Journal Article

The Large Hadron Collider at CERN, delivering proton–proton collisions at much higher energies and far higher luminosities than previous machines, has enabled a comprehensive programme of measurements of the standard model (SM) processes by the CMS experiment. These unprecedented capabilities facilitate precise measurements of the properties of a wide array of processes, the most fundamental being cross sections. [...]

In situ nuclear forward scattering shows a thermally induced cation exchange between a 57 Fe3 ⁢O4 thin-film and a Fe3⁢ O4 (001) substrate predominantly in the octahedral sublattice for a temperature range between 470 and 710 K. The overall activation barrier in this temperature range is found to be 19±32  kJ/mol, which is significantly lower than expected from extrapolating a bulk diffusion model. [...]

Collective oscillations in dense neutrino gases (flavor waves) are notable for their instabilities that cause fast flavor conversion. We develop a quantum theory of interacting neutrinos and flavor wave quanta, which are analogous to plasmons, but also carry flavor. [...]

Slow flavor evolution (defined as driven by neutrino masses and not necessarily ``slow'') is receiving fresh attention in the context of compact astrophysical environments. In Part~I of this series, we have studied the slow-mode dispersion relation following our recently developed analogy to plasma waves. [...]

A ubiquitous feature of accreting black hole systems is their hard X-ray emission which is thought to be produced through Comptonization of soft photons by electrons and positrons in the vicinity of the black hole, in a region with optical depth of order unity. The origin and composition of this Comptonizing region, known as the corona, is a matter open for debate. [...]

The paper presents the development and performance of the $^{57}$Fe Synchrotron Mössbauer Source (SMS) at the beamline P01 at PETRA III. A detailed description of the experimental setup is provided, including the optical elements and the critical role of high-quality iron borate crystals used as the Mössbauer source. [...]

The development of persistent ultraviolet-emitting phosphors is advancing rapidly because of their promisingapplications in alternative cancer treatments. In this work, we developed a novel Pr$^{3+}$-doped RbCaF3 phosphorexhibiting intense long-persistent luminescence in the 220–340 nm range, sustained for more than an hour afterjust 15 min of X-ray irradiation [...]

This work investigates the luminescence properties and energetic structure of emission centers created by NaCsisoelectronic impurities in a well-known CsI:Na scintillation crystal. Using synchrotron radiation excitation at 8K, high-resolution spectroscopic techniques were employed to probe the electronic transitions and luminescentdynamics within the crystal. [...]

We present a measurement of the branching fraction and fraction of longitudinal polarization of $B^0 \to \rho^+ \rho^-$ decays, which have two $\pi^0$'s in the final state. We also measure time-dependent $CP$ violation parameters for decays into longitudinally polarized $\rho^+ \rho^-$ pairs. [...]

We measure the branching fraction and $\it CP$-violating flavor-dependent rate asymmetry of $B^{0} \to \pi^{0} \pi^{0}$ decays reconstructed using the Belle II detector in an electron-positron collision sample containing $387 \times 10^{6}$$B\overline{B}$ pairs. Using an optimized event selection, we find $126\pm 20$ signal decays in a fit to background-discriminating and flavor-sensitive distributions. [...]