62 research outputs found

    Laser performance of perylenebis (dicarboximide) dyes with long secondary alkyl chains

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    The laser performance and related photophysical properties of two very soluble perylene dyes with long chain secondary alkyl groups were investigated in cyclohexane solution. With a dye laser as pump source a tuning range of 555–580 nm was obtained at an optimum concentration of 3×10–4 M. The quantum efficiencies (=0.29 and 0.21) were better than 1/2 that of rhodamine 6G. No photodegradation was observed over an excitation period of several hours

    Search for neutral color-octet weak-triplet scalar particles in proton-proton collisions at √s= 8TeV

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    A search for pair production of neutral color-octet weak-triplet scalar particles (Θ0) is performed in processes where one Θ0 decays to a pair of b quark jets and the other to a Z boson plus a jet, with the Z boson decaying to a pair of electrons or muons. The search is performed with data collected by the CMS experiment at the CERN LHC corresponding to an integrated luminosity of 19.7 fb−1 of proton-proton collisions at √s = 8TeV. The number of observed events is found to be in agreement with the standard model predictions. The 95% confidence level upper limit on the product of the cross section and branching fraction is obtained as a function of the Θ0 mass. The 95% confidence level lower bounds on the Θ0 mass are found to be 623 and 426 GeV, for two different octo-triplet theoretical scenarios. These are the first direct experimental bounds on particles predicted by the octo-triplet model. © 2015, The Author(s)

    Search for heavy gauge W ′ bosons in events with an energetic lepton and large missing transverse momentum at √s = 13 TeV

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    A search is presented for W′ bosons in events with an electron or muon and large missing transverse momentum, using proton–proton collision data at √s=13 TeV collected with the CMS detector in 2015 and corresponding to an integrated luminosity of 2.3 fb−1. No evidence of an excess of events relative to the standard model expectations is observed. For a W′ boson described by the sequential standard model, upper limits at 95% confidence level are set on the product of the production cross section and branching fraction and lower limits are established on the new boson mass. Masses below 4.1 TeV are excluded combining electron and muon decay channels, significantly improving upon the results obtained with the 8 TeV data. Exclusion limits at 95% confidence level on the product of the W′ production cross section and branching fraction are also derived in combination with the 8 TeV data. Finally, exclusion limits are set for the production of generic W′ bosons decaying into this final state using a model-independent approach

    Passive Q-switching and mode-locking for the generation of nanosecond to femtosecond pulses

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    Measurement of the cross section ratio in collisions at σtt¯bb¯/σtt¯jj in pp collisions at s=8 TeV

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    The first measurement of the cross section ratio σ t t ¯ b b ¯ / σ t t ¯ jj is presented using a data sample corresponding to an integrated luminosity of 19.6 fb−1 collected in pp collisions at s = 8   TeV with the \{CMS\} detector at the LHC. Events with two leptons (e or μ) and four reconstructed jets, including two identified as b quark jets, in the final state are selected. The ratio is determined for a minimum jet transverse momentum p T of both 20 and 40 GeV/c. The measured ratio is 0.022 ± 0.003 ( stat ) ± 0.005 ( syst ) for p T > 20   GeV / c . The absolute cross sections σ t t ¯ b b ¯ and σ t t ¯ jj are also measured. The measured ratio for p T > 40   GeV / c is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order

    Angular analysis of the decay B0→K*0μ+μ- from pp collisions at s=8 TeV

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    The angular distributions and the differential branching fraction of the decay B0→K⁎(892)0μ+μ− are studied using data corresponding to an integrated luminosity of 20.5 fb −1 collected with the CMS detector at the LHC in pp collisions at s=8 TeV . From 1430 signal decays, the forward–backward asymmetry of the muons, the K⁎(892)0 longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions

    Search for neutral MSSM Higgs bosons decaying to μ+μ- in pp collisions at √s=7 and 8 TeV

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    A search for neutral Higgs bosons predicted in the minimal supersymmetric standard model (MSSM) for μ+μ- decay channels is presented. The analysis uses data collected by the CMS experiment at the LHC in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.3 fb-1, respectively. The search is sensitive to Higgs bosons produced either through the gluon fusion process or in association with a bb quark pair. No statistically significant excess is observed in the μ+μ- mass spectrum. Results are interpreted in the framework of several benchmark scenarios, and the data are used to set an upper limit on the MSSM parameter tanβ as a function of the mass of the pseudoscalar A boson in the range from 115 to 300 GeV. Model independent upper limits are given for the product of the cross section and branching fraction for gluon fusion and b quark associated production at s=8 TeV. They are the most stringent limits obtained to date in this channel. © 2015 The Authors

    Generation of 16-μm radiation by four-wave mixing in para-hydrogen

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    A 16-μm source based upon the combined effects of stimulated rotational Raman scattering and four-wave mixing in gaseous para-hydrogen has been experimentally demonstrated. The input beams were synchronized pulses from a ruby laser and a CO2 TEA laser. Pulses with ∼2 μJ of energy were generated at 627.8 cm-1
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