Dynamical coupled-channels study of meson production reactions from Hiroyuki Kamano (Excited Baryon Analysis Center, Jefferson Lab) MENU2010, May 31th - June 4th, 2010

Outline Motivation for the N* study at Excited Baryon Analysis Center (EBAC) of Jefferson Lab Brief review of EBAC analysis in (Preliminary) results of K  production reactions

Objectives and goals: Through the comprehensive analysis of world data of  N,  N, N(e,e’) reactions, Determine N* spectrum (masses, widths) Extract N* form factors Provide information about reaction mechanism necessary to interpret the N* properties, structures, dynamical origins Excited Baryon Analysis Center (EBAC) of Jefferson Lab N* properties QCDQCDQCDQCD Lattice QCDHadron Models Dynamical Coupled-Channels EBAC Reaction Data Founded in January 2006 “Dynamical coupled-channels model of meson production reactions” A. Matsuyama, T. Sato, T.-S.H. Lee Phys. Rep. 439 (2007) 193

Partial wave (LSJ) amplitude of a  b reaction: Reaction channels: Transition potentials: coupled-channels effect Dynamical coupled-channels model of EBAC (EBAC-DCC model) exchange potentials of ground state mesons and baryons exchange potentials of ground state mesons and baryons bare N* states For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)

EBAC-DCC analysis ( )  N   N : fitted to the data up to W = 2 GeV. Julia-Diaz, Lee, Matsuyama, Sato, PRC (2007)  N    N : cross sections calculated with the  N model. Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC (2009)  N   N : fitted to the data up to W = 2 GeV Durand, Julia-Diaz, Lee, Saghai, Sato, PRC (2008)   N   N : fitted to the data up to W = 1.6 GeV and Q 2 = 1.5 GeV 2 (photoproduction) Julia-Diaz, Lee, Matsuyama, Sato, Smith, PRC (2008) (electroproduction) Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC (2009)  N    N : cross sections calculated with the  N &  N model. Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC (2009) Extraction of N* pole positions & new interpretation of dynamical origin of P11 N* states. Suzuki, Julia-Diaz, Kamano, Lee, Matsuyama, Sato, PRL (2010) Extraction of  N  N* electromagnetic transition form factors. Suzuki, Sato, Lee, arXiv: [nucl-th] Hadronic part Electromagnetic part Extraction of N* parameters  N,  N,  N ( ,  N,  N) coupled- channels calculations were performed.  N,  N,  N ( ,  N,  N) coupled- channels calculations were performed.

EBAC-DCC analysis ( ) Coupled-channels effect in various reactions Coupled-channels effect in various reactions Full c.c. effect of  N( ,  N,  N) &  N off Full c.c effect off c.c. effect of  N( ,  N,  N) &  N off

EBAC-DCC analysis 2010 ~ Full combined analysis (global fit) of   N   N (W < 2 GeV)   N   N (W < 2 GeV)   N  KY (W < 2 GeV)   N   N (W < 1.6 GeV  2 GeV)   N   N(W < 2 GeV)   N  KY (W < 2 GeV)   N   N(W < 2 GeV)   N   N(W < 1.5 GeV  2 GeV) “Complete experiments” are planned by CLAS. “Complete experiments” are planned by CLAS. ~ End of ~ 2011 EBAC “second generation” model

pi- p  K 0 Lambda Julia-Diaz, Saghai, Lee, Tabakin PRC Preliminary EBAC-DCC

gamma p  K+ Lambda Preliminary d  /d  at 1.65 < W < 2 GeV

gamma p  K+ Lambda Polarization observables P P Cx’ Cz’ Additional bare N* states will be needed to improve the fit to the polarization observables. May correspond to new N* states!! Formula for calculations of the polarization observables  Sandorfi, Hoblit, Kamano, Lee arXiv: [nucl-th] Preliminary

Coupling effect of KY channels on piN PWA Preliminary KY on KY off SAID-EDS P11 Re P11 ImP13 Im D13 Im D15 ImF15 Im F17 Im S11 Re P13 Re D13 Re F15 Re F17 Re S11 Im D15 Re

Coupling effect of piN, pipiN, etaN channels on KY observables Couplings to  N,  N,  N channels off Current EBAC-DCC result Preliminary (At least) about 20% reduction is observed except backward angles.

Summary Full-combined analysis of  N,  N   N,  N, KY reactions is under way. Polarization observables will be a key to finding new N* states and complete experiments planned by CLAS are much desired. Effect of channel couplings (in the current model): Reaction model is kept improving:  KY channel couplings to  N amps.: Negligible (visible a little in P11,P13)   N,  N,  N, channel couplings to KY observables: Visible (~ 20%)  Add new bare N* states & meson-exchange processes.   Add new reaction channels (  N, KKN,  N,…)

Back up

Figure: E. Pasyuk’s talk at Hall-B/EBAC meeting “Priority” of coupled-channels effect  N (also  N) reaction cross sections in the resonance region are dominated by  N and  N final states. At least, the couplings of  N and  N channels should be taken into account in the analyses of any  N (  N)  MB reactions.

Exchange potentials for channels with strange hadrons 3 diagrams s-ch N u-ch  t-ch K* 4 diagrams s-ch N u-ch  t-ch  t-ch  Total 18 diagrams At present, KY couples to non-strange channels through  N channel only. (  N  KY is implementing) 3 diagrams s-ch N u-ch  u-ch  t-ch K* 3 diagrams s-ch N u-ch  t-ch  5 diagrams s-ch N u-ch  t-ch  t-ch  t-ch 

2-body “v” potentials (non-strange channels) 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

gamma N  MB potentials 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 32 diagrams 5 diagrams s-ch N u-ch N u-ch  t-ch  contact 6 diagrams s-ch N u-ch  u-ch  t-ch K t-ch K* contact 6 diagrams s-ch N u-ch  u-ch  t-ch K t-ch K* contact

Coupling effect of piN, pipiN, etaN channels on KY observables Meson-exchange amplitudes Amplitude with Dressed N*

Partial wave (LSJ) amplitude of a  b reaction: Reaction channels: Transition potentials: coupled-channels effect Dynamical coupled-channels model of EBAC (EBAC-DCC model) exchange potentials of ground state mesons and baryons exchange potentials of ground state mesons and baryons bare N* states For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)  In future, the form factors will be replaced with those from hadron structure calculations and the N* structure will be examined.

Strategy for the N* EBAC Stage 3 Make a connection to hadron structure calculations; Explore the structure of the N* states.  CQM, DSE, Large Nc, Soliton models,…  Connection to the Lattice QCD data Stage 1 Construct a reaction model through the comprehensive analysis of meson production reactions Stage 2  N* pole positions; N*   N, MB transition form factors  Confirm/reject N* with low-star status; Search for new N* Extract resonance information from the reaction model constructed

unpolarized diff. crs. sec. single spin beam-target beam-recoil target-recoil “Complete Experiment” of pseudoscalar meson photoproduction reactions Measurement of  N  KY pol. obs. is very active. OVER-complete experiments planned by CLAS for  p  K + ,  n  KY. Provides critical information on N*  KY decays !! Much room for new N* state searches Measure ALL polarization observables needed to determine amplitudes up to overall phase “Complete Experiment” = 8 /16 observables needed! Chiang, Tabakin PRC (1997) 8 /16 observables needed! Chiang, Tabakin PRC (1997)