the other hand, higher twist effects may cancel, so APV may have little dependence on Q2.  PV in Electron Scattering at JLab P. A. Souder

  18. APV in DIS on 1H + small corrections • Allows d/u measurement on a single proton! • Vector quark current! (electron is axial-vector) • Determine that higher twist is under control • Determine standard model agreement at low x • Obtain high precision at high x PV in Electron Scattering at JLab P. A. Souder

  19. d/u at High x Deuteron analysis has nuclear corrections APV for the proton has no such corrections The challenge is to get statistical and systematic errors ~ 2% PV in Electron Scattering at JLab P. A. Souder

  20. Summary of PV DIS Program • Hydrogen and Deuterium targets • Better than 2% errors • It is unlikely that any effects are larger than 10% • x-range 0.25-0.75 • W2 well over 4 GeV2 • Q2 range a factor of 2 for each x point • (Except x~0.7) • Moderate running times • With HMS/SHMS: search for TeV physics • With larger solid angle apparatus: higher twist, CSV, d/u… PV in Electron Scattering at JLab P. A. Souder

  21. Need high rates at high x • For the first time: sufficient rates to make precision PV DIS measurements • solid angle > 200 msr • Count at 100 kHz • online pion rejection of 102 to 103 Large Acceptance: Concept • CW 90 µA at 11 GeV • 40-60 cm liquid H2 and D2 targets • Luminosity > 1038/cm2/s JLab Upgrade PV in Electron Scattering at JLab P. A. Souder

  22. Summary • Strange Quarks and Elastic Scattering • Hint of positive effect • More data soon (G0, HAPPEX II) • Parity Violation in DIS (JLab at 11 GeV) • Electroweak test • Hadron structure • d/u at large x • δu-δd (Charge symmetry violation) • Clean higher twist study PV in Electron Scattering at JLab P. A. Souder

More Related