Showing papers by "G. Chiefari published in 2022"
TL;DR: In this article , the spectrum of π + π − invariant mass in a sample of 6 . 7 × 10 5 e + e − → π+ π− γ events with the photon at large polar angle ( θ γ > 45 ◦ ) at a centre of mass energy √ s around the φ mass.
Abstract: We measured, with the KLOE detector, the spectrum of π + π − invariant mass in a sample of 6 . 7 × 10 5 e + e − → π + π − γ events with the photon at large polar angle ( θ γ > 45 ◦ ) at a centre of mass energy √ s around the φ mass. We observe in this spectrum a clear contribution from the intermediate process φ → f 0 (980) γ . A sizeable effect is also observed in the distribution of the pion forward-backward asymmetry. We use different theoretical models to fit the spectrum and we determine the f 0 mass and coupling constants to the φ , to π + π − and to K ¯ K .
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TL;DR: The average of the KLOE results is R πS = 2 . 2549 ± 0 . 0054, reducing the total error by a factor of three to 0 . 25% as discussed by the authors .
Abstract: = Γ( K S → π + π − ( γ )) / Γ( K S → π 0 π 0 ) has been measured with the KLOE detector. The result is R πS = 2 . 2555 ± 0 . 0012 stat ± 0 . 0021 syst - stat ± 0 . 0050 syst , which is in good agreement with the previously published result based on the KLOE data sample from the year 2000. The average of the KLOE results is R πS = 2 . 2549 ± 0 . 0054, reducing the total error by a factor of three, to 0 . 25%.
TL;DR: In this paper , data collected by the KLOE experiment in years 2001/2002 for a total integrated luminosity of 410 pb − 1 , corresponding to 17 million of produced η ’s from the Φ → ηγ radiative decay, have been analyzed to look for the C-violating decay η → γγγ .
Abstract: Data collected by the KLOE experiment in years 2001/2002 for a total integrated luminosity of 410 pb − 1 , corresponding to 17 million of produced η ’s from the Φ → ηγ radiative decay, have been analyzed to look for the C-violating decay η → γγγ . The signal is searched in events with 4 photons in the final state by using the spectrum of the most energetic photon. The background is evaluated from the data themself, doing a fifth degree polynomial fit outside the signal region, and extrapolating inside it. No signal has been observed and taking into account a selection efficiency ǫ = 20 . 3% we get from a likelihood fit Br( η → γγγ ) ≤ 1 . 6 × 10 − 5 at 95% CL. The procedure has a systematic ambiguity at the 35 % level.
TL;DR: In this paper , the authors performed a preliminary measurement of the ratio of the partial decay widths of the K0S into two charged and two neutral pions: B(K0S → π π) = 2.23 × (1 ± 0.3 (stat))×10; systematic effects are still under study and are presently estimated to be at the few percent level.
Abstract: The KLOE detector at DAΦNE , the Frascati φ-factory, has collected about 30 pb by the end of year 2000. The φ(1020) meson decays about 34% of the times into a K0L-K 0 S pair; DAΦNE is therefore an exceptional source of almost monochromatic, tagged K0S particles, allowing for detailed studies of their more rare decays. The above mentioned integrated luminosity corresponds to about 30 millions produced K0S. In KLOE the presence of a K0S is easily tagged by the observation of the corresponding K0L impinging onto the electromagnetic calorimeter before decay. Thanks to this technique we have performed a preliminary measurement of the ratio of the partial decay widths of the K0S into two charged and two neutral pions: B(K0S → π π)/B(KS → π π) = 2.23 × (1 ± 0.35× 10 (stat) ± 1.5× 10 (syst) ). We have also observed several hundreths semileptonic decays of the K0S by far the largest sample of this decay mode ever observed by any experiment so far. The preliminary estimate of the corresponding branching ratio is B(K0S → π eν) = (6.8 ± 0.3 (stat))×10; systematic effects are still under study and are presently estimated to be at the few percent level.
TL;DR: In this article , the authors measured the ratio R = Γ( K L → γγ ) / Γ (K L → π 0 π γ + π − ) using the KLOE detector and obtained R = (2 . 79 ± 0.02 stat ± 0 . 02 syst ) × 10 − 3 .
Abstract: We have measured the ratio R = Γ( K L → γγ ) / Γ( K L → π 0 π 0 π 0 ) using the KLOE detector. From a sample of ∼ 10 9 φ -mesons produced at DAΦNE, the Frascati φ − factory, we select ∼ 1 . 6 10 8 K L -mesons tagged by observing K S → π + π − following the reaction e + e − → φ → K L K S . From this sample we select 27,375 K L → γγ events and obtain R = (2 . 79 ± 0 . 02 stat ± 0 . 02 syst ) × 10 − 3 . Using the world average value for BR ( K L → π 0 π 0 π 0 ), we obtain BR ( K L → γγ ) = (5 . 89 ± 0 . 07 ± 0 . 08) × 10 − 4 where the second error is due to the uncertainty on the π 0 π 0 π 0 branching fraction.