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 _{Λ}^{3}H→^{3}He+π^{-} and referencing it to the _{Λ}^{4}H→^{4}He+π^{-} decay, we determined the Λ binding energy of _{Λ}^{3}H with unprecedented accuracy. The obtained value, B_{Λ}(_{Λ}^{3}H)=0.523±0.013_{stat}±0.075_{syst}.  MeV, is consistent with the STAR result, but indicates a significantly deeper binding than inferred from earlier measurements. This result implies a stronger Λ-deuteron interaction and provides stringent constraints on hyperon-nucleon interactions.

We performed high-precision decay-pion spectroscopy of light A hypernuclei at the Mainz Microtron (MAMI) using the A1 spectrometer facility. By measuring the monochromatic pi- momentum from the two-body weak decay 3 AH -* 3He + pi- and referencing it to the 4AH -* 4He + pi- decay, we determined the A binding energy of 3 AH with unprecedented accuracy. The obtained value, BA(3AH) = 0.523 + 0.013stat + 0.075syst: MeV, is consistent with the STAR result, but indicates a significantly deeper binding than inferred from earlier measurements. This result implies a stronger A-deuteron interaction and provides stringent constraints on hyperon-nucleon interactions.

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_ΛH→^3He + π^- and referencing it to the ^4_ΛH→^4He + π^- decay, we determined the Λ binding energy of ^3_ΛH with unprecedented accuracy. The obtained value, B_Λ(^3_ΛH) = 0.523 ± 0.013 (stat.) ± 0.075 (syst.) MeV, is consistent with the STAR result, but indicates a significantly deeper binding than inferred from earlier measurements. This result implies a stronger Λ-deuteron interaction and provides stringent constraints on hyperon-nucleon interactions.

The potential of the intense secondary muon, neutrino, and (hypothetical) light dark matter beams at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) is explored. These are produced in the high-power dumps with high-current electron beams. Light dark matter searches with the approved Beam Dump eXperiment (BDX) are driving the realization of a new underground vault behind Hall A that could be extended to a Beamdump Facility with little additional installations. High-energy muons created via the Bethe–Heitler process uniquely do not proceed through the more common pion production and decay channels. Several possible muon physics applications are highlighted. Neutrino detector technologies and experiments suitable for a beamdump facility are outlined.

The neutron-rich hydrogen isotope (6)His produced for the first time in an electron-scattering experiment at MAMI-A1. Making use of the three-spectrometer setup in the A1-hall, triple coincidences between the scattered electron, produced proton, and pi(+), were measured with the reaction 7Li(e,e ' p pi(+))H-6 which allowed to determine the missing-mass spectrum of H-6. The preliminary analysis signals a ground state energy of H-6 near 3 MeV. Our work presents a new possibility to produce neutron-rich nuclei with electron-scattering experiments.

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, but also simultaneous accurate monitoring of the primary beam in order to correct any non-physical asymmetries. For this purpose, a dedicated data acquisition set-up was developed using FPGAs and fast discriminators for electron counting and voltage-to-frequency converters for beam monitoring. The performance of the new set-up was evaluated in experiments at the Mainz Microtron.

This White Paper is exploring the potential of intense secondary muon, neutrino, and (hypothetical) light dark matter beams produced in interactions of high-intensity electron beams with beam dumps. Light dark matter searches with the approved Beam Dump eXperiment (BDX) are driving the realization of a new underground vault at Jefferson Lab that could be extended to a Beamdump Facility with minimal additional installations. The paper summarizes contributions and discussions from the International Workshop on Secondary Beams at Jefferson Lab (BDX Beyond). Several possible muon physics applications and neutrino detector technologies for Jefferson Lab are highlighted. The potential of a secondary neutron beam will be addressed in a future edition.

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 well-defined state. It requires a longitudinally polarized electron beam and out-of-plane proton detection. This structure function vanishes in the absence of final-state interactions (FSI) involving the ejected proton. Presented are the dependencies of f01′ on the missing momentum (closely related to the initial proton’s Fermi momentum) and the angle between the knocked-out proton and the virtual photon momenta. The role of the spin-orbit interaction in FSI through the L→·S→ term in a nuclear optical potential is discussed.

Abstract The knowledge of scintillation quenching of $$\alpha $$ α -particles plays a paramount role in understanding $$\alpha $$ α -induced backgrounds and improving the sensitivity of liquid argon-based direct detection of dark matter experiments. We performed a relative measurement of scintillation quenching in the MeV energy region using radioactive isotopes ( $$^{222}$$ 222 Rn, $$^{218}$$ 218 Po and $$^{214}$$ 214 Po isotopes) present in trace amounts in the DEAP-3600 detector and quantified the uncertainty of extrapolating the quenching factor to the low-energy region.

For the first time the neutron-rich hydrogen isotope ^{6}H was produced in an electron scattering experiment in the reaction ^{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 scattered electron, the produced proton, and π^{+}, the missing mass spectrum of ^{6}H was obtained. A clear peak above ^{3}H+n+n+n energy threshold was seen resulting in a ground state energy of ^{6}H at 2.3±0.5(stat.)±0.4(syst.)  MeV with a width of 1.9±1.0(stat.)±0.4(syst.)  MeV. This Letter challenges the understandings of multinucleon interactions and presents a new method to study light neutron-rich nuclei with electron scattering experiments.

