Parity-Violation and Strange Quarks: Theoretical Perspectives

Parity-Violation and Strange Quarks: Theoretical Perspectives

M.J. Ramsey-Musolf

Hall A Collaboration Meeting: December ‘05

Outline

• Historical Context

• Strange quarks: what havewe learned?

• Other aspects of parity-violationand QCD: radiative corr,N to ,

PV: Past, Present, & Future

1970’s SLAC DIS Standard ModelAtomic PV sin2W ~ 10%

1980’s Mainz 8Be PV eq couplingsMIT 12C ~ 10%

Prehistory


2000’s SLAC Moller Standard Model & beyondJLab QWeak sin2W < 1%APV Anapole moment

JLab GAN

Mainz HWI (S=0): dA

VVCS: An

1990’s MIT GsE,M ~ few %

JLab GA & rad correctionsMainz n(r)APV sin2W ~ 1%

Anapole moment

Modern Era

2010’s JLab DIS-Parity Standard Model & beyondMoller (2) sin2W < 1%

2020’s NLC Moller (3) sin2W < 0.1%

Future


Quarks, Gluons, & the Light Elements

How does QCD make hadronic matter?

1.0

1.5

2.0

2.5

qq Mesons

L = 01 2 3 4H

ybrids

exoticnonets

PV & strange quarks

Gluonic effects

GPD’s: “Wigner Distributions” (X. Ji)

Pentaquark,

mq-dependence of nuclear properties

Lattice QCD

• What is the internal landscape of the nucleon?

• What does QCD predict for the properties of nuclear matter?

• Where is the glue that binds quarks into strongly-interactingparticles and what are its properties?

Tribble Report

Strange Quarks in the Nucleon:What have we learned?

Effects in are much less pronounced than in ,

€

N s γ μ s N

€

N s s N

€

N s γ μγ 5s N

Jaffe ‘89

Hammer, Meissner, Drechsel ‘95

• Dispersion Relations• Narrow Resonances• High Q2 ansatz

OZI violation

€

gφNN

gωNN

≈1

2

Strange Quarks in the Nucleon:What have we learned?

Effects in are much less pronounced than in ,

€

N s γ μ s N

€

N s s N

€

N s γ μγ 5s N

HAPPEX

SAMPLE

MAINZ

G0

K. Aniol et al, nucl-ex/0506011

Strange Quarks in the Nucleon: What have we learned?

• Strange quarks don’t appear in the conventional Quark Model picture of the nucleon

• Perturbation theory is limited

QCD / ms ~ 1 No HQET

mK / ~ 1/2 PT ?

• Symmetry is impotent

Js = JB - 2 JEM, I=0 Unknown constants

Theory: how do we understand dynamics of small ss effects in vector current channel ?

Challenge to understand QCD at deep, detailed level

What PT can (cannot) say

Strange magnetismIto & R-M; Hemmert, Meissner, Kubis; Hammer, Zhu, Puglia, R-M

The SU(3) chiral expansion for B :

O (p2)

mq -independent




O (p3)

non-analytic in mq

unique to loops leading SU(3)




O (p4)

non-analytic in mq (logs)




SU(3) Sym breaking

O (p4)

Two-deriv operators

+ 1/mN terms

M = diag (0,0,1)




O (p2) O (p3) O (p4)• converges as (mK / )n

• good description of SU(3) SB



Implications fors :

O (p2) singlet

O (p3,p4) loop only

O (p2,p4) octet

• Near cancellation of O (p2,p4) octet & loop terms• Exp’t: b0 + 0.6 b8 terms slightly > 0• Models: different assumptions for b0 + 0.6 b8 terms

