Scattering of positrons and electrons from protons

Bartel, W.; Dudelzak, B.; Krehbiel, H.; McElroy, J.; Morrison, R. J.; Schmidt, W.; Walther, Valentin; Weber, G.

doi:10.1016/0370-2693(67)90055-x

Cited by 40 publications

(39 citation statements)

References 8 publications

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“…Earlier data from elastic e + p and e − p experiments in the 1960s from SLAC [69,70], Cornell [71], DESY [72] and Orsay [73] gave some hints of a small enhancement of R 2γ at forward angles and low Q 2 , but were in the region (at large ε) where TPE is relatively small and were consistent within errors with R 2γ = 1. Data from the VEPP-3 experiment at Novosibirsk [26,27], taken at energies E ≈ 1 GeV ε values the trend in the data is towards values of the ratio slightly below unity, whereas the calculated dispersive TPE corrections give a ratio that has a small, 1% enhancement above unity.…”

Section: Verification Of Tpe Effectssupporting

confidence: 59%

Dispersive approach to two-photon exchange in elastic electron-proton scattering

Blunden

Melnitchouk

2017

Phys. Rev. C

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We examine the two-photon exchange corrections to elastic electron-proton scattering within a dispersive approach, including contributions from both nucleon and ∆ intermediate states. The dispersive analysis avoids off-shell uncertainties inherent in traditional approaches based on direct evaluation of loop diagrams, and guarantees the correct unitary behavior in the high energy limit.Using empirical information on the electromagnetic nucleon elastic and N ∆ transition form factors, we compute the two-photon exchange corrections both algebraically and numerically. Results are compared with recent measurements of e + p to e − p cross section ratios from the CLAS, VEPP-3 and OLYMPUS experiments, as well as with polarization transfer observables.

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Section: Verification Of Tpe Effectssupporting

confidence: 59%

Dispersive approach to two-photon exchange in elastic electron-proton scattering

Blunden

Melnitchouk

2017

Phys. Rev. C

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“…In run II, the data in the LA angular range were broken down into three intervals in ε. Figure 9 also gives the results obtained in previous experiments and reported in [30][31][32][33][34]. The errors in them were substantially greater.…”

Section: Results Of Measurements and Discussionsupporting

confidence: 53%

“…The closed circles stand for the data of the present experiment that were obtained in (a) run I and (b) run II. The remaining data were borrowed from (closed triangles) [34], (open boxes) [32], (inverted closed triangle) [31], (closed diamonds) [30], and (closed box) [33]. The curves represent the theoretical predictions and parametrizations of (1) Qattan et al [38], (2) Blunden et al [36], (3) Borisyuk and Kobushkin [40], (4) Bernauer et al [41], (5) Arrington and Sick [37], and (6) Tomasi-Gustafsson et al [39].…”

Section: Results Of Measurements and Discussionmentioning

confidence: 99%

“…Attempts at determining the TPE contribution to the cross section for electron-proton scattering were undertaken earlier in the 1960s (see [29][30][31][32][33][34][35]), but they were impeded by a poor measurement precision at that time. The contradiction in the data on the proton form factors revived interest in the role of twophoton exchange.…”

Section: Two-photon Exchangementioning

confidence: 99%

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Proton form factors and two-photon exchange in elastic electron-proton scattering

et al. 2015

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Proton electromagnetic form factors are among the most important sources of information about the internal structure of the proton. Two different methods for measuring these form factors, the method proposed by Rosenbluth and the polarization-transfer method, yield contradictory results. It is assumed that this contradiction can be removed upon taking into account the hard part of the contribution of two-photon exchange to the cross section for elastic electron-proton scattering. This contribution can measured experimentally via a precision comparison of the cross sections for the elastic scattering of positrons and electrons on protons. Such a measurement, performed at the VEPP-3 storage ring in Novosibirsk at the beam energies of 1.6 and 1.0 GeV for positron (electron) scattering angles in the ranges of θ e = 15 • −25 • and 55 • −75 • in the first case and in the range of θ e = 65 • −105 • in the second case is described in the present article. Preliminary results of this experiment and their comparison with theoretical predictions are described.

