Transcript 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.

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?
•
What is to be the new Standard Model?
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
Outline
• PVES and Nucleon Structure
• PVES and Nucleonic Matter
• PVES and the New Standard Model
Parity-Violating Asymmetry
e
e
p

Z
p
0
QPW, GPW

ALR

N  N 
N  N
GF Q2
4 2
[
p
e
p
e

2 Re APV APC*
2
APC
QPW + F(Q2, )
GPW
]
PV Electron Scattering Experiments
MIT-Bates
Mainz
SLAC
Jefferson
Lab
PV Electron Scattering Experiments
Deep Inelastic eD (1970’s)
PV Moller Scattering (now)
Deep Inelastic eD (2005?)
SLAC
PV Electron Scattering Experiments
MIT-Bates
Elastic e 12C (1970’s - 1990)
Elastic ep, QE eD (1990’s - now)
PV Electron Scattering Experiments
Mainz
QE e 9Be (1980’s)
Elastic ep (1990’s - now)
PV Electron Scattering Experiments
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?)
Jefferson
Lab
PVES and Nucleon Structure
What are the relevant degrees of freedom for
describing the properties of hadrons and why?
q
q
Constituent quarks (QM)
Current quarks (QCD)
QP ,P
FP2(x)
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)
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 ?
We can uncover the sea with GPW
Light QCD quarks:
Heavy QCD quarks:
u
mu ~ 5 MeV
c
mc ~ 1500 MeV
d
md ~ 10 MeV
b
mb ~ 4500 MeV
s
ms ~ 150 MeV
t
mt ~ 175,000 MeV
Effects in GP suppressed by
QCD/mq) 4 < 10 -4
QCD ~ 150 MeV
Neglect
them
We can uncover the sea with GPW
Light QCD quarks:
Heavy QCD quarks:
u
mu ~ 5 MeV
c
mc ~ 1500 MeV
d
md ~ 10 MeV
b
mb ~ 4500 MeV
s
ms ~ 150 MeV
t
mt ~ 175,000 MeV
ms ~ QCD : No suppression
not necessarily negligible
We can uncover the sea with GPW
Light QCD quarks:
Heavy QCD quarks:
u
mu ~ 5 MeV
c
mc ~ 1500 MeV
d
md ~ 10 MeV
b
mb ~ 4500 MeV
s
ms ~ 150 MeV
t
mt ~ 175,000 MeV
Lives only in the sea
g
s
s
Parity-Violating Electron Scattering
Neutral Weak Form Factors
Kaplan and Manohar
McKeown
GP = Qu Gu + Qd Gd + Qs Gs

Gn = Qu Gd + Qd Gu + Qs Gs
, isospin
GPW = QuW Gu + QdW Gd + QsW Gs
Z0
SAMPLE (MIT-Bates), HAPPEX
(JLab), PVA4 (Mainz), G0 (JLab)
Gu , Gd , Gs
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
at Q2=0.1 (GeV/c)2
GMs  0.14  0.29  0.31
GAe T  1  0.22  0.45  0.39
• s-quarks contribute less
than 5% (1s) to the proton’s
magnetic form factor.
• proton’s axial structure is
complicated!
Models for s
Radiative corrections
R. Hasty et al., Science 290, 2117 (2000).
Axial Radiative Corrections
e
“Anapole” effects : Hadronic
Weak Interaction
p

 
e
p
Z

+
Z

Nucleon Green’s Fn :
Analogous effects in
neutron -decay, PC
electron scattering…
“Anapole” Effects

Hadronic PV



p



Zhu, Puglia, Holstein, R-M (cPT)
Maekawa & van Kolck (cPT)
Riska (Model)
Can’t account for a large reduction in GeA
Zhu et al.
Nuclear PV Effects


PV NN
interaction
Carlson, Paris, Schiavilla
Liu, Prezeau, Ramsey-Musolf
Suppressed
by ~ 1000
R. Hasty et al., Science 290, 2117 (2000).
SAMPLE Results
at Q2=0.1 (GeV/c)2
D2
200 MeV data
Mar 2003
Zhu, et al.
H2
• s-quarks contribute less
than 5% (1s) to the proton’s
magnetic moment.
200 MeV update 2003:
Improved EM radiative corr.
Improved acceptance model
Correction for  background
125 MeV:
no  background
similar sensitivity
to GAe(T=1)
Radiative corrections
E. Beise, U Maryland
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 / c
~
1/2
cPT ?
• Symmetry is impotent
Js = JB + 2 JEM, I=0
s
 s  GM
(Q 2
 0)
Theoretical predictions
Happex projected
Q2 -dependence
of GsM
G0 projected
Lattice QCD theory
Dispersion theory
Chiral perturbation theory
“reasonable range” for slope
What cPT can (cannot) say
Strange magnetism as an illustration
G (q )  s 
s
M
s
Ito, R-M
Hemmert,
Meissner, Kubis
Hammer, Zhu, Puglia, R-M
1 2 2
6
s, M
qr

