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Parity Violation: Past, Present, and Future

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Parity Violation: Past, Present, and Future M.J. Ramsey-Musolf – PowerPoint PPT presentation

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Title: Parity Violation: Past, Present, and Future


1
Parity Violation Past, Present, and Future
M.J. Ramsey-Musolf
2
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?

3
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
4
Outline
  • PVES and Nucleon Structure
  • PVES and Nucleonic Matter
  • PVES and the New Standard Model

5
Parity-Violating Asymmetry
6
PV Electron Scattering Experiments
MIT-Bates
Mainz
SLAC
Jefferson Lab
7
PV Electron Scattering Experiments
Deep Inelastic eD (1970s) PV Moller Scattering
(now) Deep Inelastic eD (2005?)
SLAC
8
PV Electron Scattering Experiments
MIT-Bates
Elastic e 12C (1970s - 1990) Elastic
ep, QE eD (1990s - now)
9
PV Electron Scattering Experiments
Mainz
QE e 9Be (1980s) Elastic ep (1990s - now)
10
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
11
PVES and Nucleon Structure
What are the relevant degrees of freedom for
describing the properties of hadrons and why?
12
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)

13
PVES and Nucleon Structure
What are the relevant degrees of freedom for
describing the properties of hadrons and why?
14
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
15
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
16
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
17
Parity-Violating Electron Scattering
Kaplan and Manohar McKeown
Neutral Weak Form Factors
18
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
19
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).
20
Axial Radiative Corrections
21
Anapole Effects
Hadronic PV
Cant account for a large reduction in GeA
22
Nuclear PV Effects
PV NN interaction
Carlson, Paris, Schiavilla Liu,
Prezeau, Ramsey-Musolf
23
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
24
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
25
Theoretical predictions
26
Q2 -dependenceof GsM
27
What ?PT can (cannot) say
Ito, R-M Hemmert, Meissner, Kubis
Hammer, Zhu, Puglia, R-M
Strange magnetism as an illustration
28
What ?PT can (cannot) say
Strange magnetism as an illustration
29
Dispersion theory gives a model-independent
prediction
Jaffe Hammer,
Drechsel, R-M
30
Dispersion theory gives a model-independent
prediction
Hammer R-M
31
Dispersion theory gives a model-independent
prediction
Hammer R-M
32
Dispersion theory gives a model-independent
prediction
Experiment will give an answer
33
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
34
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
35
PVES and Neutron Stars
Neutron star
Horowitz Piekarewicz
208Pb
Crust thickness decreases with Pn
Skin thickness (Rn-Rp) increases with Pn
36
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 )
37
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?

38
PVES and the New Standard Model
39
PVES and the New Standard Model
A near miss for grand unification
40
PVES and the New Standard Model
Weak scale is unstable against new physics in the
desert
GF would be much smaller
41
PVES and the New Standard Model
Not enough CP-violation for weak scale
baryogenesis
42
Neutral current mixing depends on electroweak
symmetry
??JmWNC ??Jm0 4 Q sin2?W ??JmEM
43
Weak mixing also depends on scale
Czarnecki Marciano Erler, Kurylov, R-M
44
sin2?W(?) depends on particle spectrum
45
sin2?W(?) depends on particle spectrum
46
sin2?W(?) depends on particle spectrum
47
New Physics Parity Violation
sin2?W is scale-dependent
48
Weak mixing also depends on scale
49
Additional symmetries in the early universe can
change scale-dependence
Supersymmetry
50
Electroweak strong couplings unify with
supersymemtry
Supersymmetry
Weak scale GF are protected
51
SUSY will change sin2?W(?) evolution
52
SUSY will change sin2?W(?) evolution
53
Comparing Qwe and QWp
Kurylov, R-M, Su
SUSY loops
3000 randomly chosen SUSY parameters but effects
are correlated
54
Can SUSY explain dark matter?
Expansion
Rotation curves
Cosmic microwave background
55
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

56
B and/or L Violation in SUSY can also affect
low-energy weak interactions
?L1
?L1
QPW in PV electron scattering
?-decay, ?-decay,
57
Comparing Qwe and QWp
Kurylov, R-M, Su
n is Majorana
58
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.
59
Weak mixing also depends on scale
60
Comparing Qwe and QWp
Kurylov, R-M, Su
??? SUSY dark matter
61
Interpretation of precision measurements
How well do we now the SM predictions? Some QCD
issues
Proton Weak Charge
62
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
63
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

64
QCD Effects in QWP
?QCD lt kloop lt MW non-perturbative
65
Box graphs, contd.
66
Box graphs, contd.
67
Neutron ?-decay
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