Compton-Scattering Cross Section on the Proton at High Momentum Transfer

Danagoulian, Areg; Mamyan, V.; Roedelbronn, M.; Aniol, K.; Annand, J. R. M.; Bertin, P.Y.; Bimbot, L.; Bosted, P.; Calarco, J. R.; Camsonne, A.; Chang, C. C.; Chang, T. H.; Chen, J. P.; Choi, S.; Chudakov, E.; Degtyarenko, P. V.; Jager, C. W. de; Deur, A.; Dutta, D.; Egiyan, K. S.; Gao, H.; Garibaldi, F.; Gayou, O.; Gilman, R.; Glamazdin, A.; Glashausser, C.; Gómez, J.; Hamilton, D.; Hansen, J. O.; Hayes, D.; Higinbotham, D. W.; Hinton, W.; Horn, T.; Howell, C.R.; Hunyady, T.; Hyde‐Wright, C. E.; Jiang, X.; Jones, M. K.; Khandaker, M.; Ketikyan, A.; Kubarovsky, V.; Kramer, K.; Kumbartzki, G.; Laveissière, G.; LeRose, J. J.; Lindgren, R.; Margaziotis, D. J.; Markowitz, P.; McCormick, K.; Meekins, D.; Meziani, Z. E.; Michaels, R.; Moussiegt, P.; Nanda, S.; Nathan, A. M.; Nikolenko, D. M.; Nelyubin, V.; Norum, B.; Paschke, K.; Pentchev, L.; Perdrisat, C. F.; Piasetzky, E.; Pomatsalyuk, R.; Punjabi, V.; Rachek, I. A.; Radyushkin, Anatoly; Reitz, B.; Roché, R.; Ron, G.; Sabatié, F.; Saha, A.; Savvinov, N.; Shahinyan, A.; Shestakov, Yu. V.; Širca, S.; Slifer, K.; Solvignon, P.; Stoler, P.; Tajima, S.; Sulkosky, V.; Todor, L.; Vlahović, Branislav; Weinstein, L. B.; Wang, K.; Wojtsekhowski, B.; Voskanyan, H.; Xiang, Hua; Zheng, X.; Zhu, L.

doi:10.1103/physrevlett.98.152001

Cited by 47 publications

(44 citation statements)

References 29 publications

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“…Although it was not possible to actually measure the Compton background contribution from the data of this experiment, a reasonable estimate was obtained by extrapolating from the data of [130] using the empirical s −8 scaling behavior of dσ/dt, which showed that the Compton scattering background, while irreducible, was safely below the level where it could significantly impact the form factor ratio results.…”

Section: Proton δ-θ Correlationmentioning

confidence: 99%

“…The authors of [130] found a scaling behavior of s −8 for the Compton scattering cross section at fixed momentum transfer, to be contrasted with the approximate s −7 scaling of the photoproduction cross section found in [129]. Although it was not possible to actually measure the Compton background contribution from the data of this experiment, a reasonable estimate was obtained by extrapolating from the data of [130] using the empirical s −8 scaling behavior of dσ/dt, which showed that the Compton scattering background, while irreducible, was safely below the level where it could significantly impact the form factor ratio results.…”

Section: Proton δ-θ Correlationmentioning

confidence: 99%

“…The highest available momentum transfer measured for γp → π 0 p is approximately 7.5 GeV 2 for a photon energy of 5 GeV [129], or s ≈ 10.3 GeV 2 . For Compton scattering, high momentum transfer data have recently become available [130] for s up to 11 GeV 2 and t up to 6.5 GeV 2 . The highest momentum transfer data point for the differential cross section for Compton scattering from [130] was dσ/dt = 5.6 pb/GeV 2 at s = 10.9 GeV 2 and −t = 6.5 GeV 2 , whereas for π 0 photoproduction [129], a result of dσ/dt = 8.4 nb/GeV 2 was obtained at s = 10.3 GeV 2 and −t = 7.5 GeV 2 .…”

