We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the un...We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N* pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.展开更多
We have developed an analytic continuation method for extracting parameters of nucleon resonances within a Hamiltonian formulation of meson-nucleon reactions. The method was tested for simple solvable models and then ...We have developed an analytic continuation method for extracting parameters of nucleon resonances within a Hamiltonian formulation of meson-nucleon reactions. The method was tested for simple solvable models and then applied for our recent coupled channels model (πN, ηN, π△, ρN, and σN ) of the π*N and γ*N reactions. The resonance pole positions and their properties are studied for P11and P11 channels.展开更多
Within the Excited Baryon Analysis Center we have performed a dynamical coupled-channels analysis of the available p(e,e'π)N data in the region of W ≤ 1.6 GeV and Q2 ≤1.45 (GeV/c)2. The channels included are ...Within the Excited Baryon Analysis Center we have performed a dynamical coupled-channels analysis of the available p(e,e'π)N data in the region of W ≤ 1.6 GeV and Q2 ≤1.45 (GeV/c)2. The channels included are γ*N, π*N, ηN, and ηN which has π△, pN, and σN components. With the hadronic parameters of the model determined in our previous investigations of πN→ πN reaction, we have found that the available data in the considered W ≤ 1.6 GeV region can be fitted well by only adjusting the bare γ*N → N* helicity amplitudes for the lowest N* states in P33, P11, S11 and D13 partial waves. The meson cloud effect, as required by the unitarity conditions, on the γ*N → N* form factors are examined.展开更多
The reactions π-p →ηn and γ'p →ηP are investigated within a dynamical coupledJchannels model of meson production reactions in the nucleon resonance region. The meson-baryon channels included are πN, ηN, π△,...The reactions π-p →ηn and γ'p →ηP are investigated within a dynamical coupledJchannels model of meson production reactions in the nucleon resonance region. The meson-baryon channels included are πN, ηN, π△, σN, and pN. The direct wphotoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6)0(3) symmetry. In the models search, the following known nucleon resonances are embodied: Sll (1535), $11(1650), Pll (1440), Pl1(1710), P13(1720), D13(1520), D13(1700), D15(1675), and F15(1680). Data for the π-p →ηnreaction from threshold up to a total center-of-mass energy of W ≈ 2 GeV are satisfactorily reproduced. For the photoproduction channel, two additional higher mass known resonances, P13 (1900) and F15 (2000), are also considered. However, reproducing the data for γ'p →ηP requires, within our approach, two new nucleon resonances, for which we extract mass and width.展开更多
We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those fr...We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude.展开更多
基金Supported by U.S. Department of Energy, Office of Nuclear Physics Division, under contract No. DE-AC02-06CH11357Contract No. DE-AC05-06OR23177 under which Jefferson Science Associates operates Jefferson LabNotice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
文摘We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N* pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.
基金Supported by Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research(C) 20540270U.S. Department of Energy, Office of Nuclear Physics Division, under contract No. DE-AC02-06CH11357Contract No. DE-AC05-060R23177 under which Jefferson Science Associates operates Jefferson Lab
文摘We have developed an analytic continuation method for extracting parameters of nucleon resonances within a Hamiltonian formulation of meson-nucleon reactions. The method was tested for simple solvable models and then applied for our recent coupled channels model (πN, ηN, π△, ρN, and σN ) of the π*N and γ*N reactions. The resonance pole positions and their properties are studied for P11and P11 channels.
基金Supported by U.S. Department of Energy, Office of Nuclear Physics Division(DE-AC02-06CH11357, DE-AC05-06OR23177)under which Jefferson Science Associates operates Jefferson Lab
文摘A summary of the contributions to this workshop is given. The status and future development of N* physics are discussed.
基金Supported by a CPAN Consolider INGENIO CSD 2007-0042 (FIS2008-1661) (Spain)by the U.S. Department of Energy, Office of Nuclear Physics Division, (DE-AC02-06CH11357, DE-AC05-06OR23177) under which Jefferson Science Associates operates Jefferson LabThis work used resources of the National Energy Research Scientific Computing Center which is supported by the Office of Science of the U.S. Department of Energy (DE-AC02-05CH11231)
文摘Within the Excited Baryon Analysis Center we have performed a dynamical coupled-channels analysis of the available p(e,e'π)N data in the region of W ≤ 1.6 GeV and Q2 ≤1.45 (GeV/c)2. The channels included are γ*N, π*N, ηN, and ηN which has π△, pN, and σN components. With the hadronic parameters of the model determined in our previous investigations of πN→ πN reaction, we have found that the available data in the considered W ≤ 1.6 GeV region can be fitted well by only adjusting the bare γ*N → N* helicity amplitudes for the lowest N* states in P33, P11, S11 and D13 partial waves. The meson cloud effect, as required by the unitarity conditions, on the γ*N → N* form factors are examined.
基金Supported by a CPAN CSD 2007-0042 contract, Consolider Ingenio 2010 and by grants No. FIS2008-01661 and 2009SGR-1289
文摘The reactions π-p →ηn and γ'p →ηP are investigated within a dynamical coupledJchannels model of meson production reactions in the nucleon resonance region. The meson-baryon channels included are πN, ηN, π△, σN, and pN. The direct wphotoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6)0(3) symmetry. In the models search, the following known nucleon resonances are embodied: Sll (1535), $11(1650), Pll (1440), Pl1(1710), P13(1720), D13(1520), D13(1700), D15(1675), and F15(1680). Data for the π-p →ηnreaction from threshold up to a total center-of-mass energy of W ≈ 2 GeV are satisfactorily reproduced. For the photoproduction channel, two additional higher mass known resonances, P13 (1900) and F15 (2000), are also considered. However, reproducing the data for γ'p →ηP requires, within our approach, two new nucleon resonances, for which we extract mass and width.
基金Supported by Helmholtz Association through funds provided to the virtual institute 'Spin and strong QCD' (VH-VI-231)EU Integrated Infrastructure Initiative Hadron Physics Project (RII3-CT-2004-506078), DFG (SFB/TR 16, 'Subnuclear Structure of Matter'), JLab (SURA-06-C0452) and COSY FFE (41760632)
文摘We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude.