6,662 research outputs found

    Results on Multiple Coulomb Scattering from 12 and 20 GeV electrons on Carbon targets

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    Multiple scattering effects of 12 and 20 GeV electrons on 8 and 20 mm thickness carbon targets have been studied with high-resolution silicon microstrip detectors of the UA9 apparatus at the H8 line at CERN. Comparison of the scattering angle between data and GEANT4 simulation shows excellent agreement in the core of the distributions leaving some residual disagreement in the tails.Comment: 14 pages, 16 figures. Updated to match published versio

    Physics Behind Precision

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    This document provides a writeup of contributions to the FCC-ee mini-workshop on "Physics behind precision" held at CERN, on 2-3 February 2016.Comment: https://indico.cern.ch/event/469561

    QCD corrections to the forward-backward asymmetries of cc and bb quarks at the Z pole

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    Measurements of the forward-backward production asymmetry of heavy quarks in Z decays provide a precise determination of \swsqeffl . The asymmetries are sensitive to QCD effects, in particular hard gluon radiation. In this paper QCD corrections for \AFBbb~ and \AFBcc~ are discussed. The interplay between the experimental techniques used to measure the asymmetries and the QCD effects is investigated using simulated events. A procedure to estimate the correction needed for experimental measurements is proposed, and some specific examples are given

    Identification of a glucocorticoid response element in the human gamma chain fibrinogen promoter

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    The effect of the synthetic glucocorticoid hormone dexamethasone on human gamma chain fibrinogen gene expression was examined. The whole promoter region of 3.8 kb of this gene and progressive 5'-deletions were inserted into a promoterless expression vector, upstream of the luciferase gene and transiently transfected into the human hepatoma HepG2 cells, in the presence or in the absence of dexamethasone stimulation. Deletion analysis allowed to identify a region located between -1359 and -954 bp upstream from the transcription start site, involved in hormone inducibility. On the basis of a computer-assisted analysis, a putative GRE was found in this region at bases -1116 to -1102. Specific point mutations eliminating this putative GRE led to complete loss of glucocorticoid inducibility, thus indicating its functional role. Binding of the rat glucocorticoid receptor to this site was demonstrated by mobility-shift assays

    New constraint on the existence of the mu+-> e+ gamma decay

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    The analysis of a combined data set, totaling 3.6 \times 10^14 stopped muons on target, in the search for the lepton flavour violating decay mu^+ -> e^+ gamma is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 \times 10^-13 (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.Comment: 5 pages, 3 figures, a version accepted in Phys. Rev. Let

    The MEG detector for μ+→e+γ{\mu}+\to e+{\gamma} decay search

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    The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay \meg\ by using one of the most intense continuous μ+\mu^+ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.Comment: 59 pages, 90 figure

    MEG Upgrade Proposal

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    We propose the continuation of the MEG experiment to search for the charged lepton flavour violating decay (cLFV) \mu \to e \gamma, based on an upgrade of the experiment, which aims for a sensitivity enhancement of one order of magnitude compared to the final MEG result, down to the 6×10−146 \times 10^{-14} level. The key features of this new MEG upgrade are an increased rate capability of all detectors to enable running at the intensity frontier and improved energy, angular and timing resolutions, for both the positron and photon arms of the detector. On the positron-side a new low-mass, single volume, high granularity tracker is envisaged, in combination with a new highly segmented, fast timing counter array, to track positron from a thinner stopping target. The photon-arm, with the largest liquid xenon (LXe) detector in the world, totalling 900 l, will also be improved by increasing the granularity at the incident face, by replacing the current photomultiplier tubes (PMTs) with a larger number of smaller photosensors and optimizing the photosensor layout also on the lateral faces. A new DAQ scheme involving the implementation of a new combined readout board capable of integrating the diverse functions of digitization, trigger capability and splitter functionality into one condensed unit, is also under development. We describe here the status of the MEG experiment, the scientific merits of the upgrade and the experimental methods we plan to use.Comment: A. M. Baldini and T. Mori Spokespersons. Research proposal submitted to the Paul Scherrer Institute Research Committee for Particle Physics at the Ring Cyclotron. 131 Page

    Measurement of the radiative decay of polarized muons in the MEG experiment

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    We studied the radiative muon decay μ+→e+ννˉγ\mu^+ \to e^+\nu\bar{\nu}\gamma by using for the first time an almost fully polarized muon source. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon decays collected in the MEG experiment in the years 2009--2010 and measured the branching ratio B(μ+→e+ννˉγ\mu^+ \to e^+\nu\bar{\nu}\gamma) = (6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for μ+→e+γ\mu^+ \to e^+\gamma process.Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which was recently calculated. Published versio
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