s  2MN  c bs 
Unknown lowenergy constant
(incalculable)
Kaon loop contributions
(calculable)
What cPT can (cannot) say
Strange magnetism as an illustration
G (q )  s 
s
M
2
s,M
r
s
6

c
{
2MN  r

bs
  c 
1 2 2
6
s, M
qr

NLO, unknown LEC

1
mK 
2
2  MN
 
 (5D  6DF  9F )
 7ln
18
 mK
 
LO, parameter free
}
NLO, cancellation
Dispersion theory gives a modelindependent prediction
Slope of
GMs
6
r 

2
s, M

s
M
2
ImG (t)
9m2 dt t

Strong interaction scattering amplitudes
e+ e-
K+ K-, etc.
Jaffe
Hammer, Drechsel, R-M
Dispersion theory gives a modelindependent prediction
6
r 

2
s, M

Hammer & R-M
s
M
2
ImG (t)
dt
4m 2 t
K
K



Perturbation theory (1-loop)
Dispersion theory gives a modelindependent prediction
6
r 

2
s, M

Hammer & R-M
s
M
2
ImG (t)
dt
4m 2 t
K
All orders
 resonance
s s
Perturbation theory (1-loop)
Dispersion theory gives a modelindependent prediction
6
r 

2
s, M

s
M
2
ImG (t)
dt
4m 2 t
K
Can’t do the whole integral
• Are there higher mass
excitations of s s pairs?
• Do they enhance or cancel
low-lying excitations?
Experiment will give an answer
?
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
PVES and Nucleonic Matter
The Z0 boson probes neutron properties
QW =
Donnelly,
Dubach, Sick
Z(1 - 4 sin2W) - N
~ 0.1
PREX (Hall A): 208Pb
Horowitz, Pollock,
Souder, & Michels
PVES and Neutron Stars
Neutron star
Horowitz &
Piekarewicz
208Pb
Crust thickness
decreases with Pn
PREX
Skin thickness (Rn-Rp)
increases with Pn
PVES and Neutron Stars
Horowitz &
Piekarewicz
Neutron star properties
are connected to densitydependence of symmetry
energy
PREX probes Rn-Rp
a meter of E ( r
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?
PVES and the New Standard Model
Present universe
Early universe
Standard Model
4
2
gi
High energy desert
Weak scale
log10 ( / 0 )
Planck scale
PVES and the New Standard Model
Present universe
Early universe
Standard Model
A “near miss” for
grand unification
High energy desert
Weak scale
log10 ( / 0 )
Planck scale
PVES and the New Standard Model
Present universe
Early universe
Standard Model
Weak scale is
unstable against new
physics in the desert
GF would be
much smaller
Weak scale
High energy desert
log10 ( / 0 )
Planck scale
PVES and the New Standard Model
Present universe
Early universe
Not enough
CP-violation
for weak scale
baryogenesis
Standard Model
High energy desert
10
nB  nB ~10 n
Weak scale
log10 ( / 0 )
Planck scale
Neutral current mixing depends
on electroweak symmetry
JWNC =
JEM
J0 + 4 Q sin2W
2
Y
g
sin W  2
2
g  gY
2
SU(2)L
U(1)Y
Weak mixing also depends on scale
Standard Model
sin2W
Czarnecki & Marciano
Erler, Kurylov, R-M
(GeV)
MZ
sin2W() depends on particle
spectrum
p
e
Z
0
e
Z

p
e

0
e
p
 
p
e
Z
0


Z

0
e

 
sin2W() depends on particle
spectrum
p
e
Z
0
e
Z

p
e

0
e
p
 
p
q
Z
0


Z

0
q
 
sin2W() depends on particle
spectrum
p
e
Z
0
e
Z

p
e

0
e
p
 
p
W
Z
0


Z

0
W

 
New Physics & Parity Violation
QeW =
-1 + 4 sin2W
Q PW =
1 - 4 sin2W
QCsW =
Z(1 - 4 sin2W) - N
sin2W is scale-dependent
Weak mixing also depends on scale
Atomic PV
N deep inelastic
sin2W
e+e- LEP, SLD
SLAC E158
JLab Q-Weak
(GeV)
Additional symmetries in the early
universe can change scale-dependence
Supersymmetry
Fermions
Bosons
e L,R , q L,R
e˜ L,R , q˜ L,R
gauginos
˜ , Z˜ ,
˜, g
˜
W
W , Z , , g
Higgsinos
˜ ,H
˜
H
u
d
sfermions
Hu , Hd

