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Coarsening behavior and strengthening mechanisms of L12–Ni(Al, Ti) precipitates in a (CoCrNi)AlTi medium-entropy alloy
No full textL12 precipitate-hardened high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) exhibit outstanding mechanical properties. A comprehensive understanding of L12 precipitate behavior is essential to optimize the mechanical performance of these alloys. In this study, the precipitation behavior and corresponding mechanical properties of a (CoCrNi)94Al3Ti3 MEA were systematically investigated under various aging treatments. Aging at 900°C significantly improved the strength–ductility balance compared to conventional L12-hardened MEAs. In particular, the specimen aged at 900°C for 1 h showed an ultimate tensile strength (UTS) of 1102 MPa, a yield strength (YS) of 632 MPa, and an elongation (EL) of 45.7 %. However, prolonged aging to 48 h resulted in a reduction in strength due to the coarsening of the L12 precipitates. Quantitative analysis of the precipitate strengthening contribution revealed that the variation in strength was governed by distinct precipitate strengthening mechanisms: dislocation shearing and dislocation bypassing mechanisms. These findings provide valuable insights for optimizing aging conditions in L12 precipitate-hardened HEAs and MEAs, facilitating the design of next-generation structural materials
Measurement of spin correlation andentanglement in ATLAS and CMS
No full textThe exceptionally large dataset collected by the ATLAS and CMS detectors at the highest proton-proton collision energies provided by the LHC enables precision testing of theoretical predictions using an extensive sample of top quark events. One example of this is the spin correlation of top quarks, which can uniquely be probed due to the decay time being shorter than hadronisation time. This wealth of data has also opened the door to new measurements of top quark properties including those particularly sensitive to the ttbar threshold region, such as quantum entanglement, which were previously beyond reach. This contribution presents the latest highlights in this area from the ATLAS and CMS experiments
Development of systematic uncertainty-aware neural network trainings for binned-likelihood analyses at the LHC
No full textWe propose a neural network training method capable of accounting for the effects of systematic variations of the data model in the training process and describe its extension towards neural network multiclass classification. The procedure is evaluated on the realistic case of the measurement of Higgs boson production via gluon fusion and vector boson fusion in the decay channel at the CMS experiment. The neural network output functions are used to infer the signal strengths for inclusive production of Higgs bosons as well as for their production via gluon fusion and vector boson fusion. We observe improvements of 12 and 16% in the uncertainty in the signal strengths for gluon and vector-boson fusion, respectively, compared with a conventional neural network training based on cross-entropy
Search for electroweak production of vector-like leptons in -lepton and -jet final states in collisions at = 13 TeV with the ATLAS detector
No full textA search for pair-production of vector-like leptons is presented, considering their decays into a third-generation Standard Model (SM) quark and a vector leptoquark () as predicted by an ultraviolet-complete extension of the SM, referred to as the ‘4321’ model. Given the assumed decay of into third-generation SM fermions, the final state can contain multiple -leptons and b-quarks. This search is based on a dataset of pp collisions at TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of up to . No significant excess above the SM background prediction is observed, and 95% confidence level limits on the cross-section times branching ratio are derived as a function of the vector-like lepton mass. A lower observed (expected) limit of 910 GeV (970 GeV) is set on the vector-like lepton mass. Additionally, the results are interpreted for a supersymmetric model with an R-parity violating coupling to the third-generation quarks and leptons. Lower observed (expected) limits are obtained on the higgsino mass at 880 GeV (940 GeV) and on the wino mass at 1170 GeV (1170 GeV)
Magnetometric Studies on Flux Trapping Sensitivity of Superconducting Radiofrequency Cavities
