229,231 research outputs found
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
Get PDFThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
Insertion of phenylchlorocarbenes in the C-H bonds of alkanes: measurement of the rate constants by laser flash photolysis
No full textPhenylchlorocarbenes, produced by photolysis of the parent diazirines, have a very limited lifetime in alkane solvents. The rate of disappearance of p-methyl- and p-chlorophenylchlorocarbenes has been measured in iso-octane, cyclohexane and n-hexane as well as in benzene for comparison. The rate constants of several processes (dimerization, addition to the diazirine, reaction with the solvent, etc. ) contributing to the disappearance of the phenylchlorocarbenes have been determined. The rate of reaction with the solvent, which is much lower in benzene than in alkanes and depends strongly on the nature of the alkane, is assumed to be an insertion of the carbene in the C-H bonds of the solvent. Consequences of this reaction on the chemistry of carbenes produced by continuous irradiation (or thermolysis) of diazirines in alkanes are briefly discussed.PT: J; CR: BENSASSON R, 1971, T FARADAY SOC, V67, P1904 BONNEAU R, 1986, NOUV J CHIM, V10, P425 BONNEAU R, 1991, PURE APPL CHEM, V63, P289 DOYLE MP, 1988, TETRAHEDRON LETT, V29, P5863 GOULD IR, 1985, TETRAHEDRON, V41, P1587 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 LIU MTH, 1987, CHEM DIAZIRINES LIU MTH, 1990, J CHEM SOC CHEM COMM, P1482 LIU MTH, 1992, J AM CHEM SOC, V114, P3604 LIU MTH, 1992, J ORG CHEM, V57, P2483 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LUTZ H, 1973, J PHYS CHEM-US, V77, P1758 MORGAN S, 1991, J AM CHEM SOC, V113, P2782 MOSS RA, 1990, J AM CHEM SOC, V112, P5642 MOSS RA, 1990, KINETICS SPECTROSCOP; NR: 15; TC: 11; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 10; GA: JQ196Source type: Electronic(1
Search for new hadronic decays of h c and observation of h c → p p ¯ η
No full textAbstract A search for the hadronic decays of the h c meson to the final states p p ¯ π + π − π 0, p p ¯ η , and p p ¯ π 0 via the process ψ(3686) → π 0 h c is performed using (4.48 ± 0.03) × 108 ψ(3686) events collected with the BESIII detector. The decay channel h c → p p ¯ η is observed for the first time with a significance greater than 5σ and a branching fraction of (6.41 ± 1.74 ± 0.53 ± 1.00) × 10 −4, where the uncertainties are statistical, systematic, and that from the branching fraction of ψ(3686) → π 0 h c . Strong evidence for the decay h c → p p ¯ π + π − π 0 is found with a significance of 4.9σ and a branching fraction of (3.84 ± 0.83 ± 0.69 ± 0.58) × 10 −3. The significances include systematic uncertainties. No clear signal of the decay h c → p p ¯ π 0 is found, and an upper limit of 6.59 × 10 −4 on its branching fraction is set at the 90% confidence level
Structural controls on the formation of BSR offshore southwestern Taiwan from a dense seismic reflection survey
No full textDifference based Ridge and Liu type Estimators in Semiparametric Regression Models
Get PDFWe consider a difference based ridge regression estimator and a Liu type estimator of the regression parameters in the partial linear semiparametric regression model, y = Xβ + f + ε. Both estimators are analysed and compared in the sense of mean-squared error. We consider the case of independent errors with equal variance and give conditions under which the proposed estimators are superior to the unbiased difference based estimation technique. We extend the results to account for heteroscedasticity and autocovariance in the error terms. Finally, we illustrate the performance of these estimators with an application to the determinants of electricity consumption in Germany.Difference based estimator; Differencing estimator, Differencing matrix, Liu estimator, Liu type estimator, Multicollinearity, Ridge regression estimator, Semiparametric model
Studies on the meiotic stability and agronomic characters of 5D, 5R chromosomal isogenic lines in secondary Triticale
No full text
- …
