Dynamical coupled-channels channels study of meson production reactions from EBAC@JLab 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 2007-2009 (Preliminary) results of KΛ production reactions
Excited Baryon Analysis Center (EBAC) of Jefferson Lab Founded in January 2006 http://ebac-theory.jlab.org/ Reaction Data Objectives and goals: Dynamical Coupled-Channels Analysis @ EBAC Through the comprehensive analysis of world data of πn, γn, N(e,e ) reactions, Determine N* spectrum (masses, widths) N* properties Extract N* form factors Hadron Models QCD Lattice QCD Provide information about reaction mechanism necessary to interpret the N* properties, structures, dynamical origins
Excited Baryon Analysis Center (EBAC) of Jefferson Lab Founded in January 2006 http://ebac-theory.jlab.org/ Reaction Data Objectives and goals: Dynamical Coupled-Channels Analysis @ EBAC Through the comprehensive analysis of world data of πn, γn, N(e,e ) reactions, Determine N* spectrum (masses, widths) N* properties Extract N* form factors Dynamical coupled-channels channels model of meson production reactions Hadron Models QCD A. Matsuyama, T. Sato, T.-S.H. Lee Phys. Rep. 439 (2007) 193 Lattice QCD Provide information about reaction mechanism necessary to interpret the N* properties, structures, dynamical origins
Dynamical coupled-channels model of EBAC (EBAC-DCC model) Partial wave (LSJ) amplitude of a b reaction: For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007) Reaction channels: coupled-channels effect Transition potentials: exchange potentials of ground state mesons and baryons bare N* states
Dynamical coupled-channels model of EBAC (EBAC-DCC model) For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)
Hadronic part π N π N π N π π N π N η N Electromagnetic part EBAC-DCC analysis (2007-2009) : fitted to the data up to W = 2 GeV. Julia-Diaz, Lee, Matsuyama, Sato, PRC76 065201 (2007) : cross sections calculated with the πn model. Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC79 025206 (2009) : fitted to the data up to W = 2 GeV Durand, Julia-Diaz, Lee, Saghai, Sato, PRC78 025204 (2008) γ ( ) N π N : fitted to the data up to W = 1.6 GeV and Q 2 = 1.5 GeV 2 γ N π π N Extraction of N* parameters (photoproduction) Julia-Diaz, Lee, Matsuyama, Sato, Smith, PRC77 045205 (2008) (electroproduction) Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC80 025207 (2009) : cross sections calculated with the γn & πn model. Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC80 065203 (2009) Extraction of N* pole positions & new interpretation of dynamical origin of P11 N* states. Suzuki, Julia-Diaz, Kamano, Lee, Matsuyama, Sato, PRL104 065203 (2010) Extraction of γn N* electromagnetic transition form factors. Suzuki, Sato, Lee, arxiv:0910.1742 [nucl-th] πn, ηn, ππn (π π,ρn,σn) coupledchannels calculations were performed.
EBAC-DCC analysis (2007-2009) Full c.c. effect of ππn(π π,ρn,σn) & ηn off Coupled-channels effect in various reactions Full c.c. effect of ππn(π π,ρn,σn) & ηn off π p π + π n 20 Full c.c effect off 10 0 1.2 1.4 1.6 1.8 2 W (GeV)
EBAC-DCC analysis 2010 ~ EBAC second generation model Full combined analysis (global fit) of ~ End of 2010 πn πn πn ηn (W < 2 GeV) (W < 2 GeV) πn KY (W < 2 GeV) γn πn (W < 1.6 GeV 2 GeV) 2010 ~ 2011 γn ηn γn KY πn ππn γn ππn (W < 2 GeV) (W < 2 GeV) (W < 2 GeV) (W < 1.5 GeV 2 GeV) Complete experiments are planned by CLAS.
