In- and ex-situ study of the deformation behavior of the βo(ωo)β_{o}(ω_{o}) phase in a Ti4_4Al3_3Nb alloy during high-temperature compression

In-situ synchrotron-based high energy X-ray diffraction (HEXRD) and ex-situ Gleeble tests were conducted to investigate the deformation behavior of the $β_{o}(ω_{o})$ phase in a Ti$_4$Al$_3$Nb alloy. In samples compressed at 600 and 800 °C, the brittle $ω_o$ phase deforms mostly elastically, resulting in the failure of the Ti$_4$Al$_3$Nb alloy by premature fracture. In a sample deformed at 900 °C, the $ω_o$ phase mostly transforms into the $β_o$ phase under uniaxial loading. Moreover, the ductility of a Ti$_4$Al$_3$Nb alloy is largely enhanced at this temperature. In a sample deformed at 1000 °C, dynamic recrystallization (DRX) of the $β_o$ phase extensively takes place. Direction 1 (D1) and Direction 2 (D2) deviating from the loading direction with an angle of 65° ± 5° and 15° ± 5° are selected to analyze the lattice strain evolution of (110)$_{β_{o}}$ lattice planes. At the late stage of macro strain hardening, deformed $_{β_{o}}$//D1 oriented grains bear a higher load due to the occurrence of DRX in βo//D2 oriented grains. Subsequently, DRX continues in $_{β_{o}}$//D1 oriented $β_o$ grains. The coordinated deformation of $β_o$ grains ensures the good deformability of a Ti$_4$Al$_3$Nb alloy at 1000 °C

Photoelectron spectroscopy and dissociative photoionization of fulminic acid, HCNO

We report a joint experimental and computational study of the photoelectron spectroscopy and the dissociative photoionization of fulminic acid, HCNO. The molecule is of interest to astrochemistry and astrobiology as a potential precursor of prebiotic molecules. Synchrotron radiation was used as the photon source. Dispersive photoelectron spectra were recorded from 10 to 22 eV, covering four band systems in the HCNO cation, and an ionization energy of 10.83 eV was determined. Transitions into the Renner–Teller distorted X+2Π state of the cation were simulated using wavepacket dynamics based on a vibronic coupling Hamiltonian. Very good agreement between experiment and theory is obtained. While the first excited state of the cation shows only a broad and unstructured spectrum, the next two higher states exhibit a well-resolved vibrational progression. Transitions into the excited electronic states of HCNO+ were not simulated due to the large number of electronic states that contribute to these transitions. Nevertheless, a qualitative assignment is given, based on the character of the orbitals involved in the transitions. The dissociative photoionization was investigated by photoelectron–photoion coincidence spectroscopy. The breakdown diagram shows evidence for isomerization from HCNO+ to HNCO+ on the cationic potential energy surface. Zero Kelvin appearance energies for the daughter ions HCO+ and NCO+ have been derived

First shot of the smoking gun: probing the electroweak phase transition in the 2HDM with novel searches for A → ZH in ℓ+ℓ−tt‾ {\ell}^{+}{\ell}^{-}t\overline{t} and ννbb‾ \nu \nu b\overline{b} final states

Recently the ATLAS collaboration has reported the first results of searches for heavy scalar resonances decaying into a Z boson and a lighter new scalar resonance, where the Z boson decays leptonically and the lighter scalar decays into a top-quark pair, giving rise to ${\ell}^{+}{\ell}^{-}t\overline{t}$ final states. This had previously been identified as a smoking-gun signature at the LHC for a first-order electroweak phase transition (FOEWPT) within the framework of two Higgs doublet models (2HDMs). In addition, ATLAS also presented new limits where the Z boson decays into pairs of neutrinos and the lighter scalar resonance into bottom-quark pairs, giving rise to the $\nu \nu b\overline{b}$ final state. We analyze the impact of these new searches on the 2HDM parameter space, with emphasis on their capability to probe currently allowed 2HDM regions featuring a strong FOEWPT. We also study the complementarity of these new searches with other LHC probes that could target the FOEWPT region of the 2HDM. Remarkably, the ATLAS search in the ${\ell}^{+}{\ell}^{-}t\overline{t}$ final state shows a local 2.85 σ excess (for masses of about 650 GeV and 450 GeV for the heavy and light resonance) in the 2HDM parameter region that would yield a FOEWPT in the early universe, which could constitute the first experimental hint of baryogenesis at the electroweak scale. We analyze the implications of this excess, and discuss the detectability prospects for the associated gravitational wave signal from the FOEWPT. Furthermore, we project the sensitivity reach of the ${\ell}^{+}{\ell}^{-}t\overline{t}$ signature for the upcoming runs of the LHC. Finally, we introduce the python package thdmTools, a state-of-art tool for the exploration of the 2HDM

