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Hadron spectroscopy and interactions
No full textIn recent years, lattice QCD calculations of hadron spectroscopy have concentrated on resonances and shallow bound states detected via poles in two- and three-hadron scattering amplitudes. Hadron interactions have therefore become a key focus. In these proceedings, I review the current state of the art and recent advances in methods for studying hadron interactions via finite-volume spectroscopy and finite-volume quantization conditions. I will also review recent spectroscopy studies and results presented at Lattice 2025, with a focus on charmed mesons, the doubly charmed tetraquark, and the doubly bottom tetraquark
Observation of (1S) + Z associated production and measurement of the effective double-parton scattering cross section in proton-proton collisions at = 13 TeV
No full textThe observation of associated production of an (1S) meson with a Z boson and a measurement of the ratio of its fiducial cross section to the fiducial cross section of the Z boson are presented. Both the (1S) meson and the Z boson are identified via decays into a pair of opposite-sign muons. The analysis is based on proton-proton (pp) collision data at = 13 TeV, collected with the CMS detector in 20162018 and corresponding to an integrated luminosity of 138 fb. Using the production of the Z boson decaying into four muons as a normalization channel, the ratio of the fiducial cross sections (pp Z (1S))(Z )((1S) ) to (pp Z)(Z 4) is measured to be = (21.1 55 (stat) 0.6 (syst) 10), where stat and syst denote the statistical and systematic uncertainties, respectively. The result is used to extract the effective double-parton scattering cross section = 13.0. In addition, for the first time, is measured in bins of the transverse momentum of the (1S) meson or of the Z boson
Measurement of event shape variables using charged particles inside jets in proton-proton collisions at = 13 TeV
No full textEvent shape variables, constructed from the four-momenta of the final-state objects in an event, are sensitive to the predictions of quantum chromodynamics in multijet production. A measurement of five event shape variables is presented, using proton-proton collision data collected at a centre-of-mass energy of 13 TeV with the CMS detector during 20162018, corresponding to an integrated luminosity of 138 fb. The variables are evaluated using the charged particles inside jets. After correcting for detector effects, their distributions are compared with the results from the predictions from a number of models for multijet production. Overall, there is general agreement between several theoretical predictions and the data
Surface termination of -GaO(100) as-cleaved single crystals
No full textThe surface of -GaO single crystals cleaved along their (100) plane is investigated using surface X-ray diffraction and atomic force microscopy. The results show that the crystal cleaves at planes formed by edge-sharing oxygen octahedra, thereby breaking the longest and weakest Ga-O bonds. As a consequence, the exposed (100) surface is non-polar in nature. Owing to the crystal symmetry, terraces separated by half the a-axis length of approx. 0.6 nm are formed. These results are important in view of the use of -GaO in thin film form, as exfoliated nano-belts or as nanoribbons in semiconductor high-power applications
Synthesis-Dependent Fluorescence Properties of CsPbBrCl Supercrystals
No full textWe compare the fluorescence properties of CsPbBr2Cl nanocrystals, obtained via two distinct synthetic procedures, and self-assembled into supercrystals using the same antisolvent crystallization technique. By spatially resolved fluorescence (lifetime) measurements we demonstrate that the optical properties of the supercrystals depend on the specific synthesis conditions of the constituting nanocrystals. Using scanning electron microscopy, small-angle X-ray scattering and nuclear magnetic resonance spectroscopy, we find evidence that spatial fluctuations in the supercrystal fluorescence correlate with the ligand sphere of the nanocrystals. Specifically, homogeneous surface passivation of the nanocrystals leads to consistent interparticle distances and increased structural order within the supercrystals, resulting in a uniform fluorescence center wavelength and lifetime. The results of this study emphasize the importance of the relationship between crystalline structure and ligand configuration for the control of the optical properties of lead halide perovskite supercrystals
Challenges and limitations of accelerated stress testing in GDE half-cell set-ups
No full textCommercialisation of proton exchange membrane fuel cells (PEMFCs) depends on accurate and high throughput durability testing at the laboratory scale. With the rotating disk electrode method (RDE) unable to mimic the three-phase boundary scenario in the membrane electrode assembly (MEA), gas diffusion electrode half-cells were proposed for fundamental catalysis research. However, durability testing in such half-cell setups under realistic operational conditions has been limited, and in particular, not yet validated against RDE or FC data. In this paper, an attempt is made to fill part of this knowledge gap by performing accelerated stress tests in thin films, gas diffusion electrodes and membrane electrode assemblies. The results are compared for two selected catalysts with different Pt loading, expected to show broad variations in their degradation behaviour. Accelerated stress tests (ASTs) were performed with various start/stop potentials and load cycles, and the oxygen reduction reaction (ORR) performance studied before and after the AST protocols. The internal resistance of the half-cell was found to be influenced most significantly by gas coverage and temperature changes on the working electrode and must be compensated accordingly. The applied vertex potentials for ASTs after compensation have to be accurate in order to induce the intended degradation phenomena
