19 research outputs found
Weak magnetic anisotropy in GdRhSi studied by magnetic resonance
The antiferromagnetically (AFM) ordered state of GdRhSi which
consists of AFM-stacked ferromagnetic layers is investigated by magnetic
resonance spectroscopy. The almost isotropic Gd paramagnetic resonance
becomes anisotropic in the AFM ordered region below 107 K. The emerging
internal anisotropic exchange-fields are still small enough to allow an
investigation of their magnetization dynamics by using a standard
microwave-frequency magnetic resonance technique. We could characterize this
anisotropy in detail in the ferromagnetic layers of the excitation at 9 and 34
GHz. We derived a resonance condition for the AFM ordered phase to describe the
weak in-plane anisotropic behaviour in combination with a mean-field analysis.Comment: 7 page
GdRhSi: An exemplary tetragonal system for antiferromagnetic order with weak in-plane anisotropy
The anisotropy of magnetic properties commonly is introduced in textbooks
using the case of an antiferromagnetic system with Ising type anisotropy. This
model presents huge anisotropic magnetization and a pronounced metamagnetic
transition and is well-known and well-documented both, in experiments and
theory. In contrast, the case of an antiferromagnetic - system with weak
in-plane anisotropy is only poorly documented. We studied the anisotropic
magnetization of the compound GdRhSi and found that it is a perfect
model system for such a weak-anisotropy setting because the Gd ions in
GdRhSi have a pure spin moment of S=7/2 which orders in a simple AFM
structure with . We observed experimentally in a
continuous spin-flop transition and domain effects for field applied along the
- and the -direction, respectively. We applied a mean field model
for the free energy to describe our data and combine it with an Ising chain
model to account for domain effects. Our calculations reproduce the
experimental data very well. In addition, we performed magnetic X-ray
scattering and X-ray magnetic circular dichroism measurements, which confirm
the AFM propagation vector to be and indicate the absence of
polarization on the rhodium atoms
Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR
This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented
PANDA Phase One - PANDA collaboration
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or P¯ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper
Structural analysis of the interleukin-8/glycosaminoglycan interactions by amide hydrogen/deuterium exchange mass spectrometry
The recruitment of different chemokines and growth factors by glycosaminoglycans (GAGs) such as chondroitin sulfate or hyaluronan plays a critical role in wound healing processes. Thus, there is a special interest in the design of artificial extracellular matrices with improved properties concerning GAG interaction with common regulating proteins. In this study, amide hydrogen/deuterium (H/D) exchange mass spectrometry (HDX MS) combined with molecular modeling and docking experiments was used to obtain structural models of proinflammatory chemokine interleukin-8 (IL-8) in complex with hexameric chondroitin sulfate. Experiments on the intact protein showed a difference in deuterium labeling of IL-8 due to chondroitin sulfate binding. The extent of deuteration was reduced from 24% to 13% after 2. min exchange time, which corresponds to a reduced exchange of approximately 10 backbone amides. By local HDX MS experiments, H/D exchange information on the complete sequence of IL-8 could be obtained. A significantly reduced H/D exchange, especially of the C-terminal α-helical region comprising amino acids 70-77 and to the loop comprising amino acids 27-29 was observed in the presence of chondroitin sulfate. HDX MS data were used to model the IL-8/chondroitin sulfate complex. The binding interface of IL-8 and chondroitin sulfate determined this way correlated excellently with the corresponding NMR based atomistic model previously published. Our results demonstrate that HDX-MS in combination with molecular modeling is a valuable approach for the analysis of protein/GAG complexes at physiological pH, temperature, and salt concentration. The fact that HDX-MS requires only micrograms of protein and GAGs makes it a very promising technique to address protein-GAG interactions.</p
Study of Excited Baryons with the PANDA Detector
The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards and spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the and spectra. The future antiproton experiment PANDA will provide direct access to final states containing a pair, for which production cross sections up to b are expected in reactions. With a luminosity of in the first phase of the experiment, the expected cross sections correspond to a production rate of eventsday. With a nearly detector acceptance, PANDA will thus be a hyperon factory. In this study, reactions of the type as well as with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between and . This allows high statistics data to be collected within a few weeks of data taking