Amplitude reconstruction from complete electroproduction experiments and truncated partial-wave expansions

Tiator, L.; Workman, R. L.; Wunderlich, Y.; Haberzettl, H.

doi:10.1103/physrevc.96.025210

Cited by 23 publications

(34 citation statements)

References 18 publications

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“…A 51, 77]. This work should be useful, especially, for newcomers in the field of baryon spectroscopy, where the photoproduction reactions are a major tool for probing the baryon spectra.Spin-observables in pseudoscalar meson photoproduction [7,12,13,14,15,16,17,18,19,20,21] (for some of the related earlier works, see, e.g., Refs. [22,23,24] ).…”

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On the spin-observables in pseudoscalar meson photoproduction

Nakayama¹

2019

J. Phys. G: Nucl. Part. Phys.

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Spin-observables in pseudoscalar meson photoproduction is discussed. This work is complementary to the earlier works on this topic. Here, the reaction amplitude is expressed in Pauli-spin basis which allows to calculate all the observables straightforwardly. We make use of the fact that the underlying reflection symmetry about the reaction plane can be most conveniently and easily exploited in this basis to help finding the non-vanishing and independent observables in this reaction. The important issue of complete experiments is reviewed. By expressing the reaction amplitude in Pauli-spin basis, many sets of eight observables -distinct from those found in earlier works from the amplitude in transversity basis -capable of determining the reaction amplitude up to an overall phase are found. It is also shown that some of the combinations of the spin observables are suited for studying certain aspects of the reaction dynamics. We, then, carry out a (strictly) model-independent partialwave analysis, in particular, of the peculiar angular behavior of the beam asymmetry observed in η ′ photoproduction very close to threshold [P. Levi Sandri et al. 2015 Eur. Phys. J. A 51, 77]. This work should be useful, especially, for newcomers in the field of baryon spectroscopy, where the photoproduction reactions are a major tool for probing the baryon spectra.Spin-observables in pseudoscalar meson photoproduction [7,12,13,14,15,16,17,18,19,20,21] (for some of the related earlier works, see, e.g., Refs. [22,23,24] ). Of particular interest in this connection is the issue of whether the baryon resonances can be extracted model independently or with minimal model requirements. Efforts along this line is currently in progress [15,16,19,20].In this work, we consider those same issues mentioned above; as such, it is complementary to the earlier works on this topic [1,3,4,5,6,7]. In contrast to those studies, we consider the photoproduction amplitude in Pauli-spin basis which allows us to calculate the spin-observables, in general, in a straightforward and quite pedestrian way. We will make used of the underlying reflection symmetry about the reaction plane -which can be conveniently and easily exploited in this basis -to help find the non-vanishing observables in this reaction. Also, the Pauli-spin amplitude is simply related to that of the usual Chew-Goldberger-Low-Nambu (CGLN) form [28] due to this symmetry. The important and non-trivial issue of the complete experiments is reviewed. In particular, by using Pauli-spin representation of the reaction amplitude instead of transversity representation, we identify other sets of observables, not reported in [5,8], for complete experiments. In addition, certain combinations of the observables are shown to be useful in isolating (low) partial-wave states to learn about the reaction dynamics. Motivated by this, a model-independent analysis of the η ′ photoproduction off the proton close to threshold is performed in connection to the peculiar angular behavior exhibited by the beam asymmetry in...

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“…Spin-observables in pseudoscalar meson photoproduction [7,12,13,14,15,16,17,18,19,20,21] (for some of the related earlier works, see, e.g., Refs. [22,23,24] ).…”

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confidence: 99%

On the spin-observables in pseudoscalar meson photoproduction

Nakayama¹

2019

J. Phys. G: Nucl. Part. Phys.

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“…(a) Laboratory frame (b) Centre of mass frame (virtual photon and nucleon target) Diagrams showing the pion electroproduction reaction [27]…”

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Beam-, Target- and Double- Spin Asymmetry Measurements in Deeply Virtual π0, π+ and π- Meson Production

