low energy electroweak precision tests

P. Langacker ICHEP2004 (8/16/04)

Low Energy Electroweak Precision Tests

•Perspective–Motivations–Precision program

•WNC experiments•Universality•EDMs, g-2•FCNC


MotivationsMotivations• 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 W (new physics)• Precision low energy WNC (few percent)

still important• FCNC, g-2, EDMs complementary to

WNC, Z pole and collider


A Heavy Z’?• Strings, GUTs, LED, DSB, Little Higgs (best motivated

after SUSY)• Solution to 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


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=mmuon g-2: M=m , , new new 2x10 2x10-9-9, , expexp < 10 < 10-9 -9

-decay, -decay, -decay: M=m-decay: M=mWW , , new new 10 10-3-3, , expexp 10 10-3-3

– parity-violating electron scattering: M=mparity-violating electron scattering: M=mWW , , new new 1010-3-3

– Also, suppression QQWWe,pe,p 1-4 sin 1-4 sin22WW 0.1 0.1


(Shufang Su)


RPVRPV95% CL95% CL

MSSMMSSMlooploop

Kurylov, Ramsey-Musolf, Su (2003)


SLAC E158 Moller Scattering

e-e- polarization asymmetry, P = 85%I + II prelim: s2=0.0021Compositeness scale: 10 TeV; Z’ ~0.8 TeVRun III (summer 04): 0.0015 (Kolomensky talk on E158 website)

(Run I)


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Qweak (Jlab)s2~0.0007Complementary to MollerForm factors can be measured


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


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NuTeVNC/CC; and -bar3 discrepancy in RN


• Beyond standard model strained– Not SUSY loops or RPV– Hard to fit leptoquark– Designer Z’ possible– Mixing of- heavy + more miracles

• Radiation from final lepton in cc (needs checking)• NLO QCD: suppressed by sin4W 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


NOMAD

• e oscillations• Deep inelastic scattering

(CC and NC)• Expect 1% sin2W QuickTime™ and a

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Outlook

•NOMAD•QWEAK

•Possible APV•Possible reactor e-bar, in conjunction with oscillation experiment ( s2

W~0.001)•Near detectors for long baseline?•Neutrino factory?


CKM Universality• |Vud|2 + |Vus|2 + |Vub|2 ~ |Vud|2 + |Vus|2 1 –

– PDG 2002: = 0.0042 ± 0.0019– New physics? Constrains heavy explanations of

NuTeV– Problem in Vud?

• Superallowed: |Vud|=0.9740(5), many checks• Neutron: 0.9745 (16) (common structure-

independent rad corr)• Pion beta decay: 0.9716(39) (new)

– Problem in Vus?


• PDG value mainly from old Ke3. Radiative corrections?• New BNL865 K+, KTEV KL, KLOE KS consistent with =0.• Not CERN NA48.• Also hyperon decay data (theory errors)

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(C. Quigg)

The BNL g-2 experiment


• Discrepancy between e+e- and 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?


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 => two new

phases A = arg(A* m1/2), B = arg(B* m1/2) (300 GeV/m)2 sin A,B < 10-2

T

Sd

P

Electron EDM in various SM extensionsnot renormalizable loop diagrams

2

5 ψγψ Fe =Lγ

eeExperimental limit:|de| < 1.610-27 ecm

Physics model |de|Standard Model ~10-41 e·cm

Left-right symmetric 10-26-10-28 e·cm

Lepton flavor-changing 10-26-10-29 e·cm

Multi-Higgs 10-27-10-28 e·cmTechnicolor 10-27-10-29 e·cm

Supersymmetry < 10-25 e·cm

B. Regan, E. Commins, C. Schmidt,

D. DeMille, PRL 88, 071805 (2002)

Models assumenew physics at ~100 GeV& CP-violating phases ~1

(D. DeMille)


n (ILL,PNPI)

Hg (Seattle)

Tl (Berkeley)

EDM <710-26 <210-28 <110-24 dn 710-26 210-25 de 1510-27 1.610-27 QCD 410-10 210-10 q/l, SUSY 110-2 210-3 110-2 xq/l, LR

110-2 110-3 310-2

Higgs 3/tan 0.4/tan 0.3/tan

Current status of ALL EDM searchesBest limits on “natural” parameters from 3 complementary experiments:(D. DeMille)


A new generation of electron EDM searches

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 ??

(D. DeMille)


Flavor Violation• Lepton flavor almost conserved in SM (up to m)• Violated in SUSY, multi-Higgs, heavy , leptoquark,

non-universal Z’, compositeness• MECO (BNL): (N->eN)/(N->N) to 2 x 10-17

– Sensitive to many BSM– SINDRUM: 6.1 x 10-16

– Future: PRIME at PRISM: 10-18

• also, ->eγ at PSI: 10-13 (2 orders)• Rare B, K decays? E.g., B-> Ks (Belle, not BaBar), K;

K -> -bar • (Tree level Z’ vs SM and SUSY loops.)


TWIST• Measure decay

electron spectrum/angular distribution precisely

• Sensitive to new couplings, including RHC (eg, WR)

• 2 x 10-4 in 05/06

€

MWR (GeV )

€

Pμξ

€

Pμξδρ€

TWIST ρ

€

TWIST Pμξ

Left/Right Mixing constraints –

Anticipated TWIST Sensitivity

Mix

ing

angl

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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

low energy electroweak precision tests

Documents

types of new physics

new operators

new physicswashington

new bnl865

new 2x10

heavy z

t decaynew e e datawork

nbar3s discrepancy