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Measurement of CKM matrix elements in single top quark -channel production in proton-proton collisions at 13 TeV
No full textThe first direct, model-independent measurement is presented of the modulus of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements , , and , in final states enriched in single top quark -channel events. The analysis uses proton-proton collision data from the LHC, collected during 2016 by the CMS experiment, at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb. Processes directly sensitive to these matrix elements are considered at both the production and decay vertices of the top quark. In the standard model hypothesis of CKM unitarity, a lower limit of 0.970 is measured at the 95% confidence level. Several theories beyond the standard model are considered, and by releasing all constraints among the involved parameters, the values 0.988 0.024, and 0.06 0.06, where the uncertainties include both statistical and systematic components, are measured
Time-Scales for Nonlinear Processes in Preheating after Multifield Inflation with Nonminimal Couplings
No full textWe have conducted extensive lattice simulations to study the post-inflation dynamics of multifield models involving nonminimal couplings. We explore the parameter dependence of preheating in these models and describe the various time-scales that control such nonlinear processes as energy transfer, re-scattering, and the approach to radiation-domination and thermalization. In the limit of large nonminimal couplings (), we find that efficient transfer of energy from the inflaton condensate to radiative degrees of freedom, emergence of a radiation-dominated equation of state, and the onset of thermalization each consistently occur within -folds after the end of inflation, largely independent of the values of the other couplings in the models. The exception is the case of negative ellipticity, in which there is a misalignment between the dominant direction in field-space along which the system evolves and the larger of the nonminimal couplings . In those cases, the field-space-driven parametric resonance is effectively shut off. More generally, the competition between the scalar fields' potential and the field-space manifold structure can yield interesting phenomena such as two-stage resonances. Despite the explosive particle production, which can lead to a quick depletion of the background energy density, the nonlinear processes do not induce any super-horizon correlations after the end of inflation in these models, which keeps predictions for CMB observables unaffected by the late-time amplification of isocurvature fluctuations. Hence the excellent agreement between primordial observables and recent observations is preserved for this class of models, even when we consider post-inflation dynamics
All-order amplitudes at any multiplicity in the multi-Regge limit
No full textWe propose an all-loop expression for scattering amplitudes in planar N=4 super Yang-Mills theory in multi-Regge kinematics valid for all multiplicities, all helicity configurations, and arbitrary logarithmic accuracy. Our expression is arrived at from comparing explicit perturbative results with general expectations from the integrable structure of a closely related collinear limit. A crucial ingredient of the analysis is an all-order extension for the central emission vertex that we recently computed at next-to-leading logarithmic accuracy. As an application, we use our all-order formula to prove that all amplitudes in this theory in multi-Regge kinematics are single-valued multiple polylogarithms of uniform transcendental weight
Depth-resolved core level spectroscopy of noncentrosymmetric solid BiPd
No full textUnderstanding exotic solids is a difficult task as interactions are often hidden by the symmetry of the system. Here, we study the electronic properties of a noncentrosymmetric solid, BiPd, which is a rare material exhibiting both superconductivity and the topological phase of matter. Employing high-resolution photoemission spectroscopy with photon energies ranging from the hard x-ray to extreme-ultraviolet regime, we show that hard x-ray spectroscopy alone is not enough to reveal surface-bulk differences in the electronic structure. We derive the escape depths close to the extreme surface sensitivity and find that the photon energies used for high-resolution photoemission measurements fall in the surface sensitive regime. In addition, we discover a deviation of the branching ratio of Bi core level features derived from conventional quantum theories of the core hole final states. Such a breakdown of the atomic description of the core level spectroscopy can be attributed to the absence of a center of symmetry and spin-orbit interactions
The Two-mass Contribution to the Three-Loop Polarized Operator Matrix Element
No full textWe compute the two-mass contributions to the polarized massive operator matrix element at third order in the strong coupling constant in Quantum Chromodynamics analytically. These corrections are important ingredients for the matching relations in the variable flavor number scheme and for the calculation of Wilson coefficients in deep--inelastic scattering in the asymptotic regime . The analytic result is expressed in terms of nested harmonic, generalized harmonic, cyclotomic and binomial sums in -space and by iterated integrals involving square-root valued arguments in space, as functions of the mass ratio. Numerical results are presented. New two--scale iterative integrals are calculated
3D Multimodal X-ray microscopy of biological specimens
