Parity Violation: Past, Present, and Future

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Parity Violation Past, Present, and Future
M.J. Ramsey-Musolf
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NSAC Long Range Plan

• What is the structure of the nucleon?
• What is the structure of nucleonic matter?
• What are the properties of hot nuclear matter?
• What is the nuclear microphysics of the universe?
• What is to be the new Standard Model?

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NSAC Long Range Plan

• What is the structure of the nucleon?
• What is the structure of nucleonic matter?
• What are the properties of hot nuclear matter?
• What is the nuclear microphysics of the universe?
• What is to be the new Standard Model?

Parity-Violating Electron Scattering
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Outline

• PVES and Nucleon Structure
• PVES and Nucleonic Matter
• PVES and the New Standard Model

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Parity-Violating Asymmetry
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PV Electron Scattering Experiments
MIT-Bates
Mainz
SLAC
Jefferson Lab
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PV Electron Scattering Experiments
Deep Inelastic eD (1970s) PV Moller Scattering
(now) Deep Inelastic eD (2005?)
SLAC
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PV Electron Scattering Experiments
MIT-Bates
Elastic e 12C (1970s - 1990) Elastic
ep, QE eD (1990s - now)
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PV Electron Scattering Experiments
Mainz
QE e 9Be (1980s) Elastic ep (1990s - now)
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PV Electron Scattering Experiments
Elastic ep HAPPEX, G0 (1990s - now) Elastic e
4He HAPPEX (2003) Elastic e 208Pb
PREX QE eD, inelastic
ep G0 (2003-2005?) Elastic ep Q-Weak
(2006-2008) Moller, DIS eD
(post-upgrade?)
Jefferson Lab
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PVES and Nucleon Structure
What are the relevant degrees of freedom for
describing the properties of hadrons and why?
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PVES and Nucleon Structure
Why does the constituent Quark Model work so
well?

• Sea quarks and gluons are inert at low
  energies
• Sea quark and gluon effects are hidden in
  parameters and effective degrees of freedom of QM
  (Isgur)
• Sea quark and gluon effects are hidden by a
  conspiracy of cancellations (Isgur, Jaffe,
  R-M)
• Sea quark and gluon effects depend on C
  properties of operator (Ji)

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PVES and Nucleon Structure
What are the relevant degrees of freedom for
describing the properties of hadrons and why?
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We can uncover the sea with GPW
Light QCD quarks u mu 5 MeV d md 10 MeV s ms
150 MeV
Heavy QCD quarks c mc 1500 MeV b mb 4500
MeV t mt 175,000 MeV
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We can uncover the sea with GPW
Light QCD quarks u mu 5 MeV d md 10 MeV s ms
150 MeV
Heavy QCD quarks c mc 1500 MeV b mb 4500
MeV t mt 175,000 MeV
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We can uncover the sea with GPW
Light QCD quarks u mu 5 MeV d md 10 MeV s ms
150 MeV
Heavy QCD quarks c mc 1500 MeV b mb 4500
MeV t mt 175,000 MeV
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Parity-Violating Electron Scattering
Kaplan and Manohar McKeown
Neutral Weak Form Factors
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Parity-Violating Electron Scattering
Separating GEW , GMW , GAW
GMW , GAW SAMPLE
GMW , GEW HAPPEX, PVA4
GMW , GEW , GAW Q2-dependence G0
Published results SAMPLE, HAPPEX
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at Q20.1 (GeV/c)2

• s-quarks contribute less than 5 (1s) to the
  protons magnetic form factor.
• protons axial structure is complicated!

R. Hasty et al., Science 290, 2117 (2000).
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Axial Radiative Corrections
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Anapole Effects
Hadronic PV
Cant account for a large reduction in GeA
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Nuclear PV Effects
PV NN interaction
Carlson, Paris, Schiavilla Liu,
Prezeau, Ramsey-Musolf
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SAMPLE Results
R. Hasty et al., Science 290, 2117 (2000).
at Q20.1 (GeV/c)2

• s-quarks contribute less than 5 (1s) to the
  protons magnetic moment.

200 MeV update 2003 Improved EM radiative
corr. Improved acceptance model Correction for p
background
125 MeV no p background similar sensitivity to
GAe(T1)
E. Beise, U Maryland
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Strange Quark Form Factors
Theoretical Challenge

• Strange quarks dont appear in Quark Model
  picture of the nucleon

• Perturbation theory may not apply

?QCD / ms 1 No HQET
mK / ?c 1/2 ?PT ?

