The proton–proton elastic differential cross section at very small four momentum transfer squared has been measured at three different incident proton momenta in the range of 2.5 to 3.2 GeV/c by ...detecting the recoil proton at polar angles close to 90∘. The measurement was performed at COSY with the KOALA detector covering the Coulomb–nuclear interference region. The total cross section σtot, which has been determined precisely, is consistent with previous measurements. The values of the slope parameter B and the relative real amplitude ratio ρ determined in this experiment alleviate the lack of data in the relevant energy region. These precise data on ρ might be an important check for a new dispersion analysis.
Mapping the density distribution and monitoring density changes under volcanoes and geological reservoirs is a major challenge in geology and volcanology. Muon radiography has a high potential to ...advance this field, but often there are no inexpensive high-end detectors available that are suitable for field installations. A DIRC-type Cherenkov detector as a muon camera has a small dimension and is suited for such field applications (MagmaDIRC idea). In measuring directions and energies of the incoming muons one can turn the mass density integrals along the lines of flight into a radiography image, and by discarting low-energy muons with their blurred angular information one obtains sharper images. In particular one may detect the time variation of the mass density distributions situated above the horizon line in a volcanic edifice that occurs when magma is filling its plumbing system or when the level of a lava lake changes. Using numerical simulations, we discuss design aspects and the requirements of such a DIRC system. Two sites are identified for proof-of-principle field measurements. The required measurement times are estimated for the given site conditions and morphology based on the specifications of an operational DIRC system. The merits of DIRC sensors are contrasted to other muon radiography techniques.
The current understanding of light hypernuclei, which are sub-atomic nuclei with strangeness, is being challenged and studied in detail by several European research groups and collaborations. In ...recent years, studies of hypernuclei using high-energy heavy ion beams have reported unexpected results on the three-body hypernuclear state
3
Λ
H, named the hypertriton. For some time, reports of a shorter lifetime and larger binding energy than what was previously accepted have created a puzzling situation for its theoretical description; this is known as the "hypertriton puzzle". With the inclusion of the most recent experimental measurements, the current status of the hypertriton puzzle is evolving. Additionally, the possible neutral bound state of a Λ hyperon with two neutrons, nnΛ, has raised questions about our understanding of the formation of light hypernuclei either in bound or resonance states. These results have initiated several ongoing experimental programs all over the world to study these three-body hypernuclear states precisely. We are studying these light hypernuclear states by employing heavy ion beams at 2
A
GeV on a fixed carbon target with the WASA detector system and the Fragment Separator (FRS) at GSI. The WASA-FRS experimental campaign was performed during the first quarter of 2022, and this paper presents a short overview of the campaign and how it seeks to tackle the hypertriton and nnΛ puzzles. Data analysis is ongoing, and several preliminary results will be reported.
The fission probability P(f) of highly excited targetlike nuclei produced in reactions of 2.5 GeV protons on Au, Bi, and U was studied as a function of excitation energy E* whereby E* is deduced ...eventwise from the multiplicity of evaporated light particles. At the highest E* of 1000 MeV P(f) amounts to approximately 30% with all 3 target nuclei irrespective of the initial fissility. Statistical-model calculations satisfactorily reproduce the observed evolution of P(f) with E*--provided that no extra transient delay is introduced. Fission thus is decided upon very fast and early in the long deexcitation chain towards scission which comprises as much as approximately 80% of all evaporated alpha particles.
Absolute cross sections, energy spectra, and angular distributions have been measured for
1,2,3H,
3,4,6He,
6,7,8,9Li and
7,9,10Be isotopes produced in 1.2 GeV proton-induced spallation reactions with ...targets between Al and Th. Results of simulation calculations with the intra-nuclear cascade code INCL2.0 coupled to the statistical model GEMINI are in good agreement with these data, as to charged-particle evaporation, mean excitation energy, and mean linear momentum transfer. The pre-equilibrium emission of composite particles, not accounted for in these simulations, however, typically contributes to the total production of composite particles by 40–60% for
2H and
3He, 20–40% for
3H, 5–20% for
4He, and about 15–25% for Li and Be. The composite pre-equilibrium particles together carry off a mean energy of up to 50 MeV, i.e., about 30% compared to the mean energy released by particle evaporation. For deuterons, pre-equilibrium emission is shown to be well described by surface coalescence while definitely other mechanisms are required for
4He and heavier clusters.
We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam ...bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10^{-29} e cm.
A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by ν(s)=γG (γ is the ...Lorentz factor, G the gyromagnetic anomaly). At 970 MeV/c, the deuteron spins coherently precess at a frequency of ≈120 kHz in the Cooler Synchrotron COSY. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order 10^{-8}, and to 1×10^{-10} for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics; controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.
The reliability and relevance of experimental data and calculations for the design and construction of the target assembly of spallation neutron sources are discussed. New experimental data obtained ...in a new approach for neutron production in thick targets of Pb and U are presented for 2–5
GeV/
c hadrons. It is found that the observed mean neutron multiplicities depend essentially on the incident available energy only while the variation with particle species for p, d,
p
, K, and π is within 10%.
We have developed a compact detector for measuring beam particles using plastic scintillators readout through Multi-Pixel Photon Counters, which is employed for hypernuclear measurements in the ...WASA-FRS experiment at GSI. The Time-of-Flight resolution of the newly-developed detector has been investigated in relation to the overvoltage with respect to the breakdown voltage, a maximum counting rate of approximately 3×106/s per segment, and a maximum beam charge of Z = 6. The evaluated Time-of-Flight resolutions between the neighboring segments of the detector range from 44.6±1.3 ps to 100.3±3.6 ps (σ) depending on the segment, overvoltage values, and beam intensity. It is also observed that the Time-of-Flight resolution is inversely correlated to the beam atomic charge (Z).
Neutron experimental data relevant to the design of the target of neutron spallation sources are presented and discussed. The data include the reaction cross-sections for W, Hg and Pb investigated ...with 0.4, 0.8, 1.2, 1.8 and 2.5 GeV proton beams as well as the neutron production, neutron multiplicity distribution, as determined event per event using a high-efficiency detector. The production as a function of target material is investigated for both thin (with a single reaction) and thick targets (multiple reactions). Comparisons are made with the predictions of a high-energy transport code.
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