The ratio of the transverse and longitudinal components of polarization transfer to protons in the quasielastic ((e) over right arrow, e'(p) over right arrow) reaction, P'(x)/P'(z), 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 from distinct nuclear shells, each with different local nuclear densities, has been proposed. In this study, we present such comparisons between four shells, 1s(1/2), 1p(3/2) in C-12 and 1d(3/2), 2s(1/2) in Ca-40. In an effort to account for other many-body effects that may differ between shells, we use a state-of-the-art relativistic distorted-wave impulse-approximation (RDWIA) calculation and present the double ratios (P'(x)/P'(z))(Data)/(P'(x)/P'(z))(RDWIA) as well as the superratios [(P'(x)/P'(z))(A)/(P'(x)/P'(z))(B)](Data)/[(P'(x)/P'(z))(A)/(P'(x)/P'(z))(B)](RDWIA), for chosen shells A and B, as a function of effective local nuclear densities. We find that double ratios for individual shells show a dependence on the probed effective nuclear densities. Studying the super-ratios, we observed a systematic variation between pairs of higher- and lower-density shells.

The ratio of the transverse and longitudinal component of polarization transfer to protons in quasi-elastic $(\vec{e}, e^{\prime} \vec{p}\,)$ reaction, $P^{\prime}_x/P^{\prime}_z$, 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 from distinct nuclear shells, each with different local nuclear densities, has been proposed. In this study, we present such comparisons between four shells, $1s_{1/2}$, $1p_{3/2}$ in $^{12}\mathrm{C}$ and $1d_{3/2}$, $2s_{1/2}$ in $^{40}\mathrm{Ca}$. In an effort to account for other many-body effects that may differ between shells, we use state-of-the-art relativistic distorted-wave impulse-approximation (RDWIA) calculation and present the double ratios, $(P^{\prime}_x/P^{\prime}_z)_{\rm Data}/(P^{\prime}_x/P^{\prime}_z)_{\rm RDWIA}$ as well as the super ratios, $\left[(P^{\prime}_x/P^{\prime}_z)_{\rm A}/(P^{\prime}_x/P^{\prime}_z)_{\rm B}\right]_{\rm Data}/\left[(P^{\prime}_x/P^{\prime}_z)_{\rm A}/(P^{\prime}_x/P^{\prime}_z)_{\rm B}\right]_{\rm RDWIA}$, for chosen shells A and B, as a function of effective local nuclear densities. We find that double ratios for individual shells show a dependence on the probed effective nuclear densities. Studying the ratios, we observed a systematic variation between pairs of higher- and lower-density shells.

A new neutron polarimeter for measuring the neutron's electric form factor was designed and constructed to complement the A1 spectrometer setup at the Mainz Microtron (MAMI). The design is based on a previous polarimeter with significant improvements to halve the error of the extracted form factor. A higher granularity of the polarimeter sections and a deeper first section on the one hand, and a faster readout employing Time-over-Threshold methods to measure the signal amplitudes combined with a high-precision FPGA-based TDC on the other hand will allow to achieve this goal. The performance of the new polarimeter during a first measurement campaign in 2019 using liquid hydrogen and deuterium targets will be discussed.

We present the findings of a study based on a new inelastic electron-scattering experiment on the 12C nucleus focusing on the kinematic region of Q2=0.8 GeV2/c2. The measured cross section is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10%. PAC Codes: 12.20.-m , 25.30.Bf , 41.60.-m

The search for Dark Matter is an integral part of New Physics searches, however, Dark Matter has yet to be observed directly. Theoretical models provide a large parameter space for Dark Matter and allow for different properties of the particles. Models incorporating so-called portal interactions, where Dark Matter interacts with Standard Model particles through a mediator particle, are of special interest. Examples for these are Dark Photon and Axion models, which can be studied at low energy accelerator facilities. The DarkMESA experiment is a beam dump experiment located at the upcoming accelerator MESA at the JGU Mainz. The accelerator provides an electron beam of 155 MeV and 150 μA in extracted beam mode, which, along with the high-power beam dump of the P2 experiment, provides an ideal environment for Light Dark Matter searches. To accurately predict the expected reach and the impact of the detector design of the DarkMESA experiment on it with respect to different Dark Matter models, most notably Dark Photon and Axion mediated models, a Geant4 simulation is used. Here, the current status of the simulations is discussed.

. - Hypernuclear decay pion spectroscopy was established in 2012 at MAMI as a mass spectroscopy method for light hypernuclei. A monochromatic pion peak from 4 Lambda H was successfully observed, and the Lambda binding energy was determined to be B Lambda = 2.157 +/- 0.005(stat.)+/- 0.077(syst.) MeV in the 2014 run. In 2022, an upgrade experiment for 3 Lambda H spectroscopy was conducted using a newly developed Li target. interferometry, which will be applied with the spectrometer calibration to improve the systematic error. The decay pion spectroscopy is planned to be performed at of hypernuclear physics.

We present the findings of a study based on a new inelastic electron-scattering experiment on the ^12C nucleus focusing on the kinematic region of Q^2=0.8 GeV^2/c^2. The measured cross section is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10%.

AbstractWe 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 is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10$$\%$$ % .

In the recent past, a comprehensive experimental program has been worked out at the Mainz Energy-Recovery Superconducting Accelerator, MESA, at the Institute of Nuclear Physics in Mainz. MESA is a high-intensity, low-energy electron accelerator presently under construction and will thereby provide great opportunities to perform a new generation of high-precision scattering experiments. The versatile MAGIX experiment will use MESA's innovative energy recovery technique, with a science focus on the study of hadron structure and few-body systems, dark sector searches, and investigations into reactions pertinent to nuclear astrophysics. An external beam line will supply spin-polarized electrons to the P2 experiment, enabling the performance of sensitive tests of the Standard Model through parity-violating electron scattering. The DarkMESA beam dump experiment, situated behind P2, is dedicated to the search for light dark matter particles.

We present the findings of a study based on a new inelastic electron-scattering experiment on the C-12 nucleus focusing on the kinematic region of Q(2)=0.8GeV(2)/c(2). The measured cross section is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10%.