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Measurements of H production and the CP structure of the Yukawa interaction between the Higgs boson and top quark in the diphoton decay channel
No full textThe first observation of the process in a single Higgs boson decay channel with the full reconstruction of the final state () is presented, with a significance of 6.6 standard deviations (σ). The CP structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure CP-odd structure of the top Yukawa coupling at 3.2σ. The measurements are based on a sample of proton-proton collisions at a center-of-mass energy =13 TeV collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb. The cross section times branching fraction of the process is measured to be = , which is compatible with the standard model prediction of . The fractional contribution of the CP-odd component is measured to be = 0.00±0.33
Photon statistics and signal to noise ratio for incoherent diffraction imaging
No full textIntensity interferometry is a well known method in astronomy. Recently, a related method called incoherent diffractive imaging (IDI) was proposed to apply intensity correlations of x-ray fluorescence radiation to determine the 3D arrangement of the emitting atoms in a sample. Here we discuss inherent sources of noise affecting IDI and derive a model to estimate the dependence of the signal to noise ratio (SNR) on the photon counts per pixel, the temporal coherence (or number of modes), and the shape of the imaged object. Simulations in two- and three-dimensions have been performed to validate the predictions of the model. We find that contrary to coherent imaging methods, higher intensities and higher detected counts do not always correspond to a larger SNR. Also, larger and more complex objects generally yield a poorer SNR despite the higher measured counts. The framework developed here should be a valuable guide to future experimental design
CRL optics and silicon drift detector for P06 Microprobe experiments at 35 keV
No full textA provisional setup for X-ray microprobe experiments at 35 keV is described. It is based on compoundrefractive lenses (CRLs) for nanofocusing and a Vortex silicon drift detector with 2 mm sensorthickness for increased sensitivity at high energies. The Microprobe experiment (PETRA III) generallyuses Kirkpatrick-Baez mirrors for submicrometer focusing in the energy range of 5–21 keV.However, various types of scanning X-ray microscopy experiments require higher excitation energies.The CRL optics were characterized by X-ray ptychography and X-ray fluorescence (XRF) knife edgescans on a siemens star pattern and showed beam sizes down to 110 nm. The performance of the newsetup for microscopic X-ray diffraction (XRD)–XRF scanning X-ray microscopy measurements at35 keV is demonstrated on a cross-section of a painting fragment
Accidental SO(10) axion from gauged flavour
No full textAn accidental U(1) Peccei-Quinn (PQ) symmetry automatically arises in a class of SO(10) unified theories upon gauging the SU(3)f flavour group. The PQ symmetry is protected by the center of SO(10)×SU(3) up to effective operators of canonical dimension nine (developing high-scale contributions to the axion potential). In the pre-inflationary PQ breaking scenario the axion mass window is predicted to be ∈[7×10,10] eV, where the lower end is bounded by the seesaw scale and the upper end by iso-curvature fluctuations. A high-quality axion, that is immune to the PQ quality problem, is obtained for ≳0.02 eV. We finally offer a general perspective on the PQ quality problem in 4D grand unified theories
Search for resonant pair production of Higgs bosons in the channel in proton-proton collisions at 13 TeV
No full textA search for the production of a narrow-width resonance decaying into a pair of Higgs bosons decaying into the channel is presented. The analysis is based on data collected with the CMS detector during 2016, in proton-proton collisions at the LHC, corresponding to an integrated luminosity of 35.9 fb. The final states considered are the ones where one of the bosons decays into a pair of muons or electrons, and the other boson decays to either a pair of quarks or a pair of neutrinos. Upper limits at 95% confidence level are placed on the production of narrow-width spin-0 or spin-2 particles decaying to a pair of Higgs bosons, in models with and without an extended Higgs sector. For a resonance mass range between 260 and 1000 GeV, limits on the production cross section times branching fraction of a spin-0 and spin-2 resonance range from 0.1 to 5.0 pb and 0.1 to 3.6 pb, respectively. These results set limits in parameter space in bulk Randall-Sundrum radion, Kaluza-Klein excitation of the graviton, and next-to-minimal two-Higgs doublet models (N2HDMs). For specific choices of parameters the N2HDM can be excluded in a mass range between 360 and 620 GeV for a resonance decaying to two Higgs bosons. This is the first search for Higgs boson resonant pair production in the channel
The electronic structure of the aqueous permanganate ion: aqueous-phase energetics and molecular bonding studied using liquid jet photoelectron spectroscopy
No full textPermanganate aqueous solutions, MnO(aq.), were studied using liquid-micro-jet-based soft X-ray non-resonant and resonant photoelectron spectroscopy to determine valence and core-level binding energies. To identify possible differences in the energetics between the aqueous bulk and the solution-gas interface, non-resonant spectra were recorded at two different probing depths. Similar experiments were performed with different counter ions, Na and K, with the two solutions yielding indistinguishable anion electron binding energies. Our resonant photoelectron spectroscopy measurements, performed near the Mn L- and O K-edges, selectively probed valence charge distributions between the Mn metal center, O ligands, and first solvation shell in the aqueous bulk. Associated resonantly-enhanced solute ionisation signals revealed hybridisation of the solute constituents’ atomic orbitals, including the inner valence Mn 3p and O 2s. We identified intermolecular Coulombic decay relaxation processes following resonant X-ray excitation of the solute that highlight valence MnO-HO electronic couplings. Furthermore, our results allowed us to infer oxidative reorganisation energies of MnO and adiabatic valence ionisation energies of MnO, revealing the Gibbs free energy of oxidation and permitting estimation of the vertical electron affinity of MnO. Finally, the Gibbs free energy of hydration of isolated MnO was determined. Our results and analysis allowed a near-complete binding-energy-scaled MnO molecular orbital and a valence energy level diagram to be produced for the MnO / MnO system. Cumulatively, our mapping of the aqueous-phase electronic structure of MnO is expected to contribute to a deeper understanding of the exceptional redox properties of this widely applied aqueous transition-metal complex ion
