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Proton spin polarizabilities from polarized Compton scattering
Pasquini, B.;Drechsel, D.;Vanderhaeghen, M.
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevC.76.015203
Abstract: Polarized Compton scattering off the proton is studied within the framework of subtracted dispersion relations for photon energies up to 300 MeV. As a guideline for forthcoming experiments, we focus the attention on the role of the proton's spin polarizabilities and investigate the most favorable conditions to extract them with a minimum of model dependence. We conclude that a complete separation of the four spin polarizabilities is possible, at photon energies between threshold and the $\Delta(1232)$ region, provided one can achieve polarization measurements with an accuracy of a few percent.
Proton polarizabilities from polarized Compton scattering: low-energy expansion  [PDF]
Nadiia Krupina
Physics , 2014,
Abstract: We reexamine the low-energy expansion of polarized Compton scattering off the proton and show that the leading non-Born contribution to the beam asymmetry of low-energy Compton scattering is given by the magnetic polarizability alone, the electric polarizability cancels out. Based on this fact we propose to determine the magnetic dipole polarizability of the proton from the beam asymmetry. We also present the low-energy expansion of doubly-polarized observables, from which the spin polarizabilities can be extracted.
Single and double spin asymmetries for deeply virtual Compton scattering measured with CLAS and a longitudinally polarized proton target  [PDF]
S. Pisano,A. Biselli,S. Niccolai,E. Seder,M. Guidal,M. Mirazita,the CLAS Collaboration
Physics , 2015, DOI: 10.1103/PhysRevD.91.052014
Abstract: Single-beam, single-target, and double-spin asymmetries for hard exclusive photon production on the proton $\vec{e}\vec{p} \to e' p'\gamma$ are presented. The data were taken at Jefferson Lab using the CLAS detector and a longitudinally polarized ${}^{14}$NH$_3$ target. The three asymmetries were measured in 165 4-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of Generalized Parton Distributions. The measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the $H$ and $\tilde{H}$ Compton Form Factors, which give insight into the electric and axial charge distributions of valence quarks in the proton.
Spin Polarizabilities of the Nucleon from Polarized Low Energy Compton Scattering  [PDF]
Robert P. Hildebrandt,Harald W. Griesshammer,Thomas R. Hemmert
Physics , 2003, DOI: 10.1140/epja/i2003-10154-7
Abstract: As guideline for forthcoming experiments, we present predictions from Chiral Effective Field Theory for polarized cross sections in low energy Compton scattering for photon energies below 170 MeV, both on the proton and on the neutron. Special interest is put on the role of the nucleon spin polarizabilities which can be examined especially well in polarized Compton scattering. We present a model-independent way to extract their energy dependence and static values from experiment, interpreting our findings also in terms of the low energy effective degrees of freedom inside the nucleon: The polarizabilities are dominated by chiral dynamics from the pion cloud, except for resonant multipoles, where contributions of the Delta(1232) resonance turn out to be crucial. We therefore include it as an explicit degree of freedom. We also identify some experimental settings which are particularly sensitive to the spin polarizabilities.
Separation of proton polarizabilities with the beam asymmetry of Compton scattering  [PDF]
Nadiia Krupina,Vladimir Pascalutsa
Physics , 2013, DOI: 10.1103/PhysRevLett.110.262001
Abstract: We propose to determine the magnetic dipole polarizability of the proton directly from the beam asymmetry of low-energy Compton scattering based on the fact that the leading non-Born contribution to the asymmetry is due to the magnetic polarizability alone; the electric polarizability cancels out. The beam asymmetry thus provides the simplest observable with a clean separation of the magnetic polarizability from the electric one. Introducing polarizabilities in a Lorentz-invariant fashion we compute the higher-order (recoil) effects of polarizabilities on beam asymmetry and show that these effects are most suppressed in forward kinematics. With the prospects of precision Compton experiments at the MAMI and HIGS facilities in mind, we argue why the beam asymmetry could be the best way to measure the elusive magnetic polarizability of the proton.
Single spin asymmetries in transversely polarized proton(antiproton) - proton inclusive processes  [PDF]
Mauro Anselmino,Francesco Murgia
Physics , 1998, DOI: 10.1016/S0370-2693(98)01267-2
Abstract: We consider several single spin asymmetries in inclusive, transversely polarized proton(antiproton) - proton processes as higher twist QCD contributions, taking into account spin and intrinsic transverse momentum effects in the quark distribution functions. This approach has been previously applied to the description of the single spin asymmetries observed in transversely polarized proton - proton -> pion + X reactions and all its parameters fixed: we give here predictions for new processes, which agree with experiments for which data are available, and suggest further possible measurements.
GDH2000 Convenor's Report: Spin Polarizabilities  [PDF]
Barry R. Holstein
Physics , 2000,
Abstract: The subject of low energy polarized Compton scattering from the proton, which is characterized by phenomenological spin-polarizabilities, is introduced and connection is made to new theoretical and experimental developments which were reported to this meeting.
Virtual Compton Scattering and Generalized Polarizabilities of the Proton  [PDF]
P. A. M. Guichon,G. Q. Liu,A. W. Thomas
Physics , 1996, DOI: 10.1016/0375-9474(95)00217-O
Abstract: Threshold photon electroproduction off the proton allows one to measure new electromagnetic observables which generalise the usual polarisabilities. There are -- a priori -- ten "generalised polarisabilities", functions of the virtual photon mass. The purpose of this paper is to lay down the appropriate formalism to extract these quantities from the photon electroproduction cross sections. We also give a first estimate of the generalised polarisabilities in the non relativistic quark model.
Dispersion relation formalism for virtual Compton scattering off the proton  [PDF]
B. Pasquini,M. Gorchtein,D. Drechsel,A. Metz,M. Vanderhaeghen
Physics , 2001, DOI: 10.1007/s100500170084
Abstract: We present in detail a dispersion relation formalism for virtual Compton scattering (VCS) off the proton from threshold into the $\Delta(1232)$-resonance region. Such a formalism can be used as a tool to extract the generalized polarizabilities of the proton from both unpolarized and polarized VCS observables over a larger energy range. We present calculations for existing and forthcoming VCS experiments and demonstrate that the VCS observables in the energy region between pion production threshold and the $\Delta(1232)$-resonance show an enhanced sensitivity to the generalized polarizabilities.
Single spin asymmetries in polarized proton-proton, polarized antiproton-proton inclusive processes  [PDF]
M. Anselmino,M. Boglione,F. Murgia
Physics , 1998,
Abstract: Single spin asymmetries in polarized proton(antiproton) + proton -> pion + X have been measured to be large. They can be understood within perturbative QCD by introducing new k_perp and spin dependences in fragmentation and/or distribution functions. We discuss first how these effects in distribution functions alone can account for existing data and predict single spin asymmetries in other processes; then we see how similar effects in fragmentation functions alone can fit the existing data; finally we devise strategies to discriminate between the two contributions
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