CaloClouds II: ultra-fast geometry-independent highly-granular calorimeter simulation

Fast simulation of the energy depositions in high-granular detectors is needed for future collider experiments with ever increasing luminosities. Generative machine learning (ML) models have been shown to speed up and augment the traditional simulation chain in physics analysis. However, the majority of previous efforts were limited to models relying on fixed, regular detector readout geometries. A major advancement is the recently introduced CaloClouds model, a geometry-independent diffusion model, which generates calorimeter showers as point clouds for the electromagnetic calorimeter of the envisioned International Large Detector (ILD). In this work, we introduce CaloClouds II which features a number of key improvements. This includes continuous time score-based modelling, which allows for a 25 step sampling with comparable fidelity to CaloClouds while yielding a $6\times$ speed-up over Geant4 on a single CPU ($5\times$ over CaloClouds). We further distill the diffusion model into a consistency model allowing for accurate sampling in a single step and resulting in a $46\times$ ($37\times$) speed-up. This constitutes the first application of consistency distillation for the generation of calorimeter showers

Analytic and Algebraic Studies of Feynman Integrals

Feynman integrals are central to the calculation of scattering amplitudes both in particle and gravitationalwave physics. This thesis presents advancements in both the analytical and algebraicstructure of these integrals and shows how this can be used for efficient evaluation of these integrals.Paper I. In this paper the focus is on one-loop integrals. The singularities of these integrals arefully described and used to derive the full symbol alphabet and canonical differential equation forany number of external particles. It is proven that a large family of one-loop integrals satisfy theCohen-Macaulay property.Paper II. Two infinite families of Feynman integrals satisfying the Cohen-Macaulay propertyare classified. This property implies that both the singularities and the number of master integralsis independent of space-time dimension and propagator powers.Paper III. In this paper the singular locus of a Feynman integral is defined as the critical pointsof a Whitney stratified map. Explicit code and calculations are provided which show that thismethod captures singularities otherwise hard to detect.Paper IV-V. The algebraic properties of the integrand, especially that of its Newton polytopebeing a generalized permutohedron, is leverage together with tropical sampling to provide efficientnumerical evaluation of Feynman integrals with physical kinematics. The connection betweenthe generalized permutohedron property and the Cohen-Macaulay property is also discussed

Time-resolved crystallography of boric acid binding to the active site serine of the β-lactamase CTX-M-14 and subsequent 1,2-diol esterification

The emergence and spread of antibiotic resistance represent a growing threat to public health. Of particular concern is the appearance of β-lactamases, which are capable to hydrolyze and inactivate the most important class of antibiotics, the β-lactams. Effective β-lactamase inhibitors and mechanistic insights into their action are central in overcoming this type of resistance, and in this context boronate-based β-lactamase inhibitors were just recently approved to treat multidrug-resistant bacteria. Using boric acid as a simplified inhibitor model, time-resolved serial crystallography was employed to obtain mechanistic insights into binding to the active site serine of β-lactamase CTX-M-14, identifying a reaction time frame of 80–100 ms. In a next step, the subsequent 1,2-diol boric ester formation with glycerol in the active site was monitored proceeding in a time frame of 100–150 ms. Furthermore, the displacement of the crucial anion in the active site of the β-lactamase was verified as an essential part of the binding mechanism of substrates and inhibitors. In total, 22 datasets of β-lactamase intermediate complexes with high spatial resolution of 1.40–2.04 Å and high temporal resolution range of 50–10,000 ms were obtained, allowing a detailed analysis of the studied processes. Mechanistic details captured here contribute to the understanding of molecular processes and their time frames in enzymatic reactions. Moreover, we could demonstrate that time-resolved crystallography can serve as an additional tool for identifying and investigating enzymatic reactions