0000000001108786
AUTHOR
S. Aulenbacher
Beam-normal single spin asymmetry in elastic electron scattering off 28Si and 90Zr
We report on a new measurement of the beam-normal single spin asymmetry $A_{\mathrm{n}}$ in the elastic scattering of 570 MeV transversely polarized electrons off $^{28}$Si and $^{90}$Zr at $Q^{2}=0.04\, \mathrm{GeV}^2/c^2$. The studied kinematics allow for a comprehensive comparison with former results on $^{12}$C. No significant mass dependence of the beam-normal single spin asymmetry is observed in the mass regime from $^{12}$C to $^{90}$Zr.
Ground-state binding energy of HΛ4 from high-resolution decay-pion spectroscopy
Abstract A systematic study on the Λ ground state binding energy of hyperhydrogen H Λ 4 measured at the Mainz Microtron MAMI is presented. The energy was deduced from the spectroscopy of mono-energetic pions from the two-body decays of hyperfragments, which were produced and stopped in a 9Be target. First data, taken in the year 2012 with a high resolution magnetic spectrometer, demonstrated an almost one order of magnitude higher precision than emulsion data, while being limited by systematic uncertainties. In 2014 an extended measurement campaign was performed with improved control over systematic effects, increasing the yield of hypernuclei and confirming the observation with two indepen…
Detector response of Cherenkov radiators for calorimetry in the energy range below 14 MeV
Abstract A study of the detector response of PbF 2 crystals and three different types of lead glass blocks to electrons from a 14-MeV beam of the Mainz Microtron MAMI is presented. For the first time, signal height, signal width, and homogeneity of the response of these Cherenkov radiators were determined for energies between 10 and 14 MeV. To complement the beam tests, optical properties of the materials, in particular measured transmittances in the near UV and visible spectrum, were studied. The measured detector responses were also compared to Monte Carlo simulations of energy-loss, light production, transport, and detection. These Cherenkov radiators are considered as active material o…
Electron beam studies of light collection in a scintillating counter with embedded fibers
The light collection of several fiber configurations embedded in a box-shaped plastic scintillating counter was studied by scanning with minimum ionizing electrons. The light was read out by silicon photomultipliers at both ends. The light yield produced by the 855-MeV beam of the Mainz Microtron showed a strong dependence on the transverse distance from the beam position to the fibers. The observations were modeled by attributing the collection of indirect light inside of the counter and of direct light reaching a fiber to the total light yield. The light collection with fibers was compared to that of a scintillating counter without fibers. These studies were carried out within the develop…
Operation and characterization of a windowless gas jet target in high-intensity electron beams
Abstract A cryogenic supersonic gas jet target was developed for the MAGIX experiment at the high-intensity electron accelerator MESA. It will be operated as an internal, windowless target in the energy-recovering recirculation arc of the accelerator with different target gases, e.g., hydrogen, deuterium , helium, oxygen, argon, or xenon. Detailed studies have been carried out at the existing A1 multi-spectrometer facility at the electron accelerator MAMI. This paper focuses on the developed handling procedures and diagnostic tools, and on the performance of the gas jet target under beam conditions. Considering the special features of this type of target, it proves to be well suited for a n…
Experimental investigations of the hypernucleus $_Λ^4$H
International audience; Negatively charged pions from two-body decays of stopped _Lambda^4H hypernuclei were studied in 2012 at the Mainz Microtron MAMI, Germany. The momenta of the decay-pions were measured with unprecedented precision by using high-resolution magnetic spectrometers. A challenge of the experiment was the tagging of kaons from associated K^+∧ production off a Be target at very forward angles. In the year 2014, this experiment was continued with a better control of the systematic uncertainties, with better suppression of coincident and random background, improved particle identification, and with higher luminosities. Another key point of the progress was the improvemen…
Design and Operation of a Windowless Gas Target Internal to a Solenoidal Magnet for Use with a Megawatt Electron Beam
A windowless hydrogen gas target of nominal thickness $10^{19}$ cm$^{-2}$ is an essential component of the DarkLight experiment, which is designed to utilize the megawatt electron beam at an Energy Recovery Linac (ERL). The design of such a target is challenging because the pressure drops by many orders of magnitude between the central, high-density section of the target and the surrounding beamline, resulting in laminar, transitional, and finally molecular flow regimes. The target system was assembled and operated at Jefferson Lab's Low Energy Recirculator Facility (LERF) in 2016, and subsequently underwent several revisions and calibration tests at MIT Bates in 2017. The system at dynamic…
Beam-normal single spin asymmetry in elastic electron scattering off Si and Zr
We report on a new measurement of the beam-normal single spin asymmetry An in the elastic scattering of 570 MeV transversely polarized electrons off $^{28}$Si and $^{90}$Zr at Q2=0.04 GeV2/c2. The studied kinematics allow for a comprehensive comparison with former results on $^{12}$C. No significant mass dependence of the beam-normal single spin asymmetry is observed in the mass regime from $^{12}$C to $^{90}$Zr.