parity violation: past, present, and future
DESCRIPTION
Parity Violation: Past, Present, and Future. M.J. Ramsey-Musolf. 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? - PowerPoint PPT PresentationTRANSCRIPT
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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
e
e
p
p
e
e
p
pZ 0
QPW, GP
W
GF Q2
4 2 QPW + F(Q2, ) [ ]
ALR N N
N N
2 Re
APC
2
APV APC*
GPW
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PV Electron Scattering Experiments
MIT-Bates
Mainz
Jefferson Lab
SLAC
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PV Electron Scattering Experiments
SLAC
Deep Inelastic eD (1970’s) PV Moller Scattering (now) Deep Inelastic eD (2005?)
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PV Electron Scattering Experiments
MIT-Bates
Elastic e 12C (1970’s - 1990) Elastic ep, QE eD (1990’s - now)
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PV Electron Scattering Experiments
Mainz
QE e 9Be (1980’s) Elastic ep (1990’s - now)
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PV Electron Scattering Experiments
Jefferson Lab
Elastic ep: HAPPEX, G0 (1990’s - 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?)
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PVES and Nucleon Structure
What are the relevant degrees of freedom for describing the properties of hadrons and why?
QP ,P
Constituent quarks (QM) Current quarks (QCD)
FP2(x)
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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 parametersand 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?
Strange quarks in the nucleon:
• Sea quarks
• ms ~ QCD
• 20% of nucleon mass, possibly -10% of spin
What role in electromagnetic structure ?
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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
Effects in GP suppressed by
QCD/mq) 4 < 10 -4
QCD ~ 150 MeV
Neglect them
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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
ms ~ QCD : No suppression
not necessarily negligible
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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
Lives only in the sea
ss g
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Parity-Violating Electron Scattering
Neutral Weak Form Factors
GP = Qu Gu + Qd Gd + Qs Gs
Gn = Qu Gd + Qd Gu + Qs Gs , isospin
GPW
= QuW Gu + Qd
W Gd + QsW Gs Z0
SAMPLE (MIT-Bates), HAPPEX (JLab), PVA4 (Mainz), G0 (JLab)
Gu , Gd , Gs
Kaplan and Manohar McKeown
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Parity-Violating Electron Scattering
Separating GEW , GM
W , GAW
GMW , GA
W SAMPLE
GMW , GE
W HAPPEX, PVA4
GMW , GE
W , GAW : Q2-dependence G0
Published results: SAMPLE, HAPPEX
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at Q2=0.1 (GeV/c)2
39.045.022.01
31.029.014.0
TG
GeA
sM
R. Hasty et al., Science 290, 2117 (2000).
• s-quarks contribute less than 5% (1) to the proton’s magnetic form factor.
• proton’s axial structure is complicated!
Models for s
Radiative corrections
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Axial Radiative Corrections
e
e p
p
“Anapole” effects : Hadronic Weak Interaction
ZZ
+
Nucleon Green’s Fn : Analogous effects in neutron -decay, PC electron scattering…
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“Anapole” Effects
p
Zhu, Puglia, Holstein, R-M (PT) Maekawa & van Kolck (PT) Riska (Model)
Zhu et al.
Hadronic PV
Can’t account for a large reduction in GeA
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Nuclear PV Effects
PV NN interaction
Carlson, Paris, Schiavilla Liu, Prezeau, Ramsey-Musolf
Suppressed by ~ 1000
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at Q2=0.1 (GeV/c)2
125 MeV:no backgroundsimilar sensitivity to GA
e(T=1)
SAMPLE Results R. Hasty et al., Science 290, 2117 (2000).
200 MeV update 2003:Improved EM radiative corr.Improved acceptance modelCorrection for background
• s-quarks contribute less than 5% (1) to the proton’s magnetic moment.
200 MeV dataMar 2003
D2
H2
Zhu
, et
al.
E. Beise, U MarylandRadiative corrections
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Strange Quark Form Factors
Theoretical Challenge:
• Strange quarks don’t appear in Quark Model picture of the nucleon
• Perturbation theory may not apply
QCD / ms ~ 1 No HQET
mK / ~ 1/2 PT ?
