A. Fantini

Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment

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

Measurement of the φ→π0e+e- transition form factor with the KLOE detector

Abstract A measurement of the vector to pseudoscalar conversion decay ϕ → π 0 e + e − with the KLOE experiment is presented. A sample of ∼9500 signal events was selected from a data set of 1.7 fb −1 of e + e − collisions at s ∼ m ϕ collected at the DAΦNE e + e − collider. These events were used to perform the first measurement of the transition form factor | F ϕ π 0 ( q 2 ) | and a new measurement of the branching ratio of the decay: BR ( ϕ → π 0 e + e − ) = ( 1.35 ± 0.05 − 0.10 + 0.05 ) × 10 − 5 . The result improves significantly on previous measurements and is in agreement with theoretical predictions.

A new limit on the CP violating decay KS→3π0 with the KLOE experiment

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.

Precision measurement of the η → π + π − π 0 Dalitz plot distribution with the KLOE detector

A bstractUsing 1.6 fb−1 of e+e− → ϕ → ηγ data collected with the KLOE detector at DAΦNE, the Dalitz plot distribution for the η → π+π−π0 decay is studied with the world’s largest sample of ∼ 4.7 · 106 events. The Dalitz plot density is parametrized as a polynomial expansion up to cubic terms in the normalized dimensionless variables X and Y . The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a gX2Y term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.

Measurement of Γ(η→π+π-γ)/Γ(η→π+π-π0) with the KLOE detector

The ratio R-eta = Gamma(eta -> pi(+)pi(-)gamma)/Gamma(eta -> pi(+)pi(-)pi(0)) has been measured by analysing 22 million phi -> eta gamma decays collected by the KLOE experiment at DANE, corresponding to an integrated luminosity of 558 pb(-1). The eta -> pi(+)pi(-)gamma proceeds both via the rho resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R-eta = 0.1856 +/- 0.0005(stat)+/- 0.0028(syst), points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the eta -> pi(+)pi(-)gamma decay could be described in a model-independent approach in terms of a(-) single free parameter, alpha. The determined value of the parameter alpha is alpha = (1.32 +/- 0.08(stat-0.09syst)(+0.10) +/- 0.02(theo)) GeV-2. 2012 Elsevier B.V. All rights reserved.The ratio R_{\eta}=\Gamma(\eta -> \pi^+\pi^-\gamma)/\Gamma(\eta -> \pi^+\pi^-\pi^0) has been measured by analyzing 22 million \phi \to \eta \gamma decays collected by the KLOE experiment at DA\PhiNE, corresponding to an integrated luminosity of 558 pb^{-1}. The \eta \to \pi^+\pi^-\gamma proceeds both via the \rho resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R_{\eta}= 0.1856\pm 0.0005_{stat} \pm 0.0028_{syst}, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the \eta -> \pi^+\pi^-\gamma decay could be described in a model-independent approach in terms of a single free parameter, \alpha. The determined value of the parameter \alpha is \alpha = (1.32 \pm 0.08_{stat} +0.10/-0.09_{syst}\pm 0.02_{theo}) GeV^{-2}

Measurement of the running of the fine structure constant below 1 GeV with the KLOE detector

Abstract We have measured the running of the effective QED coupling constant α ( s ) in the time-like region 0.6 s 0.975 GeV with the KLOE detector at DAΦNE using the Initial-State Radiation process e + e − → μ + μ − γ . It represents the first measurement of the running of α ( s ) in this energy region. Our results show a more than 5 σ significance of the hadronic contribution to the running of α ( s ) , which is the strongest direct evidence both in time- and space-like regions achieved in a single measurement. By using the e + e − → π + π − cross section measured by KLOE, the real and imaginary parts of the shift Δ α ( s ) have been extracted. From a fit of the real part of Δ α ( s ) and assuming the lepton universality the branching ratio B R ( ω → μ + μ − ) = ( 6.6 ± 1.4 s t a t ± 1.7 s y s t ) ⋅ 10 − 5 has been determined.

Measurement of \Gamma(\eta -> \pi^+\pi^-\gamma)/\Gamma(\eta -> \pi^+\pi^-\pi^0) with the KLOE Detector

The ratio R-eta = Gamma(eta -> pi(+)pi(-)gamma)/Gamma(eta -> pi(+)pi(-)pi(0)) has been measured by analysing 22 million phi -> eta gamma decays collected by the KLOE experiment at DANE, corresponding to an integrated luminosity of 558 pb(-1). The eta -> pi(+)pi(-)gamma proceeds both via the rho resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R-eta = 0.1856 +/- 0.0005(stat)+/- 0.0028(syst), points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the eta -> pi(+)pi(-)gamma decay could be described in a model-independent approach in terms of a(-) single free parameter, alpha. The determined value of the parameter alpha is alpha = (1.32 +/- 0.08(stat-0.09syst)(+0.10) +/- 0.02(theo)) GeV-2. 2012 Elsevier B.V. All rights reserved.The ratio R_{\eta}=\Gamma(\eta -> \pi^+\pi^-\gamma)/\Gamma(\eta -> \pi^+\pi^-\pi^0) has been measured by analyzing 22 million \phi \to \eta \gamma decays collected by the KLOE experiment at DA\PhiNE, corresponding to an integrated luminosity of 558 pb^{-1}. The \eta \to \pi^+\pi^-\gamma proceeds both via the \rho resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, R_{\eta}= 0.1856\pm 0.0005_{stat} \pm 0.0028_{syst}, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the \eta -> \pi^+\pi^-\gamma decay could be described in a model-independent approach in terms of a single free parameter, \alpha. The determined value of the parameter \alpha is \alpha = (1.32 \pm 0.08_{stat} +0.10/-0.09_{syst}\pm 0.02_{theo}) GeV^{-2}

Combination of KLOE

The three precision measurements of the cross section

\sigma\big(e^+e^-\rightarrow\pi^+\pi^-\gamma(\gamma)\big)

\sigma\big(e^+e^-\rightarrow\pi^+\pi^-\gamma(\gamma)\big)

measurements and determination of

using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. We present the construction of these covariance matrices and use them to determine a combined KLOE measurement for