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Probing New Physics with Neutral Current Measurements

Probing New Physics with Neutral Current Measurements. Shufang Su • U. of Arizona. Outline. -. Precision measurements vs. direct detection Neutral current measurements parity violating electron scattering ee Moller scattering (SLAC E158) ep elastic scattering (Jlab Qweak)

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Probing New Physics with Neutral Current Measurements

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  1. Probing New Physics with Neutral Current Measurements Shufang Su • U. of Arizona

  2. Outline - • Precision measurements vs. direct detection • Neutral current measurements • parity violating electron scattering ee Moller scattering (SLAC E158) ep elastic scattering (Jlab Qweak) • atomic parity violation (APV) • neutrino-nucleus deep inelastic scattering (NuTeV) - proble new physics beyond SM - some QCD issue - future experiments • Conclusion

  3. (indirect) (direct) mt=178.0  4.3 GeV Precision measurements vs. direct detection - • Direct vs. indirect detection • provide complementary information • success of SM • consistency check of any new physics scenario LEP EWWG LEP EWWG 2004 winter

  4. Low energy precision measurements - • address questions difficult to study at high energy weak interactions(parity violation) • high precision low energy experiment available - muon g-2: M=m , new  2x10-9, exp < 10-9 • -decay, -decay: M=mW , new  10-3, exp  10-3 • parity-violating electron scattering: M=mW , new  10-3, • 1/QWe,p10more sensitive to new physics • need exp  10-2 “easier” experiment size of loop effects from new physics: (/)(M/Mnew)2 QWe,p 1-4 sin2W  0.1 • probe new physics off the Z-resonance - sensitive to new physics not mix with Z

  5. E158 Runs I+II (Preliminary) Talk in neutral current session - • Norval Fortson:APV • Bob McKeown: ee (E158) • Shelley Page: ep (Qweak) • Kevin McFarland: (NuTeV) In addition • Janet Conrad (Friday): reactor based -e- scattering NuTeV • QWCs: agree Q2=0 ee E158 ep Qweak - • NuTeV: +3 Q2=20 (GeV)2 APV(Cs) MS Anticipated final errors -  sin2W  0.0007 Neutral Current: Test of sin2Wrunning - Weak mixing anglesinW courtesy of Erler and Carlini g sinW = g’ cosW = e • sin2W(0) - sin2W(mZ2) = +0.007 Weak mixing angle sin2W • parity-violating electron • scattering (PVES) Q2=0.03 (GeV)2 • - ee Moller scattering (SLAC)QWe • - ep elastic scattering (J-lab) QWp scale Q (GeV)

  6. NC exp as a indirect probe of new physics - SM is a low energy approximation of a more fundamental theory NC exp:  consistency check of SM  complementary to direct new physics searches  distinguish various new physics • SUSY: minimal Supersymmetric extension of SM (MSSM) each SM particle superpartner - with R-parity : loop corrections - without R-parity: tree-level contribution • extra Z’ - exists in extension of SM - constraints from Z-pole observable (mix with Z) • leptoquark • extra-dimension… spin differ by ½

  7. A N+-N- N++N- ALR  QWf V weak charge QWf = 2gfV = 2 If3 -4Qfs2 ep Qweak exp QWpee Moller exp QWe QWe,ptree1-4s2 -(1-4s2) QWe,ploop0.0721 -0.0449 exp precision 4% 9%  sin2W0.0007 0.0010 SM running 10  8  PVES:E158 and Qweak - geA = Ie3 • clean environment: Hydrogen target • theoretically clean: small hadronic uncertainties • tree level  0.1 sensitive to new physics QWCs : sin2W = 0.0021NuTeV: sin2W = 0.0016

  8. O(1) Sensitivity to new physics scale - Ramsey-Musolf(1999) : new physics scale Take  QWp=4% courtesy of Carlini • Non-perturbative theory g » 2 » 29 TeV • Extra Z’ (GUT) g » 0.45 mZ’» 2.1 TeV • probe new physics scale comparable to LHC • confirmation of LHC discovery (couplings, charges)

  9. MSSM correction to weak charge - QWf =  (2Tf3 - 4Qf  s2) + f Kurylov, Ramsey-Musolf, Su (2003) • QWeandQWpcorrelated dominant :  (<0)  negative shift in sin2W MSSM  (QWp)SUSY / (QWp)SM < 4%,  (QWe)SUSY / (QWe)SM < 8%

  10. RPV 95% CL MSSM loop R-parity violating (RPV) - • RPV operators contribute to QWe,p at tree level Kurylov, Ramsey-Musolf, Su (2003) • Exp constraints •  decay: |Vud| = -0.00145  0.0007 • APV(Cs):  QWCs = -0.0040  0.0066 • Re/:  Re/ = -0.0042  0.0033 • G:  G = 0.00025  0.00188 QpW No SUSY dark matter I) Obtain 95% CL allowed region in RPV coefficients II) Evaluate  QWe andQWp G

  11.  QWp  QWe 0.0029 0.0040 • exp • MSSM: • extra Z’: • RPV SUSY • leptoquark SM SM Correlation between QWp, QWe - • Distinguish new physics Erler, Kurylov and Ramsey-Musolf (2003) Distinguish via APV QWCs Combinations of NC exps could be used to distinguish various new physics