No full textStudies of biological systems typically require the application of several complementary methods able to yield statistically-relevant results at a unique level of sensitivity. Long penetration depth of X-rays makes them particularly suitable for non-destructive volumetric investigations of whole cells and tissue sections, providing structural and elemental specificity at nanoscale spatial resolutions.X-ray ptychography is a promising imaging technique for sub-100-nm structural studies of weakly-scattering extended biological specimens. It provides quantitative phase-contrast maps revealing the morphology of an investigated object. In addition, its scanning nature allows for a simultaneous acquisition of nanoscale X-ray fluorescence, yielding the element distributions at an unmatched sensitivity.Thus, the goal of this PhD project has been to combine X-ray fluorescence and ptychography to enable a robust correlation of elemental distributions with respect to the cellular morphology. Exploiting a highly intense and coherent X-ray beam at beamline P11 of the low-emittance synchrotron light source PETRA III in Hamburg, Germany, a versatile multimodal scanning X-ray microscope was developed in the framework of this PhD project. This thesis describes the consecutive stages of the microscope’s development and highlights its application in structural determination of biological samples.In the first stage of this PhD project, a 2D long-range scanning unit was developed, enabling seamless, serial measurements of many targets at nanometer precision. With this setup, the PhD work allowed to optimise the correlative imaging method at higher incident photon energies for mapping of first-row transition metals up to iron, while using a nano-focussed beam. In this way, it addressed limitations of the so-far presented demonstrations, restrained to light-element mapping in the context of organelles of single cells. The correlative imaging method was then used to quantify the iron distributions in a population of macrophages treated with Mycobacterium-tuberculosis-targeting iron-oxide nanocontainers in the context of their sub-cellular structure obtained by ptychography. In the second application, the calcium content in a human bone matrix was mapped in close proximity to osteocyte lacunae (perilacunar matrix). A concurrently acquired ptychographic image was then used to remove the mass-thickness effect from the raw calcium map.In the second stage of this work, the concept of concurrent ptychography and X-ray fluorescence was extended to 3D correlative imaging in the framework of computed tomography. For this purpose, an upgraded 3D scanning X-ray microscope was built, commissioned, and used in volumetric imaging of two specimens, using ptychographic X-ray computed tomography. The final performance of the 3D microscope reached far beyond the throughputs of the available ptychographic tomography setups which, until now, have hindered application of the method by a broader biomedical community. A tomogram of the nano-porous glass demonstrated the fastest on-the-fly ptychographic tomography, to date, at an isotropic spatial resolution of 52 nm. In the second application, ptychographic tomography of a chiton’s radular tooth provided a quantitative insight into one of the nature’s hardest biominerals, at a Nyquist-sampling limited spatial resolution of 65 nm.The work has been concluded with a prospect for future operation and opportunities of the correlative method of simultaneous ptychographic and X-ray fluorescence imaging at upcoming diffraction-limited synchrotron light sources
Sum rule improved double parton distributions in position space
No full textModels for double parton distributions that are realistic and consistent with theoretical constraints are crucial for a reliable description of double parton scattering. We show how an ansatz that has the correct behaviour in the limit of small transverse distance between the partons can be improved step by step, such as to fulfil the sum rules for double parton distributions with an accuracy around 10%
Matching small beta functions using centroid jitter and two beam position monitors
No full textMatching to small beta functions is required to preserve emittance in plasma accelerators. The plasma wake provides strong focusing fields, which typically require beta functions on the mm-scale, comparable to those found in the final focusing of a linear collider. Such beams can be time consuming to experimentally produce and diagnose. We present a simple, fast, and noninvasive method to measure Twiss parameters in a linac using two beam position monitors only, relying on the similarity of the beam phase space and the jitter phase space. By benchmarking against conventional quadrupole scans, the viability of this technique was experimentally demonstrated at the FLASHForward plasma-accelerator facility
Complete flavor decomposition of the spin and momentum fraction of the proton using lattice QCD simulations at physical pion mass
No full textWe evaluate the gluon and quark contributions to the spin of the proton using an ensemble of gauge configurations generated at physical pion mass. We compute all valence and sea quark contributions to high accuracy. We perform a nonperturbative renormalization for both quark and gluon matrix elements. We find that the contribution of the up, down, strange, and charm quarks to the proton intrinsic spin is 12∑q=u,d,s,cΔΣq+=0.191(15) and to the total spin ∑q=u,d,s,cJq+=0.285(45)(10). The gluon contribution to the spin is Jg=0.187(46)(10) yielding J=Jq+Jg=0.473(71)(14) confirming the spin sum. The momentum fraction carried by quarks in the proton is found to be 0.618(60) and by gluons 0.427(92), the sum of which gives 1.045(118) confirming the momentum sum rule. All scale and scheme dependent quantities are given in the MS¯ scheme at 2 GeV