• Symmetry is impotent
Js = JB + 2 JEM, I=0
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Theoretical predictions)0( 2 QG s
Ms
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Q2 -dependenceof Gs
M
G0 projected
Lattice QCD theory
Dispersion theory
Chiral perturbation theory “reasonable range” for slope
Happex projected
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What PT can (cannot) say
Strange magnetism as an illustration
GMs (q s ) s 1
6 q2 rs, M2
s 2MN bs
Unknown low-energy constant (incalculable)
Kaon loop contributions (calculable)
Ito, R-M Hemmert, Meissner, Kubis Hammer, Zhu, Puglia, R-M
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What PT can (cannot) say
Strange magnetism as an illustration
GMs (q s ) s 1
6 q2 rs, M2
rs,M2
6
2MN
bs
r
1
18(5D2 6DF 9F2 )
MN
mK
7lnmK
{}
LO, parameter free NLO, cancellation
NLO, unknown LEC
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Dispersion theory gives a model-independent prediction
rs, M2
6
dt
Im GMs (t)
t2
9m2
Strong interaction scattering amplitudes
e+ e- K+ K-, etc.
Slope of GMs
Jaffe Hammer, Drechsel, R-M
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Dispersion theory gives a model-independent prediction
rs, M2
6
dt
Im GMs (t)
t2
4mK2
Perturbation theory (1-loop)
K
Hammer & R-M
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Dispersion theory gives a model-independent prediction
rs, M2
6
dt
Im GMs (t)
t2
4mK2
s s
resonance
Perturbation theory (1-loop)
Hammer & R-M
All orders
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Dispersion theory gives a model-independent prediction
rs, M2
6
dt
Im GMs (t)
t2
4mK2
• Are there higher mass excitations of s s pairs?
• Do they enhance or cancel low-lying excitations?
Experiment will give an answer
Can’t do the whole integral
?
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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
The Z0 boson probes neutron properties Donnelly, Dubach, Sick
QW = Z(1 - 4 sin2W) - N
~ 0.1
PREX (Hall A): 208PbHorowitz, Pollock, Souder, & Michels
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PVES and Neutron Stars
Horowitz & Piekarewicz
Crust thickness decreases with Pn
Neutron star
208Pb
Skin thickness (Rn-Rp) increases with Pn
PREX
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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 (
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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
4gi
2
Standard Model
log10 ( / 0 )Weak scale Planck scale
High energy desert
Early universe
Present universe
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PVES and the New Standard Model
Standard Model
log10 ( / 0 )Weak scale Planck scale
High energy desert
Early universe
Present universe
A “near miss” for grand unification
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PVES and the New Standard Model
Standard Model
log10 ( / 0 )Planck scale
High energy desert
Early universe
Present universe
Weak scale is unstable against new physics in the desert
Weak scale
GF would be much smaller
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PVES and the New Standard Model
Standard Model
log10 ( / 0 )Weak scale Planck scale
High energy desert
Early universe
Present universe
Not enough CP-violation for weak scale baryogenesis
nB nB
~ 10 10 n
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Neutral current mixing depends on electroweak symmetry
JWNC = J0 + 4 Q sin2W JEM
sin2W gY
2
g2 gY2
SU(2)L U(1)Y
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Weak mixing also depends on scale
sin2W
(GeV)
Standard Model
MZ
Czarnecki & Marciano Erler, Kurylov, R-M
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sin2W() depends on particle spectrum
e
e
p
pe
e
p
p
Z 0
Z 0
Z 0 Z 0 e
e
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sin2W() depends on particle spectrum
e
e
p
pe
e
p
p
