The normalized differential cross section for top quark pair () production is measured in pp collisions at a centre-of-mass energy of 8 at the CERN LHC using the CMS detector in data corresponding to an integrated luminosity of 19.7. The measurements are performed in the leptonjets (jets) and in the dilepton (, , and ) decay channels. The cross section is measured as a function of the kinematic properties of the charged leptons, the jets associated to b quarks, the top quarks, and the system. The data are compared with several predictions from perturbative quantum chromodynamic up to approximate next-to-next-to-leading-order precision. No significant deviations are observed relative to the standard model predictions.Electronic supplementary materialThe online version of this article (doi:10.1140/epjc/s10052-015-3709-x) contains supplementary material, which is available to authorized users.
Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated supersymmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton–proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9 % of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.
Two phosphorus-containing acrylate monomers were synthesized from the reaction of ethyl ␣-chloromethyl acrylate and t-butyl ␣-bromomethyl acrylate with triethyl phosphite. The selective hydrolysis of the ethyl ester monomer with trimethylsilyl bromide (TMSBr) gave a phosphonic acid monomer. The attempted bulk polymerizations of the monomers at 57-60°C with 2,2Ј-azobisisobutyronitrile (AIBN) were unsuccessful; however, the monomers were copolymerized with methyl methacrylate (MMA) in bulk at 60°C with AIBN. The resulting copolymers produced chars on burning, showing potential as flame-retardant materials. Additionally, ␣-(chloromethyl)acryloyl chloride (CMAC) was reacted with diethyl (hydroxymethyl)phosphonate to obtain a new monomer with identical ester and ether moieties. This monomer was hydrolyzed with TMSBr, homopolymerized, and copolymerized with MMA. The thermal stabilities of the copolymers increased with increasing amounts of the phosphonate monomer in the copolymers. A new route to highly reactive phosphorus-containing acrylate monomers was developed. A new derivative of CMAC with mixed ester and ether groups was synthesized by substitution, first with diethyl (hydroxymethyl)phosphonate and then with sodium acetate. This monomer showed the highest reactivity and gave a crosslinked polymer. The incorporation of an ester group increased the rate of polymerization. The relative reactivities of the synthesized monomers in photopolymerizations were determined and compared with those of the other phosphorouscontaining acrylate monomers. Changing the monomer structure allowed control of the polymerization reactivity so that new phosphorus-containing polymers with desirable properties could be obtained.
A measurement is presented of differential cross sections for Higgs boson (H) production in pp collisions at . The analysis exploits the decay in data corresponding to an integrated luminosity of 19.7 collected by the CMS experiment at the LHC. The cross section is measured as a function of the kinematic properties of the diphoton system and of the associated jets. Results corrected for detector effects are compared with predictions at next-to-leading order and next-to-next-to-leading order in perturbative quantum chromodynamics, as well as with predictions beyond the standard model. For isolated photons with pseudorapidities , and with the photon of largest and next-to-largest transverse momentum () divided by the diphoton mass satisfying the respective conditions of and , the total fiducial cross section is .
New methacrylate monomers containing phosphonic acid or both phosphonic and carboxylic acids were synthesized through the reaction of t-butyl a-bromomethyl acrylate with triethyl phosphite followed by the selective hydrolysis of the phosphonate or t-butyl ester groups with trimethylsilyl bromide and trifluoroacetic acid. The copolymerization of these monomers with 2-hydroxyethylmethacrylate was investigated with photodifferential scanning calorimetry at 40 8C with 2,2 0 -dimethoxy-2-phenyl acetophenone as a photoinitiator. Quantum mechanical tools were also used to understand the mechanistic behavior of the polymerization reactions of these synthesized monomers. The propagation and chain-transfer reactions were considered and rationalized. A strong effect of the monomer structure on the rate of polymerization was observed. The polymerization reactivities of the monomers increased with decreasing steric hindrance and/or increasing hydrogen-bonding capacity because of the hydrolysis of the phosphonate and the t-butyl ester groups.
Bone tissue engineering literature conveys investigations regarding biodegradable polymers where bioactive inorganic materials are added either before or after electrospinning process. The goal is to mimic the composition of bone and enhance the biocompatibility of the materials. Yet, most polymeric materials are hydrophobic in nature; therefore, their surfaces are not favorable for human cellular adhesion. In this sense, modifications of the hydrophobic surface of electrospun polymer fibers with hydrophilic and bioactive nanoparticles are beneficial. In this work, dispersion of hydroxyapatite (HAp), which is similar to the mineral component of natural bone, within biodegradable and biocompatible polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with the aid of a surfactant has been investigated. Non-ionic TWEEN20 and 12-hydroxysteric acid (HSA), cationic dodecyl trimethyl ammonium bromide (DTAB) and anionic sodium deoxycholate and sodium dodecyl sulfate (SDS) surfactants were used for comparison in order to prepare stable and homogenous nanocomposite suspensions of HAp/PHBV for the electrospinning process. Continuous and uniform composite nanofibers were generated successfully within a diameter range of 400-1,000 nm by the mediation of all surfactant types. Results showed that incorporation of HAp and any of the surfactant types strongly activates the precipitation rate of the apatite-like particles and decreases percent crystallinity of the HAp/PHBV mats. Mineralization was greatly enhanced on the fibers produced by using DTAB, HSA, and especially SDS on where also osteoblastic metabolic activity was similarly increased. The produced HAp/PHBV nanofibrous composite scaffolds would be a promising candidate as an osteoconductive bioceramic/polymer composite material for tissue engineering applications.
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