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Electroweak Physics At The EIC (Electron-Ion Collider)

This presentation discusses the interplay of electroweak physics and QCD at the Electron-Ion Collider. Key topics include weak neutral current experiments, atomic parity violation (APV), and polarized electron scattering. We explore crucial requirements for collider design, the utility of polarized beams, and the importance of high-precision measurements. The talk also covers historical developments in weak neutral currents, implications of experimental results on the electroweak mixing angle (sin²θW), and the potential for discovering “new physics” through investigations at the EIC.

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Electroweak Physics At The EIC (Electron-Ion Collider)

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  1. Electroweak Physics At The EIC (Electron-Ion Collider) William J. Marciano (May 17, 2010) 1. WEAK NC PARITY VIOLATION i) APV vs Pol Electron Scattering ii) QWEAK, Moller, DIS (eD&ep) 2. Preliminary Collider Requirements For Competitive ARL Program ~100fb-1 (K. Kumar et al.) 2009 Talk *3. Utility of Both Beams Polarized

  2. EIC Physics Case Must be primarily a Nuclear/QCD Facility Structure functions (polarized), small x gluons… Properties of quarks in nuclei (EMC effects)… Sum rules (Bj), (Q2)QCD… HERA(ep): L~1031cm-2s-11033,34,35cm-2s-1 polarized e,p,D,3He; Heavy Ions What about Electroweak Physics? Second Detector? Complementary Program!

  3. BNL/LDRD Proposal 2009Electroweak Physics with an Electron-Ion Collider(Deshpande, Kumar, Marciano, Vogelsang) • DIS & Nuclear Structure Functions (,Z,W) (Beyond HERA) Bjorken Sum Rule, Polarized EMC… • ARL,sin2W(Q2), Radiative Corrections, “New Physics” • Lepton Flavor Violation: eg epX (1000fb-1!) Various Issues That Need Thorough Study What are the Machine and Detector Requirements? Inclusion of Electroweak Radiative Corrections (Important?) High Precision & Polarization(0.5%?, 0.25%?) Proton, D, 3HE Polarization (Spin Content-Other?)

  4. 1) PV Weak Neutral Currents(Past, Present and Future) • Ancient History: By 1975 the SU(2)LxU(1)Y Weinberg-Salam Model was nearly established. Predicted Weak Neutral Currents seen in neutrino scattering at CERN! But did the NC have the right coupling? g2/cosWZf(T3f-2Qfsin2W -T3f5)f A New Form of Parity Violation! Non Maximal but Distinctive -Z Interference  Parity Violation Everywhere!

  5. Atomic Parity Violation (APV) • QW(Z,N) =Z(1-4sin2W)-N Weak Charge W=Weak Mixing Angle QW(p)=1-4sin2W=0.07 QW(209Bi83) = -43 -332sin2W =-127 Bi Much Larger but Complicated Atomic Physics Originally APV not seen in Bi  SM Ruled Out? (Later seen in Tl, Bi, Cs…) 1978 SLAC Polarized eD Asymmetry (Prescott, Hughes…)e+De+X -Z Interference ARL= R-L/R+L2x10-4Q2GeV-2(1-2.5sin2W)~10-4Expected Exp. Gave ARLexp=1.5x10-4sin2W=0.21(2)

  6. Confirmed SU(2)LxU(1)Y SM! ±10% Determination of sin2W Precision! Seemed to agree with GUTS (SU(5), SO(10)…) sin2W=3/8 at unification =mX2x1014GeV sin2W(mZ)MS=3/8[1-109/18ln(mX/mZ)+…] 0.21! (Great Desert?) But later, minimal SU(5) ruled out by proton decay exps (pe+)>1033yr mX>3x1015GeV SUSY GUTUnification(msusy~1TeV)mX1016GeV p1035-1036yr sin2W(mZ)MS=0.233 (Good Current Agreement!)

