Harald F. Merkel

Precise measurement of the $Λ$-binding energy difference between $^3_Λ$H and $^4_Λ$H via decay-pion spectroscopy at MAMI

Ryoko Kino, Sho Nagao, Patrick Achenbach, Satoshi N. Nakamura et autres

We performed high-precision decay-pion spectroscopy of light $Λ$ hypernuclei at the Mainz Microtron (MAMI) using the A1 spectrometer facility. By measuring the monochromatic $π^-$ momentum from the two-body weak decay $^3_Λ\mathrm{H} \to {}^3\mathrm{He} + π^-$ and referencing it to the $^4_Λ\mathrm{H} \to …

Beam-Normal Single-Spin Asymmetry in Pb 208 at Low Energy: Discrepancy Resolved or New Kinematic Puzzle?

A. Esser, Nikita Kozyrev, Kurt Aulenbacher, S. Baunack et autres

A long-standing discrepancy between measured and predicted beam-normal single-spin asymmetries A_{n} in elastic electron scattering off ^{208}Pb has challenged our understanding of two-photon exchange (TPE) in heavy nuclei. We report a new measurement at 570 MeV and Q^{2}=0.04 GeV^{2}/c^{2}, yielding A_{n}=[-9.1±2.1(stat)±0.7(syst)] ppm. …

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Measurement of the helicity-dependent response in quasi-elastic proton knockout from40Ca

T. Kolar, I. Sabo-Napadensky, Patrick Achenbach, Mirco Christmann et autres

The role of the electron-helicity-dependent cross-section term and the structure function f01′ in the quasi-elastic A(e→,e′p) process was studied. The f01′ was measured for proton knockout from the 1d3/2 shell in 40Ca via the 40Ca(e→,e′p)39Kg.s. reaction, leaving the residual nucleus in a …

Measurement of the 40Ar(e,$$\hbox {e}^{\prime }$$) elastic scattering cross section with a novel gas-jet target

M. Littich, L. Doria, Peter B. Brand, Patrick Achenbach et autres

Abstract We report on a measurement of elastic electron scattering on argon performed with a novel cryogenic gas-jet target at the Mainz Microtron accelerator MAMI. The luminosity is estimated with the thermodynamical parameters of the target and by comparison to a calculation …

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Production of the neutron-rich nucleus 6H in an electron-scattering experiment at MAMI-A1

T. Shao, Patrick Achenbach, Jinhui Chen, Mirco Christmann et autres

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Measurement of H 6 Ground State Energy in an Electron Scattering Experiment at MAMI-A1

T. Shao, Jinhui Chen, Josef Pochodzalla, Patrick Achenbach et autres

For the first time the neutron-rich hydrogen isotope $^{6}\mathrm{H}$ was produced in an electron scattering experiment in the reaction $^{7}\mathrm{Li}(\mathrm{e},{\mathrm{e}}^{\ensuremath{'}}\mathrm{p}{\ensuremath{\pi}}^{+}{)}^{6}\mathrm{H}$ using the spectrometer facility of the A1 Collaboration at the Mainz Microtron accelerator. By measuring the triple coincidence between the scattered electron, …

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Measurement of the helicity-dependent response in quasi-elastic proton knockout from $^{40}{\rm Ca}$

T. Kolar, I. Sabo-Napadensky, Patrick Achenbach, M. O. Distler et autres

The role of the electron-helicity-dependent cross-section term and the structure function $f^{\prime}_{01}$ in the quasi-elastic $A(\vec{e}, e^{\prime}p)$ process was studied. The $f^{\prime}_{01}$ was measured for proton knockout from the $1\mathrm{d}_{3/2}$ shell in $^{40}\mathrm{Ca}$ via the $^{40}{\rm Ca}(\vec{e},e' p)^{39}{\rm K}_{\rm g.s.}$ reaction, leaving …

Measurement of $\rm ^{6}H$ ground state energy in an electron scattering experiment at MAMI-A1

T. Shao, Jinhui Chen, Josef Pochodzalla, Patrick Achenbach et autres

For the first time the neutron-rich hydrogen isotope $\rm ^{6}H$ was produced in an electron scattering experiment in the reaction $\rm ^{7}Li(e,~e'pπ^{+})^{6}H$ using the spectrometer facility of the A1 Collaboration at the Mainz Microtron accelerator. By measuring the triple coincidence between the …

A novel FPGA-based data acquisition for high-precision asymmetry measurements at low rates in electron scattering

A. Esser, A. Del Vincio, L. Doria, M. Hoek et autres

Asymmetry measurements in the scattering of polarized electrons on unpolarized targets are powerful tools to study the neutron distribution in nuclei and the multi-photon exchange contribution to the scattering process. Measuring these quantities requires not only precise counting of the scattered electrons, …

Nuclear density dependence of polarization transfer in quasi-elastic A ( e , e ′ p ) reactions

T. Kolar, Wim Cosyn, C. Giusti, Patrick Achenbach et autres

The ratio of the transverse and longitudinal components of polarization transfer to protons in the quasielastic $(\stackrel{P\vec}{e},{e}^{\ensuremath{'}}\stackrel{P\vec}{p}\phantom{\rule{0.16em}{0ex}})$ reaction, ${P}_{x}^{\ensuremath{'}}/{P}_{z}^{\ensuremath{'}}$, is sensitive to the proton's electromagnetic form factor ratio, ${G}_{E}/{G}_{M}$. To explore density-dependent in-medium modifications, a comparison of polarization transfer ratios involving protons …

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Measurement of the $$\mathrm {{}^{12}C}(e,e')$$ Cross Sections at $$Q^2=0.8\,\textrm{GeV}^2/c^2$$

M. Mihovilovič, L. Doria, Patrick Achenbach, Artur M. Ankowski et autres

Abstract We present the findings of a study based on a new inelastic electron-scattering experiment on the $${}^{12}$$ 12 C nucleus focusing on the kinematic region of $$Q^2=0.8\,\textrm{GeV}^2/{c}^2$$ Q 2 = 0.8 GeV 2 / c 2 . The measured cross section …

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Systematic studies of beam-normal single spin asymmetries at MAMI

M. Thiel, A. Esser, M. Hoek, Harald F. Merkel et autres

Reaching new precision frontiers in nuclear physics raises new experimental challenges as well as the demand for more sophisticated theoretical calculations. Especially in parity-violation electron scattering experiments the contribution from higher order processes, such as two-photon exchange, is comparable in size with …

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