• Symmetry is impotent

J?s J?B 2 J?EM, I0
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Theoretical predictions
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Q2 -dependenceof GsM
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What ?PT can (cannot) say
Ito, R-M Hemmert, Meissner, Kubis
Hammer, Zhu, Puglia, R-M
Strange magnetism as an illustration
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What ?PT can (cannot) say
Strange magnetism as an illustration
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Dispersion theory gives a model-independent
prediction
Jaffe Hammer,
Drechsel, R-M
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Dispersion theory gives a model-independent
prediction
Hammer R-M
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Dispersion theory gives a model-independent
prediction
Hammer R-M
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Dispersion theory gives a model-independent
prediction
Experiment will give an answer
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PVES and Nucleonic Matter
What is the equation of state of dense nucleonic
matter?
We know a lot about the protons, but lack
critical information about the neutrons
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PVES and Nucleonic Matter
Donnelly, Dubach, Sick
The Z0 boson probes neutron properties
QW Z(1 - 4 sin2?W) - N
Horowitz, Pollock, Souder, Michels
PREX (Hall A) 208Pb
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PVES and Neutron Stars
Neutron star
Horowitz Piekarewicz
208Pb
Crust thickness decreases with Pn
Skin thickness (Rn-Rp) increases with Pn
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PVES and Neutron Stars
Horowitz Piekarewicz
Neutron star properties are connected to
density-dependence of symmetry energy
PREX probes Rn-Rp a meter of E ( r )
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PVES and the New Standard Model
We believe in the Standard Model, but it leaves
many unanswered questions

• What were the symmetries of the early Universe
  and how were they broken?
• What is dark matter?
• Why is there more matter than anti-matter?

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PVES and the New Standard Model
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PVES and the New Standard Model
A near miss for grand unification
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PVES and the New Standard Model
Weak scale is unstable against new physics in the
desert
GF would be much smaller
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PVES and the New Standard Model
Not enough CP-violation for weak scale
baryogenesis
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Neutral current mixing depends on electroweak
symmetry
??JmWNC ??Jm0 4 Q sin2?W ??JmEM
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Weak mixing also depends on scale
Czarnecki Marciano Erler, Kurylov, R-M
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sin2?W(?) depends on particle spectrum
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sin2?W(?) depends on particle spectrum
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sin2?W(?) depends on particle spectrum
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New Physics Parity Violation
sin2?W is scale-dependent
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Weak mixing also depends on scale
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Additional symmetries in the early universe can
change scale-dependence
Supersymmetry
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Electroweak strong couplings unify with
supersymemtry
Supersymmetry
Weak scale GF are protected
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SUSY will change sin2?W(?) evolution
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SUSY will change sin2?W(?) evolution
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Comparing Qwe and QWp
Kurylov, R-M, Su
SUSY loops
3000 randomly chosen SUSY parameters but effects
are correlated
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Can SUSY explain dark matter?
Expansion
Rotation curves
Cosmic microwave background
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SUSY provides a DM candidate
Neutralino

• Stable, lightest SUSY particle if baryon (B) and
  lepton (L) numbers are conserved

• However, B and L need not be conserved in
  SUSY, leading to neutralino decay

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B and/or L Violation in SUSY can also affect
low-energy weak interactions
?L1
?L1
QPW in PV electron scattering
?-decay, ?-decay,
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Comparing Qwe and QWp
Kurylov, R-M, Su
n is Majorana
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Comparing Qwe and QWp

• Can be a diagnostic tool to determine whether or
  not
• the early Universe was supersymmetric
• there is supersymmetric dark matter

The weak charges can serve a similar diagnostic
purpose for other models for high energy
symmetries, such as left-right symmetry, grand
unified theories with extra U(1) groups, etc.
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Weak mixing also depends on scale
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Comparing Qwe and QWp
Kurylov, R-M, Su
??? SUSY dark matter
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Interpretation of precision measurements
How well do we now the SM predictions? Some QCD
issues
Proton Weak Charge
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Interpretation of precision measurements
How well do we now the SM predictions? Some QCD
issues
Proton Weak Charge
FP(Q2, ? -gt 0) Q2
Use ?PT to extrapolate in small Q2 domain and
current PV experiments to determine LECs
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Summary

• Parity-violating electron scattering provides us
  with a well-understood tool for studying several
  questions at the forefront of nuclear physics,
  particle physics, and astrophysics
• Are sea quarks relevant at low-energies?
• How compressible is neutron-rich matter
• What are the symmetries of the early Universe?
• Jefferson Lab is the parity violation facility
• We have much to look forward to in the coming
  years

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QCD Effects in QWP
?QCD lt kloop lt MW non-perturbative
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Box graphs, contd.
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Box graphs, contd.
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Neutron ?-decay