Measurement of the generalized forward spin polarizabilities of the neutron
Abstract
The generalized forward spin polarizabilities {gamma}{sub 0} and {delta}{sub LT} of the neutron have been extracted for the first time in a Q{sup 2} range from 0.1 to 0.9 GeV{sup 2}. Since {gamma}{sub 0} is sensitive to nucleon resonances and {delta}{sub LT} is insensitive to the {Delta} resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on {delta}{sub LT} show significant disagreement with Chiral Perturbation Theory calculations, while the data for {gamma}{sub 0} at low Q{sup 2} are in good agreement with a nexttolead order Relativistic Baryon Chiral Perturbation theory calculation. The data show good agreement with the phenomenological MAID model.
 Authors:
 more »
 Publication Date:
 Research Org.:
 Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
 Sponsoring Org.:
 USDOE Office of Energy Research (ER) (US)
 OSTI Identifier:
 824400
 Report Number(s):
 JLABPHY04230; DOE/ER/401502665
TRN: US0402026
 DOE Contract Number:
 AC0584ER40150
 Resource Type:
 Journal Article
 Resource Relation:
 Other Information: No journal information given for this preprint; PBD: 1 May 2004
 Country of Publication:
 United States
 Language:
 English
 Subject:
 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BARYONS; BENCHMARKS; ENANTIOMORPHS; NEUTRONS; NUCLEONS; PERTURBATION THEORY; QUANTUM CHROMODYNAMICS; RESONANCE; SPIN
Citation Formats
Moskov Amarian, Leonard Auerbach, Todd Averett, J. Berthot, Pierre Bertin, William Bertozzi, Tim Black, Edward Brash, David Brown, Etienne Burtin, John Calarco, Gordon Cates, Zhengwei Chai, JianPing Chen, Seonho Choi, Eugene Chudakov, Evaristo Cisbani, Cornelis de Jager, Alexandre Deur, Rachele Di Salvo, Sonja Dieterich, Pibero Djawotho, John Finn, and Kevin Fissum. Measurement of the generalized forward spin polarizabilities of the neutron. United States: N. p., 2004.
Web.
Moskov Amarian, Leonard Auerbach, Todd Averett, J. Berthot, Pierre Bertin, William Bertozzi, Tim Black, Edward Brash, David Brown, Etienne Burtin, John Calarco, Gordon Cates, Zhengwei Chai, JianPing Chen, Seonho Choi, Eugene Chudakov, Evaristo Cisbani, Cornelis de Jager, Alexandre Deur, Rachele Di Salvo, Sonja Dieterich, Pibero Djawotho, John Finn, & Kevin Fissum. Measurement of the generalized forward spin polarizabilities of the neutron. United States.
Moskov Amarian, Leonard Auerbach, Todd Averett, J. Berthot, Pierre Bertin, William Bertozzi, Tim Black, Edward Brash, David Brown, Etienne Burtin, John Calarco, Gordon Cates, Zhengwei Chai, JianPing Chen, Seonho Choi, Eugene Chudakov, Evaristo Cisbani, Cornelis de Jager, Alexandre Deur, Rachele Di Salvo, Sonja Dieterich, Pibero Djawotho, John Finn, and Kevin Fissum. 2004.
"Measurement of the generalized forward spin polarizabilities of the neutron". United States.
doi:. https://www.osti.gov/servlets/purl/824400.
@article{osti_824400,
title = {Measurement of the generalized forward spin polarizabilities of the neutron},
author = {Moskov Amarian and Leonard Auerbach and Todd Averett and J. Berthot and Pierre Bertin and William Bertozzi and Tim Black and Edward Brash and David Brown and Etienne Burtin and John Calarco and Gordon Cates and Zhengwei Chai and JianPing Chen and Seonho Choi and Eugene Chudakov and Evaristo Cisbani and Cornelis de Jager and Alexandre Deur and Rachele Di Salvo and Sonja Dieterich and Pibero Djawotho and John Finn and Kevin Fissum},
abstractNote = {The generalized forward spin polarizabilities {gamma}{sub 0} and {delta}{sub LT} of the neutron have been extracted for the first time in a Q{sup 2} range from 0.1 to 0.9 GeV{sup 2}. Since {gamma}{sub 0} is sensitive to nucleon resonances and {delta}{sub LT} is insensitive to the {Delta} resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on {delta}{sub LT} show significant disagreement with Chiral Perturbation Theory calculations, while the data for {gamma}{sub 0} at low Q{sup 2} are in good agreement with a nexttolead order Relativistic Baryon Chiral Perturbation theory calculation. The data show good agreement with the phenomenological MAID model.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2004,
month = 5
}

We discuss the lowenergy behavior of the spinaveraged amplitude of virtual Compton scattering off a nucleon. Based on gauge invariance, Lorentz invariance, and the discrete symmetries, it is shown that to first order in the frequency of the final real photon only two generalized polarizabilities appear. Different lowenergy expansion schemes are discussed and put into perspective. {copyright} {ital 1997} {ital The American Physical Society}

New predictions for generalized spin polarizabilities from heavy baryon chiral perturbation theory
We extract the nexttonexttoleading order results for spinflip generalized polarizabilities (GPs) of the nucleon from the spindependent amplitudes for virtual Compton scattering (VCS) at {Omicron}(p{sup 4}) in heavy baryon chiral perturbation theory. At this order, no unknown low energy constants enter the theory, allowing us to make absolute predictions for all spinflip GPs. Furthermore, by using constraint equations between the GPs due to nucleon crossing combined with charge conjugation symmetry of the VCS amplitudes, we get a nexttonexttonexttoleading order prediction for one of the GPs. We provide estimates for forthcoming double polarization experiments which allow to access these spinflip GPsmore » 
New predictions for generalized spin polarizabilities from heavy baryon chiral perturbation theory
We extract the nexttonexttoleading order results for spinflip generalized polarizabilities (GPs) of the nucleon from the spindependent amplitudes for virtual Compton scattering at O(p{sup 4}) in heavy baryon chiral perturbation theory. At this order, no unknown lowenergy constants enter the theory, allowing us to make absolute predictions for all spinflip GPs. Furthermore, by using constraint equations between the GPs due to nucleon crossing combined with charge conjugation symmetry of the virtual Compton scattering amplitudes, we get a nexttonexttonexttoleading order prediction for one of the GPs. We provide estimates for forthcoming doublepolarization experiments which allow one to access these spinflip GPsmore » 
Measurement of the Generalized Polarizabilities of the Proton in Virtual Scattering at Q{sup 2}=0.92 AND 1.76 GeV{sup 2}: I. Low Energy Expansion Analysis
Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility at low CenterofMass energies, below pion threshold. Following the Low Energy Theorem for the ep {yields} ep{gamma} process, we obtain values for the two structure functions P{sub LL}  P{sub TT}/{var_epsilon} and P{sub LT} at fourmomentum transfer squared Q{sup 2} = 0.92 and 1.76 GeV{sup 2}. 
Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2= 0.92 and 1.76 GeV2
We report a Virtual Compton Scattering study of the proton at low CM energies. We have determined the structure functions P{sub LL}  P{sub TT}/{epsilon} and P{sub LT}, and the electric and magnetic Generalized Polarizabilities (GPs) {alpha}{sub E}(Q{sup 2}) and {beta}{sub M}(Q{sup 2}) at momentum transfer Q{sup 2} = 0.92 and 1.76 GeV{sup 2}. The electric GP shows a strong falloff with Q{sup 2}, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a longdistance diamagnetic pion cloud at lowmore »