The helicity-dependent recoil proton polarizations P_{x}^{'} and P_{z}^{'} as well as the helicity-independent component P_{y} have been measured in the p(eover →,e^{'}pover →)π^{0} reaction at ...four-momentum transfer Q^{2}≃0.1 GeV^{2}, center-of-mass proton emission angle θ_{p}^{*}≃90°, and invariant mass W≃1440 MeV. This first precise measurement of double-polarization observables in the energy domain of the Roper resonance P_{11}(1440) by exploiting recoil polarimetry has allowed for the extraction of its scalar electroexcitation amplitude at an unprecedentedly low value of Q^{2}, establishing a powerful instrument for probing the interplay of quark and meson degrees of freedom in the nucleon.
The MAGIX focal plane time projection chamber Caiazza, S S; Achenbach, P; Aulenbacher, S ...
Journal of physics. Conference series,
04/2020, Letnik:
1498, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The MAGIX experiment is a versatile system optimized for low-energy nuclear and particle physics measurements. The setup is currently under development and will be installed at the MESA electron ...accelerator, at the Institute for Nuclear Physics of the University of Mainz. The main detectors of that experiment are a couple of high-precision magnetic spectrometers, each of them equipped with a GEM-based TPC at the focal plane to achieve a momentum resolution and angular resolution at the scattering vertex respectively of ≈δPP<10−4and≈1 1 mrad on scattered electron momenta between 1 MeV/c and 105 MeV/c. The limiting factor to achieve those results is the amount and uniformity of the material before the focal plane and even the presence of the TPC field cage can be relevant. Therefore we developed, and hereby introduce, an open field-cage TPC to fulfil those challenging requirements.
The cross section of the p(e,e′π+)n reaction has been measured for five kinematic settings at an invariant mass of W=1094 MeV and for a four-momentum transfer of Q2=0.078 (GeV/c)2. The measurement ...has been performed at MAMI using a new short-orbit spectrometer (SOS) of the A1 collaboration, intended for detection of low-energy pions. The transverse and longitudinal cross section terms were separated using the Rosenbluth method and the transverse-longitudinal interference term has been determined from the left-right asymmetry. The experimental cross section terms are compared with the calculations of three models: DMT2001, MAID2007 and χMAID. The results show that we do not yet understand the dynamics of the fundamental pion.
We report on a new experimental method based on initial-state radiation (ISR) in e–p scattering, which exploits the radiative tail of the elastic peak to study the properties of electromagnetic ...processes and to extract the proton charge form factor (GEp) at extremely small Q2. The ISR technique was implemented in an experiment at the three-spectrometer facility of the Mainz Microtron (MAMI). This led to a precise validation of radiative corrections far away from elastic line and provided first measurements of GEp for 0.001≤Q2≤0.004(GeV/c)2.
The BESIII experiment at the BEPCII electron positron collider at IHEP (Beijing) is collecting data in the charm-τ mass region. Electron positron collisions are a very well suited environment for the ...study of initial state radiation (ISR). However, the photons from ISR are strongly peaked towards small polar angles and are currently detected with limited efficiency. In order to increase the detection efficiency of ISR photons, we are developing small-size calorimeters to be placed in the very forward and backward regions. Each detector will consist of two 4×3 arrays of 1×1×14cm3 LYSO crystals. A 1cm gap separating each of the two arrays will reduce the contamination from background at very low angles. The scintillation light will be collected by silicon photomultipliers (SiPMs). The expected event rate in the MHz range requires flash ADCs recording the preamplified SiPM outputs.The digitized waveforms will be analyzed in realtime yielding data reduction and pile-up detection. This high bandwidth data stream will be transmitted via optical fibers to FPGA-based hardware performing sub-event building, buffering, and event correlation with the BESIII trigger. The sub-events with a corresponding trigger will be sent to the BESIII event builder via TCP/IP. A single crystal equipped with a SiPM was instrumented as a prototype detector. Tests with radioactive sources were performed successfully.
.
The differential cross section was measured for the
12
C(e,e’pp)
10
Be
g.s.
reaction at energy and momentum transfers of 163MeV and 198MeV/
c
, respectively. The measurement was performed at the ...Mainz Microtron by using two high-resolution magnetic spectrometers of the A1 Collaboration and a newly developed silicon detector telescope. The overall resolution of the detector system was sufficient to distinguish the ground state from the first excited state in
10
Be. We chose a super-parallel geometry that minimizes the effect of two-body currents and emphasizes the effect of nucleon-nucleon correlations. The obtained differential cross section is compared to the theoretical results of the Pavia reaction code in which different processes leading to two-nucleon knockout are accounted for microscopically. The comparison shows a strong sensitivity to nuclear-structure input and the measured cross section is seen to be dominated by the interplay between long- and short-range nucleon-nucleon correlations. Microscopic calculations based on the
ab initio
self-consistent Green’s function method give a reasonable description of the experimental cross section.
Offline Software for the PANDA Luminosity Detector Karavdina, A; Denig, A; Feldbauer, F ...
Journal of physics. Conference series,
06/2014, Letnik:
513, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
In 2018 data taking for hadronphysics facility PANDA is planned to commence. It will be build at the antiproton accelerator HESR, which itself is a part of the FAIR complex (GSI, Darmstadt, Germany). ...The luminosity at PANDA will be measured by a dedicated sub-detector, which will register scattered antiproton tracks from pp elastic scattering. From a software point of view, the Luminosity Detector is a tracking system. Therefore the most of its offline software parts are typical for a track reconstruction. The basic concept and Monte Carlo based performance studies of each reconstruction step is presented in this paper.
At the Institute for Nuclear Physics in Mainz the new electron accelerator MESA will go into operation within the next years. The high-power beam dump of the P2 experiment is ideally suited for a ...parasitic dark sector experiment — DarkMESA. In the first stage 1,000 high density Cherenkov radiators from a previous experiment will be used. The experiment is studied with a simulation based on MadGraph and Geant4. The simulation includes an optical photon study, where the response of possible calorimeter materials – PbF2, BGO, the Pb glasses SF5, SF6 and SF57HTultra from Schott – was investigated. The simulation outcomes are compared with the results of prototypes tested at the Mainz Microtron (MAMI) with 6 to 14 MeV electrons. The exclusion limits for PbF2 are shown, together with the limits obtained incrementally adding Pb glass blocks in two successive phases. The current development status of a prototype detector will be described, including a concept for a cosmics veto system.
A new Silicon Detector Telescope has been constructed and installed within the experimental facility of the A1 collaboration at Mainz Microtron, with the goal to detect low-energy protons. It ...consists of seven silicon layers for energy and angle measurement and a plastic scintillator for triggering purposes. The detector subtends a solid angle up to 88msr, depending on the distance from the target and covers the proton kinetic energy range of 25–41 MeV with the mean energy resolution σE=0.47MeV, operating at 500kHz. Digital signal processing methods applied for energy reconstruction have been important for keeping the acceptable energy resolution at high counting rates. The Silicon Detector Telescope has been successfully used in double and triple coincidence measurements along with the magnetic spectrometers of the A1 collaboration.
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