0
˜ , Z˜ ,
˜  c
˜, H
˜
˜
W
,
c
u, d
Charginos,
neutralinos
Electroweak & strong couplings
unify with supersymemtry
Present universe
Early universe
Standard Model
4
2
gi
Supersymmetry
Weak scale &
GF are protected
Weak scale
log10 ( / 0 )
Planck scale
SUSY will change sin2W() evolution
p
e
Z
0
e
Z

p
e

0
e
p
 
p
˜c
Z
0


Z

0
˜
c
 
SUSY will change sin2W() evolution
p
e
Z
0
e
Z

p
e

0
e
p
 
p
q˜
Z
0


Z

0
q˜
 
Comparing Qwe and QWp
Kurylov, R-M, Su
SUSY
SUSY
loopsloops
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
3000 randomly chosen
SUSY parameters but
effects are correlated
Can SUSY explain dark matter?
Expansion
Rotation curves
Cosmic microwave
background
SUSY provides a DM candidate
˜
c
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
e.g.
0
 
˜
c e   e
B and/or L Violation in SUSY can also
affect low-energy weak interactions
e
e
12k
˜e Rk
12k
L=1
-decay, -decay,…
e
1j1


d
q˜ Lj
1j1
d
e
L=1
QPW in PV electron
scattering
Comparing Qwe and QWp
Kurylov, R-M, Su
SUSY loops
 SUSY
dark matter
 -> e+
c
e
QuickTime™ and a TIFF (Uncompressed) decompressor
are needed to see this picture.
is Majorana
RPV 95% CL
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.
Weak mixing also depends on scale
Atomic PV
N deep inelastic
DIS-Parity, JLab
DIS-Parity, SLAC
sin2W
e+e- LEP, SLD
SLAC E158
Moller, JLab
JLab Q-Weak
(GeV)
Comparing Qwe and QWp
Kurylov, R-M, Su
SUSY loops
 SUSY
dark matter
E158 &QWeak
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
JLab Moller
RPV 95% CL
Interpretation of precision measurements
How well do we now the SM predictions? Some
QCD issues
Proton Weak Charge
2
GFQ
p
p
2
ALR 
QW  F (Q , )

4 2
Weak charge
Form factors: MIT,
JLab, Mainz
Q2=0.03 (GeV/c)2
Q2>0.1 (GeV/c)2
Interpretation of precision measurements
How well do we now the SM predictions? Some
QCD issues
Proton Weak Charge
2
GFQ
p
p
2
ALR 
QW  F (Q , )

4 2
FP(Q2,  -> 0) ~ Q2
Use cPT to extrapolate in small Q2
domain and current PV experiments
to determine LEC’s
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
QCD Effects in QWP
Box graphs
e
W
Z
Z
W
Z

p
QW ~ 26%
e
p
QW ~ 3%
kloop ~ MW : pQCD
e
p
QW ~ 6%
QCD < kloop < MW :
non-perturbative
Box graphs, cont’d.
Protected by symmetry
W
W
2
ˆ  

GF 

(M
s
W ) 

MWW  
2 2  5 1 
2 2 4sˆ  
 

Short-distance correction: OPE
QWp(QCD) ~ -0.7%
QWp(QCD) ~ -0.08%
WW
ZZ
Box graphs, cont’d.
Z

+
Z
Long-distance physics:
not calculable

[
ˆ
GF 5
2
ˆ
MZ  
1  4s 

2 2 2
ln
]
2

M
 Z  C ()
 2  Z
Fortuitous suppression factor: box + crossed ~
 kJ JZ ~ A
gve = (1+4 sin2W)
Neutron -decay
e
p
W
MW 

e
G F ˆ

2 2
[
ln
]
2

M
 Z  C ()
 2  W
n
|CW| < 2
to avoid exacerbating CKM
non-unitarity
|CZ| < 2
QWp < 1.5%