  12. ? Extract QWp - use kinematics to simplify: at forward angle  Musolf et. al., (1994) • measure F(,q2) over finite range in q2, extrapolate F • to small q2 • existing PVES: SAMPLE, HAPPEX, G0, A4 • minimize effect of F by making q2 small • q2  0.03 GeV2, still enough statistics  QpW / QpW | hadronic effects  2 %

  13. e e e p p p W Z Z suppression non-calculable Similar to nuclear -decay p e  Z W e- p p p p  e e e Z W e n  |CW|  2 (CKM unitarity) |CZ|  2 e p QCD correction to ep scattering - Box diagram contribution to QWP Erler, Kurylov and Ramsey-Musolf (2003) QWP 26% 3% 6% kloop» O(mW) kloop» O(mZ) QCD kloop  O(mZ) non-perturbative using OPE (pQCD) QWP (QCD) -0.08% 0.65% -0.7% Total theoretical uncertainty » 0.8%

  14. Outlook: PV electron scattering Kurylov, Ramsey-Musolf, Su (2003) MSSM Linear Collider e-e- RPV DIS-Parity,JLab DIS-Parity, SLAC JLab Moller (ee) - Erler NuTeV sin2W APV e+e- LEP, SLD SLAC E158 (ee) JLab QWeak (ep) Q (GeV)

  15. atomic structure • 1%Blundell et. al. (1990, 1992) • Dzuba et. Al. (1989) • reduced error 0.6% (exp + theory) via transit dipole amplitude measurement Bennett and Wieman (1999) finite nuclear size nucleon substructure nuclear spin-dependent term » 0.15% Pollock and Wieman (2001) Musolf (1994) Erler, Kurylov and Ramsey-Musolf (2003) QW(Z,N)=(2Z+N)QWu+(Z+2N)QWd ¼ Z(1-4 sin2W)-N ¼ -N Atomic parity violation - • Two approaches • rotation of polarization plane of linearly polarized light • apply external E field  parity forbidden atomic transition Boulder group: cesium APV 0.35% exp uncertainty wood et. Al. (1997) • + 2.5  deviation (2002) • Breit interactionDerevianko (2000), Dzuba et. al. (2001) • Uehling potentialJohnson et. al. (2001), Milstein et. al. (2002) • QED self-energy and vertex • Dzuba et. Al. (2002), Kuchiev and Flambaum (2002), Milstein et. al. (2002) QWCs (exp) = -72.69  0.48 QWCs(SM)=-73.16 agree

  16.  QWp  QWe  QWCs 0.0029 0.0040 • exp • MSSM: • extra Z’: •  QW(Z,N) / QW(Z,N) < 0.2 % for Cs small sizable SM SM •  QW (Z,N)=(2Z+N)  QWu +(2N+Z)  QWd •  QWu >0 •  QWd <0 Sensitivity to new physics - • Distinguish new physics MSSM Erler, Kurylov and Ramsey-Musolf (2003)

  17. Outlook -- APV - • Paris group: more precise Cs APV • Seattle group: Ba+ APV 6S1/2 5D3/2 • Berkeley group: isotope Yb APV eliminate large atomic structure theory uncertainties 0.2% uncertainties comparable to QWp in sensitivity to new physics Ramsey-Musolf(1999)

  18. - R=-0.0033  0.0015 R=-0.0019  0.0026 NuTeV experiment - NC CC gL,R2=(uL,R)2+(dL,R)2 • exp fit: (gLeff)2=0.30050.0014, (gReff)2=0.03100.0011 • SM EW fit: (gLeff)2=0.3042, (gReff)2=0.0301

  19. NuTeV anomaly - • exp fit (=1): sin2Won-shell = 0.2277  0.0016 • SM fit to Z-pole: sin2Won-shell = 0.2227  0.00037 (3  away) To explain NuTeV anomaly • nuclear shadowing • Miller and Thomas (2002), Zeller et. Al. (2002), Kovalenkov, schmidt and Yang (2002) • asymmetry in strange sea distribution • Davidson, Forte, Gambino, Rius and Strumia (2002), Goncharov et. al. (2001) • isospin symmetry breaking • Bodek et. al. (1999), Zeller et. Al. (2002) • QCD corrections • Dobrescu and Ellis (2003), Kretzer et. al. (2003), Davidson et. al. (2002) • …

  20. - RPV reactor based -e- scattering  sin2W Conrad, Link and Shaevitz (2004) (Janet Conrad, Friday) MSSM New physics explanation - Difficult ! • Supersymmetry:  R,  0 Kurylov, Ramsey-Musolf, Su (2003), Davidson, Forte, Gambino, Rius and Strumia (2002) • Extra Z’ : family non-universal, finetuning Langacker and Plumacher (2000) • Leptoquark: tune mass splitting Davidson, Forte, Gambino, Rius and Strumia (2002) •  mixing with extra heavy neutrino: constraints from other observables Babu and Pati (2002), Loinaz et. al. (2003) -

  21. Conclusion - • NC exp: precision measurements of sin2W at low energy - PV ee, ep scattering (E158, Qweak) - APV measurements - NuTeV • consistency check of SM • sensitive to new physics complementary to direct searches • combinations of several NC exp  distinguish various new physics • uncertainties caused by QCD - extract from experimental measurements - SM predictions

  22. Talk in neutral current session • Norval Fortson:APV • Bob McKeown: ee (E158) • Shelley Page: ep (Qweak) • Kevin McFarland: (NuTeV) In addition • Janet Conrad (Friday): reactor based -e- scattering - Talks in this workshop -

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