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Detecting LHC neutrinos at surface level
No full textThe first direct detection of neutrinos at the LHC not only marks the beginning of a novel collider neutrino program at CERN but also motivates considering additional neutrino detectors to fully exploit the associated physics potential. As the existing forward neutrino detectors are located underground, it is interesting to investigate the feasibility and physics potential of neutrino experiments located at the surface-level. A topographic desk study is performed to identify all points at which the LHC’s neutrino beams exit the earth. The closest location lies about 9 km east of the CMS interaction point, at the bottom of Lake Geneva. Several detectors to be placed at this location are considered, including a water Cherenkov detector and an emulsion detector. The detector designs are outlined at a conceptual level, and projections for their contribution to the LHC forward neutrino program and searches for dark sector particles are presented. However, the dilution of the neutrino flux over distance reduces the neutrino yield significantly, necessitating large and coarse detector designs. We identify the experimental challenges to be overcome by future research, and conclude that at present the physics potential of surface-level detectors is limited in comparison to ones closer to the interaction point, including the proposed Forward Physics Facility
Exploration at the high-energy frontier: ATLAS Run 2 searches investigating the exotic jungle beyond the Standard Model
No full textThis report presents a comprehensive collection of searches for new physics performed by the ATLAS Collaboration during the Run 2 period of data taking at the Large Hadron Collider, from 2015 to 2018, corresponding to about 140 fb of =13 TeV proton–proton collision data. These searches cover a variety of beyond-the-standard model topics such as dark matter candidates, new vector bosons, hidden-sector particles, leptoquarks, or vector-like quarks, among others. Searches for supersymmetric particles or extended Higgs sectors are explicitly excluded as these are the subject of separate reports by the Collaboration. For each topic, the most relevant searches are described, focusing on their importance and sensitivity and, when appropriate, highlighting the experimental techniques employed. In addition to the description of each analysis, complementary searches are compared, and the overall sensitivity of the ATLAS experiment to each type of new physics is discussed. Summary plots and statistical combinations of multiple searches are included whenever possible
UTe2: A narrow-band superconductor
No full textWe investigate the nature of the 5 electrons in the unconventional odd-parity superconductor UTe, focusing on the degree of covalency, localization versus itinerancy, and dominant electronic configuration. This is achieved using density functional theory (DFT) in combination with dynamical mean-field theory (DMFT) calculations. A key aspect of our approach is the material-specific tuning of the double-counting correction parameter, , within the DFT+DMFT part. This tuning is guided by the energy dependence of photoionization cross sections in valence band photoelectron spectroscopy. The reliability of the parameters is confirmed by the accurate reproduction of the angle-resolved valence-band photoemission spectra and the U4core-level data. The DFT+DMFT model reveals that in UTe U5^ configurations with =1–4 contribute to the ground state, with the 5configuration being most prevalent and an average 5 shell filling close to 2.5. The model further suggests that the 5 electrons form narrow bands and that charge fluctuations due to degeneracy play a role in addition to coherent valence dynamics arising from hybridization with the conduction bath. Additionally, the significance of the U6 states in UTe is discussed
The Helmholtz Model Zoo: A Cloud-Based Platform for AI Model Sharing and Inference in the Helmholtz Association
No full textThe Helmholtz Model Zoo (HMZ) is a cloud-based platform enabling seamless sharing and inference of deep learning models across the HelmholtzAssociation’s 18 research centers. By automating model deployment andproviding both web and programmatic interfaces, the HMZ lowers technicalbarriers to AI adoption in scientific research. Integrated with Helmholtzinfrastructure (Helmholtz ID authentication, dCache storage, DESY’s HPCcluster with NVIDIA L40S GPUs), the platform ensures secure, scalable inference while maintaining data sovereignty. NVIDIA Triton Inference Serverand Slurm manage GPU resources efficiently, supporting data-sets from gigabytes to terabytes. Virtual organizations enable fine-grained access controlfor specialized models. Launched in July 2025 in beta, the HMZ focuseson domain-specific applications, with future plans for model quality metricsand agentic capabilities
Colossal Effect of Nanopore Surface Ionic Charge on the Dynamics of Confined Water
No full textInterfacial interactions significantly alter the fundamental properties of water confined in mesoporous structures with crucial implications for geological, physicochemical, and biological processes. Herein, we focused on the effect of changing the surface ionic charge of nanopores with comparable pore sizes (3.5–3.8 nm) on the dynamics of confined liquid water. The control of the pore surface ionicity was achieved by using two periodic mesoporous organosilicas (PMOs) containing either neutral or charged forms of a chemically similar bridging unit. The effect on the dynamics of water at the nanoscale was investigated in the temperature range 245–300 K, encompassing the glass transition by incoherent quasi-elastic neutron scattering (QENS). For both types of PMOs, the water dynamics revealed two distinct types of molecular motions: rapid local movements and translational jump diffusion. While the neutral PMO induces a moderate confinement effect, we show that the charged PMO drastically slows down water dynamics, reducing translational diffusion by a factor of 4 and increasing the residence time by an order of magnitude. Notably, by changing the pore filling values, we demonstrate that for charged PMOs, this effect extends beyond the interfacial layer of surface-bound water molecules to encompass the entire pore volume. Thus, our observation indicates a dramatic change in the long-range character of the interaction of water confined in nanopores with surface ionic charge compared to a simple change in hydrophilicity. This is relevant for the understanding of a broad variety of applications in (nano)technological phenomena and processes such as nanofiltration and membrane design
The Non-Planar Four-Point Integrand and Konishi Dimension in = 4 Super Yang-Mills Theory at Five Loops