  7. 1980s - Age of EW Precision sin2W needed better than 1% determination Renormalization Prescription Required EW Radiative Corrections Computed Finite and Calculable: DIS N, ve, APV (A. Sirlin &WJM) mZ, mW, Z, ALR,AFB Define Renormalized Weak Mixing Angle:sin2WR sin20W=1-(m0W/m0Z)2=(e0/g0)2 Natural Bare Relation sin2W1-(mW/mZ)2 On Shell Definition, Popular in1980s Induces large (mt/mW)2 corrections Now Largely Abandoned sin2W()MSe2()MS/g2()MS Good for GUT running No Large RC Induced Theoretically Nice/ But Unphysical

  8. sin2Wlep =Z coupling at the Z pole very popular at LEP = sin2W(mZ)MS+0.00028 (best feature) sin2W(Q2) = Physical Running Angle Continuous Incorporates Z mixing loops: quarks, leptons, W Precision measurements at the Z Pole (e+e-Zff) Best Determinations sin2W(mZ)MS = 0.23070(26) ALR (SLAC) sin2W(mZ)MS = 0.23193(29) AFB(bb) (CERN) (3.2 sigma difference!)

  9. Leptonic vs Hadronic Z Pole Averages sin2W(mZ)MS = 0.23085(21) Leptonic sin2W(mZ)MS = 0.23194(27) Hadronic (Also differ by > 3sigma) World Average: sin2W(mZ)MS=0.23125(16) IS IT CORRECT? (Major Implications)

  10. -1=137.035999, G=1.16637x10-5Gev-2,mZ=91.1875GeV + mW=80.398(25)GeVsin2W(mZ) = 0.23104(15) Implications: 114GeV<mHiggs<150GeV. New Physics Constraints From: mW, sin2W, ,& G S=ND/6 (ND=# of heavy new doublets, eg 4th generationND=4) mW*= Kaluza-Klein Mass (Extra Dimensions) GG(1+0.0085S+O(1)(mW/mW*)2+…) sin2W(mZ)MS S ND&mW* Average 0.23125(16) +0.11(11) 2(2), mW*3TeV ALR 0.23070(26) -0.18(15) (SUSY) AFB(bb) 0.23193(29) +0.46(17) 9(3)! Heavy Higgs, mW*~1-2TeV Very Different Interpretations. We failed to nail sin2W(mZ)MS!

  11. What about low energy measurements? • DIS  Scattering: R(NX)/(NX) loops  mt heavy, sin2W(mZ)MS=0.233SUSY GUTS NuTeV sin2W(mZ)MS=0.236(2) High? Rad. Corr.?Nuclear-Charge Symmetry Violation? Atomic Parity Violation Strikes Back 1990 QW(Cs)exp=-71.04(1.38)(0.88) C. Wieman et al. Electroweak RCQW(Cs)SM=PV(-23-220PV(0)sin2W(mZ)MS) =-73.19(3) 1999 QW(Cs)exp=-72.06(28)(34) Better Atomic Th. 2008 QW(Cs)exp=-72.69(28)(39)sin2W(mZ)MS=0.2290(22) 2009 QW(Cs)exp=-73.16(28)(20)sin2W(mZ)MS=0.2312(16)! 0.5%  Major Constraint On “New Physics” QW(Cs)=QW(Cs)SM(1+0.011S-0.9(mZ/mZ)2+…) eg S=0.00.4 mZ>1.2TeV, leptoquarks, …

  12. Radiative Corrections to APV QW(Z,N)= PV(-N+Z(1-4PVsin2W(mZ)MS) PV=1-/2(1/s2+4(1-4s2)(ln(mZ/M)2+3/2)+….)0.99 PV(0)=1-/2s2((9-8s2)/8s2+(9/4-4s2)(1-4s2)(ln(mZ/M)2+3/2) -2/3(T3fQf-2s2Qf2)ln(mZ/mf)2+…)1.003 s2sin2W(mZ)MS=0.23125, M=Hadronic Mass Scale Radiative Corrections to APV small and insensitive to hadronic unc. Same Corrections Apply to elastic eN scattering as Q20, Ee<<mN

  13. E158 at SLAC Pol eeee Moller)Ee50GeV on fixed target, Q2=0.02GeV2 ALR(ee)=-131(14)(10)x10-9  (1-4sin2W) EW Radiative Corretions -50%! (Czarnecki &WJM) Measured to 12% sin2W to 0.6% sin2W(mZ)MS=0.2329(13) slightly high Best Low Q2 Determination of sin2W ALR(ee)exp=ALR(ee)SM(1+0.13T-0.20S+7(mZ/mZ)2…) Constrains “New Physics” eq mZ>0.6TeV, H--,S, Anapole Moment, … Together APV(Cs) & E158 sin2W(Q2) running sin2W(mZ)MS=0.232(1)

  14. Goals of Future Experiments • High Precision: sin2W0.00025 or better • Low Q2 Sensitivity to “New Physics” mZ’ >1TeV, S<0.1-0.2, SUSY Loops, Extra Dim., 4th Generation….

