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

Outline Precision measurements vs. direct detection - 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 S. Su subZ2004

Precision measurements vs. direct detection - mt=178.0  4.3 GeV (direct) (indirect) Direct vs. indirect detection provide complementary information success of SM consistency check of any new physics scenario LEP EWWG LEP EWWG 2004 winter S. Su subZ2004

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 10 more 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 S. Su subZ2004

Neutral Current: Test of sin2W running - Weak mixing angle sinW courtesy of Erler and Carlini MS g sinW = g’ cosW = e Norval Fortson:APV Bob McKeown: ee (E158) Shelley Page: ep (Qweak) Kevin McFarland: (NuTeV) In addition Janet Conrad (Friday): reactor based -e- scattering Talk in neutral current session - sin2W(0) - sin2W(mZ2) = +0.007 - QWCs: agree Q2=0 E158 Runs I+II (Preliminary) NuTeV APV(Cs) - NuTeV: +3 Q2=20 (GeV)2 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 Anticipated final errors ee E158 ep Qweak  sin2W  0.0007 scale Q (GeV) S. Su subZ2004

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 S. Su subZ2004

PVES:E158 and Qweak A N+-N- ALR  QWf N++N- V geA = Ie3 weak charge QWf = 2gfV = 2 If3 -4Qfs2 ep Qweak exp QWp ee Moller exp QWe QWe,p tree 1-4s2 -(1-4s2) QWe,p loop 0.0721 -0.0449 exp precision 4% 9%  sin2W 0.0007 0.0010 SM running 10  8  clean environment: Hydrogen target theoretically clean: small hadronic uncertainties tree level  0.1  sensitive to new physics QWCs :  sin2W = 0.0021 NuTeV:  sin2W = 0.0016 S. Su subZ2004

Sensitivity to new physics scale - Ramsey-Musolf(1999) O(1) : 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) S. Su subZ2004

MSSM correction to weak charge - QWf =  (2Tf3 - 4Qf  s2) + f Kurylov, Ramsey-Musolf, Su (2003) QWe and QWp correlated dominant :  (<0)  negative shift in sin2W MSSM  (QWp)SUSY / (QWp)SM < 4%,  (QWe)SUSY / (QWe)SM < 8% S. Su subZ2004

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 RPV 95% CL MSSM loop QpW No SUSY dark matter I) Obtain 95% CL allowed region in RPV coefficients II) Evaluate  QWe and  QWp G S. Su subZ2004

Correlation between QWp , QWe - Distinguish new physics Erler, Kurylov and Ramsey-Musolf (2003) exp MSSM: extra Z’: RPV SUSY leptoquark  QWp  QWe SM  0.0029  0.0040 Distinguish via APV QWCs Combinations of NC exps could be used to distinguish various new physics S. Su subZ2004

? Extract QWp use kinematics to simplify: at forward angle  - 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 % S. Su subZ2004

QCD correction to ep scattering - Box diagram contribution to QWP Erler, Kurylov and Ramsey-Musolf (2003) e p Z  e p W e p Z e p Z  suppression non-calculable Similar to nuclear -decay e e- n p  W  QWP 26% 3% 6% kloop » O(mW) kloop » O(mZ) QCD  kloop  O(mZ) |CW|  2 (CKM unitarity) |CZ|  2 non-perturbative using OPE (pQCD)  QWP (QCD) -0.7% -0.08% 0.65% Total theoretical uncertainty » 0.8% S. Su subZ2004

Outlook: PV electron scattering - Kurylov, Ramsey-Musolf, Su (2003) MSSM RPV Erler NuTeV Linear Collider e-e- sin2W DIS-Parity,JLab DIS-Parity, SLAC APV e+e- LEP, SLD SLAC E158 (ee) JLab Moller (ee) JLab QWeak (ep) Q (GeV) S. Su subZ2004

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) QW(Z,N)=(2Z+N)QWu+(Z+2N)QWd ¼ Z(1-4 sin2W)-N ¼ -N finite nuclear size nucleon substructure nuclear spin-dependent term  »  0.15% Pollock and Wieman (2001) Musolf (1994) Erler, Kurylov and Ramsey-Musolf (2003) 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) + 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 S. Su subZ2004

Sensitivity to new physics - Distinguish new physics  QW (Z,N)=(2Z+N)  QWu +(2N+Z)  QWd  QWu >0  QWd <0   QW(Z,N) / QW(Z,N) < 0.2 % for Cs MSSM exp MSSM: extra Z’:  QWp  QWe  QWCs small sizable SM  0.0029  0.0040 Erler, Kurylov and Ramsey-Musolf (2003) S. Su subZ2004

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) S. Su subZ2004

NuTeV experiment NC CC gL,R2=(uL,R)2+(dL,R)2 - NC CC gL,R2=(uL,R)2+(dL,R)2 R=-0.0033  0.0015 R=-0.0019  0.0026 - 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 S. Su subZ2004

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) … S. Su subZ2004

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) - MSSM RPV reactor based -e- scattering  sin2W Conrad, Link and Shaevitz (2004) (Janet Conrad, Friday) - S. Su subZ2004

Conclusion NC exp: precision measurements of sin2W at low energy - 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 S. Su subZ2004

Talks in this workshop 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 Talk in neutral current session - S. Su subZ2004