Toward Future Discovery In Electroweak Physics Toward Future Discovery In Electroweak Physics Chris Tully Princeton University March 28, 2003 Amherst, MA Chris Tully Princeton University March 28, 2003 Amherst, MA 20 Years of the W and Z Bosons UA1 UA2 Spontaneous Symmetry Breaking Hypercharge(Y) U(1) Y Symmetry Left-Handed Isospin(T) SU(2) L Symmetry Two Primordial Gauge Interactions: Higgs Field 1-complex doublet T Y Properties of the Physical Vacuum Self-Interacting Effective Potential: (tree-level) (top-loop) Electric Charge(Q) U(1) EM Symmetry missing link Is the Z just a massive W 0 ? If isospin (T) were an unbroken symmetry, The measurement of gives us Precision Measurements at the Z pole N = (83) M Z = (21) GeV Z = (23) GeV 0 = (37) nb Polarization of the tau lepton P (0) = -A e polarization polarization Global Electroweak Analysis More than 1000 measurements involving the W and Z bosons have been made, but most have correlated uncertainties. Reduced to 20 precision pseudo-observables: Z-pole (SLD, LEP-1): 5 Z lineshape and leptonic forward-backward asymmetries 2 Polarized lepton asymmetries P , A LR(FB) 6 Heavy flavor results (b,c) 1 Hadronic charge asymmetry Other: 2 W mass and width (Tevatron, LEP-2) 1 Top-quark mass (Tevatron) 1 Neutrino-nucleon scattering (NuTeV) 1 Atomic parity violation (Cs) 1 Hadronic vacuum polarization (Z-pole) 20 plus constants such as the Fermi constant G F + Mller scattering Global Electroweak Analysis Each observable is calculated as a function of: had, s (M Z ), M Z, M top, M higgs (and G F ) Emission and absorption of a virtual Higgs particle r H log M higgs r top G F M top 2 Top quark loop Mixing Angle from LEP/SLD sin 2 eff = (17) 2 /dof =10.2/5 [7%] Difference also seen here: (21) leptons (29) hadrons 2.9 Spread: A l (SLD) vs. A fb b(LEP) Atomic Parity Violation Parity-violating t-channel contribution due to /Z interference Weak charge Q W of the nucleus (Z protons, N neutrons): Electron-nucleus interaction: Q W (Z,N) = -2 [ (2Z+N)C 1u + (Z+2N)C 1d ] with C 1q (Q 2 =0) = 2g Ae g Vq Most precise measurement from Cs 6S 7S Q W (Cs) = 0.29 (exp) 0.39 (theo) compared to latest prediction: Q W (Cs) = 0.46 NuTeV Neutrino-Nucleon Scattering Muon-(anti-)neutrino quark scattering: W Z Paschos-Wolfenstein relation (iso-scalar target): + electroweak radiative corrections Measures effective couplings: g L, g R at -20 GeV 2 NuTeV Neutrino-Nucleon Scattering Interpreted in terms of yields a low value for M W M W = corresponding to a large value of sin 2 W at -20 GeV 2 eff Global fit value: NuTeV shows difference of 2.9 Determination of W Mass from LEP2 Threshold Production Measurements were overwhelmed by above threshold direct reconstruction methods in semi-leptonic W pair events Determination of W Mass from LEP2 4-Jet W Mass measurements became less important due to FSI systematics (BE,CR) Mass difference: M W (qqqq) M W (qql ) = 22 43 MeV (calculated with FSI errors) W Mass from the Tevatron Substantial Cross Section (pp W+X)Br(W ) 2 nb p p W q q MWMW Comparison of W Mass Measurements } Improvement expected from Tevatron Run-2 Direct measurements are higher than expected Parity Violation in Mller Scattering Plot of Running of sin 2 W NuTeV value is high relative to LEP/SLD E158 precision of will confront the NuTeV result eff Polarized e - e - e - e - Scattering: Parity-violating t-channel contribution due to /Z interference High Q 2 Running of No Running CL=10 -8 Running 2 /dof =81/80 e beam ee Low Q 2 Running of had Suffers from large uncertainties in the 1-5 GeV Range Top Mass from Tevatron Run-1 Run-1 result: M top = 3.2 (stat.) 4.0 (syst.) GeV Recent re-evaluation of the Run-1 top mass from Dzero: M top = 3.6 (stat.) GeV (compared with 5.6 GeV) Dominant systematic from Jet Energy Scale will be reduced by scanning M W Run-2 Top Mass Expected Soon ChannelLum(pb -1 )Expected Background Expected Signal Obs. e+jet502.7+/ +jet / e+jet/ / +jet/ / / /0.042 ee / /0.011 Cross-section measurements for are being reported. Candidates seen in all channels. Recent Peak Luminosity record of Measured/Fit W Mass Constraint Heinemeyer and Weiglein hep-ph/7307 } } Shrink the uncertainties on M W and M top Standard Model Precision Electroweak Data Low Mass Preference for the Higgs Boson Measured/Fit sin 2 eff Constraint Low Mass Preference for the Higgs Boson Mass and Mixing Angle Constraints Direct Mass Measurements: Tevatron and LEP2 Z-Pole Measurements: Predict M W and M top from sin 2 eff Both data sets prefer a light Higgs Boson Global Fit Consistency Probability of 2 fit 4.4 % Probability of 2 fit (without NuTeV) 27.3 % Largest Pulls in Standard Model Electroweak Fit AfbAfb 0,b NuTeV Electroweak Working Group: + Mller scattering Range of Higgs Mass Predictions Two largest pulls both prefer large Higgs Mass Closing-in on the Higgs Boson log M H 1.96 0.21 M H