Low Energy Electroweak Precision Tests

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Low Energy Electroweak Precision Tests

• Perspective
• Motivations
• Precision program
• WNC experiments
• Universality
• EDMs, g-2
• FCNC

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Motivations

• WNC, Z, W established SU(2) X U(1) SM
• Z pole most precise (0.1) and excluded many BSM
  scenarios
• However, Z pole is blind or less sensitive to
  many types of new physics (Z, SUSY loops, RPV,
  new operators, exotics, leptoquarks, LED)
• Running sin2 qW (new physics)
• Precision low energy WNC (few percent) still
  important
• FCNC, g-2, EDMs complementary to WNC, Z pole and
  collider

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A Heavy Z?

• Strings, GUTs, LED, DSB, Little Higgs (best
  motivated after SUSY)
• Solution to m problem
• Highly nonstandard Higgs (doublet-singlet mixing)
  and neutralino sectors
• Chiral exotics
• Electroweak baryogenesis
• Cold dark matter
• Family nonuniversality tree level contribution
  to rare B decays

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Weak Neutral Current below the Z-pole

• Z-pole insensitive to effects not directly
  involving Z
• Loop effects from new physics (?/?)(M/Mnew)2
  (Shufang Su)
• muon g-2 Mm? , ?new ? 2x10-9, ?exp lt 10-9
• ?-decay, ?-decay MmW , ?new ? 10-3, ?exp ? 10-3
• parity-violating electron scattering MmW , ?new
  ? 10-3
• Also, suppression QWe,p ? 1-4 sin2?W ? 0.1

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(Shufang Su)
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Kurylov, Ramsey-Musolf, Su (2003)
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SLAC E158 Moller Scattering
e-e- polarization asymmetry, P 85 I II
prelim Ds20.0021 Compositeness scale 10 TeV
Z 0.8 TeV Run III (summer 04) 0.0015
(Kolomensky talk on E158 website)
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Qweak (Jlab)
Ds20.0007 Complementary to Moller Form factors
can be measured
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Atomic Parity Violation

• Very sensitive to Z, leptoquarks, RPV
• Washington thallium (optical rotation) 1, but
  theory 2.7
• Boulder cesium (Stark)
• QW -72.69(48) (SM -73.19(3))
• turbulent 2 yr (Breit, vacuum pol., aZ vertex,
  nuclear skin)
• Anapole discrepancy with nuclear physics
  expectations
• Future
• Paris cesium- may become competitive
• Berkeley Yb isotopes (wave functions cancel, but
  nuclear radius reduced sensitivity to new
  physics)
• Washington Ba ions (0.1 may be possible)
• KVI Ra considered

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NuTeV
NC/CC n and n-bar 3s discrepancy in RnN
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• Beyond standard model strained
• Not SUSY loops or RPV
• Hard to fit leptoquark
• Designer Z possible
• Mixing of n- nheavy more miracles
• Radiation from final lepton in cc (needs
  checking)
• NLO QCD suppressed by sin4qW but may be
  important
• New analysis very important
• Nuclear effects unlikely
• 30 s-sbar asymmetry possible (controversial)
• 5 isospin breaking possible, but naively expect
  0.5
• NOMAD, Qweak, other JLAB

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NOMAD

• nm -gt nt, ne oscillations
• Deep inelastic scattering (CC and NC)
• Expect 1 sin2qW

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Outlook

• NOMAD
• QWEAK
• Possible APV
• Possible reactor ne-bar, in conjunction with
  oscillation experiment (D s2W0.001)
• Near detectors for long baseline?
• Neutrino factory?

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CKM Universality

• Vud2 Vus2 Vub2 Vud2 Vus2 ? 1
  D
• PDG 2002 D 0.0042 0.0019
• New physics? Constrains n-nheavy explanations of
  NuTeV
• Problem in Vud?
• Superallowed Vud0.9740(5), many checks
• Neutron 0.9745 (16) (common structure-independent
  rad corr)
• Pion beta decay 0.9716(39) (new)
• Problem in Vus?

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• PDG value mainly from old Ke3. Radiative
  corrections?
• New BNL865 K, KTEV KL, KLOE KS consistent with
  D0.
• Not CERN NA48.
• Also hyperon decay data (theory errors)

(C. Quigg)
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The BNL g-2 experiment
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• Discrepancy between ee- and t decay
• New ee- data
• Work on isospin violation
• Hadronic light by light
• If real discrepancy then SUSY with large tan b
  and low masses is possibility tan
  b/(MSUSY/100 GeV)22
• Proposal to improve experimental error by 2
• Can theory error keep up?

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Electric Dipole Moments

• New probe of T (CP) violation
• New phases needed for baryogenesis
• EDMs small in SM, large in most BSM, e.g. SUSY
• MSSM 62 new real parameters and 43 new phases
• Universal soft breaking gt two new phases
• fA arg(A m1/2), fB arg(B m m1/2)
• (300 GeV/m)2 sin fA,B lt 10-2

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Electron EDM in various SM extensions
not renormalizable ? loop diagrams
Experimental limit de lt 1.6?10-27 e?cm
B. Regan, E. Commins, C. Schmidt, D. DeMille,
PRL 88, 071805 (2002)
Models assume new physics at 100 GeV
CP-violating phases 1
(D. DeMille)
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Current status of ALL EDM searches
(D. DeMille)
Best limits on natural parameters from 3
complementary experiments
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A new generation of electron EDM searches
(D. DeMille)
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Flavor Violation

• Lepton flavor almost conserved in SM (up to mn)
• Violated in SUSY, multi-Higgs, heavy n,
  leptoquark, non-universal Z, compositeness
• MECO (BNL) (mN-gteN)/(mN-gtnN) to 2 x 10-17
• Sensitive to many BSM
• SINDRUM 6.1 x 10-16
• Future PRIME at PRISM 10-18
• also, m-gteg at PSI 10-13 (2 orders)
• Rare B, K decays? E.g., B-gt fKs (Belle, not
  BaBar), pK K -gt p n n-bar
• (Tree level Z vs SM and SUSY loops.)

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TWIST

• Measure m decay electron spectrum/angular
  distribution precisely
• Sensitive to new couplings, including RHC (eg,
  WR)
• 2 x 10-4 in 05/06

Left/Right Mixing constraints Anticipated TWIST
Sensitivity
Mixing angle ?
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Summary

• Intellectual prospects in high energy physics
  have never been higher
• Theoretical opportunities for standard model of
  everything, but must make connections
• Experimental exploration of TeV scale and beyond
• Collider searches LHC is likely to be a rich but
  complicated discovery machine
• Precision, rare/suppressed, neutrino experiments
  will give complementary constraints
• 10 yr ago almost every extension of SM yields
  neutrino masses/mixings at some level
• Now almost every extension of SM yields EDMs,
  FCNC at some level, and may be other surprises