Preliminary pi- p K 0 Lambda dσ/dω (µb/sr) 100 80 60 40 20 1000 80 60 40 20 1000 80 60 40 20 W=1.661 GeV W=1.683 GeV W=1.724 GeV W=1.758 GeV W=1.847 GeV W=1.879 GeV W=2.059 GeV W=2.159 GeV W=2.259 GeV Saxon Baker Knasel 0-1 0-1 0 cos(θ) -1 0 1 Asymmetry 1.5 1 0-1 1 0-1 1 0 W=1.661 GeV W=1.683 GeV W=1.724 GeV W=1.758 GeV W=1.847 GeV W=1.879 GeV -1-1 0 W=2.059 GeV W=2.159 GeV W=2.259 GeV -1 0 cos(θ) -1 0 1 EBAC-DCC Julia-Diaz, Saghai, Lee, Tabakin PRC73 055204
gamma p K+ Lambda dσ/dω at 1.65 < W < 2 GeV Preliminary
gamma p K+ Lambda Polarization observables Formula for calculations of the polarization observables Sandorfi, Hoblit, Kamano, Lee arxiv:0912.3505 [nucl-th] Preliminary = 1125 MeV = 1150 MeV P P P = 975 MeV = 1025 MeV = 1075 MeV = 1175 MeV = 1225 MeV = 1250 MeV = 1275 MeV = 1325 MeV = 1350 MeV = 1375 MeV = 1425 MeV = 1475 MeV P = 1450 MeV = 1525 MeV = 1575 MeV = 1625 MeV P Cx = 1550 MeV = 1650 MeV Cz C x = 1150 MeV = 1250 MeV = 1350 MeV C z = 1150 MeV = 1250 MeV = 1350 MeV C x = 1450 MeV = 1550 MeV = 1650 MeV C z = 1450 MeV = 1550 MeV = 1650 MeV
Polarization observables P P P gamma p K+ Lambda = 1175 MeV Preliminary = 1125 MeV = 975 MeV = 1025 MeV = 1075 MeV = 1225 MeV May correspond to new N* states!! Formula for calculations of the polarization observables Sandorfi, Hoblit, Kamano, Lee arxiv:0912.3505 [nucl-th] = 1150 MeV = 1250 MeV = 1275 MeV = 1325 MeV = 1350 MeV = 1375 MeV = 1425 MeV = 1475 MeV P Cx P = 1550 MeV = 1450 MeV Additional E γ bare N* states will = 1525 MeV be needed = 1575 MeV to improve = 1625 MeV the fit to the polarization observables. = 1650 MeV Cz C x = 1150 MeV = 1250 MeV = 1350 MeV C z = 1150 MeV = 1250 MeV = 1350 MeV C x = 1450 MeV = 1550 MeV = 1650 MeV C z = 1450 MeV = 1550 MeV = 1650 MeV
Coupling effect of KY channels on pin PWA Preliminary S11 Re S11 Im P11 Re P11 Im P13 Re P13 Im D13 Re D13 Im D15 Re D15 Im F15 Re F15 Im F17 Re F17 Im KY on KY off SAID-EDS
Coupling effect of pin, pipin, etan channels on KY observables Preliminary dσ/dω (µb/sr) 0.4 0.2 0 0.4 0.2 0 = 1150 MeV = 1250 MeV = 1350 MeV = 1450 MeV = 1550 MeV Current EBAC-DCC result Couplings to πn, ηn, ππn channels off = 1650 MeV (At least) about 20% reduction is observed except backward angles.
Summary Full-combined analysis of πn, γn πn, ηn, 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): KY channel couplings to πn amps.: Negligible (visible a little in P11,P13) πn, ηn, ππn, channel couplings to KY observables: Visible (~ 20%) Reaction model is kept improving: Add new bare N* states & meson-exchange processes. Add new reaction channels (ωn, KKN, πηn, )
Back up
dσ/dω (µb/sr) 0.4 0.2 0 0.6 0.4 0.2 0 = 1150 MeV = 1250 MeV = 1350 MeV = 1450 MeV Current EBAC-DCC result = 1550 MeV t-channel K* exchange potentials off = 1650 MeV
Priority of coupled-channels effect γn (also πn) reaction cross sections in the resonance region are dominated by πn and ππn final states. At least, the couplings of πn and ππn channels should be taken into account in the analyses of any γn (πn) MB reactions. Figure: E. Pasyuk s talk at Hall-B/EBAC meeting
Exchange potentials for channels with strange hadrons 3 diagrams u-ch Σ t-ch K* 4 diagrams u-ch Ξ t-ch ω t-ch φ 5 diagrams u-ch Ξ t-ch ρ t-ch ω t-ch φ 3 diagrams u-ch Σ u-ch Λ t-ch K* 3 diagrams u-ch Ξ t-ch ρ Total 18 diagrams At present, KY couples to non-strange channels through πn channel only. (ηn KY is implementing)
2-body v potentials (non-strange channels) 5 diagrams u-ch t-ch ρ t-ch σ 2 diagrams 4 diagrams u-ch t-ch ρ 3 diagrams t-ch π 4 diagrams t-ch π t-ch ω 2 diagrams 1 diagram 2 diagrams 2 diagrams 2 diagrams t-ch ρ 1 diagram 2 diagrams 2 diagrams 2 diagrams 2 diagrams Total 36 diagrams
gamma N MB potentials 7 diagrams u-ch t-ch π t-ch ρ t-ch σ contact 2 diagrams 5 diagrams u-ch t-ch π contact 2 diagrams 4 diagrams t-ch ρ contact 6 diagrams u-ch Λ u-ch Σ t-ch K t-ch K* contact Total 32 diagrams 6 diagrams u-ch Λ u-ch Σ t-ch K t-ch K* contact
Strategy for the N* study @ EBAC Stage 1 Construct a reaction model through the comprehensive analysis of meson production reactions Stage 2 Extract resonance information from the reaction model constructed N* pole positions; N* γn, MB transition form factors Confirm/reject N* with low-star status; Search for new N* 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
Complete Experiment of pseudoscalar meson photoproduction reactions Complete Experiment = Measure ALL polarization observables needed to determine amplitudes up to overall phase unpolarized diff. crs. sec. 8 /16 observables needed! Chiang, Tabakin PRC55 2054 (1997) single spin Measurement of γn KY pol. obs. is very active. beam-target beam-recoil OVER-complete experiments planned by CLAS for γ p K + Λ, γ n KY. target-recoil Provides critical information on N* KY decays!! Much room for new N* state searches