We perform the first global QCD analysis of polarized inclusive and semi-inclusive deep-inelastic scattering and single-inclusive e^{+}e^{-} annihilation data, simultaneously fitting the parton ...distribution and fragmentation functions using the iterative Monte Carlo method. Without imposing SU(3) symmetry relations, we find the strange polarization to be very small, consistent with zero for both inclusive and semi-inclusive data, which provides a resolution to the strange quark polarization puzzle. The combined analysis also allows the direct extraction from data of the isovector and octet axial charges, and is consistent with a small SU(2) flavor asymmetry in the polarized sea.
We perform the first global QCD analysis of parton distribution functions (PDFs) in the pion, combining πA Drell-Yan data with leading neutron electroproduction from HERA within a Monte Carlo ...approach based on nested sampling. Inclusion of the HERA data allows the pion PDFs to be determined down to much lower values of x, with relatively weak model dependence from uncertainties in the chiral splitting function. The combined analysis reveals that gluons carry a significantly higher pion momentum fraction, ∼30%, than that inferred from Drell-Yan data alone, with sea quarks carrying a somewhat smaller fraction, ∼15%, at the input scale. Within the same effective theory framework, the chiral splitting function and pion PDFs can be used to describe the dover ¯-uover ¯ asymmetry in the proton.
Superconductivity is ubiquitous as evidenced by the observation in many crystals including carrier-doped oxides and diamond. Amorphous solids are no exception. However, it remains to be discovered in ...quasicrystals, in which atoms are ordered over long distances but not in a periodically repeating arrangement. Here we report electrical resistivity, magnetization, and specific-heat measurements of Al-Zn-Mg quasicrystal, presenting convincing evidence for the emergence of bulk superconductivity at a very low transition temperature of Formula: see text K. We also find superconductivity in its approximant crystals, structures that are periodic, but that are very similar to quasicrystals. These observations demonstrate that the effective interaction between electrons remains attractive under variation of the atomic arrangement from periodic to quasiperiodic one. The discovery of the superconducting quasicrystal, in which the fractal geometry interplays with superconductivity, opens the door to a new type of superconductivity, fractal superconductivity.
To identify pathways involved in adult lung regeneration, we employ a unilateral pneumonectomy (PNX) model that promotes regenerative alveolarization in the remaining intact lung. We show that PNX ...stimulates pulmonary capillary endothelial cells (PCECs) to produce angiocrine growth factors that induce proliferation of epithelial progenitor cells supporting alveologenesis. Endothelial cells trigger expansion of cocultured epithelial cells, forming three-dimensional angiospheres reminiscent of alveolar-capillary sacs. After PNX, endothelial-specific inducible genetic ablation of
Vegfr2 and
Fgfr1 in mice inhibits production of MMP14, impairing alveolarization. MMP14 promotes expansion of epithelial progenitor cells by unmasking cryptic EGF-like ectodomains that activate the EGF receptor (EGFR). Consistent with this, neutralization of MMP14 impairs EGFR-mediated alveolar regeneration, whereas administration of EGF or intravascular transplantation of MMP14
+ PCECs into pneumonectomized
Vegfr2/Fgfr1-deficient mice restores alveologenesis and lung inspiratory volume and compliance function. VEGFR2 and FGFR1 activation in PCECs therefore increases MMP14-dependent bioavailability of EGFR ligands to initiate and sustain alveologenesis.
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► Pulmonary capillary endothelial cells (PCECs) support alveologenesis ► Autocrine VEGFR2 and FGFR1 activation in PCECs induces MMP14 expression ► MMP14 unmasks EGF receptor ligands, enhancing epithelial cell proliferation ► Injection of activated PCECs or angiocrine factors accelerates lung regeneration
Capillary endothelial cells support the regeneration of alveolar epithelial cells by secreting a matrix metalloprotease that unmasks cryptic epidermal growth factor receptor ligands.