O (p4) octet only

O (p4) singlet

Q2 -dependenceof Gs

M

G0 projected

Dispersion theory

Chiral perturbation theory “reasonable range” for slope

SAMPLE 2003

Happex projected

Lattice QCD theory


Strange magnetism

GMs (qs) = μs + 1

6 q2 rs,M2 +L

O (p4), unknown LEC

O (p3), parameter free O (p4) , cancellation

O (p4), octet


Strange magnetism

GMs (qs) = μs + 1

6 q2 rs,M2 +L

O (p3,p4), loops O (p4), octet

O (p4), unknown LEC


Strange electricityIto & R-M; Hemmert, Meissner, Kubis; Hammer, Zhu, Puglia, R-M

The SU(3) chiral expansion for s :

O (p3): non-analytic in mq (loops) + mq -independent cts


Strange electricityIto & R-M; Hemmert, Meissner, Kubis; Hammer, Zhu, Puglia, R-M

The SU(3) chiral expansion for s :

O (p3), octet

O (p3), unknown LEC

O (p3), loops


• Dispersion Theory

• Models

• Lattice QCD


It’s all in the low energy constants

€

€

K +s s

Loops “vs” poles

No dichotomy: kaon cloud is resonant



• Models

• Lattice QCD



€

€

K +s s

Kaon cloud

Not sufficient to explain Gs

E,M



• Models

• Lattice QCD



€

€

K +

Kaon cloud models

Not reliable guide to sign or magnitude of Gs

E,M



• Models

• Lattice QCD



€

€

K +

Chiral models

Implicit assumptions about b0 , c0 , b0

r , …



• Models

• Lattice QCD



€

€

K +

Disconnected Insertions

~ +…

Still a challenge

s s

Dispersion theoryJaffe Hammer, Drechsel, R-M

€

Ms = −

4mN2

πdt

ImGMs (t)

t 29mπ

2

∞

∫

Strong interaction scattering amplitudese+ e- K+ K-, etc.

Contributing States


€

Ms = −

4mN2

πdt

ImGMs (t)

t 29mπ

2

∞

∫



€

Ms = −

4mN2

πdt

ImGMs (t)

t 29mπ

2

∞

∫


Hammer & R-MDispersion theory

€

Ms = −

4mN2

πdt

ImGMs (t)

t 29mπ

2

∞

∫All orders

€

€

K +

• Naïve pert th’y O (g2)• Kaon cloud models• Unitarity violating

Unitarity


€

Ms = −

4mN2

πdt

ImGMs (t)

t 29mπ

2

∞

∫All orders

Unitarity

s s res

• S-quarks are not inert

• Non-perturbative effects dominate (LEC’s)

• Kaon cloud is resonant


€

Ms = −

4mN2

πdt

ImGMs (t)

t 29mπ

2

∞

∫

• Kaon cloud not dominant

• Not sufficient data to includeother states

Kaon cloud

Lattice Computations

Dong, Liu, & Williams (1998) Lewis, Wilcox, Woloshyn (2003)

• Quenched QCD

• Wilson fermions

• 2000 gauge configurations

• 60-noise estimate/config

• Quenched QCD

• Wilson fermions

• 100 gauge configurations

• 300-noise estimate/config

See also Leinweber et al

Lattice ComputationsLeinweber et al

Disconn s/d

Charge Sym

B exp’t

Lattice Computations

€

s = Fμ p

u

μ Σu , μ s

μ dloop( )

€

s ≈ −0.05 ± 0.02

Leinweber et al

€

s μdloop

dloop: Lattice

s: kaon loops

Charge Symmetry

s/d loop ratio

• Charge symmetry• Measured octet m.m.’s• Lattice d

loop

• Kaon loops



• Models

• Lattice QCD



€

€

K +

Disconnected Insertions

~ +…

Still a challenge

s s

CombiningPT, dispersion theory, & lattice QCD

€

GM(s)(Q2 = 0.1) = 0.37 ± 0.20 ± 0.26 ± 0.07

€

s = GM(s)(Q2 = 0.1) − 0.13bs

r

€

=0.37 ± 0.20 ± 0.26 ± 0.15

RA

“Reasonable range”: lattice & disp rel

SAMPLE



• Models

• Lattice QCD



€

€

K +

Chiral models


r , …



• Models

• Lattice QCD



Jido & Weise


r , …

No

b0,8=0



• Models

• Lattice QCD




r , … s > 0

Jido & Weise



• Models

• Lattice QCD




r , …

Zou & Riska (QM)

€

€

K +Give wrong sign ???

