Weak probe of the nucleon in electron scattering Weak Current far from the Z pole History Elastic Scattering and strange content of the nucleon Perspectives in charged current and DIS kinematics Conclusion David Lhuillier , CEA Saclay

Principle + 2 g(Q2) e- N e- X = Z0 N X N X Nice perturbative probe Q2 << MZ2 at typical “hadronic scale” But weak interaction violates P  Build a pseudo-scalar observable, prop. to MZ: ALR~GFQ2/4pa ALR~10-4 at Q2=1 (GeV/c)2 David Lhuillier , CEA Saclay

A Bit of History: E122 @ SLAC g e 2H X ,Z0 e’ DIS off deuteron target: x=Q2/2Mn y=n/E Isoscalar target: fu(x)=fd(x) Neglect sea distributions: x > 0.2 x dependence factorizes out David Lhuillier , CEA Saclay

A bit of History: E122 @ SLAC C.Y.Prescot et al, Phys. Lett. 84B, 524 (1979) Weinberg-Salam First constraint establishing the Weinberg-Salam Model: Hybrid sin2qW= 0.224+/-0.020 Extensions: Low x: probe sea contribution with sin2qW as input Larger x: precise test of sin2qW (Jlab LOI, complementary to E158 and Qweak) David Lhuillier , CEA Saclay

Parity Violation in e- Scattering Test SM Elastic e--N Factor 1000 ! Mutual enrichment between test of SM and hadronic structure Impressive performances of polarized beam David Lhuillier , CEA Saclay

Experimental Techniques Injector Beam line Hall Key elements: l/2 Source High Pe and I Rapid helicity flip Feedbacks “Table-Top” Experiments Half-wave plate reversals IN OUT Charge asymmetry at 1 GeV Final: AI=-8.4+/-7.8 ppb (10-9) ! David Lhuillier , CEA Saclay

Elastic Scattering + 2 g(Q2) e- N e- N = GFQ2 Z0 + e’ e- N e- N = 2 Electromagnetic FF Weak FF ALR= f(F1g,F2g,F1Z,F2Z,GA) GFQ2 2pa 2 few ppm at Q2<1 (GeV/c)2 David Lhuillier , CEA Saclay

Strange content of the Nucleon Sum over 3 quarks flavours (u,d,s) weighted by elec. and weak charges Charge symmetry Motivation triggered by DIS results on Ds but the measured matrix elements are independent: vector <N|sgms|N> instead of pseudo-vector <N|sgmg5s|N> Extraction of the strange quarks contribution 3x3 equations Same relations stand for GE/GM… David Lhuillier , CEA Saclay

Leading Non Zero Moments Measurements at low Q2 Strange Charge Radius: <rs2>Sachs (fm2) Scale: <r2n>Sachs=0.12 fm2 Strange Magnetic Moment: Scale: mN David Lhuillier , CEA Saclay

Elastic e-p Asymmetry Forward angle: GsE,GsM Backward angle: GsM,GA <rs2>Sachs= 0.33 fm2 ms= -0.3 Forward angle: GsE,GsM Backward angle: GsM,GA David Lhuillier , CEA Saclay

Experimental Strategy Complete Separation GE/GM/GA over Q2=0.11 (GeV/c)2 Rosenbluth Method Forward and backward measurements with the same detector setup G0 @ Jlab Q2=0.3-0.8 (Gev/c)2 PVA4 @ MAMI Q2=0.1 and 0.25 (Gev/c)2 but not enough lever arm to extract the 3 contributions David Lhuillier , CEA Saclay

Experimental Strategy Complete Separation GE/GM/GA over Q2=0.11 (GeV/c)2 Different targets Quasi-elastic e-Deuteron Elastic e-4He: Isoscalaire Transition pure GE SAMPLE MIT-Bates HAPPEx2 JLab Q2=0.1 GeV/c2 David Lhuillier , CEA Saclay

Experimental Program Q2 dependence First moments G0, PVA4, HAPPEx1 0.2 < Q2 < 0.8 (GeV/c)2 First moments SAMPLE, HAPPEx2, PVA4 Q2 = 0.1 (GeV/c)2 First Constraint on ms: ms=0.37+/-0.20stat+/-0.26syst+/-0.15theo Expected combined accuracy: dms ~ 0.16 mN d<rs2>Sachs ~ 0.020 fm2 ~ <rn2>Sachs/6 David Lhuillier , CEA Saclay

Weak Charged Current in e-p scattering Z0 The NEPTUNE experiment n e- W- Letter Of Intent at JLab (A. Deur) High luminosity Direct measurement + p n - Only detected particle = n GE,M V GA GP David Lhuillier , CEA Saclay

NEPTUNE Experimental Setup Background reduction: Backward kinematic Sweepnig magnet Recoil detector Pulsed beam S/B~0.1 e- APV=10% Accurate normalization despite bad S/B. Symmetric w.r.t. beam axis (not represented) David Lhuillier , CEA Saclay

NEPTUNE Projected Results p electroproduction e-pnn GA E=1-2 GeV qe=120deg Q2=0.8-2.7 Q2 (GeV/c)2 Accurate data in an unexplored kinematical domain of a fundamental observable of the nucleon David Lhuillier , CEA Saclay

Parity Violating Asymmetry in e-p DIS e+,e- p X ,Z0 e’ Extract G3  separate valence and sea contributions … David Lhuillier , CEA Saclay

Parity Violating Asymmetry in e-p DIS Single spin asymmetry: G3 term is suppressed but ratio G2/F2 depends on d/u ALR ~ 10-5 Q2, allows accurate measurements Charge asymmetry: First data from HERA, Stat. Limited Intense neutrino beams [se+-se-] a xG3 David Lhuillier , CEA Saclay

Conclusion Weak Neutral Current in e- scattering: New probe of the nucleon structure Important experimental program ongoing to extract the contribution of strange quarks to the vector matrix element <N|sgms|N>. Development of experimental techniques Perspectives in charged current (GA) and DIS neutral current (d/u). Precise test of the interaction itself David Lhuillier , CEA Saclay

Back to the Future New results from ALR in Moller scattering from E158 at SLAC. Parity violating asymmetries allow precise test of SM at low energy David Lhuillier , CEA Saclay