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A detailed study of two-photon exchange in unpolarized and polarized elastic electron--nucleon scattering is presented, taking particular account of nucleon finite size effects. Contributions from nucleon elastic intermediate states are…

Nuclear Theory · Physics 2014-11-18 P. G. Blunden , W. Melnitchouk , J. A. Tjon

One possible explanation for the proton form factor discrepancy is a contribution to the elastic electron-proton cross section from hard two-photon exchange (TPE), a typically neglected radiative correction. Hard TPE cannot be calculated in…

Nuclear Experiment · Physics 2020-04-08 Axel Schmidt

Recent experiments have discovered two exponents in the $pp$ elastic differential cross sections with two different slope parameters, of the order $(16-20)$~GeV$^{-2}$ and $(4-4.8)$~GeV$^{-2}$ in the regions $ -t \la 0.5 $~GeV$^2$ and $ -t…

High Energy Physics - Phenomenology · Physics 2021-05-12 Yu. A. Simonov

We present an exact evaluation of the two-photon exchange contribution to the elastic lepton-proton scattering process at low-energies using heavy baryon chiral perturbation theory. The evaluation is performed including next-to-leading…

High Energy Physics - Phenomenology · Physics 2023-11-30 Poonam Choudhary , Udit Raha , Fred Myhrer , Dipankar Chakrabarti

We evaluate the corrections of the two-photon exchange (TPE) process on the $\gamma^* N\Delta$ transition form factors. The contributions of the TPE process to the $eN\rightarrow e\Delta(1232)\rightarrow eN\pi$ are calculated in a hadronic…

Nuclear Theory · Physics 2017-12-06 Hai-Qing Zhou , Shin Nan Yang

Measurements of the ratio of the proton elastic form factors ($\mu_pG_E/G_M$) using Rosenbluth separation and those using polarization-based techniques show a strong discrepancy, which has persisted both in modern experimental results and…

Nuclear Experiment · Physics 2018-04-25 Brian S. Henderson

Model independent expressions for all polarization observables in $\mu+p\to \mu+p$ elastic scattering are obtained, taking into account the lepton mass and including the two-photon exchange contribution. The spin structure of the matrix…

Nuclear Theory · Physics 2015-05-20 G. I. Gakh , M. Konchatnyi , A. Dbeyssi , E. Tomasi-Gustafsson

The parity-conserving single-spin beam asymmetry of elastic electron-proton scattering is induced by an absorptive part of the two-photon exchange amplitude. We demonstrate that this asymmetry has logarithmic and double-logarithmic…

High Energy Physics - Phenomenology · Physics 2014-11-17 Andrei Afanasev , N. P. Merenkov

We consider radiative corrections to polarization observables in elastic electron-proton scattering, in particular, for the polarization transfer measurements of the proton form factor ratio $\mu G_E/G_M$. The corrections are of two types:…

High Energy Physics - Phenomenology · Physics 2014-08-27 Dmitry Borisyuk , Alexander Kobushkin

We use the world's data on elastic electron--proton scattering and calculations of two-photon exchange effects to extract corrected values of the proton's electric and magnetic form factors over the full Q^2 range of the existing data. Our…

Nuclear Experiment · Physics 2008-11-26 J. Arrington , W. Melnitchouk , J. A. Tjon

In this note we consider effects of a Two-Photon Exchange (TPE) in inclusive DIS and semi-inclusive DIS (SIDIS). In particular, transverse single spin asymmetries are generated in inclusive DIS if more than one photon is exchanged between…

High Energy Physics - Phenomenology · Physics 2009-08-24 M. Schlegel , A. Metz

The comparison of positron-proton and electron-proton elastic scattering cross sections is a sensitive test for the presence of two-photon exchange contributions. Thirty years ago, positron data were considered adequate to set tight limits…

Nuclear Experiment · Physics 2009-11-10 J. Arrington

We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer through the scattering off a parton in the proton. We relate the process on the nucleon to the generalized parton…

High Energy Physics - Phenomenology · Physics 2009-09-11 Y. C. Chen , A. Afanasev , S. J. Brodsky , C. E. Carlson , M. Vanderhaeghen

Higher-order QED effects play an important role in precision measurements of nucleon elastic form factors in electron scattering. Here we introduce a two-photon exchange QED correction to the parity-violating polarization asymmetry of…

High Energy Physics - Phenomenology · Physics 2008-11-26 Andrei V. Afanasev , Carl E. Carlson

Using the relativistic Eikonal approximation, we study the one and two photon exchange amplitudes in elastic electron-nucleon scattering for the case of transversely polarized nucleons with unpolarized electrons beam. In our approach, we…

High Energy Physics - Phenomenology · Physics 2016-05-18 Tareq Alhalholy , Roman Höllwieser

We present an improved evaluation of the two-photon exchange correction to the unpolarized lepton-proton elastic scattering process at very low-energies relevant to the MUSE experiment, where only the dominant intermediate elastic proton is…

High Energy Physics - Phenomenology · Physics 2025-04-02 Rakshanda Goswami , Pulak Talukdar , Bhoomika Das , Udit Raha , Fred Myhrer

The effects of two-photon exchange corrections, suggested to explain the difference between measurements of the proton elastic electromagnetic form factors using the polarization transfer and Rosenbluth techniques, have been studied in…

Nuclear Experiment · Physics 2014-11-18 V. Tvaskis , J. Arrington , M. E. Christy , R. Ent , C. E. Keppel , Y. Liang , G. Vittorini

We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A$_\perp$, at two Q$^2$ values of \qsquaredaveragedlow (GeV/c)$^2$ and \qsquaredaveragedhighII (GeV/c)$^2$ and a…

It is shown that the amplitude of elastic ed scattering beyond Born approximation contains six generalized form factors, but only three linearly independent combinations of them (generalized charge, quadrupole and magnetic form factors)…

Nuclear Theory · Physics 2015-03-17 A. P. Kobushkin , Ya. D. Krivenko-Emetov

We compute the two photon exchange contributions to elastic scattering of polarized electrons from target protons. We use a nonlocal field theory formalism for this calculation. The formalism maintains gauge invariance and provides a…

High Energy Physics - Phenomenology · Physics 2008-12-18 Pankaj Jain , Satish D. Joglekar , Subhadip Mitra
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