Sub-Nucleon Physics ProgrammeCurrent Status & Outlook for Hadron PhysicsD G Ireland

From quarks to nuclei…

Nuc le us

Q ua rk

Selected Topics:

• Excitation of the Nucleon

• Nucleon Structure

• Exotics and Confinement

Studying the Strong Force

QCD QCD-inspired models

Nucleon structure and dynamics

Static properties and phenomenology

Current effort

Excitation of the Nucleon

N*N*

Resonance hunting

Mostly done with Pion-N scattering or photoproduction

Missing resonances may decay through other channels

Total Cross-sections+ differential cross-sections+ Partial Wave Analysis + ...

0.5 1.0 1.5

Cro

ss s

ecti

on

E (GeV)

P33

N(1440)P11

N(1520)D13

N(1535)S11

(1600)P33

Meson Photoproduction Cross sections

Meson Photoproduction

CLAS

CLAS Results: CMU Analysis

CLAS Results: CMU Analysis

022

044066

Producing Linearly Polarized Photons

The FROzen Spin Target

Extracting Physics Information

ExperimentExperimentcross section, cross section,

spin observablesspin observables

ExperimentExperimentcross section, cross section,

spin observablesspin observables

TheoryTheoryLQCD,LQCD,

quark models,quark models,QCD sum rulesQCD sum rules,

…

TheoryTheoryLQCD,LQCD,

quark models,quark models,QCD sum rulesQCD sum rules,

…

Reaction TheoryReaction Theorydynamical frameworksdynamical frameworks

Reaction TheoryReaction Theorydynamical frameworksdynamical frameworks

Amplitude analysisAmplitude analysis→→multipole amplitudesmultipole amplitudes

→→phase shiftsphase shifts

Amplitude analysisAmplitude analysis→→multipole amplitudesmultipole amplitudes

→→phase shiftsphase shifts

σ,dσ/dΩ,Σ,P,Tσ,dσ/dΩ,Σ,P,T(beam-target)(beam-target) E, F, G, H, E, F, G, H,(beam-recoil)(beam-recoil) C Cxx,C,Czz, O, Oxx,O,Ozz,,(target-recoil)(target-recoil) L Lxx,L,Lzz, T, Txx,T,Tzz,,

PWA: PWA: Single energy solutionSingle energy solution

Coupled channels:Coupled channels: resonance parameter resonance parameter

extractionextraction

Nucleon Structure

Generalised Parton Distributions

FormfactorFormfactor PDFPDF GPDGPD

Super BigBite – Jlab Hall A

GPDs in different reactions

GPDGPDGPDGPD

Orbital angular Orbital angular momentummomentum

Orbital angular Orbital angular momentummomentum

FormfactorsFormfactorsFormfactorsFormfactors

Wide Angle Wide Angle Compton Compton ScatteringScattering

Wide Angle Wide Angle Compton Compton ScatteringScattering

Time-like Time-like ReactionsReactions

Time-like Time-like ReactionsReactions

Deeply Deeply Virtual Virtual

Compton Compton ScatteringScattering

Deeply Deeply Virtual Virtual

Compton Compton ScatteringScattering

Hard Hard Exclusive Exclusive

Meson Meson ProductionProduction

Hard Hard Exclusive Exclusive

Meson Meson ProductionProduction

Parton Parton DistributioDistributio

n n FunctionsFunctions

Parton Parton DistributioDistributio

n n FunctionsFunctions

The HERMES Spectrometer

27.6 GeV e+/e-

Recoil Detector, 2005 -2007

Angular Momentum Constraints

Kinematic dependence of single observables does not sufficiently constrain models

Combination of different observables and different experiments needed

HERMES and Jlab complement each other ideally

arXiv: 0802.2499arXiv: 0802.2499

CLAS12 (Jlab upgrade)

Exotics and Confinement

Flux

tube

forms

between

qq

Quark Models Linear qq potential

Lattice Gauge TheoryThe Flux Tube Model

Confirmation of idea

Gluonic Excitations

JPC = 0-+ 0+- 1+- 1-+ 2-+ 2+-

exoticExotic mesons are not generated when S=0

Flux tube model: 1st excited state of flux tube has J=1

Combine with S=1 for quarks to get:

