K. Spieker

activity

20152026

η

and

η^{'}

photoproduction at MAMI

55 citations · 598 across the 37 of their papers we have counts for

collaborators

37 papers

nucl-ex2026

Measurement of the Gerasimov-Drell-Hearn integrand for proton and deuteron from 200 to 1400 MeV

P. Pedroni, F. Afzal, S. Abt +59

New data for the total inclusive helicity-dependent cross section for the proton and deuteron were obtained in the photon energy interval 200-1400 MeV. The experiment was performed…

hep-ex2025

New high-statistics measurement of the $π^{0} \to e^{+} e^{-} γ$ Dalitz decay at the Mainz Microtron

S. Prakhov, L. Heijkenskjöld, S. Abt +69

The Dalitz decay $π^{0} \to e^{+} e^{-} γ$ has been measured with the highest statistical accuracy obtained so far in the $γ p \to π^{0} p$ reaction with the A2 tagged-photon facility at the M…

nucl-ex2024

First measurement using elliptically polarized photons of the double-polarization observable $E$ for $γ p \to p π^{0}$ and $γ p \to n π^{+}$

A2 Collaboration, F. Afzal, K. Spieker +74

We report the measurement of the helicity asymmetry $E$ for the $p π^{0}$ and $n π^{+}$ final states using, for the first time, an elliptically polarized photon beam in combination with…

nucl-ex2023

Evaluation of the E2/M1 ratio in the $N \to Δ (1232)$ transition from the $γ p \to p π^{0}$ reaction

E. Mornacchi, P. Pedroni, F. Afzal +59

A new data set for the helicity-dependent differential cross section of the single-meson photoproduction reaction $γ p \to p π^{0}$ was obtained for the photon energy interval 150-4…

nucl-ex2023★ 2 cited

Helicity dependent cross sections for the photoproduction of $π^{0} π^{\pm}$ pairs from quasi-free nucleons

A2 Collaboration, D. Ghosal, V. Sokhoyan +71

Photoproduction of $π^{0} π^{\pm}$ -pairs from quasifree nucleons bound in the deuteron has been investigated to study the helicity dependence of this reaction. Measurements with a liq…

nucl-ex2022

Neutron polarisation transfer, $C_{x^{'}}^{n}$ , in $π^{+}$ photoproduction off the proton

M. Bashkanov, D. P. Watts, S. J. D. Kay +63

We report a first measurement of the double-polarisation observable, $C_{x^{'}}$ , in $π^{+}$ photoproduction off the proton. The $C_{x^{'}}$ double-polarisation observable represents the t…

hep-ex2022

Target and beam-target asymmetries for the $γ p \to π^{0} π^{0} p$ reaction

S. Garni, V. L. Kashevarov, A. Fix +81

Background: Photoproduction of pion pairs allows to study sequential decays of nucleon resonances via excited intermediate states. Such decays are important e.g. for states which i…

nucl-ex2022★ 3 cited

First measurement of polarisation transfer $C_{x^{'}}^{n}$ in deuteron photodisintegration

M. Bashkanov, D. P. Watts, S. J. D. Kay +66

A first measurement of the polarisation transfer from a circularly-polarised photon to the final state neutron ( $C_{x^{'}}^{n}$ ) in deuterium photodisintegration has been carried out. T…

nucl-ex2022★ 1 cited

Measurement of the helicity dependence for single $π^{0}$ photoproduction from the deuteron

The A2 collaboration, F. Cividini, M. Dieterle +72

The helicity-dependent single $π^{0}$ photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable $E$ for the quasi-free single $…

nucl-ex2021★ 11 cited

Observation of a structure in the M $_{p η}$ invariant mass distribution near 1700 MeV/ $c^{2}$ in the $γ p \to p π^{0} η$ reaction

V. Metag, M. Nanova, J. Hartmann +74

The reaction $γ p \to p π^{0} η$ has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold…

nucl-ex2021

Measurement of Compton scattering at MAMI for the extraction of the electric and magnetic polarizabilities of the proton

A2 Collaboration, E. Mornacchi, P. P. Martel +65

A precise measurement of the differential cross-sections $d σ / d Ω$ and the linearly polarized photon beam asymmetry $Σ_{3}$ for Compton scattering on the proton below pion threshold ha…

nucl-ex2021★ 2 cited

Single $π^{0}$ Production Off Neutrons Bound in Deuteron with Linearly Polarized Photons

C. Mullen, S. Gardner, D. I. Glazier +79

The quasifree $γ d \to π^{0} n (p)$ photon beam asymmetry, $Σ$ , has been measured at photon energies, $E_{γ}$ , from 390 to 610 MeV, corresponding to center of mass energy fr…

nucl-ex2020★ 20 cited

Observation of the $p η^{'}$ Cusp in the New Precise Beam Asymmetry $Σ$ Data for $γ p \to p η$

TAPS Collaboration

Data on the beam asymmetry $Σ$ in the photoproduction of $η$ mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from $W =$ 1748 MeV to $W =$ …

nucl-ex2020★ 9 cited

Helicity-dependent cross sections for the photoproduction of $π^{0}$ pairs from nucleons