Section: Proton δ-θ Correlationmentioning

confidence: 99%

“…For Compton scattering, high momentum transfer data have recently become available [130] for s up to 11 GeV 2 and t up to 6.5 GeV 2 . The highest momentum transfer data point for the differential cross section for Compton scattering from [130] was dσ/dt = 5.6 pb/GeV 2 at s = 10.9 GeV 2 and −t = 6.5 GeV 2 , whereas for π 0 photoproduction [129], a result of dσ/dt = 8.4 nb/GeV 2 was obtained at s = 10.3 GeV 2 and −t = 7.5 GeV 2 . Though the kinematics of these two data points are not identical to each other or to E04-108 kinematics, one immediately sees that the Compton cross section at the nearest available data point is approximately three orders of magnitude smaller than the photoproduction cross section.…”

Section: Proton δ-θ Correlationmentioning

confidence: 99%

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Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Puckett

2010

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The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q 2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH 2 analyzers. The scattered electron was detected in a largeacceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors G AcknowledgmentsThis thesis would not have been possible without the support and efforts of many, many people. It would be impossible to give all due credit to all of the individual efforts that went into designing, planning, staging, and executing this experiment, and the subsequent analysis of the data. Therefore, any omissions from the following acknowledgments are in no way meant to diminish those contributions.I would like to thank the members of the GEp-III collaboration whose tireless efforts made experiments E04-108 and E04-019 a success. This includes the spokespeople; Ed Brash, Mark Jones, Charles Perdrisat and Vina Punjabi, and the other outstanding physicists involved in the core collaboration. I thank Frank Wesselmann for his successful leadership of the testing, installation, commissioning and operation of the Focal Plane Polarimeter, and his significant contribution to the data analysis in the form of the event decoding and tracking software for the FPP drift chambers. I thank Mark Jones for his encyclopedic knowledge of experimental Hall C and for his outsized contribution to making the various parts of the experiment work together as a whole, and for being called upon more often than not to troubleshoot problems with the experiment as they occurred. Mark's many important contributions to the data analysis included the optimization of the HMS reconstruction coefficients. Much of what I have learned about the actual hands-on require...

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Section: Proton δ-θ Correlationmentioning

confidence: 99%

Section: Proton δ-θ Correlationmentioning

confidence: 99%

Section: Proton δ-θ Correlationmentioning

confidence: 99%

Section: Proton δ-θ Correlationmentioning

confidence: 99%

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Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Puckett

2010

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“…The remainder, the "reduced" cross section, is assumed to be independent of the substructure of the nucleons. This 5) for the process γ(N 1 N 2 ) → N 1 N 2 , where t i is the square of the four-momentum transfer to nucleon N i . The ratio of cross sections for γ(pp) → pp and γ(pn) → pn is then given by the ratio of nucleon form factors squared,…”

Section: Photodisintegration Of the Deuteronmentioning

confidence: 99%

Hard photo-disintegration of proton pairs in <sup>3</sup>He nuclei

Pomerantz

2011

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Two-photon exchange corrections to elastic electron-proton scattering at large momentum transfer within the SCET approach

Kivel

Vanderhaeghen

2013

J. High Energ. Phys.

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Abstract:We calculate the two-photon exchange (TPE) corrections in the region where the kinematical variables describing the elastic ep scattering are moderately large momentum scales relative to the soft hadronic scale. For such kinematics we use the QCD factorization approach formulated in the framework of the soft-collinear effective theory (SCET). Such technique allows us to develop a description for the soft-spectator scattering contribution which is found to be important in the region of moderately large scales.Together with the hard-spectator contribution we present the complete factorization formulas for the TPE amplitudes at the leading power and leading logarithmic accuracy. The momentum region where both photons are hard is described by only one new nonperturbative SCET form factor. It turns out that the same form factor also arises for wide-angle Compton scattering which is also described in the framework of the SCET approach. This allows us to estimate the soft-spectator contribution associated with the hard photons in a model independent way.The main unknown in our description of the TPE contribution is related with the configuration where one photon is soft. The nonperturbative dynamics in this case is described by two unknown SCET amplitudes. We use a simple model in order to estimate their contribution.The formalism is then applied to a phenomenological analysis of existing data for the reduced cross section as well as for the transverse and longitudinal polarization observables.

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Compton-Scattering Cross Section on the Proton at High Momentum Transfer

Cited by 47 publications

References 29 publications

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Hard photo-disintegration of proton pairs in <sup>3</sup>He nuclei

Two-photon exchange corrections to elastic electron-proton scattering at large momentum transfer within the SCET approach

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