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“…The best guess available is that the form factors are well approximated by a "4-pole fit." 14 Some more recent elastic electronproton data 15 suggest that G Mp may be lower than suggested by this 4-pole fit. Figures 10, 11, and 12 show the absolute differential cross sections for the resonance Jlf*=1238 MeV compared to Adler's theory.…”

Section: Excitation Of the M*= 1238-mev Resonancementioning

confidence: 79%

Inelastic Scattering of Electrons by Protons

et al. 1967

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LEGAL N O T I C E-TMS r e p r t s;as prepared as an account of Government sponsored work. Neither the United Stares. nor the Commission. nor any person acting on behalf of the Commission:A . llakes anywarranty or representarion. expressed or Implied, w t h respect lo the accuracy. completeness. or ueelulness of the informarion contained In this reporl. or that the use of any information. apparatus. method. or process disclosed in this r e p r t may no1 infringe , ABSTRACT privately oamed rights: or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method. or process disclosed in this report.,AS "sed the above, "person aellng on behall of the Commission" includes any employee or con1ractor of the Ccmmissian. or employee of such contraclor. u, the extent that such employee or c o n~a e l o r of the Commission. or employee of such contractor prepares, The i n e l a s t i c s c a t t e r i n g of e l e c t r o n s by protons h a s been measured a t i n c i d e n t e l e c t r o n e n e r g i e s up t o 5 BeV/c and momentum U Supported by t h e United S t a t e s Atomic Energy CommissionP r e s e n t l y a t Palmer P h y s i c a l Laboratory, Princeton University,Princeton, New Jersey. @ * S r e s e n t l y a t Vancouver C i t y College, Vancouver, B r i t i s h Columbia. ?Supported by t h e National Science Foundation a t t h e time of t h i s INTRODUCTIONThe i n e l a s t i c s c a t t e r i n g of e l e c t r o n s was shown t o be a u s e f u l technique f o r s t u d y i n g atomic s t r u c t u r e by Franck and Hertz. By s t u d y i n g t h e energy spectrum of s c a t t e r e d e l e c t r o n s t h e y were a b l e t o measurethe e x c i t a t i o n spectrum o f atoms. I n t h e terminology of modern h i e h e n e r g y . p h y s i c s , t h i s would now be c a l l e d missing mass spectroscopy. . The a p p l i c a t i o n of t h i s method t o t h e study of t h e proton and i t s e x c i t e d s t a t e s w a s begun by Panofsky and A l l t o n and wasextended by Hand . These a u t h o r s s t u d i e d t h e e x c i t a t i o n of t h e 2 pion-nucleon (nucleon e x c i t e d s t a t e ) . a t a mass of 1240 MeV and w i t h quantum numbers, 1=3/2, ~= 3 / 2 + up t o a momentum t r a n s f e r q2-18 f -2 (0.7(BeV/~)~). Hand failed t o f i n d e v i d e n c e of e x c i t a t i o nof o t h e r resonances.I n t h i s work, t h e e x c i t a t i o n of t h e 1240 MeV resonance i s q2+0 fermi -2 s t u d i e d up t o a momentum t r a n s f e r and t h e e x c i t a t i o n of t h e resonances a t masses of 1512 MeV, 1690 MeV and 1920 MeV are observed. These are compared w i t h such t h e o r e t i c a l c a l c u l a t i o n s as are a v a i l a b l e . There is good agreement except for t h e e x c i t a t i o n of t h e resonance a t 1512 MeV which is t o o g r e a t KINEMATICS AND ONE PHOTON EXCHANGEThroughout t h i s paper w e w i l l use a n o t a t i o n c l o s e t o t h a t 2 of Hand diagram of Fig. 1. A t t h e s e momentum ...

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Scattering of positrons and electrons from protons

Cited by 40 publications

References 8 publications

Dispersive approach to two-photon exchange in elastic electron-proton scattering

Dispersive approach to two-photon exchange in elastic electron-proton scattering

Proton form factors and two-photon exchange in elastic electron-proton scattering

Inelastic Scattering of Electrons by Protons

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