No full textThe increasing demand for high-performance superconducting radiofrequency (SRF) cavities in particle accelerators,especially in free electron lasers, has led to intensified research on optimizing cavity treatments. One promisingrecent development is the application of medium temperature heat treatments, which are typically performed at250 ◦C - 350 ◦C in a vacuum furnace for several hours. It has been shown that these mid-T heat treatmentsenhance cavity performance by increased quality factors. However, the improved performance comes with thetrade-off of an increased sensitivity to trapped magnetic flux of the cavity, which leads to lower quality factors. Forthe first time at DESY, the sensitivity to magnetic flux trapping is deduced from parasitic cavity measurements.The data retrieval and analysis in the scope of this project was only accessible due to a new systematic approachto both experimental test conditions and data acquisition systems. The sensitivity to trapped magnetic flux issystematically investigated on four cavities with very different heat treatments. Magnetic field measurements wereconducted using three magnetic sensors mounted on the cavity equator. Additionally, the temperature gradientsduring the cooldown procedures are analyzed and showed consistencies in regard to the according cavity qualityfactors. Finally, results are compared to data of previous studies. These findings display the complex interplaybetween chemical and heat treatments, material properties and thermal dynamics on SRF niobium cavities. It canbe confirmed that mid-T heat treated cavities show significantly increased sensitivity values 3-5 times higher thanfor cavities without this heat treatment. Moreover, differences in sensor signals after applying an external magneticfield highlight the influence of cavity characteristics, such as grain structure and defects. These findings provide astrong foundation for future optimization of cavity treatments for a second generation of EuXFEL cavities, whichare required for the planned upgrade of the European XFEL accelerator
Effect of the cooldown velocity on the performance of superconducting cavities
No full textThe medium temperature heat treatment of superconducting radio frequency cavities is investigated to asses their use in an upgrade of the European X-ray Free ElectronLaser. For the medium temperature heat treatment, which alters the cavity’s surface, the question is, which influences on the performance of cavities do exist. The objectiveis, the investigation into the effects of the cooldown velocity on the cavity performance. To investigate whether this influence exists, an analytical tool, has been developed, toacquire the cooldown velocity. Furthermore, with the use of this tool the investigation of this dependency was started. The conclusion of the analysis is that the quality factor andresidual resistance are depended on the cooldown velocity. The accelerating gradient and quench limits of the cavities seem to be unaffected. The strength of this degradation of thecavities quality factor is observed to be lower than 15%. This could allow the use of these cavities even if this degradation is unavoidable during the cooldown of the cryomodulesat the European XFEL
Design Initiative for a 10 TeV pCM Wakefield Collider
No full textThis document outlines a community-driven Design Study for a 10 TeV pCM Wakefield Accelerator Collider. The 2020 ESPP Report emphasized the need for Advanced Accelerator R&D, and the 2023 P5 Report calls for the ``delivery of an end-to-end design concept, including cost scales, with self-consistent parameters throughout.' This Design Study leverages recent experimental and theoretical progress resulting from a global R&D program in order to deliver a unified, 10 TeV Wakefield Collider concept. Wakefield Accelerators provide ultra-high accelerating gradients which enables an upgrade path that will extend the reach of Linear Colliders beyond the electroweak scale. Here, we describe the organization of the Design Study including timeline and deliverables, and we detail the requirements and challenges on the path to a 10 TeV Wakefield Collider
Integral Identities from Symmetry Breaking of Conformal Defects
No full textIn conformal field theory, the insertion of a defect breaks part of the global symmetry and gives rise to defect operators such as the tilts and displacements. We establish identities relating the integrated four-point functions of such operators to their two-point functions, derived both from the geometric properties of the defect conformal manifold, which is the symmetry-breaking coset, and from the Lie algebra of the corresponding broken symmetry generators. As an explicit example, we demonstrate these integral identities in the case of the 1/2 BPS Maldacena-Wilson loop in SYM. This contribution serves as a brief review of the main ideas of Phys. Rev. Lett. 129, 201603 (2022), as well as a short preview of our forthcoming paper with Nadav Drukker and Petr Kravchuk. Here we present an independent derivation of the integral identities that will not appear in that work
Constraints on magnetism and correlations in RuO from lattice dynamics and Mössbauer spectroscopy
No full textWe provide experimental evidence for the absence of a magnetic moment in bulk RuO, a candidate altermagnetic material, by using a combination of Mössbauer spectroscopy, nuclear forward scattering, inelastic X-ray and neutron scattering, and density functional theory calculations. Using complementary Mössbauer and nuclear forward scattering, we determine the Ru magnetic hyperfine splitting to be negligible. Inelastic X-ray and neutron scattering-derived lattice dynamics of RuO are compared to density functional theory calculations of varying flavors. Comparisons among theory with experiments indicate that electronic correlations, rather than magnetic order, are key in describing the lattice dynamics