Magnetic moment quenching in small Pd clusters in solution

Small palladium clusters in vacuum show pronounced magnetic moments. With the help of Born–Oppenheimer molecular dynamics simulations based on density functional theory, we investigate for the paradigmatic examples of the Pd$$_{13}$$ and the Pd$$_8$$ cluster whether these magnetic moments prevail when the clusters are solvated. Our results show that the interaction with acetophenone quenches the magnetic moment. The reduction of the magnetic moment is a direct consequence of the electronic interaction between the Pd clusters and the solvent molecules, and not an indirect effect due to a different cluster geometry being stabilized by the solvation shell

Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

Constraints are presented on the total width of the recently discovered Higgs boson, ΓH, using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1fb−1at a center-of-mass energy √s=7TeVand 19.7fb−1at √s=8TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of ΓH\u3c22MeVat a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of mH=125.6GeV

Improved Durability of Wood Treated with Nano Metal Fluorides against Brown-Rot and White-Rot Fungi

Low-water soluble metal fluorides such as magnesium fluoride (MgF2) and calcium fluoride (CaF2) were evaluated for decay protection of wood. Initially, the biocidal efficacy of nano metal fluorides (NMFs) against wood destroying fungi was assessed with an in-vitro agar test. The results from the test showed that agar medium containing MgF2 and CaF2 was more efficient in preventing fungal decay than stand-alone MgF2 or CaF2. These metal fluorides, in their nanoscopic form synthesized using fluorolytic sol-gel synthesis, were introduced into the sapwood of Scots pine and beech wood and then subjected to accelerated ageing by leaching (EN 84). MAS 19F NMR and X-ray micro CT images showed that metal fluorides were present in treated wood, unleached and leached. Decay resistance of Scots pine and beech wood treated with NMFs was tested against wood destroying fungi Rhodonia placenta and Trametes versicolor in accordance with EN 113. Results revealed that mass losses were reduced to below 3% in wood treated with the combination of MgF2 and CaF2. It is concluded that NMFs provide full protection to wood even after it has been leached and can be used as wood preservatives in outdoor environments.Peer Reviewe

Search for pair-produced resonances decaying to jet pairs in proton–proton collisions at √s=8TeV

Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4fb−1of integrated luminosity from proton–proton collisions at a center-of-mass energy of 8TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. The first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350GeV at 95% confidence level. Previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835GeV

Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies

Measurements of two-particle angular correlations between an identified strange hadron (K0Sor Λ/Λ) and a charged particle, emitted in pPb collisions, are presented over a wide range in pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 35nb−1, were collected at a nucleon–nucleon center-of-mass energy (√sNN) of 5.02TeV with the CMS detector at the LHC. The results are compared to semi-peripheral PbPb collision data at √sNN=2.76TeV, covering similar charged-particle multiplicities in the events. The observed azimuthal correlations at large relative pseudorapidity are used to extract the second-order (v2) and third-order (v3) anisotropy harmonics of K0Sand Λ/Λparticles. These quantities are studied as a function of the charged-particle multiplicity in the event and the transverse momentum of the particles. For high-multiplicity pPb events, aclear particle species dependence of v2and v3is observed. For pT\u3c2GeV, the v2and v3values of K0Sparticles are larger than those of Λ/Λparticles at the same pT. This splitting effect between two particle species is found to be stronger in pPbthan in PbPbcollisions in the same multiplicity range. When divided by the number of constituent quarks and compared at the same transverse kinetic energy per quark, both v2and v3for K0Sparticles are observed to be consistent with those for Λ/Λparticles at the 10% level in pPbcollisions. This consistency extends over a wide range of particle transverse kinetic energy and event multiplicities

Search for lepton-flavour-violating decays of the Higgs boson

The first direct search for lepton-flavour-violating decays of the recently discovered Higgs boson (H) is described. The search is performed in the H →μτeand H →μτhchannels, where τeand τhare tau leptons reconstructed in the electronic and hadronic decay channels, respectively. The data sample used in this search was collected in pp collisions at a centre-of-mass energy of √s=8TeVwith the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 19.7fb−1. The sensitivity of the search is an order of magnitude better than the existing indirect limits. A slight excess of signal events with a significance of 2.4 standard deviations is observed. The p-value of this excess at MH=125GeVis 0.010. The best fit branching fraction is B(H →μτ) =(0.84+0.39−0.37)%. A constraint on the branching fraction, B(H →μτ) \u3c1.51%at 95% confidence level is set. This limit is subsequently used to constrain the μ–τYukawa couplings to be less than 3.6 ×10−3

Measurement of the ttproduction cross section in pp collisions at√s=8 TeV in dilepton final states containing one τ lepton

The top-quark pair production cross section is measured in final states with one electron or muon and one hadronically decaying τlepton from the process tt→(ν)(τντ)bb, where =e, μ. The data sample corresponds to an integrated luminosity of 19.6fb−1collected with the CMS detector in proton–proton collisions at √s=8TeV. The measured cross section σtt=257 ±3(stat)±24(syst)±7(lumi)pb, assuming a top-quark mass of 172.5GeV, is consistent with the standard model prediction

Search for narrow high-mass resonances in proton–proton collisions at √s=8TeVdecaying to a Z and a Higgs boson

A search for a narrow, high-mass resonance decaying into Z and Higgs (H) bosons is presented. The final state studied consists of a merged jet pair and a τpair resulting from the decays of Z and Hbosons, respectively. The analysis is based on a data sample of proton–proton collisions at a center-of-mass energy of 8TeV, collected with the CMS experiment in 2012, and corresponding to an integrated luminosity of 19.7fb−1. In the resonance mass range of interest, which extends from 0.8 to 2.5TeV, the Z and H bosons are produced with large momenta, which implies that the final products of the two quarks or the two τleptons must be detected within a small angular interval. From a combination of all possible decay modes of the τleptons, production cross sections in a range between 0.9 and 27.8fb are excluded at 95% confidence level, depending on the resonance mass

Study of W boson production in pPb collisions at √sNN=5.02TeV

The first study of W boson production in pPb collisions is presented, for bosons decaying to a muon or electron, and a neutrino. The measurements are based on a data sample corresponding to an integrated luminosity of 34.6nb−1at a nucleon–nucleon centre-of-mass energy of √sNN=5.02TeV, collected by the CMS experiment. The W boson differential cross sections, lepton charge asymmetry, and forward–backward asymmetries are measured for leptons of transverse momentum exceeding 25GeV/c, and as a function of the lepton pseudorapidity in the |ηlab| \u3c2.4range. Deviations from the expectations based on currently available parton distribution functions are observed, showing the need for including W boson data in nuclear parton distribution global fits

Determination of the top-quark pole mass and strong coupling constant from the t t-bar production cross section in pp collisions at sqrt(s) = 7 TeV

The inclusive cross section for top-quark pair production measured by the CMS experiment in proton–proton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, m[pole over t], or the strong coupling constant, α[subscript S]. With the parton distribution function set NNPDF2.3, a pole mass of 176.7[+3.8 over −3.4] GeV is obtained when constraining α[subscript S] at the scale of the Z boson mass, m[subscript Z], to the current world average. Alternatively, by constraining m[pole over t] to the latest average from direct mass measurements, a value of α[subscript S](m[subscript Z])= 0.1151[+0.0033 over −0.0032] is extracted. This is the first determination of α[subscript S] using events from top-quark production