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Träfflista för sökning "WFRF:(Messi R.) "

Sökning: WFRF:(Messi R.)

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1.
  • Amelino-Camelia, G., et al. (författare)
  • Physics with the KLOE-2 experiment at the upgraded DA Phi NE
  • 2010
  • Ingår i: European Physical Journal C. - 1434-6044 .- 1434-6052. ; 68:3-4, s. 619-681
  • Forskningsöversikt (refereegranskat)abstract
    • <p>Investigation at a f-factory can shed light on several debated issues in particle physics. We discuss: (i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, (ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled-kaon states, (iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and eta/eta' mesons, (iv) the contribution to understand the nature of light scalar mesons, and (v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the e(+)e(-) physics in the continuum with the measurements of (multi) hadronic cross sections and the study of gamma gamma processes.</p>
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2.
  • Anastasi, A., et al. (författare)
  • Combined limit on the production of a light gauge boson decaying into mu(+) mu(-) and pi(+) pi(-)
  • 2018
  • Ingår i: Physics Letters B. - ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 784, s. 336-341
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We searched for the mu(+) mu(-) decay of a light vector gauge boson, also known as dark photon, in the e(+) e(-) -&gt; mu(+) mu(-) gamma(ISR) process by means of the Initial State Radiation (ISR) method. We used 1.93fb(-1) of data collected by the KLOE experiment at the DA Phi NE phi-factory. No structures have been observed over the irreducible mu(+) mu(-) background. A 90% CL limit on the ratio epsilon(2)= alpha'/alpha between the dark coupling constant and the fine structure constant of 3 x 10(-6)-2 x 10(-7) has been set in the dark photon mass region between 519 MeV and 973 MeV. This new limit has been combined with the published result obtained investigating the hypothesis of the dark photon decaying into hadrons in e(+) e(-) -&gt; pi(+) pi(-) gamma(ISR) events. The combined 90% CL limit increases the sensitivity especially in the rho-omega interference region and excludes epsilon(2) greater than (13 - 2) x 10(-7). For dark photon masses greater than 600 MeV the combined limit is lower than 8 x 10(-7) resulting more stringent than present constraints from other experiments.</p>
3.
  • Alef, S., et al. (författare)
  • The BGOOD experimental setup at ELSA
  • 2020
  • Ingår i: European Physical Journal A. - Springer. - 1434-6001. ; 56:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The BGOOD experiment at the ELSA facility in Bonn has been commissioned within the framework of an international collaboration. The experiment pursues a systematic investigation of non-strange and strange meson photoproduction, in particular t-channel processes at low momentum transfer. The setup uniquely combines a central almost 4 π acceptance BGO crystal calorimeter with a large aperture forward magnetic spectrometer providing excellent detection of both neutral and charged particles, complementary to other setups such as Crystal Barrel, Crystal Ball, LEPS and CLAS.
4.
  • Alef, S., et al. (författare)
  • Commissioning and initial experimental program of the BGO-OD experiment at ELSA
  • 2016
  • Ingår i: 14th InternationalWorkshop on Meson Production, Properties and Interaction, MESON 2016,Cracow, Poland,2016-06-02 - 2016-06-07. - EDP Sciences.
  • Konferensbidrag (refereegranskat)abstract
    • BGO-OD is a new meson photoproduction experiment at the ELSA facility of Bonn University. It aims at the investigation of non strange and strange baryon excitations, and is especially designed to be able to detect weekly bound meson-baryon type structures. The setup for the BGO-OD experiment is presented, the characteristics of the photon beam and the detector performances are shown and the initial experimental program is discussed.
5.
  • Bantes, B., et al. (författare)
  • The BGO calorimeter of BGO-OD experiment
  • 2015
  • Ingår i: Journal of Physics: Conference Series. - IOP Publishing. - 1742-6588. ; 587:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The BGO Rugby Ball is a large solid angle electromagnetic calorimeter now installed in the ELSA Facility in Bonn. The BGO is operating in the BGO-OD experiment aiming to study meson photoproduction off proton and neutron induced by a Bremsstrahlung polarized gamma beam of energies from 0.2 to 3.2 GeV and an intensity of 5 × 107 photons per second. The scintillating material characteristics and the photomultiplier read-out make this detector particularly suited for the detection of medium energy photons and electrons with very good energy resolution. The detector has been equipped with a new electronics read-out system, consisting of 30 sampling ADC Wie-Ne-R modules which perform the off-line reconstruction of the signal start-time allowing for a good timing resolution. Performances in linearity, resolution and time response have been carefully tested at the Beam Test Facility of the INFN National Laboratories in Frascati by using a matrix of 7 BGO crystals coupled to photomultipliers and equipped with the Wie-Ne-R sampling ADCs.
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6.
