Jefferson Lab, Newport News, VA Philip Cole Idaho State
University November 1, 2008. http://conferences.jlab.org/EmNN/
Brief Summary on the which took place on October 13-15, 2008 at For
more information, see: International Organizing Committee: V.
Burkert B. Julia-Diaz R. Gothe T.-S. H. Lee V. Mokeev
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Outline [Needs Work] Excited baryons Classification N
transition form factors Low mass N* excitations, Roper A
near-threshold resonance S 11 (1535) Search for new baryon states
Coupled channels analysis Summary
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Electromagnetic Excitation of N*s The experimental N* Program
has two major components: 1) Transition form factors of known
resonances to study their internal structure and confining
potential 2) Spectroscopy of excited baryon states, search for new
states. Both parts of the program are being pursued in various
decay channels, e.g. N, p, p + -, K, K, p, p 0 using cross sections
and polarization observables.
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Electromagnetic Excitation of N*s vv N p p e e vv N NN N*, A
3/2, A 1/2, S 1/2 M l+/-, E l+/-, S l+/- Measure the
electromagnetic excitations of low-lying baryon states (
23 Helicity amplitudes of the p P 11 (1440) transition NN CLAS
data : PDG First measurements of A 1/2 at Q 2 > 0 N N combined N
preliminary p p M.Dugger et al., PR C76 025211,2007 First
measurements of S 1/2 Inna Aznauryan
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Helicity amplitudes of the p D 13 (1520) transition NN CLAS
data : N N combined N preliminary Old data: Bonn, DESY, NINA PDG p
p M. Dugger First definite results for A 1/2, A 3/2 in wide range
of Q 2 First measurements of S 1/2 Inna Aznauryan
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25 Helicity amplitudes of the p S 11 (1535) transition NN CLAS
data : PDG p p M.Dugger First measurements of S 1/2 : Results for A
1/2 obtained in and production agree with each other with PDG: NN
it is difficult to extract S 1/2 in electroproduction Slow falloff
of A 1/2 observed in production is confirmed by data Inna
Aznauryan
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P11(1440) and D13(1520) electrocouplings at Q 2
cond 3-body processes: Isobar channels included: + D 0 13
(1520), + F 0 15 (1685), - P ++ 33 (1640) isobar channels, observed
for the first time in the CLAS data at W>1.65 GeV. Direct 2
production F 0 15(1685) (P ++ 33(1640)) (-)(-) (+)(+) V.Mokeev,
V.Burkert, J. Phys. 69, 012019 (2007); arXiv0809.4158[hep-ph] in
prep. for PRC
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29 Electrocouplings of high lying N*s. D33(1700) P13(1720)
First consistent mapping of Q 2 -dependence for D33(1700),
P13(1720) electrocouplings from CLAS data on 2
electroproduction
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N(1440)P 11 s Puzzle Most of analyses of N(1440) are based on
its BW parameterization, which assumes that the Res is related to
an isolated Pole However, the latest GW PWAs for the elastic N
scattering gives evidence that N(1440) corresponds to a more
complicated case of several nearby singularities in the amplitude
Then, the BW description is only an efficient one for N(1440),
which could be different in different processes Some inelastic data
indirectly support this point: they give the N(1440) BW mass and
width essentially different from the PDG BW values GW: A 1/2 =
-50.6 1.9 The analysis of the recent CLAS + electroproduction data
[W = 1.15 - 1.69 GeV & Q 2 = 1.7 - 4.5 GeV 2 ] allows to
extract helicities for * p N(1440)P 11 transition [I.G. Aznauryan
et al, arXiv:0804.0447 [nucl-ex] Since Q 2 -dependences for
contributions of different singularities may be different, the set
of several singularities might provide the N(1440) BW mass and
width depending on the Q 2 Model predictions allow to conclude that
N(1440) is a first radial excitation of 3q ground state This
problem can be studied in future measurements with CLAS12 Igor
Strakovsky
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N(1520)D 13 s Puzzle CLAS12 is favorable for Q 2 evaluation ___
SM08 FA06 [Q 2 = 0] o CLAS [2 ] CLAS [1 ] DR [1 ] Isobar [1 ] GW: A
3/2 = 143.1 2.0 The good agreement for A 3/2 and S 1/2
determination between various resonance extractions gives a more
reliable estimate of systematics Viktor Mokeev, PC 2008 SAID very
Preliminary W < 1650 MeV Q 2 = 0.40 0.05 GeV 2 SM08 CLAS40
MAID07 Data 0 1.6 1.6 1.5 5820 + 1.5 1.2 2.2 3352 W < 1650 MeV Q
2 = 0.65 0.05 GeV 2 SM08 CLAS65 MAID07 Data 0 1.3 1.3 1.1 8271 +
1.1 1.3 1.8 2515 Resonance fit done over a narrow range in W but
for all Q 2 a and b are free prmts (no W dependence for the
