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Title: Exclusive single pion electroproduction off the proton: Results from CLAS

Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and both polarized and unpolarized proton targets. The measurements covered a broad kinematic range in the invariant mass $W$ and photon virtuality $Q^2$ with nearly full coverage in polar and azimuthal angles in the hadronic CM system. As results, several low-lying nucleon resonance states in particular from pion threshold to $W < 1.6$ GeV have been explored. These include $$\Delta$$(1232)$$\frac{3}{2}^+$$, $$N(1440)\frac{1}{2}^+$$, $$N(1520)\frac{3}{2}^-$$, and $$N(1535)\frac{1}{2}^-$$ states. In addition, we recently published the differential cross sections and helicity amplitudes of the reaction $$\gamma^*p\to n\pi^+$$ at higher $W$ (1.6 to 2.0 GeV) which are the $$N(1675)\frac{5}{2}^-$$, $$N(1680)\frac{5}{2}^+$$, and $$N(1710)\frac{1}{2}^+$$ states. These excited states with isospin $1/2$ and with masses near 1.7 GeV can be accessed in single $$n\pi^+$$ production as there are no isospin $3/2$ states present in this mass range with the same spin-parity assignments. As a result, I will briefly discuss these states from CLAS results of the single charged pion electroproduction data.
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  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Report Number(s):
JLAB-PHY-16-2249; DOE/OR/23177-3854
Journal ID: ISSN 0177-7963; PII: 1145
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Few-Body Systems
Additional Journal Information:
Conference: ECT* 2015 Workshop on Nucleon Resonances, Trento (Italy), 19-23 Oct 2015; Journal ID: ISSN 0177-7963
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CLAS; single pion electroproduction; helicity amplitude; N (1440)1/2+; N (1520)3/2-; N (1535)1/2-; N (1675)5/2-; N (1680)5/2+; N (1710)1/2+
OSTI Identifier: