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Title: Spin Asymmetries and Helicity Amplitudes in Photo-Production from Polarized Neutrons

Abstract

Pseudoscalar meson photoproduction experiments lead the search for an expanded $N^*$ spectroscopy that is required by lattice solutions of QCD. Extensive data have been collected with proton targets that can potentially over-determine the production amplitude and allow a search for weak resonances. In contrast, data on photoproduction from neutrons is drastically limited. Both are needed since the $$\gamma p N^*$$ and $$\gamma n N^*$$ photo-couplings to I = 1/2 states are different and provide complementary information on the mechanisms for resonance excitation. The main subtleties in experiments with an effective polarized neutron target are reviewed. The considerable impact of new polarization data on multipole analyses are discussed, using the example of recent $$\pi^- p$$ measurements of the beam-target helicity asymmetry ($E$) from polarized $$H\!D$$ in CLAS at Jefferson Lab. Here, new partial wave analyses incorporating these data have found significant changes in helicity amplitudes of some established resonances, and signatures of weak resonances that previously were observed only in hyperon decay channels.

Authors:
ORCiD logo [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1484448
Report Number(s):
JLAB-PHY-18-2677; DOE/OR/23177-4399
Journal ID: ISSN 0177-7963; PII: 1478
Grant/Contract Number:  
AC05-06OR23177
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Few-Body Systems
Additional Journal Information:
Journal Volume: 60; Journal Issue: 1; Related Information: JLAB Experiment: E06-101; Journal ID: ISSN 0177-7963
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS

Citation Formats

Sandorfi, Andrew M. Spin Asymmetries and Helicity Amplitudes in Photo-Production from Polarized Neutrons. United States: N. p., 2018. Web. doi:10.1007/s00601-018-1478-4.
Sandorfi, Andrew M. Spin Asymmetries and Helicity Amplitudes in Photo-Production from Polarized Neutrons. United States. doi:10.1007/s00601-018-1478-4.
Sandorfi, Andrew M. Sat . "Spin Asymmetries and Helicity Amplitudes in Photo-Production from Polarized Neutrons". United States. doi:10.1007/s00601-018-1478-4.
@article{osti_1484448,
title = {Spin Asymmetries and Helicity Amplitudes in Photo-Production from Polarized Neutrons},
author = {Sandorfi, Andrew M.},
abstractNote = {Pseudoscalar meson photoproduction experiments lead the search for an expanded $N^*$ spectroscopy that is required by lattice solutions of QCD. Extensive data have been collected with proton targets that can potentially over-determine the production amplitude and allow a search for weak resonances. In contrast, data on photoproduction from neutrons is drastically limited. Both are needed since the $\gamma p N^*$ and $\gamma n N^*$ photo-couplings to I = 1/2 states are different and provide complementary information on the mechanisms for resonance excitation. The main subtleties in experiments with an effective polarized neutron target are reviewed. The considerable impact of new polarization data on multipole analyses are discussed, using the example of recent $\pi^- p$ measurements of the beam-target helicity asymmetry ($E$) from polarized $H\!D$ in CLAS at Jefferson Lab. Here, new partial wave analyses incorporating these data have found significant changes in helicity amplitudes of some established resonances, and signatures of weak resonances that previously were observed only in hyperon decay channels.},
doi = {10.1007/s00601-018-1478-4},
journal = {Few-Body Systems},
number = 1,
volume = 60,
place = {United States},
year = {Sat Dec 01 00:00:00 EST 2018},
month = {Sat Dec 01 00:00:00 EST 2018}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on December 1, 2019
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