Probing Supersymmetry with Neutral Current Scattering Experiments

1
Probing Supersymmetry with Neutral Current
Scattering Experiments

• Shufang Su U. of Arizona

2
Sub-Z precision measurements
-

• neutral current scattering
• heavy quark physics
• CP violation, EDM
• Rare K-decay, CKM unitarity
• muon g-2
• lepton flavor violation

• polarized ee scattering (SLAC E158)
• polarized ep scattering (JLab Qweak)
• neutrino-nucleus scattering (NuTeV)

A. Kurylov, M. Ramsey-Musolf, SS
3
Outline
-

• motivation
• parity-violating electron scattering experiments
• radiative corrections to weak charge QW
• analysis of SUSY contributions to QW
• MSSM contributions
• RPV analysis
• distinguish various new physics / SUSY
• NuTeV experiment
• MSSM contributions
• RPV analysis
• conclusion

4
Motivation
-

• high precision low energy experiment available
  
• - 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,
• 1/Qe,pW ?10 more sensitive to new physics
• need ?exp ? 10-2 easier experiment
• indirectdirect complementary information
• consistency test of theory at loop level

size of loop effects from new physics
(?/?)(M/Mnew)2
Qe,pW ? 1-4 sin2?W ? 0.1

• probe new physics off the Z-resonance
• - sensitive to new physics not mix with Z

5
Test of sin2?W running
-

• sin2?W(0) - sin2?W(mZ2) 0.007
• QCsw agree Q20
• NuTeV 3? Q220 (GeV)2
• parity-violating electron
• scattering (PVES)
• ee Moller scattering (SLAC) QeW
• ep elastic scattering (J-lab) QpW

-

• clean environment Hydrogen target
• theoretically clean small hadronic
  uncertainties
• tree level ? 0.1 ? sensitive to new physics

6
Goal
-

• minimal Supersymmetric extension of SM (MSSM)
• SUSY most promising candidate for new physics
• solution to Hierarchy problem
• gauge coupling unification
• provide a natural electroweak symmetry breaking
• dark matter candidate ? (PVES)
• with R-parity loop corrections
• without R-parity tree-level contribution
• low-energy precision measurements
• PVES weak charge QeW , QpW , ( QCsW ) - NuTeV
  R?(?)

-
7
Weak charge QW
-
geA Ie3
QCsW ? sin2?W 0.0021 NuTeV ? sin2?W
0.0016
8
General structure of radiative corrections to QfW
-
Including radiative corrections
QfW ? (2If3 - 4 ? Qf s2) ?f

?, ? universal, ?f depend on fermion
species
? 1??SM??SUSY, ? 1??SM??SUSY, ?f
?fSM?fSUSY
?
9
Radiative contributions
-
QfW ? (2If3 - 4 ? Qf s2) ?f
?

?f
10
MSSM particle contents
-
Spin differ by 1/2
SM particle superpartner
mass parameter

??, tan?vu/vd
M3
M2
M1
11
SUSY interactions
-
replace two SM particles into SUSY partners
? gauge coupling
?

?
? gauge coupling
?
? Yukawa coupling
12
One loop SUSY contributions to PVES
-

• gauge boson
• self-energies

• external leg corrections

• vertex corrections

• box diagrams

13
Numerical analysis
-

• Model-independent analysis

• MSSM parameter range random scan

• hard to impose bounds on certain MSSM parameter
• show the possible range of MSSM corrections
• impose exp search limit on SUSY particles
  
• impose S-T 95 CL constraints
• impose g-2 constraints (2nd slepton LR mixing)

14
Correction to weak charge
-
QfW ? (2Tf3 - 4Qf ? s2) ?f

• QeW and QpW correlated

dominant ?? (lt0) ? negative shift in sin2?W
? (QpW)SUSY / (QpW)SM lt 4, ? (QeW)SUSY / (QeW)SM
lt 8
15
Dominant contributions
-
QfW ? (2Tf3 - 4Qf ? s2) ?f

• non-universal corrections
• vertex wavefunction cancel
• box diagrams numerically suppressed
• ?? contribution suppressed by (1-4 s2)
• dominant contribution from ??

?? (lt0) ? negative shift in sin2?W
16
Various contributions to ??
-
S

• within ??
• various terms have comparable importance
• oblique approximation gives a poor description

T

• ?? lt0 (? (Qe,pW)SUSY / (Qe,pW)SM gt0 ) ?
  reduction in effective sin2?W

17
R-parity
-

• General MSSM, including B,L-violating operators

?ijk

?ijk

• dangerous ? introduce proton decay
• R-parity SM particle even superparticle odd
• stable LSP as dark matter candidate
• RPV only look at L-violating operator

18
R-parity violating (RPV)
-

• RPV operators contribute to Qe,pW at tree level

• Exp constraints
• ? decay ?Vud -0.00145 ? 0.0007
• APV(Cs) ? QWCs -0.0040 ? 0.0066
• Re/? ? Re/? -0.0042 ? 0.0033
• G? ? G? 0.00025 ? 0.00188

?QpW
No SUSY dark matter
I) Obtain 95 CL allowed region in RPV
coefficients II) Evaluate ? QWe and ? QWp
G?
19
Correlation between QpW and QeW
-
? ? QW(Z,N) / QW(Z,N) lt 0.2 for Cs

• Distinguish new physics

20
Additional PV electron scattering ideas
-
Czarnecki, Marciano, Erler et al.
? N deep inelastic
sin2?W
APV
ee- LEP, SLD
SLAC E158 (ee)
JLab Q-Weak (ep)
??(GeV)
21
NuTeV experiment
-
NC
CC
22
Gluino contribution
-
negative gluino contribution

• CC data constraints
• Kurylov, Ramsey-Musolf,PRL88,071804,2002

• large LR-mixing
• both up/down sector
• inconsistent with current
• CC data
• constraints relaxed if first
• row CKM unitarity confirmed
• could partially account for
• deviation in sin2?W

unitarity deviation decrease by 1/3 ?
23
Deviation of sin2?W
-

• extracted using Paschos-Wolfenstein relation
• in practice, modified version
• ? different from r
• ? charm quark mass
• uncertainties
• gluino contributions
• ? ? - r

1C 0C
mc constrained free
? 0.249 0.453
?sin2?W -1.6x10-3 -1x10-4
24
R-parity violating (RPV)
-
-

• RPV operators contribute to R?(?) at tree level

• either wrong sign or too small
• hard to explain NuTeV deviation

25
Conclusion
-

• Parity-violating ee and ep scattering
• could be used to test SM and probe new physics
• MSSM contribution to QeW and QpW is 8 and 4 ? 1
  ?exp need higher exp precision to constrain SUSY
• correlation between QeW and QpW
• distinguish various new physics
• distinguish various SUSY scenario
  whether dark matter is SUSY particle ?

• SUSY contribution to NuTeV result
• MSSM with R-parity wrong sign /small
• negative gluino contribution
• size constrained by other considerations
• hard to explain NuTeV in RPV

• SUSY is not responsible for the NuTeV deviation
• other new physics ?
• hadronic effects ?