Low Energy Electroweak
Precision Tests
•Perspective
–Motivations
–Precision program
•WNC experiments
•Universality
•EDMs, g-2
•FCNC
P. Langacker
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
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
P. Langacker
ICHEP2004 (8/16/04)
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
P. Langacker
ICHEP2004 (8/16/04)
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: M=mm , 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
– Also, suppression QWe,p  1-4 sin2qW  0.1
P. Langacker
ICHEP2004 (8/16/04)
(Shufang Su)
P. Langacker
ICHEP2004 (8/16/04)
RPV
95% CL
MSSM
loop
Kurylov, Ramsey-Musolf, Su (2003)
P. Langacker
ICHEP2004 (8/16/04)
SLAC E158 Moller Scattering
e-e- polarization asymmetry, P =
85%
I + II prelim: Ds2=0.0021
Compositeness scale: 10 TeV; Z’
~0.8 TeV
Run III (summer 04): 0.0015
(Kolomensky talk on E158 website)
P. Langacker
(Run I)
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
Qweak (Jlab)
Ds2~0.0007
Complementary to Moller
Form factors can be measured
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
P. Langacker
ICHEP2004 (8/16/04)
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., Z 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
P. Langacker
ICHEP2004 (8/16/04)
NuTeV
NC/CC; n and n-bar
3s discrepancy in RnN
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
P. Langacker
ICHEP2004 (8/16/04)
• 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
P. Langacker
ICHEP2004 (8/16/04)
NOMAD
• nm -> nt, ne oscillations
• Deep inelastic scattering
(CC and NC)
• Expect 1% sin2qW
P. Langacker
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
ICHEP2004 (8/16/04)
Outlook
•NOMAD
•QWEAK
•Possible APV
•Possible reactor ne-bar, in
conjunction with oscillation
experiment (D s2W~0.001)
•Near detectors for long baseline?
•Neutrino factory?
P. Langacker
ICHEP2004 (8/16/04)
CKM Universality
• |Vud|2 + |Vus|2 + |Vub|2 ~ |Vud|2 + |Vus|2  1 – D
– PDG 2002: D = 0.0042 ± 0.0019
– New physics? Constrains n-nheavy explanations of
NuTeV
– Problem in Vud?
• Superallowed: |Vud|=0.9740(5), many checks
• Neutron: 0.9745 (16) (common structureindependent rad corr)
• Pion beta decay: 0.9716(39) (new)
– Problem in Vus?
P. Langacker
ICHEP2004 (8/16/04)
•
•
•
•
PDG value mainly from old Ke3. Radiative corrections?
New BNL865 K+, KTEV KL, KLOE KS consistent with D=0.
Not CERN NA48.
Also hyperon decay data (theory errors)
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
(C. Quigg)
P. Langacker
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
The BNL g-2 experiment
P. Langacker
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
• Discrepancy between e+e- and
t decay
• New e+e- data
• Work on isospin violation
• Hadronic light by light
• If real discrepancy then SUSY
with large tan  and low
masses is possibility: tan
/(MSUSY/100 GeV)2~2
• Proposal to improve
experimental error by 2
• Can theory error keep up?
P. Langacker
ICHEP2004 (8/16/04)
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
d
P
S
T
– Universal soft breaking => two new
phases
 fA = arg(A* m1/2), fB = arg(B* m m1/2)
 (300 GeV/m)2 sin fA,B < 10-2
P. Langacker
ICHEP2004 (8/16/04)
Electron EDM in various SM extensions
de
 Ld    5s mnFmn not renormalizable
 loop diagrams
2
e
e
Experimental limit:
|de| < 1.610-27 ecm
Physics model
|de|
Standard Model
Left-right
symmetric
Lepton flavorchanging
Multi-Higgs
Technicolor
~10-41 e·cm
10-26-10-29 e·cm
Models assume
new physics at ~100 GeV
& CP-violating phases ~1
10-27-10-28 e·cm
10-27-10-29 e·cm
(D. DeMille)
Supersymmetry
< 10-25 e·cm
B. Regan, E. Commins, C. Schmidt,
D. DeMille, PRL 88, 071805 (2002)
10-26-10-28 e·cm
P. Langacker
ICHEP2004 (8/16/04)
Current status of ALL EDM searches
(D. DeMille)
Best limits on “natural” parameters from 3 complementary experiments:
EDM
dn
n (ILL,PNPI)
Hg (Seattle)
Tl (Berkeley)
<710-26
710-26
<210-28
210-25
<110-24
1510-27
1.610-27
de
qQCD
410-10
210-10
q/l, SUSY
110-2
210-3
110-2
xq/l, LR
110-2
110-3
310-2
Higgs
3/tan
0.4/tan
0.3/tan
P. Langacker
ICHEP2004 (8/16/04)
A new generation of electron EDM searches
(D. DeMille)
Group
System
Advantages
Projected gain
D. Weiss (Penn St.)
Trapped Cs
Long coherence
~100
D. Heinzen (Texas)
Trapped C
Long coherence
~100
H. Gould (LBL)
Cs fountain
Long coherence
?
L. Hunter (Amherst)
GdIG
Huge S/N
100?
S. Lamoreaux (LANL)
GGG
Huge S/N
100?-100,000?
E. Hinds (Imperial)
YbF beam
Internal E-field
2-?
D. DeMille (Yale)
PbO* cell
Internal E-field
100-10,000?
E. Cornell (JILA)
trapped HBr+
Int. E + long T
??
N. Shafer-Ray (Okla.)
trapped PbF
Int. E + long T
??
P. Langacker
ICHEP2004 (8/16/04)
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->eN)/(mN->nN) to 2 x 10-17
– Sensitive to many BSM
– SINDRUM: 6.1 x 10-16
– Future: PRIME at PRISM: 10-18
• also, m->e at PSI: 10-13 (2 orders)
• Rare B, K decays? E.g., B-> fKs (Belle, not BaBar), K;
K ->  n n-bar
• (Tree level Z’ vs SM and SUSY loops.)
P. Langacker
ICHEP2004 (8/16/04)
P. Langacker
ICHEP2004 (8/16/04)
Left/Right Mixing
constraints – Anticipated
TWIST Sensitivity
Pm
Mixing
angle 
• Measure m decay
electron
spectrum/angular
distribution precisely
• Sensitive to new
couplings, including
RHC (eg, WR)
• 2 x 10-4 in 05/06
TWIST

TWIST 

Pm


P. Langacker
TWIST Pm


MWR (GeV)
ICHEP2004 (8/16/04)
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
P. Langacker
ICHEP2004 (8/16/04)