Beam-Recoil Polarization Measurement of π[superscript 0] Electroproduction on the Proton in the Region of the Roper Resonance

Beam-Recoil Polarization Measurement of π[superscript 0] Electroproduction on the Proton in the Region of the Roper Resonance

The helicity-dependent recoil proton polarizations P[superscript '][subscript x] and P[superscript ′][subscript z] as well as the helicity-independent component P[subscript y] have been measured in the p([→ over e],e[superscript ′][→ over p])π[superscript 0] reaction at four-momentum transfer Q...

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Main Authors: Štajner, S., Achenbach, P., Beranek, T., Beričič, J., Bosnar, D., Böhm, R., Correa, L., Denig, A., Distler, M. O., Esser, A., Fonvieille, H., Friedrich, J. M., Friščić, I., Kegel, S., Kohl, Y., Merkel, H., Mihovilovič, M., Müller, J., Müller, U., Nungesser, L., Pochodzalla, J., Schlimme, B. S., Schoth, M., Schulz, F., Sfienti, C., Širca, S., Thiel, M., Tiator, L., Tyukin, A., Weber, A., Yaron, I., Bernauer, Jan Christopher
Other Authors: Massachusetts Institute of Technology. Laboratory for Nuclear Science
Format: Article
Language:English
Published: American Physical Society 2017
Online Access:http://hdl.handle.net/1721.1/110698
Description
Summary:The helicity-dependent recoil proton polarizations P[superscript '][subscript x] and P[superscript ′][subscript z] as well as the helicity-independent component P[subscript y] have been measured in the p([→ over e],e[superscript ′][→ over p])π[superscript 0] reaction at four-momentum transfer Q[superscript 2]≃0.1  GeV[superscript 2], center-of-mass proton emission angle θ[superscript *][subscript p]≃90°, and invariant mass W≃1440  MeV. This first precise measurement of double-polarization observables in the energy domain of the Roper resonance P[subscript 11](1440) by exploiting recoil polarimetry has allowed for the extraction of its scalar electroexcitation amplitude at an unprecedentedly low value of Q[superscript 2], establishing a powerful instrument for probing the interplay of quark and meson degrees of freedom in the nucleon.

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