  15. Other ALR Experiments Strange Quark Content Program: Bates, JLAB, MAMI Proton strange charge radius and magnetic moment consistent with 0. Axial Vector effects and RC cloud strangeness. PREX Experiment: Neuton distribution Preparing the way for future experiments, pushing technology and instrumentation, polarization

  16. Future Efforts QWEAK exp at JLAB Will measure forward ALR(epep)  (1-4sin2W)=QW(p) E=1.1GeV, Q20.03GeV2, Pol=0.801%ARL(ep)3x10-7 small ARL requires long running Goal sin2W(mZ)MS=0.0008 via 4% measurement of ALR Will be best low energy measurement of sin2W ALR(ep)exp=ALR(ep)SM(1+4(mZ/mZ)2+…) eg mz~0.9TeV Sensitivity (Not as good as APV) • The Gorchtein - Horowitz Nightmare (PRL) Z box diagrams: O(2Ee/mp) 6% of QW(p)! Recently Confirmed (Improved): Sibirtev et al.; Gorchtein et al. Proposed Qweak Theory Uncertainty < 2% JLAB Flagship Experiment

  17. Longer Future Efforts: Polarized Moller at JLAB After 12GeV Upgrade ALR(eeee) to 2.5% sin2W(mZ)MS=0.00025! Comparable to Z pole studies! ALR(ee)exp=ALR(ee)SM(1+7(mZ/mZ)2+…) Explores mZ1.5TeV Better than APV, S0.1 etc. Future JLAB Flagship Experiment!

  18. HPV=G/2[(C1uuu+C1ddd)e5e+HPV=G/2[(C1uuu+C1ddd)e5e+ (C2uu5u+C2dd5d)ee+…] QW(p)=2(2C1u+C1d) QW(Cs)=2(188C1u+211C1d) What about the C2q?

  19. What About C2u and C2d? • Renormalized at low Q2 by Strong Interactions Measure in Deep-Inelastic Scattering (DIS), eD & ep ARL(eDeX)2x10-4GeV-2Q2[(C1u-C1d/2)+f(y)(C2u-C2d/2)] f(y)=[1-(1-y)2]/[1+(1-y)2] Standard Model: C1u= (1-8sin2W/3)/2  0.20 C1d=-(1-4sin2W/3)/2 -0.32 C2u= (1-4sin2W)/2 0.04 C2d =-(1-4sin2W)/2-0.04 C2q sensitive to RC & “New Physics” eg Z (SO(10)) Measure ARL to 1/2%? Measure C2q to 1-2%? Theory (loops)?

  20. JLAB 6 GeV DIS eDeX Proceeding JLAB 12 GeV DIS eD Future Goals: Measure C2qs, “New Physics”, Charge Sym. Violation … Effective Luminosity (Fixed Target) 1038cm-2sec-1! What can ep and eD at e-Ion contribute? Asymmetry F.O,M,A2N, AQ2, N1/Q2 (acceptance?) High Q2 Better (but Collider Luminosity?) K. Kumar Talk 100fb-1 (L1034cm-2s-1) Needed Program can be started with lower luminosity Do DIS ep, eD, eN at factor of 10 lower (Polarized p & Nuclei)Bjorken Sum Rule, Pol Structure Functions, Spin Distribution…

  21. Single and Double Polarization Asymmetries Polarized e: AeRL=(RR+RL-LL-LR)/(RR+RL+LL+LR)Pe Polarized p: ApRL=(RR+LR-RL-LL)/(RR+LR+RL+LL)Pp Polarized e&p AepRRLL= (RR-LL)/(RR+LL)Peff Peff=(Pe-Pp)/(1-PePp) opposite signs like relativistic velocities addition1 eg Pe=0.80.008, Pp=-0.70.03 Peff=0.9620.004 small uncertainty How to best utilize Peff? Measure: RR,LL,RL,LR Fit  Polarization Dist.

  22. Example: Polarized Protons or Deuterons (Unpolarized Electrons) C1q C2q  (1-4sin2W) Use to measure sin2W?

  23. LDRD ARL GOALS Examine Machine and Detector Requirements For 1% Include EW Radiative Corrections to DIS Is 100fb-1 Sufficient? Utility of Proton Polarization? Stage 1 e-Ion aim for 4% Study Nuclear Effects (EMC, CSV, Sum Rules) Important Secondary e-Ion Goal? Improves Proposal?

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