Development of a Tree-Based Model for the Fast Generation of Large Point Clouds Representing Particle Showers in Calorimeters
No full textIn High-Energy Physics, detailed and time-consuming simulations are neededto describe particle showers in calorimeters. These particle showers arerecorded as energy deposits (hits) in the cells of the detector. To mitigate thecomputational demands of such simulations, surrogate models are widelystudied. In this thesis, Generative Adversarial Networks (GANs) are investigatedas a fast and flexible approach. If the cells of the detector could berepresented by a regular grid, a GAN model would usually use (De-)Convolutionlayers to up/down-scale the number of voxels. However, due tothe often irregular geometry in modern high-granular calorimeters and thesmall fraction of cells with a hit in such detectors, a grid representation isoften not feasible. By representing the shower as a point cloud (PC), i.e., aset of real vectors, these issues can be addressed. In PCs, the complex dependenciesbetween the points must be correctly modeled. Particle showersare inherently tree-like processes, as each particle is produced by the decayor the detector interaction of a particle of the previous generation. With thisinductive bias, a GAN has been developed, that generates such PCs in a treebasedmanner. For this model, numerous new components for Graph NeuralNetworks (GNNs) have been developed that allow up/down-scaling of PCs.This model is applied to two popular benchmark datasets, which both canbe represented as PCs: JetNet, a dataset containing jet constituents, andCaloChallenge, a dataset containing particle showers in calorimeters. Thenovel model achieves a good fidelity on both datasets
Observation of the decay at Belle II
No full textWe measure the branching fraction of the decay using data collected with the Belle II detector at the SuperKEKB collider. The data contain meson pairs produced in energy-asymmetric collisions at the resonance. The measured branching fraction , where the first uncertainty is statistical and the second is systematic, is more precise than previous results and constitutes the first observation of the decay with a significance of standard deviations
Metastability-engineering strategy in CoCrFeMnNi-based medium- and high-entropy alloys: Unraveling the interplay with recrystallization, grain growth, and mechanical properties
No full textNovel face-centered cubic (FCC) phase CoCrFeMnNi-based medium- and high-entropy alloys (M/HEAs) with the following nominal compositions CoCrFeMnNi (Co15Cr15), CoCr-FeMnNi (Co20Cr20), and CoCrFeMnNi (Co25Cr25) in at.%, were designed viametastability-engineering strategy to trigger different deformation mechanisms, such astwinning-induced plasticity (TWIP) and/or transformation-induced plasticity (TRIP). Bothmechanisms are governed by the stacking fault energy (SFE), which depends on composition.Fully recrystallized samples with different grain sizes ranging from 2.7 to 102.5 μm were obtained.Tensile tests were conducted at room temperature (298 K), and Hall-Petch relationshipswere established. The annealed and deformed samples were characterized by a combination ofelectron backscatter diffraction (EBSD), high-energy synchrotron X-ray diffraction (HE-SXRD),and transmission electron microscopy (TEM) to correlate deformation microstructures with phasestability. It was revealed that grain refinement was more effective in the Co25Cr25 alloy, given bythe high Hall-Petch coefficients ( = 516 MPa.μm and = 198 MPa). For a grain size of 2.7μm, the product of yield strength (~500 MPa) and uniform elongation (~45 %) in the Co25Cr25alloy reaches its maximum (~23 GPa%), achieving the optimal strength-ductility synergy. Due tothe decrease in the effective SFE (from 26.6 to 3.5 mJ m), a transition in the dominant deformationbehavior occurred from TWIP (Co15Cr15) to TWIP/TRIP (Co20Cr20) and finally to TRIP(Co25Cr25). The calculations further showed that and the total dislocation density exhibit aninverse relationship with the effective SFE. Such findings highlight the potential of compositionaltuning for developing high-performance M/HEAs with designed deformation mechanisms
Know your footprint - Evaluation of the professional carbon footprint for individual researchers in high energy physics and related fields
No full textUnderstanding the environmental impact of professional activities is becoming paramount in current times, especially within sectors that historically have had significant resource utilisation, such as High Energy Physics (HEP) and related fields. The young High Energy Physicists (yHEP) association launched the Know your footprint (Kyf) campaign to evaluate the CO-equivalent emissions generated by HEP-related research. This study delves into the carbon footprints associated with four distinct categories: Experiments, tied to extensive collaborations with substantial infrastructure; Institutional, representing the resource consumption of research institutes and universities; Computing, focusing on simulations and data analysis; and Travel, covering professional trips such as to conferences, meetings, and workshops. The findings in this assessment are integrated into a tool for self-evaluation, the Know-your-footprint (Kyf) calculator, which allows colleagues to assess their personal and professional footprint, and optionally share their data with the yHEP association. The aim of the Kyf campaign is to heighten awareness, foster sustainability, and inspire the community to adopt more environmentally-responsible research methodologies