Searches for lepton number violating K+ decays

The NA62 experiment at CERN reports a search for the lepton number violating decays K+→π−e+e+ and K+→π−μ+μ+ using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of 2.2 x 10^-10 and 4.2 x 10^-11 are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively

Search for heavy neutral lepton production in K+ decays to positrons

A search for heavy neutral lepton (N) production in K+→e+N decays using the data sample collected by the NA62 experiment at CERN in 2017-2018 is reported. Upper limits of the extended neutrino mixing matrix element |Ue4|^2 are established at the level of 10^−9 over most of the accessible heavy neutral lepton mass range 144-462 MeV/c^2, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The |Ue4|^2 range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/c^2

Description and performance of track and primary-vertex reconstruction with the CMS tracker

A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For tbar t events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of pT > 0.9GeV is 94% for pseudorapidities of |η| < 0.9 and 85% for 0.9 < |η| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of pT = 100GeV emitted at |η| < 1.4, the resolutions are approximately 2.8% in pT, and respectively, 10μm and 30μm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10–12μm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung

Measurements of differential and double-differential Drell–Yan cross sections in proton–proton collisions at √s = 8TeV

Measurements of the differential and double-differential Drell–Yan cross sections in the dielectron and dimuon channels are presented. They are based on proton–proton collision data at vs = 8TeV recorded with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb-1. The measured inclusive cross section in the ZZ peak region (60–120 GeV), obtained from the combination of the dielectron and dimuon channels, is 1138±8(exp)±25(theo)±30(lumi)\,pb, where the statistical uncertainty is negligible. The differential cross section ds/dm in the dilepton mass range 15–2000 GeV is measured and corrected to the full phase space. The double-differential cross section d2s/dmd|y| is also measured over the mass range 20 to 1500 GeV and absolute dilepton rapidity from 0 to 2.4. In addition, the ratios of the normalized differential cross sections measured at vs = 7 and 8 TeV are presented. These measurements are compared to the predictions of perturbative QCD at next-to-leading and next-to-next-to-leading (NNLO) orders using various sets of parton distribution functions (PDFs). The results agree with the NNLO theoretical predictions computed with fewz 3.1 using the CT10 NNLO and NNPDF2.1 NNLO PDFs. The measured double-differential cross section and ratio of normalized differential cross sections are sufficiently precise to constrain the proton PDFs.[…] the Secretaría de Estado de Investigación, Desarrollo e Innovación and Programa Consolider-Ingenio 2010, Spain […

Role of water resources in the modern world

The problems of water use and water availability have a long history. For thousands of years, the people had used water in agriculture and for satisfying their own needs, while in the recent centuries the water supply of industry has been added here. However, beginning from the mid-twentieth century, the use, distribution, and reproduction of water resources have acquired special relevance. The quickly growing world population, industry development, and expanding agricultural lands have led to the water deficit which is increasing with every passing year. The water demand runs ahead of the population growth rate. Many international organizations and individual states exerted enormous efforts to find the way to cope with this issue but so far without success. In the recent decades this has led to the growth of interstate contradictions of interests which gave rise to international instability and even to conflicts. This issue is so acute that the conflicting parties fail to find compromise. It means that in the nearest decades, we may witness the revival of “water wars” which will affect enormously the political map of the world. © Springer Nature Switzerland AG 2020

Functionalisation of graphene as a tool for developing nanomaterials with predefined properties

Graphene based nanomaterials (GBN) have been recently applied in a broad range of science and technology fields such as nanobiomedicine, electronics, energy storage and power generation exploiting their unique electronic structure, physical properties, and opportunities for modifying their surface using covalent and non-covalent interactions. In the present review we systematised the origins of GBN functionalisation using organic and inorganic molecules, polymers, biomolecules, and anticancer drugs. We show that varying the procedure of GBN functionalisation allows to obtain nanomaterials with desired properties that can be applied to the development of materials with enhanced physicochemical properties, nanoplatforms for drug delivery, nanobiosensors for detection of various biomolecules, as well as nanomaterials for bioimaging and diagnostics. The review can be useful for experts in the fields of material science and nanobiomedicine

Graphene Oxide of Extra High Oxidation: A Wafer for Loading Guest Molecules

We present a new modification of graphene oxide with very high content (85 wt %) of oxygen-containing functional groups (hydroxy, epoxy, lactol, carboxyl, and carbonyl groups) that forms stable aqueous dispersion in up to 9 g·L–1 concentration solutions. A novel faster method of the synthesis is described that produces up to 1 kg of the material and allows controlling the particle size in solution. The synthesized compound was characterized by various physicochemical methods and molecular dynamics modeling, revealing a unique structure in the form of a multilayered wafer of several sheets thick, where each sheet is highly corrugated. The ragged structure of the sheets forms pockets with hindered mobility of water that leads to the possibility of trapping guest molecules