Btk SH2-kinase interface is critical for allosteric kinase activation and its targeting inhibits B-cell neoplasms
No full textBruton’s tyrosine kinase (Btk) is critical for B-cell maturation and activation. Btk loss-of-function mutations cause human X-linked agammaglobulinemia (XLA). In contrast, Btk signaling sustains growth of several B-cell neoplasms which may be treated with tyrosine kinase inhibitors (TKIs). Here, we uncovered the structural mechanism by which certain XLA mutations in the SH2 domain strongly perturb Btk activation. Using a combination of molecular dynamics (MD) simulations and small-angle X-ray scattering (SAXS), we discovered an allosteric interface between the SH2 and kinase domain required for Btk activation and to which multiple XLA mutations map. As allosteric interactions provide unique targeting opportunities, we developed an engineered repebody protein binding to the SH2 domain and able to disrupt the SH2-kinase interaction. The repebody prevents activation of wild-type and TKI-resistant Btk, inhibiting Btk-dependent signaling and proliferation of malignant B-cells. Therefore, the SH2-kinase interface is critical for Btk activation and a targetable site for allosteric inhibition
Role of intraband dynamics in the generation of circularly polarized high harmonics from solids
No full textRecent studies have demonstrated that the polarization states of high harmonics from solids can differfrom those of the driving pulses. To gain insights on the microscopic origin of this behavior, we performone-particle intraband-only calculations and reproduce some of the most striking observations. For instance,our calculations yield circularly polarized harmonics from elliptically polarized pulses that sensitively dependon the driving conditions. Furthermore, we perform experiments on ZnS and find characteristics partly similarto those reported from silicon. Comparison to our intraband-only calculations shows reasonable qualitativeagreement for a below-band-gap harmonic. We show that intraband dynamics predict depolarization effectsthat gain significance with higher field strengths and we observe such effects in the experimental data. Forharmonics above the band gap, interband dynamics become important and the high-harmonic response toelliptical excitation looks systematically different. Our work proposes a method to distinguish between differenthigh-harmonic generation mechanisms and it could pave the way to compact solid-state high-harmonic sourceswith controllable polarization states
Cobalt hyperaccumulation in Rinorea cf. bengalensis (Violaceae) from Sabah: accumulation potential and tissue and cellular-level distribution of cobalt
No full textKnowledge on the ecophysiology of cobalt hyperaccumulator species is limited. The nickel hyperaccumulator Rinorea cf. bengalensis from Borneo can accumulate high concentrations of cobalt in nature. This study investigates the cobalt accumulation potential of Rinorea cf. bengalensis in relation to nickel concentrations in soils and the subsequent tissue and cellular-level distributions of cobalt, nickel and major cations.Seedlings of Rinorea cf. bengalensis were grown in mixed treatments on ultramafic soil containing a high concentration of available nickel. Cobalt and nickel salts were then added to the soil to study their interactions. The tissue and cellular-level distributions of cobalt, calcium, nickel, and potassium were investigated using synchrotron-based X-ray fluorescence microscopy.The maximum foliar cobalt concentration reached 1200 μg g. Accumulation of cobalt competed with nickel accumulation although nickel seems to stimulate cobalt phloem translocation. Plants suffered toxicity in the treatment with the highest soil cobalt concentration. Cobalt and nickel have contrasting distribution patterns in the leaves of Rinorea cf. bengalensis, with cobalt mainly excreted on the surface of the leaves, whereas nickel is localised in foliar epidermal cells.Rinorea cf. bengalensis can accumulate high concentrations of cobalt, but is intrinsically more tolerant to nickel. It does not rely on a similar sequestration mechanism for both metals, which could explain the lesser tolerance for cobalt. Nickel appears to be essential for the plant to tolerate high cobalt concentrations. Further studies intending to develop agronomic practices are needed to determine the viability of Rinorea cf. bengalensis for nickel-cobalt agromining
Indentation response of a superlattice thin film revealed by in-situ scanning X-ray nanodiffraction
No full textNanocrystalline materials such as thin films, and in particular, multilayers with a periodicity in the nanometer range, i.e. superlattice films, possess properties that cannot be found in their coarse-grained bulk counterparts. Mechanical characterization of such structures is therefore of high interest, but also very challenging, due to the small length scales involved and has therefore most often been performed ex-situ using electron microscopy. In this work, however, we report on the first in-situ micromechanical analysis of a CrN-AlN superlattice thin film cross-section. The sample was deposited using reactive magnetron sputtering and sublayer thicknesses were chosen so as to stabilize AlN in its cubic crystal structure. Using a synchrotron X-ray nanoprobe, maps of internal stresses and morphological changes were tracked by means of wide-angle X-ray diffraction and simultaneous small-angle X-ray scattering, while the sample was loaded to various degrees with a wedged diamond tip. The results reveal a high compressive strength of about 13 GPa, while through-thickness cracks form, following tensile stresses >1.4 GPa and thereby provide a relaxation mechanism. Layer rotation up to several degrees and significant layer compression up to 7% were also found, but along with the internal stress response, their nature is mostly elastic, meaning that in the post-loading state only a fraction of the effects observed under load remains