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Polarization transfer in hard x-ray Rayleigh scattering for non-coplanar geometry
No full textWe present an experimental study of the Rayleigh scattering of highly linearly polarized hard x rays. For thisstudy, photons produced by a synchrotron source with an energy of 175 keV are scattered by a thin gold foiltarget. While the linear polarization in terms of degree of polarization and its orientation of the incident photonbeam are well known, the outgoing scattered photons are analyzed by means of Compton polarimetry. For this,a polarimeter detector is positioned at different observation angles with respect to the incident photon beam. Forthe first time the polarization of elastically scattered photons outside of the polarization plane of the incidentradiation is investigated, enabling novel access to a so-far untested component of the polarization transfer. Theexperimental findings are compared to predictions of two theoretical models. It is found that, when leaving thepolarization plane of the incident photon beam, a strong deviation from the form factor approximation is evident,while calculations of the Rayleigh scattering in the S-matrix approach agree with the experimental results.Furthermore, this study is a foundation for future experiments dedicated to a polarization-resolved analysis ofDelbrück scattering
Inhibitors of GapN-dependent NADPH supply as potential lead compounds for novel therapeutics against Streptococcus pyogenes
No full textInfections with Streptococcus pyogenes are among the most important diseases caused by bacteria and are responsible for around 500,000 deaths every year. In 2024, macrolide-resistant S. pyogenes was added to the WHO’s list of priority pathogens. The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase GapN has been identified as a potential drug target in S. pyogenes. SpyGapN is the major NADP-reducing enzyme in these bacteria as they lack the oxidative part of the pentose phosphate pathway. In this study, in silico docking of compound libraries to the glyceraldehyde 3-phosphate binding pocket of SpyGapN was used to screen for potential competitive inhibitors. Among the candidates identified with this approach, 1,2-dihydroxyethane-1,2-disulfonate (glyoxal bisulfite) showed the strongest inhibition of SpyGapN activity in vitro. In a complementary approach, crystallographic fragment screening was conducted, which identified the ultra-low-molecular-weight compounds pyrimidine-5-amine and 4-hydroxypyridazine targeting the cofactor-binding pocket of SpyGapN. Both low-molecular-weight compounds were experimentally confirmed to inhibit the activity of purified SpyGapN. Combinations of glyoxal bisulfite with either pyrimidine-5-amine or 4-hydroxypyridazine enhanced the inhibitory effect of SpyGapN. Glyoxal bisulfite was able to kill S. pyogenes. This effect was accelerated by combining glyoxal bisulfite with 4-hydroxypyridazine. While these findings suggest that inhibition of SpyGapN probably contributes to the observed antibacterial activity, the exact mechanism of action remains to be confirmed, as the compounds also affect other G3P-converting enzymes. Nevertheless, these compounds provide a promising starting point for the development of more specific SpyGapN inhibitors
Study of via initial-state radiation at Belle~II
No full textUsing a data sample of 427.9 fb collected by the Belle~II detector at or near the and resonances, the cross sections for at center-of-mass energies ranging from 3.8 GeV or the production threshold to 5.5/6.0/7.0 GeV have been measured via initial-state radiation. The cross sections for the processes and are consistent with previously published results. The cross sections for these channels obtained by combining with previous Belle results are also given. The process is investigated for the first time. The yields are small and no significant structure is observed in the cross section versus energy. Searches for vector charmonium-like states in the systems, and for associated intermediate states in the systems, are also presented
Measurement of time-dependent CP asymmetries in decays at Belle and Belle II
No full textWe present a measurement of the time-dependent CP asymmetry in decays using a data set of 365 fb recorded by the Belle II experiment and the final data set of 711 fb recorded by the Belle experiment at the Υ(4S) resonance. The direct and mixing-induced time-dependent CP violation parameters C and S are determined along with two additional quantities, S and S, defined in the two halves of the plane. The measured values are C = −0.17 ± 0.09 ± 0.04, S = −0.29 ± 0.11 ± 0.05, S = −0.57 ± 0.23 ± 0.10 and S = 0.31 ± 0.24 ± 0.05, where the first uncertainty is statistical and the second systematic.[graphic not available: see fulltext
Searching for axion dark matter near relaxing magnetars
No full textAxion dark matter passing through the magnetospheres of magnetars can undergo hyperefficient resonant mixing with low-energy photons, leading to the production of narrow spectral lines that could be detectable on Earth. Since this is a resonant process triggered by the spatial variation in the photon dispersion relation, the luminosity and spectral properties of the emission are highly sensitive to the charge and current densities permeating the magnetosphere. To date, a majority of the studies investigating this phenomenon have assumed a perfectly dipolar magnetic field structure with a near-field plasma distribution fixed to the minimal charge-separated force-free configuration. While this may be a reasonable treatment for the closed field lines of conventional radio pulsars, the strong magnetic fields around magnetars are believed to host processes that drive strong deviations from this minimal configuration. In this work, we study how realistic magnetar magnetospheres impact the electromagnetic emission produced from axion dark matter. Specifically, we construct charge and current distributions that are consistent with magnetar observations and use these to recompute the prospective sensitivity of radio and submillimeter telescopes to axion dark matter. We demonstrate that the two leading models yield vastly different predictions for the frequency and amplitude of the spectral line, indicating systematic uncertainties in the plasma structure are significant. Finally, we discuss various observational signatures that can be used to differentiate the local plasma loading mechanism of an individual magnetar, which will be necessary if there is hope of using such objects to search for axions
