Possible method for measuring the proton form factors in processes with and without proton spin flip

Abstract

The ratio of the squares of the electric and magnetic proton form factors is shown to be proportional to the ratio of the cross sections for the elastic scattering of an unpolarized electron on a partially polarized proton with and without proton spin flip. The initial proton at rest should be polarized along the direction of the motion of the final proton. Similar results are valid for both radiative ep scattering and the photoproduction of pairs on a proton in the Bethe-Heitler kinematics. When the initial proton is fully polarized in the direction of the motion of the final proton, the cross section for the ep → ep process, as well as for the ep → epγ and γp → eēp processes, without (with) proton spin flip is expressed only in terms of the square of the electric (magnetic) proton form factor. Such an experiment on the measurement of the cross sections without and with proton spin flip would make it possible to acquire new independent data on the behavior of G 2 E (Q 2 ) and G 2 M (Q 2 ), which are necessary for resolving the contradictions appearing after the experiment of the JLab collaboration on the measurement of the proton form factors with the method of polarization transfer from the initial electron to the final proton.

Alternative way to understand the unexpected results of the JLab polarization experiments to measure the Sachs form factors ratio

“…In fact, it is G M (G E ) rather than F 1 (F 2 ) that is responsible for helicity-conserving (helicityflip) transitions at high q 1 and q 2 [see Eqs. ( 9), ( 10), (15)]. We note that in the literature sometimes there is no clear understanding of the physical meaning of the quantity ε in formula (1).…”

“…It is an experiment at the VEPP-3 storage ring in Novosibirsk, the OLYM-PUS experiment at the DORIS accelerator at DESY, and the EG5 CLAS experiment at JLab. In [15], we proposed a new alternative to the method [4] for determining the Sachs FFs in the process e p → e p on the basis of measuring cross sections for spin-flip and non-spin-flip transitions for protons.…”

Alternative way to understand the unexpected results of the JLab polarization experiments to measure the Sachs form factors ratio

“…In [15], we proposed a new alternative to the method [4] for determining the Sachs FFs in the process e p → e p on the basis of measuring cross sections for spin-flip and non-spin-flip transitions for protons.…”

On the Measurement of Sachs Form Factors in Processes without and with Proton Spin Flip

“…Cross section for the e p → e p process in the laboratory reference frame.-In this work, we propose a new method for measuring the squares of the Sachs form factors in the e p → e p elastic scattering, where G 2 E and G 2 M can be determined independently from each other from direct measurements of cross sections for the process without and with proton spin flip when the initial proton at rest is fully polarized along the direction of motion of the scattered proton. This work is development of our work [11].…”

“…M can be determined independently from each other from direct measurements of cross sections for the process without and with proton spin flip when the initial proton at rest is fully polarized along the direction of motion of the scattered proton. This work is development of our work [11].…”