1,524 research outputs found

    A next-to-leading order study of photon-pion and pion pair hadro-production in the light of the Higgs boson search at the LHC

    Get PDF
    We discuss the production of photon-pion and pion pairs with a large invariant mass at collider energies. We present a study based on a perturbative QCD calculation at full next-to-leading order accuracy, implemented in the computer programme DIPHOX. We give estimations for various observables, which concern the reducible background to the Higgs boson search in the channel H --> gamma gamma, in the mass range 80-140 GeV at the LHC. We critically discuss the reliability of these estimates due to our imperfect knowledge of fragmentation functions at high z and a subtle interplay between higher order corrections and realistic experimental cuts. We conclude that, whereas the invariant mass spectrum of photon-pion pairs is theoretically better under control, in the dipion case large uncertainties remain.Comment: 26 pages Latex, 14 eps figures, replaced by published versio

    Stable One-Dimensional Integral Representations of One-Loop N-Point Functions in the General Massive Case: I - Three Point Functions

    Get PDF
    In this article we provide representations for the one-loop three point functions in 4 and 6 dimensions in the general case with complex masses. The latter are part of the GOLEM library used for the computation of one-loop multileg amplitudes. These representations are one-dimensional integrals designed to be free of instabilites induced by inverse powers of Gram determinants, therefore suitable for stable numerical implementations.Comment: 40 pages, 1 figur

    A full Next to Leading Order study of direct photon pair production in hadronic collisions

    Get PDF
    We discuss the production of photon pairs in hadronic collisions, from fixed target to LHC energies. The study which follows is based on a QCD calculation at full next-to-leading order accuracy, including single and double fragmentation contributions, and implemented in the form of a general purpose computer program of "partonic event generator" type. To illustrate the possibilities of this code, we present the comparison with observables measured by the WA70 and D0 collaborations, and some predictions for the irreducible background to the search of Higgs bosons at LHC in the channel h→γγh \to \gamma \gamma. We also discuss theoretical scale uncertainties for these predictions, and examine several infrared sensitive situations which deserve further study.Comment: 45 pages Latex, 16 eps files plus some metafont files; replaced by the version to appear in Eur. Phys. J.

    Improving preschoolers\u27 memories for the sources of events: A comparison of two source-monitoring training techniques

    Get PDF
    Preschoolers have a tendency to confuse the sources of events when recalling information. Two source-monitoring training (SMT) techniques were compared to see whether source confusions can be reduced in 3- to 4-year-old children (N = 37). After watching a puppet-show and story, children were randomly assigned to one of three conditions: two SMT conditions (explicit and implicit) and one control condition (memory training) where they were trained on non-target puppet-show and story events. The explicit method consisted of a clear mention of both sources (story, puppet show) and their modality (hearing and seeing, respectively) during training, specific instruction to utilize the strategy during the target interview and a definition, and clear mention to beware of misleading questions. The implicit condition utilized a general mention of both sources (hear, see) as well as no mention of misleading questions or instruction to continue utilizing the strategy. Children in the control condition were not given source training, but rather were trained to recognize the presence of items in each event. No differences were found between conditions in response to yes-no questions. However planned comparisons revealed differences between the explicit and control groups with regards to source-recognition, with the explicit group performing more accurately with regards to identification. Children in the implicit group were more likely to respond \u27I don\u27t know\u27 in comparison to the control group with regards to open-ended questions. Implications for strategy development are discussed

    A critical phenomenological study of inclusive photon production in hadronic collisions

    Get PDF
    We discuss fixed target and ISR inclusive photon production and attempt a comparison between theory and experiments. The dependence of the theoretical predictions on the structure functions, and on the renormalization and factorization scales is investigated. The main result of this study is that the data cannot be simultaneously fitted with a single set of scales and structure functions. On the other hand, there is no need for an additional intrinsic kTk_{_T} to force the agreement between QCD predictions and experiments, with the possible exception of one data set. Since the data cover almost overlapping kinematical ranges this raises the question of consistency among data sets. A comparative discussion of some possible sources of experimental uncertainties is sketched.Comment: 22 pages, 3 tables, 10 figures, Late

    Enseignements

    Get PDF

    First Report of Reticulitermes flavipes (Isoptera: Rhinotermitidae) in Italy

    Get PDF
    The first record of Reticuliterms flavipes (Kol l?r) (Isoptera: Rhinotermitidae) in Europe was in 1837, in Vienna, Austria, after infested plants im ported from the U.S. were discovered in the green house of the Sch?nbrunn Palace (Kollar 1837). In 1924, R. flavipes was found on the French Atlan tic coast and initially described as a new species, R. santonensis (Feytaud 1924). The synonymy of R. santonensis with R. flavipes was eventually confirmed by mitochondrial DNA analyses (Aus tin et al. 2002). In France, R. flavipes is currently distributed in an area extending from the Gi ronde region up to Paris and Normandy, and causes structural damage to buildings and trees (Lohou et al. 1997). During the 1930s, R. flavipes was discovered in wooden forepoles of channel construction in the steam heating district of Hamburg, Germany, where populations were sup ported by the favorable microclimate (Weidner 1937). Today, populations of R. flavipes remain es tablished in Hamburg, and cause damage to buildings and trees (Hertel & Plarre 2006). In Oct 2008, a subterranean termite infesta tion was discovered by a homeowner in a de tached house and adjacent garden situated in a residential district built in the 1970s in the out skirts of Olgiate Olona (Varese), in northern Italy. Termite workers and soldiers were observed and collected during a structural inspection in Nov 2008. Specimens are maintained in the Marini termite collection at the University of Bologna. Molecular analysis was used to determine the termite species, which were preserved in 100% ethanol prior to DNA extraction. A 684-bp region of the mitochondrial cytochrome oxidase subunit II gene and a 491-bp region of the mitochondrial 16S ribosomal RNA gene were amplified by PCR. Sequencing was performed by Macrogen Inc. (Seoul, South Korea). Closely related sequences were identified from GenBank using the BLAST network service (Altschul et al. 1990) at NCBI. For both genes, nucleotide sequences were identical in the 2 workers (GenBank Accession GU070788 and GU070789). Sequences from the Olgiate Olona house corresponded (97-100% cov erage, 100% similarity for COII sequence; 92 100% coverage, 100% similarity for 16S sequence) to GenBank sequences of R. flavipes from North America and France and of R. arenincola Goell ner (Table 1). This latter species appears to be identical to R. flavipes based on the DNA se quences obtained so far
    • …
    corecore