An experimental procedure is proposed to perform measurements of differential cross sections for vector boson production which can be compared to fixed-order QCD predictions with improved accuracy. ...The procedure relies on applying theoretical acceptance corrections computed as a function of the transverse momentum of the
W
/
Z
boson,
p
T
, to the experimental measurement, rather than comparing data directly against fiducial fixed-order predictions. It is demonstrated that, contrary to standard fiducial computations, these acceptance factors vary little at low
p
T
, so they can be reliably computed using fixed-order perturbation theory. An example analysis is performed using the ATLAS measurement of the
Z
-boson production cross section at center-of-mass energy of 8 TeV. The resulting full phase space measurement of the cross section differential in the boson rapidity is compared to theoretical predictions computed with next-to-next-to leading-order accuracy in QCD. Further extensions of the approach which include different types of measurements and improved theoretical predictions are discussed.
The results of numerical simulation of an ogee spillway with a step on the crest are described. Quantitative estimates confirming the efficiency of the crest step are given. It is concluded that it ...is necessary to study in detail the operation of such spillways by numerical and physical simulation.
Charged lepton pairs are produced copiously in high-energy hadron collisions via electroweak gauge boson exchange, and are one of the most precisely measured final states in proton-proton collisions ...at the Large Hadron Collider (LHC). We propose that measurements of lepton angular distributions can be used to improve the accuracy of theoretical predictions for Higgs boson production cross sections at the LHC. To this end, we exploit the sensitivity of the lepton angular coefficient associated with the longitudinal Z-boson polarization to the parton density function (PDF) for gluons resolved from the incoming protons, in order to constrain the Higgs boson cross section from gluon fusion processes. By a detailed numerical analysis using the open-source platform xFitter, we find that high-statistics determinations of the longitudinally polarized angular coefficient at the LHC Run III and high-luminosity HL-LHC improve the PDF systematic uncertainties of the Higgs boson cross section predictions by 50% over a broad range of Higgs boson rapidities.
Small RNAs derived from snoRNAs Taft, Ryan J; Glazov, Evgeny A; Lassmann, Timo ...
RNA (Cambridge),
07/2009, Letnik:
15, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Small nucleolar RNAs (snoRNAs) guide RNA modification and are localized in nucleoli and Cajal bodies in eukaryotic cells. Components of the RNA silencing pathway associate with these structures, and ...two recent reports have revealed that a human and a protozoan snoRNA can be processed into miRNA-like RNAs. Here we show that small RNAs with evolutionary conservation of size and position are derived from the vast majority of snoRNA loci in animals (human, mouse, chicken, fruit fly), Arabidopsis, and fission yeast. In animals, sno-derived RNAs (sdRNAs) from H/ACA snoRNAs are predominantly 20-24 nucleotides (nt) in length and originate from the 3' end. Those derived from C/D snoRNAs show a bimodal size distribution at approximately 17-19 nt and >27 nt and predominantly originate from the 5' end. SdRNAs are associated with AGO7 in Arabidopsis and Ago1 in fission yeast with characteristic 5' nucleotide biases and show altered expression patterns in fly loquacious and Dicer-2 and mouse Dicer1 and Dgcr8 mutants. These findings indicate that there is interplay between the RNA silencing and snoRNA-mediated RNA processing systems, and that sdRNAs comprise a novel and ancient class of small RNAs in eukaryotes.
An analytical hydraulic method for calculating the flow parameters downstream of an overfall taking into account the characteristic features of a falling jet is described. Design formulas are ...presented. The calculated results are compared with experimental data to validate the method proposed.
The magnetic moment μ of a bound electron, generally expressed by the g-factor μ=-g μB s ħ(-1) with μB the Bohr magneton and s the electron's spin, can be calculated by bound-state quantum ...electrodynamics (BS-QED) to very high precision. The recent ultra-precise experiment on hydrogen-like silicon determined this value to eleven significant digits, and thus allowed to rigorously probe the validity of BS-QED. Yet, the investigation of one of the most interesting contribution to the g-factor, the relativistic interaction between electron and nucleus, is limited by our knowledge of BS-QED effects. By comparing the g-factors of two isotopes, it is possible to cancel most of these contributions and sensitively probe nuclear effects. Here, we present calculations and experiments on the isotope dependence of the Zeeman effect in lithium-like calcium ions. The good agreement between the theoretical predicted recoil contribution and the high-precision g-factor measurements paves the way for a new generation of BS-QED tests.
The joint recurrence analysis is used to reveal differences in the phase synchronization between intermittent photic stimulation and brain responses of patients with cardiac fibrillation of ...paroxysmal and persistent types. As a measure of phase synchronization between two signals, we consider the mutual correlation factor between recurrence probabilities of corresponding phase trajectories. The value of this coefficient increases upon an increase in the cardiac fibrillation time and in the extent of decline of cognitive functions for brain responses to theta-range frequencies.
MicroRNA (miRNA) and other types of small regulatory RNAs play a crucial role in the regulation of gene expression in eukaryotes. Several distinct classes of small regulatory RNAs have been ...discovered in recent years. To extend the repertoire of small regulatory RNAs characterized in chickens we used a deep sequencing approach developed by Solexa (now Illumina Inc.). We sequenced three small RNA libraries prepared from different developmental stages of the chicken embryo (days five, seven, and nine) to produce over 9.5 million short sequence reads. We developed a bioinformatics pipeline to distinguish authentic mature miRNA sequences from other classes of small RNAs and short RNA fragments represented in the sequencing data. Using this approach we detected almost all of the previously known chicken miRNAs and their respective miRNA* sequences. In addition we discovered 449 new chicken miRNAs including 88 miRNA candidates. Of these, 430 miRNAs appear to be specific to the avian lineage. Another six new miRNAs had evidence of evolutionary conservation in at least one vertebrate species outside of the bird lineage. The remaining 13 putative miRNAs appear to represent chicken orthologs of known vertebrate miRNAs. We discovered 39 additional putative miRNA candidates originating from miRNA generating intronic sequences known as mirtrons.
HERAFitter Alekhin, S.; Behnke, O.; Belov, P. ...
The European physical journal. C, Particles and fields,
07/2015, Letnik:
75, Številka:
7
Journal Article
Recenzirano
Odprti dostop
HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum ...Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton–proton deep inelastic scattering and proton–proton (proton–antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help to visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.
PDF
