Proton compton effect

Bernardini, G.; Hanson, A. O.; Odian, A.; Yamagata, T.; Auerbach, L. B.; Filosofo, I.

doi:10.1007/bf02733177

Cited by 63 publications

(26 citation statements)

References 23 publications

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“…Both processes are kinematically very similar. For given energy and angle of the proton the primary photon energy K of process (2) is only slightly higher than that of process (1). Taking into account the finite acceptances of the experiment the K-distributions of the two processes overlapped at all average energies For this reason the competing process could be separated or at least strongly suppressed by a proper choice of the endpoint energy gma x of the gamma ray beam (Fig.…”

Section: Methodsmentioning

confidence: 96%

“…During the last 15 years the fundamental process of elastic photon proton scattering ~+p--,~+p (1) has been experimentally investigated by various groups. Nevertheless, the information provided by these experiments is still rather incomplete due to the special difficulties which will be discussed below.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, the information provided by these experiments is still rather incomplete due to the special difficulties which will be discussed below. In particular in the resonance region there exist only few measurements [1][2][3][4][5] compared with, e.g., the data of pion photoproduction which are nowadays available. Systematical measurements of angular distributions are needed for a theoretical analysis of the process (1).…”

Section: Introductionmentioning

confidence: 99%

“…In particular in the resonance region there exist only few measurements [1][2][3][4][5] compared with, e.g., the data of pion photoproduction which are nowadays available. Systematical measurements of angular distributions are needed for a theoretical analysis of the process (1). Moreover, the statistical and systematical errors of the published data are relatively large because of the difficulties the experimenter has to face.…”

Section: Introductionmentioning

confidence: 99%

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Proton Compton effect in the ?(1232) energy region

et al. 1976

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The proton Compton effect 7 +P--+ 7 +P in the A (1232) energy region has been thoroughly studied. At the Bonn 500 MeV synchrotron differential cross sections were measured covering a large range of the CM scattering angle (50~ 130 ~ and an energy range from 240 to 440 MeV (LAB energy of the primary photon). A contribution to the counting rate from the competing process of rc ~ photoproduction was strongly suppressed by detecting both particles in the final state and by a proper choice of the endpoint energy of the gamma ray beam. The remaining contribution was monitored experimentally. The measured data were complemented by cross sections at 0 ~ which were computed from the total y p cross sections with an input from a multipole analysis of single pion photoproduction. Preliminary results of this experiment have been published in Lett. Nuovo Cimento. In the meantime the experimental data were reanalyzed. The final data presented here are larger than the preliminary ones by about 15 %.

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Section: Methodsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Proton Compton effect in the ?(1232) energy region

et al. 1976

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“…These can be grouped into two general categories, those based on the baryon resonance spectrum or its underlying quark structure [5][6][7], and those relying upon unitarity and dispersion relations to phenomenologically describe elastic scattering in terms of photopion production [3,4,8-10]. These calculations give significantly different predictions, particularly in the region of the D resonance.A number of measurements of proton Compton scattering have been reported [1,[11][12][13][14][15][16], and several authors of dispersion calculations have pointed out a significant inconsistency between many of these experiments and p photoproduction data near the peak of the D [3,8-10]. Compton scattering can be described by six independent amplitudes.…”

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confidence: 99%

Polarized Compton Scattering from the Proton

et al. 1996

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New precision measurements of cross sections and polarization asymmetries in the p͑ g, gp͒ reaction at 90 ± c.m. are presented for incident energies between 213 and 333 MeV. A long-standing problem with earlier experiments that appeared to violate unitarity at the peak of the D is resolved. Data are compared to theories based on baryon resonance structure and to dispersion relations. Recent calculations using the proton polarizabilities are closest to the data, although inconsistencies are observed near the D resonance. PACS numbers: 13.60.Fz, 13.88.+e, 14.20.Gk, 25.20.Dc Elastic (Compton) scattering of intermediate energy photons from the proton is a potentially rich source of structure information. It is sensitive to the proton's electric (a) and magnetic (b) polarizabilities [1], to the deformation of the nucleon through the electric gND coupling [2], and even to the sign of the p 0 decay constant, F p [3,4]. There are many published calculations for Compton scattering. These can be grouped into two general categories, those based on the baryon resonance spectrum or its underlying quark structure [5][6][7], and those relying upon unitarity and dispersion relations to phenomenologically describe elastic scattering in terms of photopion production [3,4,8-10]. These calculations give significantly different predictions, particularly in the region of the D resonance.A number of measurements of proton Compton scattering have been reported [1,[11][12][13][14][15][16], and several authors of dispersion calculations have pointed out a significant inconsistency between many of these experiments and p photoproduction data near the peak of the D [3,8-10]. Compton scattering can be described by six independent amplitudes. Their imaginary parts can be calculated from (g, p) multipoles using s-and u-channel unitarity, and dispersion integrals can be written for their real parts. Four of these integrals converge rapidly with energy. However, the remaining two, those involving a photon helicity flip, do not converge rapidly, making subtractions essential. One of these is dominated by t-channel p 0 exchange, the Low amplitude [17], and can be readily evaluated in terms of the p 0 lifetime. However, the other contains contributions from multiple meson exchange in the t channel that are quite poorly determined. In principle, the beam-polarization asymmetry constrains this other amplitude [4]. But prior to our new measurements, only a single datum with large errors had been published for this observable [18]. Alternatively, sum rules can be used to write the subtraction function for this spin-flip amplitude in terms of the difference of the proton polarizabilities, a 2 b, which can then be fixed by fitting a perturbative expansion of the cross section to data below the p threshold [3,4]. Although this provides a good description of scattering below the D [1,19], the peak cross sections appear to be overestimated [3,4].A lower unitarity bound on the Compton cross sections, which avoids the uncertainties of the dispersion calcul...

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