796 research outputs found

    JetWeb: A WWW Interface and Database for Monte Carlo Tuning and Validation

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    A World Wide Web interface to a Monte Carlo validation and tuning facility is described. The aim of the package is to allow rapid and reproducible comparisons to be made between detailed measurements at high-energy physics colliders and general physics simulation packages. The package includes a relational database, a Java servlet query and display facility, and clean interfaces to simulation packages and their parameters.Comment: See http://jetweb.hep.ucl.ac.uk for further informatio

    HZTool and Rivet: Toolkit and Framework for the Comparison of Simulated Final States and Data at Colliders

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    A common problem in particle physics is the requirement to reproduce comparisons between data and theory when the theory is a (general purpose) Monte Carlo simulation and the data are measurements of final state observables in high energy collisions. The complexity of the experiments, the obervables and the models all contribute to making this a highly non-trivial task. We describe an existing library of Fortran routines, HZTool, which enables, for each measurement of interest, a comparable prediction to be produced from any given Monte Carlo generator. The HZTool library is being maintained by CEDAR, with subroutines for various measurements contributed by a number of authors within and outside the CEDAR collaboration. We also describe the outline design and current status of a replacement for HZTool, to be called Rivet (Robust Independent Validation of Experiment and Theory). This will use an object-oriented design, implemented in C++, together with standard interfaces (such as HepMC and AIDA) to make the new framework more flexible and extensible than the Fortran HZTool.Comment: Contribution to CHEP06 conferenc

    WW scattering at the CERN LHC

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    A detailed study is presented of elastic WW scattering in the scenario that there are no new particles discovered prior to the commissioning of the CERN LHC. We work within the framework of the electroweak chiral Lagrangian and two different unitarization protocols are investigated. Signals and backgrounds are simulated to the final-state-particle level. A new technique for identifying the hadronically decaying W is developed, which is more generally applicable to massive particles which decay to jets where the separation of the jets is small. The effect of different assumptions about the underlying event is also studied. We conclude that the channel WW-->jj+lőĹ may contain scalar and/or vector resonances which could be measurable after 100 fb-1 of LHC data

    Non-global logarithms in inter-jet energy flow with kt clustering requirement

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    Recent work in inter-jet energy flow has identified a class of leading logarithms previously not considered in the literature. These so-called non-global logarithms have been shown to have significant numerical impact on gaps-between-jets calculations at the energies of current particle colliders. Here we calculate, at fixed order and to all orders, the effect of applying clustering to the gluonic final state responsible for these logarithms for a trivial colour flow 2 jet system. Such a clustering algorithm has already been used for experimental measurements at HERA. We find that the impact of the non-global logarithms is reduced, but not removed, when clustering is demanded, a result which is of considerable interest for energy flow observable calculations.Comment: 13 pages, 4 figure

    Multiple GF-1 binding sites flank the erythroid specific transcription unit of the human carbonic anhydrase I gene

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    AbstractSix potential GF-1 sites which bind an erythroid factor are present in the 5' and 3' regions flanking the erythroid-speciflc transcription unit of the human carbonic anhydrase 1 (HCAI) gene. When two of these sites are placed upstream of a minimal eukaryotic promoter they confer upregulated expression in erythroid over non-erythroid cells. The presence of the erythroid factor in TPA-treated HEL cells in which the level of HCAI transcript has greatly decreased and in non-HCAI-expressing K562 cells suggests that in these cases the presence of the factor is not sufficient for HCAI expression

    FastJet user manual

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    FastJet is a C++ package that provides a broad range of jet finding and analysis tools. It includes efficient native implementations of all widely used 2-to-1 sequential recombination jet algorithms for pp and e+e- collisions, as well as access to 3rd party jet algorithms through a plugin mechanism, including all currently used cone algorithms. FastJet also provides means to facilitate the manipulation of jet substructure, including some common boosted heavy-object taggers, as well as tools for estimation of pileup and underlying-event noise levels, determination of jet areas and subtraction or suppression of noise in jets.Comment: 69 pages. FastJet 3 is available from http://fastjet.fr

    Magnetically Stabilized Luminescent Excitations in Hexagonal Boron Nitride

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    Magnetically stabilized luminescence is observed in hexagonal boron nitride. The luminescence is induced by absorption of cold neutrons and is in the visible region. In the absence of a magnetic field, the photon emission level is observed to decay over several hundred seconds. A fraction of this luminescence can be suppressed if the temperature is T <~ 0.6 K and the magnetic field is B >~ 1.0 T. Subsequent to irradiation and suppression, luminescence can be induced by an increase in T or lowering of B. Possible explanations include stabilization of triplet states or the localization and stabilization of excitons.Comment: 11 pages, 7 figures, to appear in the Journal of Luminescenc

    The underlying event and fragmentation

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    A good fit to the CDF underlying event is obtained in the multiple parton scattering picture using HERWIG, after modifying the cluster hadronization algorithm as suggested by our previous study and adopting a larger maximum cluster size. The number of scatters per event is generated simply as a Poisson distribution. If our picture is correct, the baryon yield should be enhanced in the underlying event. This effect may be studied by measuring the proton-to-pion ratio.Comment: 23 pages, 8 figure

    Multiparton Interactions in Photoproduction at HERA

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    The high energy photoproduction of jets is being observed at the ep collider, HERA. It may be that the HERA centre-of-mass energy is sufficiently large that the production of more than one pair of jets per ep collision becomes possible, owing to the large number density of the probed gluons. We construct a Monte Carlo model of such multiparton interactions and study their effects on a wide range of physical observables. The conclusion is that multiple interactions could have very significant effects upon the photoproduction final state and that this would for example make extractions of the gluon density in the photon rather difficult. Total rates for the production of many (i.e. > 2) jets could provide direct evidence for the presence of multiple interactions, although parton showering and hadronization significantly affect low transverse energy jets.Comment: 21 pages, 8 figures include

    A complete parton level analysis of boson-boson scattering and ElectroWeak Symmetry Breaking in lv + four jets production at the LHC

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    A complete parton level analysis of lv + four jets production at the LHC is presented, including all processes at order O(alpha^6), O(alpha^4*alpha_s^2) and O(alpha^2*alpha_s^4). The infinite Higgs mass scenario, which is considered as a benchmark for strong scattering theories and is the limiting case for composite Higgs models, is confronted with the Standard Model light Higgs predictions in order to determine whether a composite Higgs signal can be detected as an excess of events in boson--boson scattering.Comment: More detailed discussion of the effects of the reconstruction of the longitudinal neutrino momentum. Improved figures. To be published in JHE
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