Z 0
Z 0
Z 0 Z 0
q
q
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sin2W() depends on particle spectrum
e
e
p
pe
e
p
p
Z 0
Z 0
Z 0 Z 0 W
W
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New Physics & Parity Violation
QeW = -1 + 4 sin2W
QPW = 1 - 4 sin2W
QCsW = Z(1 - 4 sin2W) - N
sin2W is scale-dependent
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Weak mixing also depends on scale
sin2W
(GeV)
N deep inelastic
SLAC E158 JLab Q-Weak
e+e- LEP, SLD
Atomic PV
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Additional symmetries in the early universe can change scale-dependence
Supersymmetry
eL,R , qL,R
W ,Z ,, g
Hu , Hd
˜ W , ˜ Z , ˜ , ˜ H u, d ˜ , ˜ 0Charginos, neutralinos
Fermions Bosons
˜ e L,R , ˜ q L,R sfermions
˜ W , ˜ Z , ˜ , ˜ g gauginos
˜ H u , ˜ H dHiggsinos
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Electroweak & strong couplings unify with supersymemtry
4gi
2
Standard Model
log10 ( / 0 )Weak scale Planck scale
Early universe
Present universe
Supersymmetry
Weak scale & GF are protected
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SUSY will change sin2W() evolution
e
e
p
pe
e
p
p
Z 0
Z 0
Z 0 Z 0
˜
˜
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SUSY will change sin2W() evolution
e
e
p
pe
e
p
p
Z 0
Z 0
Z 0 Z 0
˜ q
˜ q
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Comparing Qwe and QW
p
SUSY loops
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
SUSY loops
Kurylov, R-M, Su
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
˜ 0 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
˜ 0 e ee.g.
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e e
˜ e Rk
12k 12k
e
d e
d
˜ q Lj
1j1
1j1
L=1 L=1
B and/or L Violation in SUSY can also affect low-energy weak interactions
-decay, -decay,… QPW in PV electron
scattering
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Comparing Qwe and QW
p
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
SUSY loops
SUSY dark matter
-> e+e
RPV 95% CL
Kurylov, R-M, Su
is Majorana
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Comparing Qwe and QW
p
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
sin2W
(GeV)
N deep inelastic
SLAC E158 JLab Q-Weak
e+e- LEP, SLD
Atomic PV
DIS-Parity, SLACDIS-Parity, JLab
Moller, JLab
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Comparing Qwe and QW
p
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
SUSY dark matter
SUSY loops
RPV 95% CL
E158 &Q-Weak
JLab Moller
Kurylov, R-M, Su
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Interpretation of precision measurements
How well do we now the SM predictions? Some QCD issues
Proton Weak Charge
ALR GFQ
2
4 2QW
p Fp (Q2 ,)
Weak charge
Q2=0.03 (GeV/c)2
Form factors: MIT, JLab, Mainz
Q2>0.1 (GeV/c)2
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Interpretation of precision measurements
How well do we now the SM predictions? Some QCD issues
Proton Weak Charge
ALR GFQ
2
4 2QW
p Fp (Q2 ,)
FP(Q2, -> 0) ~ Q2
Use PT to extrapolate in small Q2 domain and current PV experiments to determine LEC’s
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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
Box graphs
e p e p e p
W
W
Z
Z
Z
QW ~ 26% QW ~ 6%QW ~ 3%
kloop ~ MW : pQCD QCD < kloop < MW : non-perturbative
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Box graphs, cont’d.
W
WMWW
GF
2 2
ˆ 4ˆ s 2
2 5 1 s (MW
2 )
Protected by symmetry
Short-distance correction: OPE
QWp(QCD) ~ -0.7% WW
QWp(QCD) ~ -0.08% ZZ
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Box graphs, cont’d.
ZZ
+
MZ GF
2 2
5 ˆ 2
1 4ˆ s 2 MZ2
2
CZ()[ ]ln
Long-distance physics: not calculable
Fortuitous suppression factor: box + crossed ~ kJ JZ ~ A gv
e = (-1+4 sin2W)
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Neutron -decay
W
MW GF
2
ˆ 2
MZ2
2
CW()[ ]ln
e p
e n
|CW| < 2 to avoid exacerbating CKM non-unitarity
|CZ| < 2 QWp < 1.5%