The status of the Excited Baryon Analysis Center B. Juliá-Díaz Departament d’Estructura i Constituents de la Matèria Universitat de Barcelona (Spain)

Summary Motivation Model used at , , , production: Hadronic production   Photoproduction   Electroproduction  *   Expected during 2010

Baryon Resonances Exciting the substructure we can learn about the forces which keep the quarks together, e.g. using the quark model picture some of the predicted states are: P11 (939) 0s 0p L=0, S=1/2, J  =1/2 + P33 Δ(1232) L=0, S=3/2, J  =3/2 + S11 (1535) L=1, S=1/2, J  =1/2 - D13 (1520) L=1, S=1/2, J  =3/2 - S31 (1620) L=1, S=1/2, J  =1/2 - D33 (1700) L=1, S=1/2, J  =3/2 - J=1/2 J=3/2 J=1/2 qqq

The Δ (1232) and others The Delta (1232) resonance stands as a clear peak The region 1.4 GeV – 2 GeV hosts ~ 20 resonances πN  X, πN N*: 1440, 1520, 1535, 1650, 1675, 1680,... Δ : 1600, 1620, 1700, 1750, 1900, … Δ (1232) 100

E.m. probes Jefferson LAB (USA) GRAAL (Grenoble) MAMI (Mainz) BATES (MIT) ELSA (Bonn) SPring 8 (Japan) (Courtesy of D. Leinweber) Originaly, the hope was that probing the structure with electrons would minimize the “hadronic” debris and would give a cleaner access to the properties of nucleons and resonances

Electroproduction of mesons ** N N* N N M Main elements: 1. Strong-strong interactions 2. Hadronic structure of Resonances 3. Electromagnetic structure of Resonances Coupled-channels

EBAC plan and method

N* properties N-N* form factors QCDQCDQCDQCD Lattice QCD Hadron Models Dynamical Coupled-Channels EBAC Reaction Data

Formalism (DCC) Non-resonant + resonant Dressed resonant vertex Resonance self energies Non-resonant amplitude (resummation)

Partial wave amplitude of a  b reaction: Reaction channels: Potential: 2-body v potential (no  N cut) 2-body v potential (no  N cut) bare N* state 2-body Z potential (with  N cut) 2-body Z potential (with  N cut) EBAC-DCC A. Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007

5 diagrams s-ch N u-ch N u-ch  t-ch  t-ch  2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 3 diagrams s-ch N u-ch N t-ch  2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 4 diagrams s-ch N u-ch N t-ch  t-ch  2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 4 diagrams s-ch N u-ch N u-ch  t-ch  1 diagram s-ch N 1 diagram s-ch N 2 diagrams s-ch N u-ch N 2 diagrams s-ch N t-ch  Total 36 diagrams Two body v’s (strong)

7 diagrams s-ch N u-ch N u-ch  t-ch  t-ch  t-ch  contact 2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 4 diagrams s-ch N u-ch N t-ch  contact Total 20 diagrams 5 diagrams s-ch N u-ch N u-ch  t-ch  contact Two body v’s (e.m.)

EBAC framework overview Physics: Non-resonant obtained from phenomenological Lagrangians Unitarity fulfilled within the model Most relevant channels included Up to now , ,  ( , ,  ), near future  Consistent study of all production reactions Correct treatment of 3 body cut Technical Parallel computing version of the codes needed

Hadronic part (essential starting point)

MB  MB (up to 2 GeV) We introduce explicitly (impose) a minimal number of bare poles, 16 of 23 (4* and 3* from PDG): N: S11(2), P11(2), P13(1), D13(2), D15(1), F15(1) Δ: S31(1), P31(1), P33(2), D33(1), F35(1), F37(1)

Technical aspects Need for extensive parameter search. Several unknowns : e.g. couplings of resonances to MB states Supercomputing Resources NERSC LBNL (>500 kh, 07/10) PI: TSH Lee BSC, Spain (340 kh, 07/08), PI: B. Julia-Diaz Involved system of coupled integral equations with singularities.

 : comparisons to data EBAC SAID06

Data obtained through R. Arndt et al, SAID, gwdac.phys.gwu.edu B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, (2007) d  /d  Polarization  : comparisons to data (ii)

 : comparing amplitudes Amplitudes compared to GWU/SAID amplitudes for the I=1/2 sector B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, (2007 ) Real part of the AmplitudesImaginary part of the Amplitudes

 : comparing TCS Total Cross sections compared to experimental data B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, (2007) Prediction for the total cross sections for each individual channel

 : vs other approaches From M. Paris talk at INT 2009 and R. Arndt talk at Badhonnef 2009

   TCS s H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009) Not used to constrain the model. Previous works, mostly tree level: Meissner et al (1995  ) Oset et al (1985  )

  , distributions Data handled with the help of R. Arndt Invariant mass distributions Phase space Full model H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009)

Properties of N* (strong)

I. Analytic continuation of T(W) to the unphysical sheet by using contour deformation II. Poles can be both in the non-resonant and resonant amplitudes III. One can search for poles of T as a function of W (p’s are arbitrary) Resonance states Extraction of Resonances from Meson-Nucleon Reactions. N. Suzuki, T. Sato, T.-S.H. Lee, Phys. Rev. C 79 (2009) ; arXiv: , part of Suzuki’s PhD Thesis Resonance Mass

