Sub-Nucleon Physics Programme Current Status & Outlook for Hadron Physics D G Ireland

From quarks to nuclei… Selected Topics: Excitation of the Nucleon Nucleon Structure Exotics and Confinement

Studying the Strong Force QCDQCD-inspired models Nucleon structure and dynamics Static properties and phenomenology

Current effort

Excitation of the NucleonN*

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 Cross section E  (GeV )   P 33 N(1440)P 11 N(1520)D 13 N(1535)S 11  (1600)P 33

Meson Photoproduction Cross sections

Meson Photoproduction

CLAS

CLAS Results: CMU Analysis

Producing Linearly Polarized Photons

The FROzen Spin Target

Extracting Physics InformationExperiment cross section, spin observables Experiment cross section, spin observables TheoryLQCD, quark models, QCD sum rules QCD sum rules, …TheoryLQCD, quark models, QCD sum rules QCD sum rules, … Reaction Theory dynamical frameworks Reaction Theory dynamical frameworks Amplitude analysis → multipole amplitudes → phase shifts Amplitude analysis → multipole amplitudes → phase shifts σ,dσ/dΩ,Σ,P,T (beam-target) E, F, G, H, (beam-recoil) C x,C z, O x,O z, (target-recoil) L x,L z, T x,T z, PWA: Single energy solution Coupled channels: resonance parameter resonance parameterextraction

Nucleon Structure

Generalised Parton DistributionsFormfactor PDFGPD

Super BigBite – Jlab Hall A

GPDs in different reactionsGPDGPD Orbital angular momentum Orbital angular momentum FormfactorsFormfactors Wide Angle Compton Scattering Time-like Reactions Deeply Virtual Compton Scattering Hard Exclusive Meson Production Parton Distribution Functions

The HERMES Spectrometer 27.6 GeV e + /e - Recoil Detector,

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:

CLAS12 (Jlab upgrade)

Exotics and Confinement Quark Models  Linear qq potential Lattice Gauge Theory The Flux Tube Model Confirmation of idea

Gluonic Excitations J PC = exotic Exotic mesons are not generated when S=0 Flux tube model: 1 st excited state of flux tube has J=1 Combine with S=1 for quarks to get: Quantum number rules for quark-antiquark pair:- J PC = 0 – – – 1 + – 2 ++ … J PC = 0 – – 0 + – 1 – – … Allowed combinations  Not-allowed: exotic 

Meson Map qq Mesons L = Each box corresponds to 4 nonets (2 for L=0) Radial excitations (L = qq angular momentum) exotic nonets 0 – – – 1 – + 1 – – 2 – – – + 2 – Glueballs Hybrids

Jlab 12GeV Upgrade

The GlueX Project at Jlab

Charmonium – the Positronium of QCD 3 D  c (3590)  c (2980) h c (3525)  (3097)  (3686)  (3770)  (4040)  0 (3415)  1 (3510)  2 (3556) 3 D 1 3 D 3 1 D 2 3 P 2 (~ 3940) 3 P 1 (~ 3880) 3 P 0 (~ 3800) 1 fm C C ~ 600 meV S S S S P P P P S D D D D 2 Ionisationsenergie 3 3 S 1 e + e nm Binding energy [meV] Mass [MeV] Threshold 8·10 -4 eV eV Positronium Charmonium

The PANDA detector

Mass Range

Why Antiprotons? e+e- annihilation via virtual photon: only states with J pc = 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 g g g C. Morningstar PRD60, (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

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 H 2 /D 2, 208 Pb, 40 Ca, 16 O, 12 C 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