Measurement of the $p(e,e'\pi^+)n$ reaction close to threshold and at low $Q^2$

A1 Collaboration; I. Friščić; P. Achenbach; C. Ayerbe Gayoso; D. Baumann; R. Böhm; D. Bosnar; L. Debenjak; A. Denig; M. Ding; M. O. Distler; A. Esser; H. Merkel; D. G. Middleton; M. Mihovilovič; U. Müller; J. Pochodzalla; B. S. Schlimme; M. Schoth; F. Schulz; C. Sfienti; S. Širca; M. Thiel; Th. Walcher

doi:10.1016/j.physletb.2017.01.033

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arXiv · 1606.00970

Measurement of the $p(e,e'\pi^+)n$ reaction close to threshold and at low $Q^2$

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Abstract

The cross section of the $p(e,e'\pi^+)n$ reaction has been measured for five kinematic settings at an invariant mass of $W = 1094$ MeV and for a four-momentum transfer of $Q^2 = 0.078$ (GeV/$c$)$^2$. The measurement has been performed at MAMI using a new short-orbit spectrometer (SOS) of the A1 collaboration, intended for detection of low-energy pions. The transverse and longitudinal cross section terms were separated using the Rosenbluth method and the transverse-longitudinal interference term has been determined from the left-right asymmetry. The experimental cross section terms are compared with the calculations of three models: DMT2001, MAID2007 and $\chi$MAID. The results show that we do not yet understand the dynamics of the fundamental pion.

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A1 Collaboration, I. Friščić, P. Achenbach, C. Ayerbe Gayoso, D. Baumann, R. Böhm, D. Bosnar, L. Debenjak, A. Denig, M. Ding, M. O. Distler, A. Esser, H. Merkel, D. G. Middleton, M. Mihovilovič, U. Müller, J. Pochodzalla, B. S. Schlimme, M. Schoth, F. Schulz, C. Sfienti, S. Širca, M. Thiel, Th. Walcher. 2016-06-03. Measurement of the $p(e,e'\pi^+)n$ reaction close to threshold and at low $Q^2$. https://doi.org/10.1016/j.physletb.2017.01.033

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