Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session X3: Invited Session: New Development in Baryon Resonance Spectrum |
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Sponsoring Units: DNP GHP Chair: Latifa Elouadrhiri, Jefferson Laboratory Room: Plaza E |
Tuesday, April 16, 2013 10:45AM - 11:21AM |
X3.00001: Latest results from the CLAS N* polarization program Invited Speaker: Michael Dugger One of the major thrusts in hadronic physics targets more fully understanding the internal structure of the proton and neutron. The challenges presented in understanding nucleon structure are large, in part due to the complexity of this strongly interacting system and the presence of many broad and overlapping resonances. In order to better determine the reaction amplitudes for the production of these excited states, polarization observables are an essential tool. To this end, the CLAS detector at Jefferson Lab has been combined with polarized beams and targets to study excited nucleon states. The data obtained will provide measurements that are nearly complete descriptions of the reaction mechanism. These new measurements will allow for extraction of the reactions amplitudes in a nearly model-independent manner. An overview of the CLAS N* polarization program and recent results will be presented. [Preview Abstract] |
Tuesday, April 16, 2013 11:21AM - 11:57AM |
X3.00002: $\gamma_{v}NN^*$ Transition Amplitudes and Excited Baryon Structure from CLAS Invited Speaker: Victor Mokeev Studying excited nucleon structure through exclusive-meson electroproduction reactions is key for understanding the nature of the strong interaction in the non-perturbative regime. With its nearly complete coverage of the final-state phase space, the CLAS detector at JLab has provided the lion's share of the world's meson-electroproduction data for differential cross sections and the asymmetries arising from single- and double-polarization observables. Electrocouplings for most of the excited nucleon states ($N^*$) in mass range of up to 1.8~GeV have been determined from several analyses of the CLAS data for photon virtualities ($Q^2$) up to 5.0 GeV$^2$ for the $\pi^+n$, $\pi^0p$, and $\eta p$ channels [1,3] as well as for the $\pi^+\pi^-p$ reaction for $Q^2 < 1.5$~GeV$^2$ [2,3]. Physics analyses of these $N^*$ electrocouplings [2,3] have revealed that the structure of excited nucleon is formed of an internal core of dressed quarks with an external meson-baryon cloud. Our $N^*$-electrocoupling results afford access to the non-perturbative strong interaction responsible for generating the different $N^*$ states and will also provide testing ground for the inspired by QCD quark model predictions. A dedicated experiment will run after the 12 GeV upgrade to JLab on the extraction of the $N^*$ electrocouplings in the yet unexplored region of high photon virtualities ranging from 5.0 to 12 GeV$^2$. The anticipated results are of particular importance in providing a understanding of the nature of confinement and dynamical chiral symmetry breaking in baryons based upon the QCD [3].\\[4pt] [1] I.G. Aznauryan and V.D. Burkert, Prog. Part. Nucl. Phys. \textbf{67}, 1 (2012).\\[0pt] [2] V.I. Mokeev \textit{et~al.} (CLAS Collaboration), Phys. Rev. \textbf{C86}, 035203 (2012).\\[0pt] [3] I.G. Aznauryan \textit{et~al.}, ``Studies of Nucleon Resonance Structure in Exclusive Meson Electroproduction,'' arXiv:1212.4891[nucl-th]. [Preview Abstract] |
Tuesday, April 16, 2013 11:57AM - 12:33PM |
X3.00003: The Bonn-Gatchina PWA: Search for New States and Study of Resonance Properties Invited Speaker: Andrey Sarantsev The latest combined analysis of the meson photo-production data and data from pion-induced reactions is presented. The data base was extended by including the latest double polarization data on pion photoproduction off proton and data on the $\eta$, $\pi^0$ and $\pi^-$ photoproduction off neutron. The analysis is done in the framework of the old K-matrix approach and new N/D-based method which fully satisfies unitarity and analyticity conditions. The property of observed resonances are presented and different interpretations of the spectrum are discussed. [Preview Abstract] |
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