1. Exciting Hadrons Vladimir Pascalutsa
European Centre for Theoretical Studies
in Nuclear Physics and Related Areas
Trento, Italy
Supported by
NUPECC Meeting ( ECT*, Trento, Italy, Mar 16, 2007)

2. The quest for understanding the strong interaction (QCD) continues
The running coupling of QCD:
For asymptotic freedom
Perturbative QCD (using factorization theorems)
For
non-perturbative phenomena:
color confinement,
spontaneous chiral symmetry breaking,
generation of the nucleon mass (mass gap),
hadron spectrum (mesons, baryons, pentaquarks, glueballs),
nucleon structure (FFs, GPDs, spin content)
nuclear forces
Lattice QCD (severely limited by comp. power)
Chiral Effective-Field Theory of QCD
(very limited in energy, matching to QCD is a”?”)
Models:
quark, bag, NJL, chiral-soliton, instanton, AdS/QCD,…

3. Selected topics Nucleon mass and the 1st nucleon excitation:
lattice QCD vs chiral EFT
Nucleon structure:
electromagnetic form factors,
generalized parton distributions (GPDs)
Hadron spectrum:
statistical properties (“quantum chaos”, “missing resonances”)

4. N and Δ masses : pion-mass dependence
ChEFT
Lattice :
MILC
Introduce the Delta – the first excited state of the nucleon
physical
world
V.P. & Vanderhaeghen, PLB 636 (2006)

5. Electromagnetic excitation of the nucleon*
3 e.m. transitions : N Δ
M1, E2, C2
non-zero values for REM =E2/M1and RSM =C2/M1: measure of non-spherical distribution of charges

6. Prediction of the mq dependence of REM=E2/M1 and RSM=C2/M1
Q2 = 0.1 GeV2
Nicosia – MIT group [Alexandrou et al., PRL 94 (2005)]
quenched lattice QCD results :
mπ = 0.37, 0.45, 0.51 GeV
linear extrapolation
in mq ~ mπ2
ChEFT prediction
[V.P. & Vanderhaeghen, PRL 95 (2005); PRD 73 (2006)]
data points : MAMI, MIT-Bates

7. Rosenbluth vs polarization transfer measurements of GE/GM of proton
SLAC
Rosenbluth data
Jlab/Hall A
Polarization data
Jones et al. (2000)
Gayou et al. (2002)
Two methods, two different results !

8. Two-photon exchange calculation : elastic contribution
world Rosenbluth data N
Polarization Transfer

9. Nucleon Form Factors: charge/current distribution
curves : parameterizations
C. Perdrisat et al. JLab (E01-109)
SHMS in JLab / Hall C at 11 GeV

10. Elastic Scattering DIS GPDs
Generalized Parton Distributions (GPDs)
3-dim quark structure of nucleon
Elastic Scattering
transverse quark
distribution in
Coordinate space
DIS
longitudinal
quark distribution
in momentum space
GPDs
Fully-correlated
quark distribution in
both coordinate and
momentum space

12. Hadron spectrum below 2.5 GeV (PDG 2002)
Quark models
yield many more
states, problem of
“Missing Resonances”
Search for this states motivated CEBAF (now Jefferson Lab)
What about the
statistical properties?

13. Nearest-neighbor spacing distribution of quantum billiard (circular vs hart-shaped)
Wave-function (quantum chaos)

14. Quantum chaos in hadrons
V.P., EPJA 16 (2003)
C. Fernandez-Ramirez, A. Relano, PRL 98 (2007).
Statistical analysis of baryon spectra in
various quark models
shows no correlation (failure of QMs),
“missing resonances” will be missed!

15. Outlook
Hadrons are exciting and will be exciting for years to come, at
LHC (CERN)
DESY (Hamburg)
GSI (Darmstadt)
RHIC (Brookheaven)
Jefferson Lab (Virginia)
MAMI (Mainz)
ELSA (Bonn)
HIGS (Duke) …