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 + Møller 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 Möller 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 e–e–

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 ee / /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: + Møller 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 <211 95% CL Electroweak Fit: M H = 91 GeV +58 –37

68% 95% Scanning the Higgs Boson Mass Range Measure median separation of hypotheses Compare with widths of distributions Scan versus Mass

LEP Higgs Boson Results Very Slight Excess Compatible with Predicted Rates above: Lower Limit Set at CL=95%: 115,116,117 GeV

Bounce Massive scalar or vector particles Self-Coupling is negative for m t =175 GeV at 1000 TeV What can be done? Isidori, Ridolfi, Strumia hep-ph/

Fermion Masses in a 1-doublet Model 1-doublet Model: Down-type mass Up-type mass Same v

Fermion Masses in a 2-doublet Model Down-type mass Up-type mass Electroweak Energy Scale m top /m bottom ? 8 degrees of freedom – 3 longitudinal polarizations (W L ,Z L ) leaves 5 Higgs bosons: h, H, A, H 

Higgs-Fermion Couplings in the MSSM b quarks and  leptons couple strongly to A Large tan  : top quarks couple weakly to A A A Higgsstrahlung off a b quark: Production Mechanisms

Search for bbA Production in the MSSM at the Tevatron No Mixing Maximal Mixing M h (GeV/c 2 ) tan 

Extending the Search LEP Ends Here H  bb Drops Off H  WW* WH and ZH Production Falls Off Slowly

Extending the Search LEP Ends Here ( V ) H  bb Tevatron Run 2 Performance Signal Expectation X+H  WW* 

Relative Channel Sensitivity LEP Ends Here ZH  bbWH  bbZH  bbZH  qqbb X+H  WW* 

Precision of Electroweak Constraints Uncertainty on  M H / M H from W mass (Snowmass study hep-ph/ ) Uncertainty on  M H / M H from sin 2  eff ( M top ) Total Uncertainty on  M H / M H log M H  1.96 ± 0.21 M H <211 95% CL log M H  X.XX ± 0.06 Electroweak Fit: M H = 91 GeV +58 –37 M H = 115 GeV +19 –16 For Example:

Higgs’ Quest Fermilab (Chicago, USA) LEP (Geneva, Switzerland) 7 years Startup of LHC Scheduled for 2007 Tevatron Run II Picked up speed in 2002 LEP Dismantled in 2000

Scanning the Higgs Boson Mass Range Measure median separation of hypotheses Compare with widths of distributions Scan versus Mass