LS

S

1

2

S = S + S1 2

J = L + S

C = (-1)L + S

P = (-1)L + 1

Quantum number rules for quark-antiquark pair:-

JPC = 0– + 0++ 1– – 1+ – 2++ …

JPC = 0– – 0+ – 1– + 2+ – …

Allowed combinations

Not-allowed: exotic

Meson Map

1.0

1.5

2.0

2.5

qq Mesons

L = 0 1 2 3 4

Each box correspondsto 4 nonets (2 for L=0)

Radial excitations

(L = qq angular momentum)

exoticnonets

0 – +

0 + –

1 + +

1 + –

1– +

1 – –

2 – +

2 + –2 + +

0 – +

2 – +

0 + +

Glueballs

Hybrids

Jlab 12GeV Upgrade

The GlueX Project at Jlab

Charmonium – the Positronium of QCD

3D2

2900

3100

3300

3500

3700

3900

4100

c(3590)

c(2980)

hc(3525)

(3097)

(3686)

(3770)

(4040)

0(3415)

1(3510) 2(3556)

3D1

3D3

1D2

3P2(~ 3940)

3P1(~ 3880)

3P0(~ 3800)

(~ 3800)

1 fm

C C

~ 600 meV

-1000

-3000

-5000

-700011S

0

13S1

2 1S0 23S

12 1P

1 23P2

23P1

23P0

03 1S

0 3 1D

2 33D 2

33D 1

33D 2

Ionisationsenergie33S

1

e+ e-0.1 nm

Binding energy [meV] Mass [MeV]

DDThreshold

8·10-4 eV

10-4 eV

Positronium Charmonium

The PANDA detector

Mass Range

Why Antiprotons?

e+e- annihilation via virtual photon: only states with Jpc = 1--

In pp annihilation all mesons can be formed

Resolution of the mass and width is only limited by the beam momentum resolution

Measured rate

Beam

Resonance cross

section

CM Energy

Glueballs

gg

g

RG

GR

BGGRRB

C. Morningstar PRD60, 034509 (1999)Self interaction between gluons

Construction of color-neutral hadrons with gluons possible

exotic glueballs don‘t mix with mesons (qq)

0--, 0+-, 1-+, 2+-, 3-+,...

Current Status

• Excitation of the nucleon– Advance to goal of complete measurement; many observables already measured

– Use of spin-polarised targets started

• Nucleon structure– Major programme of measurement started at HERMES

– Will continue at CLAS12 (Jlab)

• Exotics and Confinement– Pilot measurements started

– GluEx and PANDA to address the issue

Outlook

• Complete nucleon resonance programme (MAMI, CLAS,…)

• Continue nucleon structure studies (HERMES, CLAS12,…)

• Develop searches for “exotics” (CLAS, GluEx, PANDA,…)

“Complete” Measurements

Observable Experiment Type

dσ/dt - - - Single

Σ dσ/dt L - -

T dσ/dt - y -

P dσ/dt - - y

G dσ/dt L z - Beam Target

H dσ/dt L x -

E dσ/dt C z -

F dσ/dt C x -

Ox dσ/dt L - x’ Beam Recoil

Oz dσ/dt L - z’

Cx dσ/dt C - x’

Cz dσ/dt C - z’

Tx dσ/dt - x x’ Target Recoil

Tz dσ/dt - x z’

Lx dσ/dt - z x’

Lz dσ/dt - z z’

Sivers Effect

Motion of quarks induces emission in a preferred direction

Leading hadron carries information on struck quark

Measurement requires large beam energies

Pioneered at HERMES, precision studies to follow at CLAS 12

up to 1.5 GeV/c polarised electron beam

A1: Electron scattering off nucleons and nuclei

A2: photoexcitations of nucleons and nuclei with polarised photons

Glasgow tagger and goniometer essential ingredients to facility

MAinz MIcrotron

Crystal Ball at MAMI A2

High rate, polarised, tagged photon beam up to 1.4 GeV with 2 MeV resolution (and microscope)

Liquid H2/D2, 208Pb, 40Ca, 16O, 12C and other nuclear targets

Two EM calorimeters for full solid angle coverage

MWPC & PID for tracking and ID of charged particles

Ideal for high precision / low cross section measurements

Magnetic Moments of Resonances