Charged-pion electroproduction above the resonance region

Abstract

Background: Above the nucleon resonance region, the N (e,e π ± )N data cannot be explained by conventional hadronic models. For example, the observed magnitude of the transverse cross section is significantly underestimated in a framework with Reggeized background amplitudes. Purpose: Develop a phenomenological framework for the N (e,e π ± )N reaction at high invariant mass W and deep photon virtuality Q 2 . Method: Building on the work of Kaskulov and Mosel [Phys. Rev. C 81, 045202 (2010)], a gauged pion-exchange current is introduced with a running cutoff energy for the proton electromagnetic transition form factor. A new transition form factor is proposed. It respects the correct on-shell limit, has a simple physical interpretation, and reduces the number of free parameters by one. Results: A study of the W dependence of the N (e,e π ± )N lends support for the newly proposed transition form factor. In addition, an improved description of the separated and unseparated cross sections at −t 0.5 GeV 2 is obtained. The predictions overshoot the measured unseparated cross sections for −t > 0.5 GeV 2 . Introducing a strong hadronic form factor in the Reggeized background amplitudes brings the calculations considerably closer to the high −t data. Conclusions: Hadronic models corrected for resonance-parton duality describe the separated pion electroproduction cross sections above the resonance region reasonably well at low −t. In order to validate the applicability of these models at high −t, separated cross sections are needed. These are expected to provide a more profound insight into the relevant reaction mechanisms.

Separated response functions in exclusive, forwardπ±electroproduction on deuterium

“…For any choice for the ρπγ monopole mass, it underpredicts the transverse cross sections by a large factor, which increases with Q 2 . As briefly mentioned in the introduction, the VGL Regge model was extended by Kaskulov and Mosel (KM) [15] and more recently by Vrancx and Ryckebusch (VR) [16]. KM add to the Regge model a hadronic model, which incorporates DIS π ± electroproduction at the amplitude level.…”

“…14, 15; i.e. dotted black curves are the VGL Regge model [3], short-dashed green curves are Kaskulov and Mosel [15], dot-dashed blue curves are Vrancx and Ryckebusch [16], long-dashed magenta curves are the MAID07 model [38], and solid red curves are Goloskokov and Kroll [12]. electroproduction data in the canonical resonance region (W < 2 GeV).…”

“…However, the model has consistently failed to provide a good description of p(e, e ′ π + )n σ T data [14]. The VGL Regge model was recently extended [15,16] by the addition of a hard deep-inelastic scattering (DIS) of virtual photons off nucleons. The DIS process dominates the transverse response at moderate and high Q 2 , providing a better description of σ T .…”

Electroweak single-pion production off the nucleon: From threshold to high invariant masses

“…[34,35,37,40] are the pion-exchange t-channel amplitude and the s-and u-channel amplitudes with pseudoscalar coupling, which are included to restore CVC. In Ref.…”

“…In this way, each (t-channel) Regge amplitude includes an entire family of hadrons. The great success achieved by this model [34] in reproducing highenergy forward-scattering photoproduction data, motivated its extension to other reactions such as electroproduction [35,[37][38][39][40][41], which is of major interest to us. In the framework of Ref.…”