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

Sökning: WFRF:(Messi F.)

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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.
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3.
  • Archilli, F., et al. (författare)
  • Search for a vector gauge boson in phi meson decays with the KLOE detector KLOE-2 Collaboration
  • 2012
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 251-255
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The existence of a light dark force mediator has been tested with the KLOE detector at DA Phi NE. This particle, called U. is searched for using the decay chain phi -&gt; eta U, eta -&gt; pi(+)pi(-)pi(0), U -&gt; e(+)e(-). No evidence is found in 1.5 fb(-1) of data. The resulting exclusion plot covers the mass range 5 &lt; M-U &lt; 470 MeV, setting an upper limit on the ratio between the U boson coupling constant and the One structure constant, alpha'/alpha, of &lt;= 2 x 10(-5) at 90% C.L. for 50 &lt; M-U &lt; 420 MeV.</p>
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4.
  • 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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5.
  • Babusci, D., et al. (författare)
  • Precision measurement of sigma (e(+)e(-) -&gt; pi(+)pi(-)gamma)/sigma(e(+)e(-) -&gt;mu(+)mu(-)gamma) and determination of the pi(+)pi(-) contribution to the muon anomaly with the KLOE detector
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 720:4-5, s. 336-343
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We have measured the ratio cr (e(+)e(-) -&gt; pi(+)pi(-)gamma)/sigma(e(+)e(-) -&gt; mu(+)mu(-)gamma), with the KLOE detector at DA Phi NE for a total integrated luminosity of similar to 240 pb(-1). From this ratio we obtain the cross section sigma (e(+)e(-) -&gt; pi(+)pi(-)gamma). From the cross section we determine the pion form factor vertical bar F-pi vertical bar(2) and the two-pion contribution to the muon anomaly a(mu) for 0.592&lt; M-pi pi &lt; 0.975 GeV, Delta(pi pi) a(mu) = (385.1 +/- 1.1(stat) +/- 2.7(sys+theo)) x 10(-10). This result confirms the current discrepancy between the Standard Model calculation and the experimental measurement of the muon anomaly. (c) 2013 Elsevier B.V. All rights reserved.</p>
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6.
  • Babusci, D., et al. (författare)
  • Limit on the production of a light vector gauge boson in phi meson decays with the KLOE detector
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 720:1-3, s. 111-115
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a new limit on the production of a light dark-force mediator with the KLOE detector at DA Phi NE. This boson, called U, has been searched for in the decay phi -&gt; eta U, U -&gt; e(+)e(-), analyzing the. decay eta -&gt; pi(0)pi(0)pi(0) in a data sample of 1.7 fb(-1). No structures are observed in the e(+)e(-) invariant mass distribution over the background. This search is combined with a previous result obtained from the decay eta -&gt; pi(+)pi(-)pi(0), increasing the sensitivity. We set an upper limit at 90% C.L. on the ratio between the U boson coupling constant and the fine structure constant of alpha'/alpha &lt; 1.7 x 10(-5) for 30 &lt; M-U &lt; 400 MeV and alpha'/alpha &lt;= 8 x 10(-6) for the sub-region 50 &lt; M-U &lt;210 MeV. This result assumes the Vector Meson Dominance expectations for the phi eta gamma* transition form factor. The dependence of this limit on the transition form factor has also been studied.</p>
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7.
  • Babusci, D., et al. (författare)
  • Measurement of eta meson production in gamma gamma interactions and Gamma(eta -&gt; gamma gamma) with the KLOE detector
  • 2013
  • Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :1, s. 119
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a measurement of eta meson production in photon-photon interactions produced by electron-positron beams colliding with root s = 1 GeV. The measurement is done with the KLOE detector at the phi-factory DA Phi NE with an integrated luminosity of 0.24 fb(-1). The e(+)e(-) -&gt; e(+)e(-)eta cross section is measured without detecting the outgoing electron and positron, selecting the decays eta -&gt; pi(+)pi(-)pi(0) and eta -&gt; pi(0)pi(0)pi(0). The most relevant background is due to e(+)e(-) -&gt; eta gamma when the monochromatic photon escapes detection. The cross section for this process is measured as sigma(e(+)e(-) -&gt; eta gamma) = (856 +/- 8(stat) +/- 16(syst)) pb. The combined result for the e(+)e(-) -&gt; e(+)e(-)eta cross section is sigma(e(+)e(-) -&gt; e(+)e(-)eta) = (32.72 +/- 1.27(stat) +/- 0.70(syst)) pb. From this we derive the partial width Gamma(eta -&gt; gamma gamma) = (520 +/- 20(stat) +/- 13(syst)) eV. This is in agreement with the world average and is the most precise measurement to date.</p>
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8.
  • Babusci, D., et al. (författare)
  • Measurement of Γ(η→π+π-γ)/Γ(η→π+π-π0) with the KLOE detector
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 718:3, s. 910-914
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The ratio Rη=Γ(η→π+π-γ)/Γ(η→π+π-π0) has been measured by analysing 22 million φ→ηγ decays collected by the KLOE experiment at DAΦNE, corresponding to an integrated luminosity of 558 pb-1. The η→π+π-γ proceeds both via the ρ resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, Rη=0.1856±0.0005stat±0.0028syst, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the η→π+π-γ decay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter α is α=(1.32±0.08stat-0.09syst+0.10±0.02theo) GeV-2.</p>
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9.
  • 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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10.
  • Babusci, D., et al. (författare)
  • Search for light vector boson production in e(+)e(-) -&gt; mu(+)mu(-)gamma interactions with the KLOE experiment
  • 2014
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 736, s. 459-464
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We have searched for a light vector boson U, the possible carrier of a "dark force", with the KLOE detector at the DA Phi NE e(+)e(-) collider, motivated by astrophysical evidence for the presence of dark matter in the Universe. Using e(+)e(-) collisions collected with an integrated luminosity of 239.3 pb(-1), we look for a dimuon mass peak in the reaction e(+)e(-) -&gt; mu(+)mu(-)gamma, corresponding to the decay U -&gt; mu(+)mu(-). We find no evidence for a U vector boson signal. We set a 90% CL upper limit for the mixing parameter squared between the photon and the U boson of 1.6 x 10(-5) to 8.6 x 10(-7) for the mass region 520 &lt; m(U) &lt; 980 MeV.  </p>
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