We present a new set of leading-twist parton distribution functions, referred to as "CJ15," which take advantage of developments in the theoretical treatment of nuclear corrections as well as new ...data. The analysis includes, for the first time, data on the free neutron structure function from Jefferson Lab and new high-precision charged lepton and W-boson asymmetry data from Fermilab. These significantly reduce the uncertainty on the d/u ratio at large values of x and provide new insights into the partonic structure of bound nucleons.
We perform the first simultaneous extraction of unpolarized parton distributions and fragmentation functions from a Monte Carlo analysis of inclusive and semi-inclusive deep-inelastic scattering, ...Drell-Yan lepton-pair production, and single-inclusive e+e− annihilation data. We use data resampling techniques to thoroughly explore the Bayesian posterior distribution of the extracted functions, and use k -means clustering on the parameter samples to identify the configurations that give the best description across all reactions. Inclusion of the semi-inclusive data reveals a strong suppression of the strange quark distribution at parton momentum fractions x ≳ 0.01 , in contrast with the ATLAS observation of enhanced strangeness in W ± and Z production at the LHC. Our study reveals significant correlations between the strange quark density and the strange → kaon fragmentation function needed to simultaneously describe semi-inclusive K ± production data from COMPASS and inclusive K ± spectra in e+e− annihilation from ALEPH and SLD, as well as between the strange and light antiquark densities in the proton.
A
bstract
We present the details of a new factorized approach to semi-inclusive deep-inelastic scattering which treats QED and QCD radiation on equal footing, and provides a systematically improvable ...approximation to the extraction of transverse momentum dependent parton distributions. We demonstrate how the QED contributions can be well approximated by collinear factorization, and illustrate the application of the factorized approach to QED radiation in inclusive scattering. For semi-inclusive processes, we show how radiation effects prevent a well-defined “photon-nucleon” frame, forcing one to use a two-step process to account for the radiation. We illustrate the utility of the new method by explicit application to the spin-dependent Sivers and Collins asymmetries.
From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic (FM) superconductor UCoGe (T(Curie)∼2.5 K and T(SC)∼0.6 K), we show that superconductivity in UCoGe is tightly coupled ...with longitudinal FM spin fluctuations along the c axis. We found that magnetic fields along the c axis (H∥c) strongly suppress the FM fluctuations and that the superconductivity is observed in the limited magnetic-field region where the longitudinal FM spin fluctuations are active. These results, combined with model calculations, strongly suggest that the longitudinal FM spin fluctuations tuned by H∥c induce the unique spin-triplet superconductivity in UCoGe. This is the first clear example that FM fluctuations are intimately related with superconductivity.
The chemical properties of an element are primarily governed by the configuration of electrons in the valence shell. Relativistic effects influence the electronic structure of heavy elements in the ...sixth row of the periodic table, and these effects increase dramatically in the seventh row--including the actinides--even affecting ground-state configurations. Atomic s and p1/2 orbitals are stabilized by relativistic effects, whereas p3/2, d and f orbitals are destabilized, so that ground-state configurations of heavy elements may differ from those of lighter elements in the same group. The first ionization potential (IP1) is a measure of the energy required to remove one valence electron from a neutral atom, and is an atomic property that reflects the outermost electronic configuration. Precise and accurate experimental determination of IP1 gives information on the binding energy of valence electrons, and also, therefore, on the degree of relativistic stabilization. However, such measurements are hampered by the difficulty in obtaining the heaviest elements on scales of more than one atom at a time. Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is 4.96(+0.08)(-0.07) electronvolts. The IP1 of Lr was measured with (256)Lr (half-life 27 seconds) using an efficient surface ion-source and a radioisotope detection system coupled to a mass separator. The measured IP1 is in excellent agreement with the value of 4.963(15) electronvolts predicted here by state-of-the-art relativistic calculations. The present work provides a reliable benchmark for theoretical calculations and also opens the way for IP1 measurements of superheavy elements (that is, transactinides) on an atom-at-a-time scale.
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