Three-body study of the from lattice QCD
No full textWe discuss an ongoing first lattice study of the doubly-charmed tetraquark (3875) via a three-body approach. We investigate the system in the , sector, where the appears as a pole in the elastic scattering amplitude. The approach automatically incorporates two-body and three-body effects and treats left-hand cuts due to single exchanges. Two CLS ensembles, X252 and X253, with pion mass MeV, are used, and an operator set comprised of two- and three-hadron and tetraquark operators is employed to extract finite-volume energies. Additional inputs are required for the three-body finite-volume analysis, in the form of amplitudes for the and two-body subsystems. We present preliminary results for these subchannels and perform exploratory three-body spectra determinations for simple choices of the three-particle K-matrix , allowing a first comparison to the lattice spectrum
Inducing Ferroquadrupolar Order with Applied Magnetic Field in
No full textIn this work, we demonstrate a remarkable field-induced ferroquadrupolar phase emanating from the magnetoelastic coupling. Using synchrotron x-ray and neutron diffraction, heat capacity measurements, as well as mean-field modeling, we show that above the critical magnetic field, ferroquadrupolar order is stabilized as the main order parameter, in competition with the field-induced magnetic polarization. This is revealed by a severe lattice distortion and the suppression of antiferromagnetic ordering of the dipole moments. Even in zero magnetic field, the previously reported antiferromagnetic order is a mixed quadrupolar-dipolar phase, further highlighting the crucial role of spin-lattice interactions. This complete understanding of the magnetoelastic phase diagram establishes as a model system for studying nematic-antiferromagnetic transitions and provides key Hamiltonian parameters for its description
In situ observation of a transient intermediate state during metastable solidification of a Fe–Cr–Ni alloy
No full textLiquid-to-solid phase transformations mediated by intermediary transitional metastable states have garnered significant interest due to their potential to uncover materials with unique morphologies and functionalities absent under equilibrium conditions. In this study, the metastable-to-stable transformation from a body-centered cubic (bcc) to a face-centered cubic (fcc) structure is investigated during the solidification of an undercooled Fe–16Cr–12Ni alloy using containerless electromagnetic levitation combined with in situ synchrotron X-ray diffraction (XRD). Time-resolved diffraction patterns reveal unexpected peak shifts and splitting during the early stage of the transformation, indicating pronounced lattice distortions in the emerging fcc phase. Detailed analysis of multiple symmetry-sensitive reflections suggests that the transformation proceeds through a transient intermediate state characterized by a short-lived, symmetry-lowering lattice distortion with an fct-like character. This distortion relaxes rapidly as the system evolves toward the thermodynamically stable fcc structure. These observations point to a non-equilibrium transformation pathway in which localized strain and defect-mediated processes play an important role during rapid solidification. The findings provide new insight into multistep, non-equilibrium phase transformation dynamics relevant to alloy design, additive manufacturing, and rapid solidification processing
A quantitative study of two-loop splitting in double parton distributions
No full textDouble parton distributions at small distances between the two partons are dominated by a mechanism in which the two observed partons originate from the splitting of a single parton. This contribution can be computed in terms of single-parton distributions and perturbative splitting kernels. We demonstratethat two-loop corrections to these kernels can have a substantial quantitative impact and considerably improve the stability of predictions for double parton scattering. We also consider the impact of heavy quark masses in the two-loop splitting kernels in an approximate manner
Observation of production at 13 TeV with the ATLAS detector
No full textThis paper presents the first observation of top-quark pair production in association with two photons (). The measurement is performed in the single-lepton decay channel using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider. The data correspond to an integrated luminosity of 140 fb recorded during Run 2 at a centre-of-mass energy of 13 TeV. The production cross section, measured in a fiducial phase space based on particle-level kinematic criteria for the lepton, photons, and jets, is found to be , corresponding to an observed significance of 5.2 standard deviations. Additionally, the ratio of the production cross section of to top-quark pair production in association with one photon is determined, yielding