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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder 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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

Weak-Electromagnetic Interference Electron Scattering off Nucleons & Nuclei April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

Introduction to Elastic Sacttering Neglecting recoil and spin: Obtain Fourier transform of charge distribution Nucleon charge and magnetization distributions: GE(Q2), GM(Q2) GEp(0) = 1 GMp(0) = +2.79  p electric and magnetic form factors GEn(0) = 0 GMn(0) = -1.91  n Q2 (GeV/c)2 GEn r2 rs(r) r [fm] GE for the neutron charge distribution: +ρ core, -ρ fringe, charge radius April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

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?? Various theoretical approaches: Quark models Dispersion Relations Lattice Gauge theory Skyrme models Chiral Solitons Data: HAPPEX I; Effects are surprisingly small. Due to cancellations? April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder 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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

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) April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder Add New HAPPEX Results Dc2 = 1 95% c.l. Optimistic predictions: GEs~0.07, GMs~0.7 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

World Data vs Q2: Past, Present, and Future Severe limit on strangeness If GEs~Q2ρsGEp/4M2 GEs+xGMs GMs GEs Separate form factors April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

Parity Violating Electron DIS 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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder 2H Experiment at 11 GeV E’: 5.0 GeV ± 10% lab = 12.5o Ibeam = 90 µA 60 cm LD2 target Use both HMS and SHMS to increase solid angle ~2 MHz DIS rate, π/e ~ 2-3 APV = 217 ppm 1000 hours (APV)=0.65 ppm (2C2u-C2d)=±0.0086±0.0080 PDG (2004): -0.08 ± 0.24 Theory: +0.0986 xBj ~ 0.235, Q2 ~ 2.6 GeV2, W2 ~ 9.5 GeV2 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder Physics Implications (2C2u-C2d)=0.012 (sin2W)=0.0009 Examples: 1 TeV extra gauge bosons (model dependent) TeV scale leptoquarks with specific chiral couplings Unique, unmatched constraints on axial-vector quark couplings: Complementary to LHC direct searches April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder Search for CSV in PV DIS For APV in electron-2H 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 measure or constrain higher twist effects at x ~ 0.5-0.6 precision measurement of APV at x ~ 0.7 to search for CSV Strategy: April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder 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. April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder 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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

Deuteron analysis has nuclear 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% April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

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… April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

Large Acceptance: Concept CW 90 µA at 11 GeV 40-60 cm liquid H2 and D2 targets Luminosity > 1038/cm2/s JLab Upgrade 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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder

PV in Electron Scattering at JLab P. A. Souder 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 April 29, 2005 PV in Electron Scattering at JLab P. A. Souder