M. Dieterle, L. Witthauer, A. Fix +88

The double-polarization observable $E$ and helicity-dependent cross sections $σ_{1/2}$ , $σ_{3/2}$ have been measured for the photoproduction of $π^{0}$ pairs off quasi-free protons a…

nucl-ex2019★ 20 cited

Signatures of the $d^{*} (2380)$ hexaquark in d( $γ$ , $p n$ )

M. Bashkanov, D. P. Watts, S. J. D. Kay +74

We report a measurement of the spin polarisation of the recoiling neutron in deuterium photodisintegration, utilising a new large acceptance polarimeter within the Crystal Ball at…

nucl-ex2019★ 14 cited

Spin polarizabilities of the proton by measurement of Compton double-polarization observables

D. Paudyal, P. P. Martel, G. M. Huber +90

The Compton double-polarization observable $Σ_{2 z}$ has been measured for the first time in the $Δ (1232)$ resonance region using a circularly polarized photon beam incident on a lo…

nucl-ex2019★ 27 cited

Cross Section for $γ n \to π^{0} n$ measured at Mainz/A2

W. J. Briscoe, M. Hadzimehmedovi, A. E. Kudryavtsev +89

The $γ n \to π^{0} n$ differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195-1.553 GeV) and the pion c.m. polar production angles,…

nucl-ex2019★ 3 cited

Measurement of the beam-helicity asymmetry in photoproduction of $π^{0} η$ pairs on carbon, aluminum, and lead

V. Sokhoyan, S. Prakhov, A. Fix +88

The beam-helicity asymmetry was measured, for the first time, in photoproduction of $π^{0} η$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The result…

nucl-ex2019★ 2 cited

Measurement of the Helicity Asymmetry $E$ for the reaction $γ p \to π^{0} p$

TAPS collaboration, M. Gottschall, F. Afzal +66

A measurement of the double-polarization observable $E$ for the reaction $γ p \to π^{0} p$ is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn…

nucl-ex2018★ 21 cited

Experimental study of the $γ p \to K^{0} Σ^{+}$ , $γ n \to K^{0} Λ$ , and $γ n \to K^{0} Σ^{0}$ reactions at the Mainz Microtron

C. S. Akondi, K. Bantawa, D. M. Manley +78

This work measured $d σ / d Ω$ for neutral kaon photoproduction reactions from threshold up to a c.m.\ energy of 1855MeV, focussing specifically on the $γ p \to K^{0} Σ^{+}$ , $γn\righ…

nucl-ex2018★ 9 cited

First measurement of helicity-dependent cross sections in pi0-eta photoproduction from quasi-free nucleons

A. Käser, M. Dieterle, L. Witthauer +80

The helicity-dependent cross sections for the photoproduction of $π^{0} η$ pairs have been measured for the first time. The experiment was performed at the tagged photon facility of t…

nucl-ex2018★ 20 cited

Deuteron photodisintegration by polarized photons in the region of the $d^{*} (2380)$

M. Bashkanov, S. Kay, D. P. Watts +70

We report the first large-acceptance measurement of the beam-spin asymmetry for deuteron photodisintegration ( $γ d \to p n$ ) in the photon energy range $400 < E_{γ} < 630$ ~MeV. The mea…

hep-ex2018★ 16 cited

High-statistics measurement of the eta->3pi^0 decay at the Mainz Microtron

S. Prakhov, S. Abt, P. Achenbach +85

The largest, at the moment, statistics of 7x10^6 eta->3pi^0 decays, based on 6.2x10^7 eta mesons produced in the gamma p -> eta p reaction, has been accumulated by the A2 Collabora…

hep-ex2017★ 9 cited

Measurement of the decay $η^{'} \to π^{0} π^{0} η$ at MAMI

P. Adlarson, F. Afzal, C. S. Akondi +75

An experimental study of the $η^{'} \to π^{0} π^{0} η \to 6 γ$ decay has been conducted with the best up-to-date statistical accuracy, by measuring $η^{'}$ mesons produced in the $γ p \to η^{'} p$ re…

Measurement of the Gerasimov-Drell-Hearn integrand for proton and deuteron from 200 to 1400 MeV

New high-statistics measurement of the π0→e+e−γ Dalitz decay at the Mainz Microtron

First measurement using elliptically polarized photons of the double-polarization observable E for γp→pπ0 and γp→nπ+

Evaluation of the E2/M1 ratio in the N→Δ(1232) transition from the γ​p​→pπ0 reaction

Helicity dependent cross sections for the photoproduction of π0π± pairs from quasi-free nucleons

Neutron polarisation transfer, Cx′n​, in π+ photoproduction off the proton

Target and beam-target asymmetries for the γp→π0π0p reaction

First measurement of polarisation transfer Cx′n​ in deuteron photodisintegration

Measurement of the helicity dependence for single π0 photoproduction from the deuteron

Observation of a structure in the Mpη​ invariant mass distribution near 1700 MeV/c2 in the γp→pπ0η reaction

Measurement of Compton scattering at MAMI for the extraction of the electric and magnetic polarizabilities of the proton

Single π0 Production Off Neutrons Bound in Deuteron with Linearly Polarized Photons

Observation of the pη′ Cusp in the New Precise Beam Asymmetry Σ Data for γp→pη

Helicity-dependent cross sections for the photoproduction of π0 pairs from nucleons

Signatures of the d∗(2380) hexaquark in d(γ,pn)