Murdoch

2019

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This thesis presents measurements of spin asymmetries in single pion electroproduction from the EG1-DVCS experiment carried out at the Thomas Jefferson National Accelerator Facility in 2009 with use of the CEBAF Large Acceptance Spectrometer. The experiment made use of a 6 GeV longitudinally polarised electron beam and (dynamically) longitudinally polarised targets of 14 NH 3 and 14 ND 3 (giving access to protons and deuterons), providing the means to measure three spin asymmetries: beam-, target-, and double-spin. Deeply Virtual Meson Production for the π 0 , π + and π − channels were studied for the kinematic range of Q 2 > 1 GeV 2 and W > 2 GeV. The collection of measurements includes the analysis of numerous reconstruction topologies, as well as making use of different target materials. These are the world's first charged pion spin asymmetry measurements in this kinematic regime. The sPlot maximum likelihood fitbased background subtraction technique was implemented in the data analysis, showing strong agreement with a traditional and commonly used cuts-based approach. This novel technique was thoroughly tested to develop implementation and execution. The results obtained will provide a reference point for future analyses at the upgraded experimental facility and motivate the use of the sPlot technique. These measurements will provide insight into the structure of nucleons through their interpretation in relation to Generalised Parton Distributions which describe substructure correlations between longitudinal momentum and transverse position of partons. In particular, here the spin asymmetries dependence on t, the squared four-momentum transfer to the target nucleon, carries information on the spatial parton distributions in the transverse plane.

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“…The separately shown Regge contribution (lower blue lines) contain trajectory and cuts with natural and un-natural parity. comparison with different theoretical models and partial wave analysis (PWA) -investigations of CGLN, helicity and invariant amplitudes -PWA with electric, magnetic and charge multipoles nucleon resonances N * and ∆ * in Breit-Wigner parametrization transverse and longitudinal transition form factorsThe second group are indirect applications, where numerical results of the MAID programs are used for further calculations:-T-matrix pole positions and residues of nucleon resonances[23; 24] transverse transition densities on the light-front[25] complete experiment analyses[26] fixed-t dispersion relations for meson photo-and electroproduction[27] dispersion relations in real and virtual Compton scattering[28] -Gerasimov-Drell-Hearn sum rule and spin structure of the nucleon[29] nucleon polarizabilities and light-front interpretation [30; 31] -two-photon exchange corrections to elastic e-p scattering[32]…”

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The MAID Legacy and Future

Tiator

2018

Few-Body Syst

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The MAID project is a collection of theoretical models for pseudoscalar meson photo-and electroproduction from nucleons. It is online available and produces results in real time calculations. In addition to kinematical variables also model parameters, especially for baryon resonances, can be online changed and investigated. Over 20 years MAID has become quite popular and the MAID web pages have been called more than 7.7 million times. Keywords pion electroproduction · baryon resonances · transition form factors 1 IntroductionAfter the exploration of the baryonic spectrum with pion scattering in the 1980s, photo-and electroproduction of mesons, mainly at Mainz, Bonn and JLab have become the main source of further investigations of N and ∆ resonances. Among them, pion electroproduction is the main source for investigations of the transition form factors of the nucleon to excited N and ∆ baryons. In addition also two-pion and eta electroproduction have been very useful for studies of selected nucleon resonances. After early measurements of the G * M form factor of the N → ∆(1232) transition already in the 1960s, in the 1990s a large program was running at Mainz, Bonn, Bates and JLab in order to measure the very small E/M ratio of the N → ∆ transition and the Q 2 dependence of the E/M and S/M ratios in order to get information on the internal quadrupole deformation of the nucleon and the ∆. In parallel large progress was achieved in various kinds of quark models that gave predictions to N → N * and N → ∆ * transition form factors. Only at JLab both the energy and the photon virtuality were available to measure those form factors for a set of nucleon resonances up to Q 2 ≈ 5 GeV 2 . Two recent review articles on the electromagnetic excitation of nucleon resonances give a very good overview over experiment and theory and latest developments [1; 2].

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Amplitude reconstruction from complete electroproduction experiments and truncated partial-wave expansions

Cited by 23 publications

References 18 publications

On the spin-observables in pseudoscalar meson photoproduction

On the spin-observables in pseudoscalar meson photoproduction

Beam-, Target- and Double- Spin Asymmetry Measurements in Deeply Virtual π<sup>0</sup>, π<sup>+</sup> and π<sup>-</sup> Meson Production

The MAID Legacy and Future

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