No full textWe compute the complete non-planar integrand for the correlation function of four lightest scalar operators in = 4 super Yang-Mills theory at five-loop order. This is equivalent to the super-correlator of nine stress-tensor multiplets in the self-dual theory. Starting with an ansatz of f-graphs, we impose constraints from light-cone limits, and fix the remaining freedom by using the reformulation of the theory in twistor space. We develop an efficient GPU-based algorithm for the numerical evaluation of the twistor rules. As an application, we extract the five-loop non-planar anomalous dimension of the Konishi operator. Our code and result are provided in ancillary files
Toward realistic multiscale simulations of nanoparticle injection devices used for single particle diffractive imaging
No full textSingle-particle diffractive imaging (SPI) is a powerful technique used in structural biology and nanoscience to determine the three-dimensional structure of individual nanoparticles, biomolecules, and viruses without the need for crystallization. By exposing freely flowing particles to ultrafast X-ray free-electron laser (XFEL) pulses, SPI captures diffraction patterns that can be reconstructed into high-resolution images. Efficient and accurate modeling and simulation of nanoparticle injection systems are essential for designing and optimizing injectors that deliver high-density, well-collimated particle streams – an important requirement for maximizing hit rates and image quality in SPI experiments. This thesis addresses these challenges by developing and optimizing multiscale simulation methodologies for nanoparticle injection devices, with a particular focus on aerodynamic lens systems (ALS) and its combination with cryogenically cooled buffer-gas cells (BGC). A hybrid molecular-continuum simulation framework, integrating classic Computational Fluid Dynamics (CFD) based on the continuum assumption and the Direct Simulation Monte Carlo (DSMC) method based on the kinetic theory of gases, is employed to accurately capture the carrier gas flow and nanoparticle trajectories across diverse flow regimes. The approach improves the computational efficiency by selectively applying DSMC in regions where molecular-scale effects dominate, while using CFD for low Knudsen number regions. Comprehensive evaluations of drag force models from the literature including molecular drag formulations are conducted, along with the introduction of a relaxation-based correction for highly rarefied, low-speed flows, to enhance particle trajectory predictions, particularly in transitional and rarefied regimes. The framework’s scalability and computational performance are assessed through detailed benchmarking, while sensitivity analyses on DSMC parameters such as particle number, grid size, and time step size further guide efficient model implementation. Key benchmark cases, including gas dynamic nozzles and re-entry vehicles, demonstrate the framework’s versatility in simulating internal and external flows. The ALS configuration highlights the framework’s applicability to injector modeling, where the hybrid DSMC/CFD approach combined with improved drag models achieve excellent agreement with experimental data, outperforming conventional CFD. Further validation against measured beam widths and focus positions is carried out for BGC and combined BGC-ALS setups across different particle sizes and inlet pressures. This validated setup is then used to assess the injector performance, with emphasis on proteinsized nanoparticles, enabling an insightful evaluation of the focusing efficiency and beam quality under realistic SPI conditions. Notably, the BGC-ALS configuration, through cryogenic cooling, enhances the focusing of smaller particles by reducing thermal velocities and suppressing Brownian motion, thereby improving the beam collimation – ideal for SPI experiments. By bridging gaps in current methodologies, validating simulation results against experimental data, and advancing drag force modeling techniques, this thesis establishes a robust foundation for optimizing SPI injector systems and paving the way for future innovations in nanoparticle injection technologies
Emergent Spin‐Glass Behavior in an Iron(II)‐Based Metal–Organic Framework Glass
No full textMetal–organic framework (MOF) glasses combine the structural tunability of crystalline MOFs with the processability of amorphous materials, offering exciting opportunities for functional hybrid materials. Here, a one-pot, solvent-free synthesis is reported of an Fe2+-based MOF glass, gFe-tBubipy, with the composition [Fe2(im)3.12(bim)0.88(tBubipy)0.11]·[Fe(Cp)2]0.09 (im− = imidazolate, bim− = benzimidazolate, tBubipy = 4,4′-di-tert-butyl-2,2′-bipyridine, Cp− = cyclopentadienyl anion). This material forms a continuous random network structure of four-connected tetrahedral and octahedral Fe2+ nodes and exhibits an exceptionally low glass transition temperature (Tg = 87 °C). Despite its amorphous nature and complex composition, gFe-tBubipy exhibits a high degree of local structural order that enables strong antiferromagnetic exchange interactions between Fe2+ centers. Remarkably, it exhibits clear signatures of spin-glass behavior, with a well-defined magnetic freezing transition ≈14 K. This combination of a MOF glass exhibiting a distinct glass transition with spin-glass magnetism arising from topological disorder and frustrated, short-range magnetic interactions represent a significant advance. This discovery underscores the transformative potential of MOF glasses as a versatile platform for exploring the interplay between structural disorder and cooperative magnetic phenomena in hybrid materials
Visualizing the strong field–induced molecular breakup of C60 via x-ray diffraction
No full textLaser-driven dynamics in polyatomic molecules poses a complex many-body problem. Understanding intense light-matter interaction is crucial for steering intramolecular quantum dynamical processes. Here, we record time-resolved x-ray diffraction images of molecules during and after their interaction with intense near-infrared fields, giving direct access to structural changes of the molecules and their fragmentation in real time. Tuning the intensity of the excitation pulses, we uncover a transition from a weak-field regime of excited but stable molecules to a high-field regime dominated by Coulomb explosion. In the transition region, the molecules expand by up to 50% of their initial size within just 140 fs, with major fragmentation only setting in afterward. This work demonstrates that x-ray diffractive imaging is capable of retrieving time-resolved structural information of large molecules reshaped by intense laser fields. Laser-driven fragmentation is a first step toward observing molecular processes modified by laser fields of increasing intensity