polynomial piece of the structure function) 2 /dp Igor
Strakovsky
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32 JLAB-MSU model (JM) for 2- electroproduction 3-body
processes: Isobar channels included: All well established N* with
decays and 3/2 + (1720) candidate, seen in CLAS 2 data. Reggeized
Born terms & effective FSI&ISI treatment. Extra contact
term. All well established N* with p decays and 3/2 + (1720)
candidate. Diffractive ansatz for non-resonant part & -line
shrinkage in N* region. - ++ pp
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Craig Roberts
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For tomography of DVCS amplitude and GPD quintessence function
see Polyakov, PLB659 (2008) 542 QCD string operator Maxim
Polyakov
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photon is hard For tomography of DVCS amplitude and GPD
quintessence function see Polyakov, PLB659 (2008) 542 Maxim
Polyakov
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Advantage of QCD strings to excite exotic baryons Strong colour
field Strong reararngenemt of colour Hard photon removes a quark
from N at once The quark returns back New Narrow Nucleon N*(1685)
Revealed in eta photoproduction /Kuznetsov, MVP, JETP Lett. 88
(2008) 399/ This is just one of examples of advantage of QCD string
probe for studies of baryon excitations. Maxim Polyakov
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Search for Exited Baryon States Experimentreactionsbeam
pol.target pol.recoil status
===================================================================================
G1/G10p N, p, p, K/ - -,complete G8 p p(,,) linear--complete
-----------------------------------------------------------------------------------------------------
G9-FROST p N, p, p, K lin./circ.long./trans.,2007 G13 D K,
Kcirc./lin.unpol., 2006/2008 G14-HD (HD) K, K,
Nlin./circ.long./trans., 2009/2010 C LAS This program will, for the
first time, provide complete amplitude information on the K final
state (more than 7 independent polarization measurements at each
kinematics), and nearly complete information on the N final
states.
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Andy Sandorfi
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45 Resonance Analysis Tools Nucleon resonances are broad and
overlapping, careful analyses of angular distributions for
differential cross sections and polarization observables are
needed. Amplitude & multipole analysis (GWU, SAID)
Phenomenological analysis procedures have been developed, e.g.
unitary isobar models (UIM), dispersion relations (DR), that
separate non-resonant and resonant amplitudes in single channels.
Dynamical coupled channel approaches for single and double pion
analysis are being developed within the Exited Baryon Analysis
Center (EBAC) effort. They are most important in the extraction of
transition form factors for higher mass baryon states. Event-based
partial wave analyses with maximum-likelihood fit, developed in the
search for new mesons states are now being utilized for baryon
resonance studies. They fully utilize correlations in the final
state (CMU). (Comments by Curtis Meyer).
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Coupled Channel Analysis (EBAC)
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Pion-nucleon and 2- pion-nucleon contributions to the
non-resonant T matrix.
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Summary Transition form factors of the N(1232) measured in
large Q 2 range. no sign of approaching asymptotic QCD limit, needs
12 GeV upgrade pion dressing of vertex needed to describe form
factors Roper P 11 transition form factor determined for the first
time. zero-crossing of magnetic form factor behaves like a Q 3
radial excitation at short distances Tantalizing hints of new
baryon states in KY and N channels require polarization data to
resolve ambiguities in analysis Measurement of multiple
polarization observables in N, p, and KY production needed to
resolve ambiguities in baryon resonance analysis. EBAC essential to
support the baryon resonance program with coupled channel
calculations.
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49 Ralf Gothe
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The Roper resonance N 1/2 +(1440)P 11 RQM: P 11 (1440) =
[56,0+] r P 11 (1440) = Q 3 G P 11 (1440) = (Q 3 ) r (QQ) The Roper
resonance is not a gluonic excitation Q 3 G. At large distances
meson couplings may be important. At short distances the Roper is
best described as a radial excitation of the nucleon. Photocoupling
amplitudes carry information on the the internal structure of the
state. First observation of a sign change for any nucleon
resonance.