N. Suzuki, B. Julia-Diaz, H. Kamano, A. Matsuyama, TSH Lee, T Sato, arXiv: Dynamical origin of N(1440) poles EBAC i i 105 R. A. Arndt et al.(SAID) i i 83 M. Doring et al.(JUELICH) i 147/ i Within our framework the three P11 states evolve from the same bare state. 2. In the fig: evolution of the pole position as we increase the self energy

EBAC current N*

Electromagnetic part

Goal : E.m. meson production Make use of the vast database for single and double pion photo and electroproduction reactions (JLAB, ELSA, MAMI, …) to: 1)Look for yet unseen resonances 2)Confirm the existence of the N*s seen in the hadronic reactions 3)Extract resonance properties: a)Couplings to meson-baryon b)Electromagnetic structure

Schematic view ** N N* N Consequence of Unitarity

Data considered: – Differential cross sections –  p   0 p (8793) –  p   + n (5063) – Photon asymmetry (Sigma) –  p   0 p(1204) –  p   + n (881) Consider up to W = 1.6 GeV. Single pion photoproduction Analysis performed at specific energies. B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, L.C. Smith, Phys. Rev. C77, (2008)

σ TOT (  b) p0pp0p Comparison to data Total cross section Differential cross sections Target polarization p+np+n Single pion photoproduction

Electroproduction Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, Phys. Rev. C 80, (2009). 1. Fit1:  T +   L,  LT,  TT, p(e,e’  0 )p [Joo et al. PRL02] 2. Fit2 all p(e,e’  + )n, p(e,e’  0 )p 3. Fit3 p(e,e’  0 )p [Joo et al. PRL (2002 & 2003)] Consider W<1.65 MeV and Q 2 <1.45 GeV 2 No assumption on the Q 2 dependence of the helicity amplitudes Resonances which play a role: S 11, P 11, P 33, D 13 Could not fit all the structure functions simultaneously  Performed several fits to clarify the situation

Data at Q 2 <1.45 GeV 2 Fit1 Fit3 Fit2

Structure functions (ii) Q 2 = 0.4 GeV 2 Solid: Fit1 Dashed:Fit2 Dotted: Fit3 p+np+n Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, Phys. Rev. C 80, (2009).

Coupled channels effects 1. Solid Full Fit1 2. Dashed only  N intermediate (in e.m. piece) 3. Data from Q 2 = 0.4 GeV 2

   H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, arXiv: (2009) (Phys. Rev. C in press) Study of two pion photoproduction: Good description near threshold Reasonable shape of angular distributions Not good description of the total cross sections of p  0  0 and p  +  - above 1440 MeV - Previous (tree level) works include Meissner (1994  ) Gomez Tejedor, Roca,(1993  ) Fix et al (2005)

In progress (~ 2010) EBAC second generation model: Full Combined (global fit) analysis of:   N   N,  N (W<2 GeV)   N    N (W<2 GeV)   N   N (W<2 GeV)   N    N (W<2 GeV)   N   N (W<2 GeV) N* structure extraction   *N   N (W<2 GeV, Q 2 <4 GeV 2 )   *N    N (W<2 GeV)   *N   N (W<2 GeV) WEBPAGE:

BACKUP

WEBPAGE: MANPOWER: Leader (ANL/JLAB): T.-S.H.Lee Postdocts (JLAB): H. Kamano S. Nakamura K. Tsushima A. Sibirtsev Starting date: 2006 EXTERNAL COLLABORATORS: T. Sato, N. Suzuki (Osaka) A. Matsuyama (Shizuoka) B. Julia-Diaz (Barcelona) B. Saghai, J. Durand (Saclay)

Timeline of EBAC results Full DCC Formalism A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rep. (2007) Hadronic piece fixed (  N   N,  N)(W<2 GeV) B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, PRC (2007) J. Durand, B. Julia-Diaz, T.-S.H. Lee, T. Sato, B. Saghai, PRC (2008)  N   N (W<1.6 GeV) B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, LC Smith, PRC (2008)  N   N H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, PRC (2008) Analytic continuation N. Suzuki, T. Sato, T.-S.H. Lee, PRC (2008)  *    N (W<1.6 GeV, Q 2 <1.5 GeV 2 ) B. Julia-Diaz, H. Kamano, T.-S.H. Lee, A. Matsuyama, T.Sato,, PRC (2009)    N (W<1.8 GeV) H. Kamano, B. Julia-Diaz, T.-S.H. Lee, A. Matsuyama, T. Sato, PRC (2010)

Multi step (unitarity) How do we produce meson-baryon states? Directly Through MB states Through MMB states  We need to incorporate all the possibilities  Unitarity Coupled-channels σ TOT (  b) pp

Structure functions Q 2 = 1.45 GeV 2 p0pp0p Solid: Fit1

H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, arXiv: (2009), Phys. Rev. C in press   , N* effects

PDG *s and N*’s origin Are they all genuine quark/gluon excitations? |N*> =| qqq > Is their origin dynamical?  E.g. some could be understood as arising from meson-baryon dynamics |N*>= | MB > Most of their properties are extracted from  N   N  N   N

Z terms Z