  • Jude, T. C., et al. (författare)
  • Strangeness photoproduction at the BGO-OD experiment
  • 2017
  • Ingår i: 17th International Conference on Hadron Spectroscopy and Structure, Hadron 2017,Salamanca, Spain,2017-09-25 - 2017-09-29.
  • Konferensbidrag (refereegranskat)abstract
    • The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the excitation spectrum of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating the photoproduction of hadrons of non-zero strangeness. The high momentum resolution at forward angles covers a kinematic region where t-channel exchange mechanisms play a dominant role. Access to this low momentum transfer region also allows the investigation of degrees of freedom not derived from constituent quark models, for example, the role of (vector) meson - baryon interactions and dynamically generated states in photoproduction reactions. Data taking for the first part of an extensive physics programme is complete and preliminary results and ongoing analysis are presented.
7.
  • Leo, Veronica De, et al. (författare)
  • Recent results of the BGO-OD experiment at ELSA facility
  • 2013
  • Ingår i: Journal of Physics: Conference Series. - IOP Publishing. - 1742-6588. ; 424:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The results obtained at the BGO-OD experiment with the BGO calorimeter, equipped with the new electronic readout based on sampling ADCs, during the tests performed with the beam time of March and June 2012 are presented. The proper functioning of the apparatus has allowed the reconstruction of the pseudo-scalar mesons π0 and η invariant masses. The simulation of the η' photoproduction reaction prepared for a proposal to the joint ELSA-MAMI Physics Advisory Committee is also presented.
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8.
  • Babusci, D., et al. (författare)
  • Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment
  • 2014
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 730, s. 89-94
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Neutral kaon pairs produced in phi decays in anti-symmetric entangled state can be exploited to search for violation of CPT symmetry and Lorentz invariance. We present an analysis of the CP-violating process phi -&gt; KSKL -&gt; pi(+)pi(-)pi(+)pi(-) based on 1.7 fb(-1) of data collected by the KLOE experiment at the Frascati phi-factory DA Phi NE. The data are used to perform a Measurement of the CPT-violating parameters Delta a(mu) for neutral kaons in the context of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are: Delta a(0) = (-6.0 +/- 7.7(stat)+/- 3.1(syst)) X 10(-18) GeV, Delta a(x) = (0.9 +/- 1.5(stat)+/- 0.6(syst)) X 10(-18) GeV, Delta a(y) = (-2.0 +/- 1.5(stat)+/- 0.5(syst)) X 10(-18) GeV, Delta a(z) = (3.1 +/- 1.7(stat)+/- 0.5(syst)) X 10(-18) GeV. These are presently the most precise measurements in the quark sector of the Standard Model Extension. (C) 2014 The Authors. Published by Elsevier B.V.</p>
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9.
  • Anastasi, A., et al. (författare)
  • Limit on the production of a low-mass vector boson in e(+)e(-) -&gt; U gamma, U -&gt; e(+)e(-) with the KLOE experiment
  • 2015
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 750, s. 633-637
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The existence of a new force beyond the Standard Model is compelling because it could explain several striking astrophysical observations which fail standard interpretations. We searched for the light vector mediator of this dark force, the U boson, with the KLOE detector at the DA Phi NE e(+)e(-) collider. Using an integrated luminosity of 1.54 fb(-1), we studied the process e(+)e(-) -&gt; U gamma, with U -&gt; e(+)e(-), using radiative return to search for a resonant peak in the dielectron invariant-mass distribution. We did not find evidence for a signal, and set a 90% CL upper limit on the mixing strength between the Standard Model photon and the dark photon, epsilon(2), at 10(-6)-10(-4) in the 5-520 MeV/c(2) mass range.</p>
10.
  • Babusci, D., et al. (författare)
  • A new limit on the CP violating decay K-S -&gt; 3 pi(0) with the KLOE experiment
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 723:1-3, s. 54-60
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We have carried out a new direct search for the CP violating decay K-S -&gt; 3 pi(0) with 1.7 fb(-1) of e(+)e(-) collisions collected by the KLOE detector at the Phi-factory DA Phi NE. We have searched for this decay in a sample of about 5.9 x 10(8) KSKL events tagging the K-S by means of the K-L interaction in the calorimeter and requiring six prompt photons. With respect to our previous search, the analysis has been improved by increasing of a factor four the tagged sample and by a more effective background rejection of fake K-S tags and spurious clusters. We find no candidates in data and simulated background samples, while we expect 0.12 standard model events. Normalizing to the number of K-S -&gt; 2 pi(0) events in the same sample, we set the upper limit on BR(K-S -&gt; 3 pi(0)) &lt;= 2.6 x 10(-8) at 90% C.L., five times lower than the previous limit. We also set the upper limit on the eta(000) parameter, vertical bar eta(000)vertical bar &lt;= 0.0088 at 90% C.L., improving by a factor two the latest direct measurement. (c) 2013 Elsevier B.V. All rights reserved.</p>
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