| 1. |
- Amelino-Camelia, G., et al.
(författare)
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Physics with the KLOE-2 experiment at the upgraded DA Phi NE
- 2010
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 68:3-4, s. 619-681
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Forskningsöversikt (refereegranskat)abstract
- 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.
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| 2. |
- Anastasi, A., et al.
(författare)
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Combined limit on the production of a light gauge boson decaying into mu(+) mu(-) and pi(+) pi(-)
- 2018
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Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 784, s. 336-341
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Tidskriftsartikel (refereegranskat)abstract
- We searched for the mu(+) mu(-) decay of a light vector gauge boson, also known as dark photon, in the e(+) e(-) -> 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(-) -> 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.
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| 3. |
- Anastasi, A., et al.
(författare)
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Measurement of the running of the fine structure constant below 1 GeV with the KLOE detector
- 2017
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Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 767, s. 485-492
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the running of the effective QED coupling constant alpha(s) in the time-like region 0.6 < root s < 0.975 GeV with the KLOE detector at DA Phi NE using the Initial-State Radiation process e(+) e(-) -> mu(+) mu(-)gamma. It represents the first measurement of the running of alpha(s) in this energy region. Our results show a more than 5 sigma significance of the hadronic contribution to the running of alpha(s), which is the strongest direct evidence both in time- and space-like regions achieved in a single measurement. By using the e(+) e(-) -> pi(+) pi(-) cross section measured by KLOE, the real and imaginary parts of the shift Delta alpha(s) have been extracted. From a fit of the real part of Delta alpha(s) and assuming the lepton universality the branching ratio BR(omega -> mu(+) mu(-)) = (6.6 +/- 1.4(stat) +/- 1.7(syst)) (.) 10 (5)has been determined.
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| 4. |
- Babusci, D., et al.
(författare)
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Measurement of the branching fraction for the decay K-S -> pi mu nu with the KLOE detector
- 2020
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Ingår i: Physics Letters B. - : ELSEVIER. - 0370-2693 .- 1873-2445. ; 804
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Tidskriftsartikel (refereegranskat)abstract
- Based on a sample of 300 million K-S mesons produced in phi -> KLKS decays recorded by the KLOE experiment at the DA Phi NE e(+)e(-) collider we have measured the branching fraction for the decay K-S -> pi mu nu. The K-S mesons are identified by the interaction of K-L mesons in the detector. The K-S -> pi mu nu decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement. Signal efficiencies are evaluated with data control samples of K-L -> pi mu nu decays. A fit to the reconstructed muon mass distribution finds 7223 +/- 180 signal events. Normalising to the K-S -> pi(+)pi(-) decay events the result for the branching fraction is B(K-S -> pi mu nu) = (4.56 +/- 0.11(stat) +/- 0.17(syst)) x 10(-4). It is the first measurement of this decay mode and the result allows an independent determination of vertical bar V-us vertical bar and a test of the lepton-flavour universality. (c) 2020 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 5. |
- Babusci, D., et al.
(författare)
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Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment
- 2014
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 730, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- 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 -> KSKL -> 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.
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| 6. |
- Anastasi, A., et al.
(författare)
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Limit on the production of a low-mass vector boson in e(+)e(-) -> U gamma, U -> e(+)e(-) with the KLOE experiment
- 2015
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 750, s. 633-637
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Tidskriftsartikel (refereegranskat)abstract
- 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(-) -> U gamma, with U -> 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.
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| 7. |
- Babusci, D., et al.
(författare)
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A new limit on the CP violating decay K-S -> 3 pi(0) with the KLOE experiment
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 723:1-3, s. 54-60
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Tidskriftsartikel (refereegranskat)abstract
- We have carried out a new direct search for the CP violating decay K-S -> 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 -> 2 pi(0) events in the same sample, we set the upper limit on BR(K-S -> 3 pi(0)) <= 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 <= 0.0088 at 90% C.L., improving by a factor two the latest direct measurement. (c) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Babusci, D., et al.
(författare)
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Measurement of Γ(η→π+π-γ)/Γ(η→π+π-π0) with the KLOE detector
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 718:3, s. 910-914
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
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| 10. |
- Anastasi, A., et al.
(författare)
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Limit on the production of a new vector boson in e+e− → Uγ, U → π+π− with the KLOE experiment
- 2016
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 757, s. 356-361
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The recent interest in a light gauge boson in the framework of an extra U(1) symmetry motivates searches in the mass range below 1 GeV. We present a search for such a particle, the dark photon, in e + e − → U γ , U → π + π − based on 28 million e + e − → π + π − γ events collected at DAΦNE by the KLOE experiment. The π + π − production by initial-state radiation compensates for a loss of sensitivity of previous KLOE U → e + e − , μ + μ − searches due to the small branching ratios in the ρ – ω resonance region. We found no evidence for a signal and set a limit at 90% CL on the mixing strength between the photon and the dark photon, ε 2 , in the U mass range between 527 and 987 MeV . Above 700 MeV this new limit is more stringent than previous ones.
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