~ s in g.s. s in excited state (p wave)



• Models

• Lattice QCD




r , …€

(1405)

€

K +Give right sign ???~ s in g.s., (s wave) s in excited state

Zou & Riska (QM)

s > 0



• Models

• Lattice QCD




r , …

Zou & Riska (QM)

s s

s < 0

t-channel resonances?



• Models

• Lattice QCD




r , …

Chiral Quark Soliton

s > 0

Implicit kaon cloud + b3-7…

€

qqq bag

€

K +s s

resonances ?



• Models

• Lattice QCD




r , …

Chiral Quark Soliton

s < 0

Implicit kaon cloud + b3-7…

€

qqq bag

€

K +s s

resonances ?



New puzzles: higher Q2-dependence

Radiative Corrections & the Hadronic Weak Interaction

• GAe

• N !

• PV photo- and electro-production (threshold)

• Vector analyzing power ()

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

Axial Radiative Corrections

e

r e p

p

+⋅⋅⋅γ

“Anapole” effects : Hadronic Weak Interaction

γ

ZZ

γ+

Nucleon Green’s Fn : Analogous effects in neutron -decay, PC electron scattering…

“Anapole” Effects

€

€

+

€

p

€

+L

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

Nuclear PV Effects

€

PV NN interaction

Carlson, Paris, Schiavilla Liu, Prezeau, Ramsey-Musolf

Suppressed by ~ 1000

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

Transition Axial Form Factor

€

GANΔ (0) =

2

3

gπNΔFπ

mN

1− Δπ( )

€

GANΔ,e (0) = GA

NΔ (0) 1+ RAΔ

( )

Off Diagonal Goldberger-Treiman Relation Zhu, R-M

O(p2) chiral corrections ~ few %N!N ~ 5%

Rad corrections, “anapole” ~ 25%Study GA

N(Q2)/ GAN(0)

Measuring GAN(Q2)

GAN & “d”””

Axial response , GAN only

ALR ~ Q2 (1-2sin2W) Zhu, Maekawa, Sacco, Holstein, R-M

Nonzero ALR(Q2= 0)

Weak interactions of s-quarks are puzzling

Hyperon weak decays

€

Σ+ → nπ + Σ+ → pπ 0 Σ− → nπ −

Λ → pπ − Λ → nπ 0 Ξ− → Λπ 0 Ξ0 → Λπ 0

€

MB → ′ B π = U B A + Bγ 5[ ]UB

S-Wave: Parity-violating

P-Wave: Parity-conserving

symmetry not sufficient


€

rΣ+ → pγ ,

r Λ → nγ ,K

€

MB → ′ B λ = −i

MB + M ′ B

U σ μν A + Bγ 5( )U F μν

M1 (PC)

E1 (PV)

€

αB ′ B =2Re A B*

A2

+ B2

€

αB ′ B ~ ms Λχ ~ 0.15

€

αΣ+ p

~ − 0.76 ± 0.08

αΞ 0Σ0 ~ − 0.63± 0.09

Th’y

Exp’t

Weak interactions of s-quarks are puzzlingResonance saturation

€

B

€

′B

€

′′B

€

€

B

€

′B

€

′′B

€

€

+Holstein & Borasoy

S11

Roper

S-Wave

P-Wave

€

12

+ 12

− 12

+

12

+ 12

+ 12

+

€

12

+ 12

− 12

+

12

+ 12

+ 12

+

Fit matrix elements

Weak interactions of s-quarks are puzzlingResonance saturation

€

B

€

′B

€

′′B

€

€

B

€

′B

€

′′B

€

€

+Holstein & Borasoy

S11

Roper

S-Wave

P-Wave

€

12

+ 12

− 12

+

12

+ 12

+ 12

+

€

12

+ 12

− 12

+

12

+ 12

+ 12

+

Fit matrix elements

€

B

€

′B

€

′′B

€

€

B

€

′B

€

′′B

€

€

+

€

B( ) = −π ′ ′ B ( ) = π ′ B ( ) S/P wave fit Close gap with αBB’


