126 research outputs found

    Tra storia e mito. Politiche e usi politici di Abraham Lincoln

    Get PDF
    Barack Obama's election brought to the forefront one of the key figures of the nineteenth century, Abraham Lincoln, considered to be a founder of the nation by the new American President. Like Lincoln, Obama put the accent on unity and national goodwill. Like Lincoln, Obama nourished the roots that connected to the common man. The deep desire for change in American politics that Obama espouses also occurred during Lincoln's presidency.This essay dwells on Lincoln's words that are impressive in many respects, especially in the way they are able to communicate the passion of political involvement, as well as are impressive the images which represent the Great Emancipator in the different period of American history. Words and images reinterpreted Lincoln's myth in a contemporary mood, showing the how Lincoln became a continuously changing icon, down to the current presidency of Barack Obama

    Democrazia, schiavitù e razzismo negli Stati Uniti. Da Frederick Douglass a Black Lives Matter.

    Get PDF
    In his speech at the dedication of the National Museum of African American History and Culture in Washington, D.C:, September 24, 2016, former President Barack Obama delivered a view of a history of African Americans in the United States. He spoke about a world of «real patriotism» rising from slavery, passing through segregation and racism, and ending successfully with his election. This happened because African Americans embraced «a lifetime of struggle and progress and enlightenment that we etched in Frederick Douglass’s mighty leonine gaze». This article started with Frederick Douglass, who put together the struggle with patriotism, reflecting on his life and writings in nineteenth century, but also in his legacies in the movement of today, such as Black Lives Matter, constantly probing American’s contradictions over race.In his speech at the dedication of the National Museum of African American History and Culture in Washington, D.C:, September 24, 2016, former President Barack Obama delivered a view of a history of African Americans in the United States. He spoke about a world of «real patriotism» rising from slavery, passing through segregation and racism, and ending successfully with his election. This happened because African Americans embraced «a lifetime of struggle and progress and enlightenment that we etched in Frederick Douglass’s mighty leonine gaze». This article started with Frederick Douglass, who put together the struggle with patriotism, reflecting on his life and writings in nineteenth century, but also in his legacies in the movement of today, such as Black Lives Matter, constantly probing American’s contradictions over race

    Search for spontaneous muon emission from lead nuclei

    Full text link
    We describe a possible search for muonic radioactivity from lead nuclei using the base elements ("bricks" composed by lead and nuclear emulsion sheets) of the long-baseline OPERA neutrino experiment. We present the results of a Monte Carlo simulation concerning the expected event topologies and estimates of the background events. Using few bricks, we could reach a good sensitivity level.Comment: 12 pages, 4 figure

    Electron/pion separation with an Emulsion Cloud Chamber by using a Neural Network

    Get PDF
    We have studied the performance of a new algorithm for electron/pion separation in an Emulsion Cloud Chamber (ECC) made of lead and nuclear emulsion films. The software for separation consists of two parts: a shower reconstruction algorithm and a Neural Network that assigns to each reconstructed shower the probability to be an electron or a pion. The performance has been studied for the ECC of the OPERA experiment [1]. The e/πe/\pi separation algorithm has been optimized by using a detailed Monte Carlo simulation of the ECC and tested on real data taken at CERN (pion beams) and at DESY (electron beams). The algorithm allows to achieve a 90% electron identification efficiency with a pion misidentification smaller than 1% for energies higher than 2 GeV

    Procedure for short-lived particle detection in the OPERA experiment and its application to charm decays

    Get PDF
    The OPERA experiment, designed to perform the first observation of νμντ\nu_\mu \rightarrow \nu_\tau oscillations in appearance mode through the detection of the τ\tau leptons produced in ντ\nu_\tau charged current interactions, has collected data from 2008 to 2012. In the present paper, the procedure developed to detect τ\tau particle decays, occurring over distances of the order of 1 mm from the neutrino interaction point, is described in detail. The results of its application to the search for charmed hadrons are then presented as a validation of the methods for ντ\nu_\tau appearance detection

    Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment

    Full text link
    The OPERA long-baseline neutrino-oscillation experiment has observed the direct appearance of ντ\nu_\tau in the CNGS νμ\nu_\mu beam. Two large muon magnetic spectrometers are used to identify muons produced in the τ\tau leptonic decay and in νμCC\nu_\mu^{CC} interactions by measuring their charge and momentum. Besides the kinematic analysis of the τ\tau decays, background resulting from the decay of charmed particles produced in νμCC\nu_\mu^{CC} interactions is reduced by efficiently identifying the muon track. A new method for the charge sign determination has been applied, via a weighted angular matching of the straight track-segments reconstructed in the different parts of the dipole magnets. Results obtained for Monte Carlo and real data are presented. Comparison with a method where no matching is used shows a significant reduction of up to 40\% of the fraction of wrongly determined charges.Comment: 10 pages. Improvements in the tex

    Limits on muon-neutrino to tau-neutrino oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam

    Get PDF
    The OPERA experiment, exposed to the CERN to Gran Sasso νμ\nu_\mu beam, collected data from 2008 to 2012. Four oscillated ντ\nu_\tau Charged Current interaction candidates have been detected in appearance mode, which are consistent with νμντ\nu_\mu \to \nu_\tau oscillations at the atmospheric Δm2\Delta m^2 within the "standard" three-neutrino framework. In this paper, the OPERA ντ\nu_\tau appearance results are used to derive limits on the mixing parameters of a massive sterile neutrino.Comment: 11 pages, 4 figures; reference to Planck result updated in the Introduction. Submitted to JHE

    Observation of nu_tau appearance in the CNGS beam with the OPERA experiment

    Get PDF
    The OPERA experiment is searching for nu_mu -> nu_tau oscillations in appearance mode i.e. via the direct detection of tau leptons in nu_tau charged current interactions. The evidence of nu_mu -> nu_tau appearance has been previously reported with three nu_tau candidate events using a sub-sample of data from the 2008-2012 runs. We report here a fourth nu_tau candidate event, with the tau decaying into a hadron, found after adding the 2012 run events without any muon in the final state to the data sample. Given the number of analysed events and the low background, nu_mu -> nu_tau oscillations are established with a significance of 4.2sigma.Comment: Submitted to Progress of Theoretical and Experimental Physics (PTEP

    Evidence for νμντ\nu_\mu \to \nu_\tau appearance in the CNGS neutrino beam with the OPERA experiment

    Full text link
    The OPERA experiment is designed to search for νμντ\nu_{\mu} \rightarrow \nu_{\tau} oscillations in appearance mode i.e. through the direct observation of the τ\tau lepton in ντ\nu_{\tau} charged current interactions. The experiment has taken data for five years, since 2008, with the CERN Neutrino to Gran Sasso beam. Previously, two ντ\nu_{\tau} candidates with a τ\tau decaying into hadrons were observed in a sub-sample of data of the 2008-2011 runs. Here we report the observation of a third ντ\nu_\tau candidate in the τμ\tau^-\to\mu^- decay channel coming from the analysis of a sub-sample of the 2012 run. Taking into account the estimated background, the absence of νμντ\nu_{\mu} \rightarrow \nu_{\tau} oscillations is excluded at the 3.4 σ\sigma level.Comment: 9 pages, 5 figures, 1 table

    Emulsion sheet doublets as interface trackers for the OPERA experiment

    Get PDF
    New methods for efficient and unambiguous interconnection between electronic counters and target units based on nuclear photographic emulsion films have been developed. The application to the OPERA experiment, that aims at detecting oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is reported in this paper. In order to reduce background due to latent tracks collected before installation in the detector, on-site large-scale treatments of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd) packages, each made of a doublet of emulsion films, have been designed, assembled and coupled to the OPERA target units ("ECC bricks"). A device has been built to print X-ray spots for accurate interconnection both within the CSd and between the CSd and the related ECC brick. Sample emulsion films have been extensively scanned with state-of-the-art automated optical microscopes. Efficient track-matching and powerful background rejection have been achieved in tests with electronically tagged penetrating muons. Further improvement of in-doublet film alignment was obtained by matching the pattern of low-energy electron tracks. The commissioning of the overall OPERA alignment procedure is in progress.Comment: 19 pages, 19 figure
    corecore