€

WB ′ ′ B ~ Λχ gπ

€

WB ′ ′ B ~ 5 Λχ gπ

Natural

Fit

€

~GF Fπ

2

2 2~ 3.8 ×10−8

Is deviation from QCD-based expectations due to presence of s-quarks or more fundamental dynamics?

We have a S=0 probe

€

N

€

€

Use PV to filter out EM transition

Zhu, Maekawa, Holstein, MR-M

€

L = ie

Λχ

dΔ Δ μ+ γ λ pF μλ + h.c.PV, E1

Amplitude

€

Aγ = 0

€

Aγ = 2dΔ

C3V

mN

Λχ

+LPV Asymmetry

Large NC , spin-flavor SU(4) Finite NC

Low energy constant

We have a S=0 probe

€

N

€

€

€

L = ie

Λχ

dΔ Δ μ+ γ λ pF μλ + h.c.

Naïve dimensional analysis (NDA)

Resonance saturation

€

N

€

€

12

−

€

€

N

€

€

32

−

€

€

+

€

HWΔS= 0

€

Aγ ~ 5 ×10−8

d~ g

€

Aγ ~ 1×10−6 d~ 25g

Measuring d

d = 100 genhanced HW

S=0

d = 0 , GAN only

ALR ~ Q2 (1-2sin2W) Zhu, Maekawa, Sacco, Holstein, R-M

N! Transition

Measure Q2-dependence of ALR to learn

• d

• GANQ2)/ GA

N0)

• RA

Radiative Corrections & the Hadronic Weak Interaction

• GAe

• N !

• PV photo- and electro-production (threshold)

• Vector analyzing power ()

Theory for RA good to ~ 25%

Further test of RAd & HW

qq

EFT for low energy good to ~ 25%; more tests!

New window on electroweak VVCS: -decay, sin2W,…

Vector Analyzing Power

€

An ~r S ⋅

r K × ′

r K

• T-odd, P-even correlation

• Doubly virtual compton scattering (VVCS):new probe of nucleon structure

• Implications for radiative corrections in other processes: GE

p/GMp, -decay…

• SAMPLE, Mainz, JLab experiments

What specifically could we learn?

Vud


γ€

V

€

V

γ+

V=: VVCS

Re M(M

boxMcross) Rosenbluth

Im MM

box VAP

V=W,Z: Electroweak VVCS

Re MV(MV

boxMVcross) -decay, RA,…

Im MVMV

box -decay T-violation

Direct probe


Mott: MN!1

SAMPLE

EFT to O(p2)

Diaconescu, R-M

I=1, r2

O(p0)

O(p4)

1460


Constrained by SAMPLE

300

Dynamical ’s?

Conclusions• Measurements of neutral weak form factors

have challenged QCD theory:

• PV program has stimulated a variety of other developments at the interface of QCD and weak interactions:

• Powerful new probes of SM & beyond: Qwe,p , DIS

• Kaon cloud is resonant, but not dominant• Loop calculations are unreliable guide• Symmetry limited by presence of unknown constants

• Models remain interesting, but ad hoc (implicit LECs)• Lattice challenged to obtain disconn insertions

• Axial radiative corrections consistent with experiment• Axial N to new QCD testing ground: GA

N, d• Electroweak box graphs: new insights from ?

Documents

Parity-Violation and Strange Quarks: Theoretical Perspectives